Saturday, August 30, 2014

Therapeutic nutrition

Diet plays a major role in curing diseases or restoring the health by supplying the needed nutrients. Diets are composed of nutrients: macronutrients (proteins, fats and carbohydrates) and the micronutrients (vitamins, minerals and trace elements). Special dietary measures may be required to maintain lives of patients, who have chronic heart, kidney, liver and gastrointestinal diseases. These diets must also consider and supplement the effects of medications on nutrients. The regular diet is a normal unrestricted diet and is the food a person eats every day. The regular diet is well balanced and has a variety of foods from the food pyramid. A therapeutic diet is usually a modification of a regular diet. Therapeutic diet is formulated to optimize the nutritional needs of a particular patient. Therapeutic diet differs from a regular diet in the amount of one or more nutrients or food components for the purpose of treating or healing a disease or illness. The therapeutic diet is also called ‘special diet’ or ‘modified diet.’ A therapeutic diet is made under a physician’s guidance.
Therapeutic diet have modified for nutrients, calorific contribution, texture or consistency and /or food allergies or food intolerances.  For example, a cardiac diet is low in fat or cholesterol. A diabetic diet is low in sugar and fat. A clear liquid diet may be used to maintain hydration during gastro-intestinal illness such as nausea, vomiting and diarrhoea. Calorie – controlled diet is served to residents who are overweight. Sodium – restricted diet is served to residents with heart or kidney disease. High fiber diets (30g or more) are believed to help prevent diverticulosis, constipation, haemorrhoids and colon cancer.

Definition of diet therapy

Diet therapy is the use of any diet for restoring or maintaining optimal nutritional status and body homeostasis. The purpose of diet therapy is to restore or maintain an acceptable nutritional status of a patient.

Therapeutic nutrition

Therapeutic nutrition is broadly defined as the use of nutrients such as vitamins, minerals, amino acids, essential fatty acids, co-factors, enzymes, antioxidants and phytonutrients to support the body’s immune and healing systems, thereby altering the course and outcome of a disease process. It can be used as a preventive or can be used as a therapy. The goals of therapeutic nutrition include the supply of appropriate, bioavailable nutrients, the reduction of inflammation and the enhancement of elimination of toxins. Therapeutic nutrition is concerned with the treatment of patients by prescribing the right type of diets in order to meet their nutritional requirements.

The role of therapeutic diet

1.       To correct dietary deficiencies
2.       To maintain the patient in good nutrition state
3.       To formulate diet to meet the need of the patient.
4.       To educate the patient and family.

Types of therapeutic diets

Simplest therapeutic diets – are mechanically altered diets.  Mechanically altered diets contain foods that are pureed, chopped/ ground or soft for patients who have difficulty in chewing or swallowing. Mechanical soft diet is produced by simply grounding or chopping the food so it requires minimum chewing. For a pureed diet, the regular food is pulverized to a pureed consistency using a food processor.
Liquid diets – the diet is liquid at body temperature. Liquid diets may clear liquid or full liquid. The diet includes fruit juices, water gruels (strained and liquefied cooked cereals). This diet may be used after surgery. This diet can replace fluid lost from vomiting or diarrhea.
Soft or bland diet – it consists of easily digested foods that do not irritate digestive tract.
Restricted residue diet or low residue diet – it eliminates or limits foods that are high in bulk or fibre. It is used for patients with digestive and rectal diseases.
Hippocrates diet – is a natural diet of unprocessed and unchanged food as it is found in nature. It consists of fruits, vegetables and greens; fresh fruit and chlorophyll juices, sprouted seeds, grains and legumes; nuts and seeds; fermented foods and small amounts of raw honey.
Palaeolithic diet – it is also called caveman diet or stone age diet or hunter- gatherer diet. It is basically a high protein, high fibre eating plan. The diet includes a lot fresh lean meats and fish and vegetables and healthier fats.
Vegetarian or  neutral  diet – the vegetarian diet is sourced from plant products, plus dairy products and egg.The neutral diet is diet that contains the least amount of contaminants, pollutants or allergens. A vegetarian diet is the healthiest diet. A vegetarian diet reduces the risk for obesity, coronary artery disease, high blood pressure, diabetes and certain types of cancers. A diet rich in animal fats is the least healthy.
Vegan diet – consists of fruits, vegetables, legumes, grains, nuts and seeds. No eggs, cheese, yogurt, ice cream, butter or other milk products are eaten.
Raw food diet – consists 70% of raw fruits and vegetables and 30% of grains, nuts, dairy products and meat. Eating fresh, organic raw fruits and vegetables will increase the vitamins and micronutrients in your diet.  The raw foods have high levels of antioxidants with health promoting and disease preventing compounds.
Gluten free diet – Gluten is a protein found in wheat, rye, barley, triticale and oats. People with celiac disease (a digestive disorder) are sensitive to the presence of gluten in the diet. Gluten free foods include meat products, fish, dairy products, fruits and vegetables, pasta and noodles, rice and potatoes.
Calcium rich diet – calcium is absolutely critical nutrient in regulating acid/alkaline balance in the blood. Calcium plays another critical role in maintaining structural integrity of our skeleton. Excess calcium can deposit in blood vessels and kidneys. The diet includes dairy foods, sardines, collards, greens, spinach, sesame seeds and scallops.
Iron rich diet – Iron is an essential nutrient required for the synthesis of haemoglobin which carries oxygen in the blood. Iron deficiency anaemia is a worldwide health problem in young women and in children. Iron rich diet consists of broccoli, soybeans, bok choy, lentils, dark green vegetables, meat, poultry and fish.
Protein restricted diet – The average person needs between 40 to 65 grams of protein each day. People with chronic liver or kidney disease should limit protein intake. Proteins contain 16% nitrogen, which the body eliminates in the urine as urea. In cases where liver or kidney function is impaired, urea, ammonia or other toxic nitrogen metabolites may build up in the blood. To control protein intake, foods such as starches, sugars, grains, fruits, vegetables, fats and oils should be eaten at levels sufficient to meet daily energy needs. The purpose of a low protein diet is to prevent worsening of kidney or liver disease.
Mediterranean diet – consists of food mainly plant sources such as vegetables, fruits, cereals, legumes, garlic, nuts, olive oil, moderate amounts of fish, chicken, yogurt, red wine; low in cheese, eggs, saturated fats, sugar and red meat. A study has reported that this diet lowers the incidence of secondary heart attacks by 70% - a 70% reduction in deaths from all causes.
Detoxification diet – a diet of fruits, raw vegetables, water and yogurt to eliminate toxins absorbed from the environment or caused by poor digestion or poor excretion waste products.
The Atkins diet – It is a high-protein, low carbohydrate diet developed by Robert Atkins during 1960s. It is the most famous weight loss diet. It is based on the simple premise of a diet high in sugar and refined carbohydrates causes weight gain and ultimately leads to obesity. There are four phases to the Atkins diet: induction phase, ongoing weight loss, pre- maintenance and lifetime maintenance phase.
The macrobiotic diet – was developed in the 1920s by George Ohsawa. It consists of a simple diet of brown rice, miso soup and sea vegetables. Whole grains such as brown rice, barley, millet, oats, corn and rye makeup the bulk of the macrobiotic diet. This diet encourages the consumption of vegetables such as cabbage, broccoli, cauliflower, kale, bok choy, collards and mustard greens. Beans, tofu and sea vegetables should be eaten on a daily basis.
Zone diet – was developed by Barry Sears. The zone diet proposes a dietary ratio of 40% carbohydrate, 30% protein and 30% fat.

Benefits of therapeutic diets

It is essential or life saving treatment in the case of coeliac disease, phenylketonuria and galactosemia. Therapeutic diets are used to replenish patients who are malnourished in the case of cancer or intestinal diseases. Therapeutic diets are used to produce a negative nitrogen balance in obese people. Therapeutic diets are used as an alternative or complementary treatment in the case of diabetes or hypertension. Therapeutic diets are used to provide standard condition for diagnostic tests in the diagnosis of food sensitivity.
     Diet therapy restores or maintains an optimal nutritional status of a patient.

Friday, August 29, 2014

The properties of human brain and brain - based learning

The brain is an organ that receives, registers and processes information. It is the most delicate and the most complicated organ. The human brain is a watery gelatinous mass of nerve cells or neurons. Neurons are the basic building blocks of human brain. Neurons communicate with one another through synapses. Recent report indicates that an average human brain has about 23 billion neurons (Rabinowicz et al 2002). Each of the neuron has about 60,000 to 100,000 synaptic connections and has a total number of synaptic connections of about 1027 . The human brain is connected to 30,000 miles (50,000 kms) of nerves. The neurons are arranged end to end and the neurotransmitters transfer signals across the gaps (synapses) of 0.02 to 0.05 microns. The brain is a dense web of interconnecting synapses. Neurons communicate using electrical impulses. The neurons actually make up less than a tenth of the cells in the brain. The other 90-98% by number is glial cells, which are involved in development and maintenance.

Computational power of human brain

The estimated computational power of the human brain is about 1013 to 1016 operations per second. The speed of conduction of message is 200 miles per hour. The performance of a brain depends upon not on the number of neurons, but upon the information network (neural pathways) and the number of synapses. The neural pathways are both the network along which energy travels and the pattern through which information is processed in the brain. The number of synapses inside a human brain is directly related to intellectual and academic performance, activities that are centered in the human cerebrum.
The human being has the highest ratio of weight of the brain to the total body weight. The human brain weighs about 1.5 kgs, about 2 percent of body weight. The brain requires 15 percent of the blood, 40- 50 percent of the oxygen supply and 25 percent of the calories we consume. A 15 sec blockage of blood to the brain will result in unconsciousness. The brain cells are sensitive to oxygen availability. The brain cells have the ability of dividing and giving rise to new healthy cells, most particularly in the hippocampus, the area most crucial to learning and memory.
              “The human brain, then is the most complicated organization 
                  of matter that we know”--Isaac       Asimov.

Growth stages of human brain 

First increase occurs at the age of two, when a child starts to walk and begin to talk.
The second increase occurs at the age of six, when the child begins to learn to read and do math. The third increase occurs at the age of twelve, when he or she begins to grasp abstract and logical concepts. The various regions of the brain develop at different rates in different people. No two people’s brain stores the same information in the same way in the same place. Biologically the brain processes 400 billion bits of information per second, but is only aware of 2000 bits any one time.

Functional properties of human brain 

The brain expands with use – the more the brain is used, the more memory associations are formed. No new nerve cells develop in the brain after birth but new synapses do seem to grow and develop. New neural circuits and networks form between the neurons.
The brain loves to explore and make sense of the world – human brain is endlessly seeking to make sense of what it experiences. The brain seeks to establish new networks to process and store knowledge. The brain’s design strikes a balance between circuit performance and circuit plasticity. More plasticity exists in cortical circuits, where new dendrites can grow and synaptic connections can be made throughout life.
The brain is a pattern detector – the brain makes sense of the world by constructing or mapping patterns of the world. Nature exists as patterns. The recognition function of the brain involves ‘pattern matching’.
The brain is ‘born’ prematurely – much of its development occurs after birth and for many years afterwards. Experience can shape the brain. Neuroplasticity is the ability of the brain to change as a result of experience. A creative brain is flexible and imaginative.
Every brain is wired differently – the rate of neural growth seems to match the intensity of real-world learning. Learning results in growing new neural networks i.e. new knowledge structures. Learners of the same age show a great deal of intellectual variability.
The brain’s ability of attention – the brain naturally focuses on concepts sequentially, one at a time. The brain operates on alternating cycles of high attention and periods of inattention. During the period of inattention, the brain engages in the process of questioning, revising, one’s understanding etc. in order to comprehend i.e. ‘concept consolidation’.
Exercise boosts brain power – Exercise stimulates one of the brain’s most powerful growth factor, brain-derived neurotrophic factor(BDNF), which aids in the development of new cells in the brain. Exercise increases blood flow to the brain and the blood brings glucose, oxygen and proteins. Proteins encourage neurogenesis
The brain does not act as a computer in a linear fashion- The brain uses multiple strategies to create meaning. The brain is incapable of multitasking.
The brain does not perform well under too much stress – stressed brain doesn’t learn at all. Stress hormones interfere with the hippocampus’s ability to grow new neurons. Stress causes brain damage.
Every brain simultaneously perceives and creates parts and wholes- The brain is a parallel processor. Thoughts, emotions and imagination operate simultaneously. The brain understands and remembers best when facts are embedded in natural spatial memory.
The brain is a social organ- it develops better in concert with other brains.
                                         The more you use,
                                         The more you get.

Functional units of human learning

The human brain is composed of thousands of functional modules i.e., mini-brains within a brain. It is through multiple, complex combinations of these functional modules, through a myriad of interconnections that our brains create functional neural systems.  The functional unit of the mental activity is not the single neuron but a circuit of interconnecting neurons all activated at the same time (neural networks). Environmental stimulation can increase the numbers of neural connections and the strength of connections. Learning is a process that establishes new connections among networks and the new skills or knowledge that learned is neural circuits and networks. The brain is continually resculpting itself in response to experience and learning.

Brain plasticity and learning

Marvin Minsky (1986) in his book ‘The Society of Mind’ quoted as ‘The principal activities of brains are making changes in themselves.’ The brain’s ability to change with experience is called plasticity. The brain is a pliable organ like plastic, hence the term brain plasticity. The plasticity does not mean large-scale physical rearrangement of regions of brain tissue. The changes occur only in the internal structure (microstructure) of the brain, not its overall shape. The education is functional plasticity i.e., the ability to change behaviour following external or internal experiences. The functional plasticity refers to the growing, dropping and strengthening of neural networks.

Brain – based learning, BBL

The brain is extremely complex, dynamic and adaptive (plasticity) system. The brain consists of hundreds of billions of neurons and inter-neurons that produce an enormous number neural nets or groups of neurons working together, from which our daily experience is created. The brain’s activity is controlled by genetics, development, experience, culture, environment and emotions.
According to Eric Jensen (2000) brain – based learning is “learning in accordance with the way the brain is naturally designed to learn.” According to Fishback (1999), “the creation of neural networks and synapses are what constitutes learning.”
There are billions of neurons and the number of synapses is more than 10,000 times the number of neurons (Hill, 2001). ‘A single neuron can have from a few thousand up to one hundred thousand synapses and each synapse can receive information from thousands of other neurons(“The neurons that fire together wire together”). The resulting 100 trillion synapses make possible the complex cognition of human learners.’

Neural changes during learning

The physical brain is literally shaped by experience; axonal circuits change, modify and redevelop as human’s age. The human brain actually maintains an amazing plasticity throughout life. This means that any learner can increase their intelligence, without limits, using proper enrichment (Jensen 2000).
Neuronal growth is initiated by learning followed by assimilation and accommodation. In assimilation, the incoming information is changed to fit in to existing knowledge structures. Accommodation occurs when an existing cognitive structure (i.e., current neuronal circuits) is changed to incorporate new information (Ally 2004). The human brain is always looking to associations between incoming information and experience. The greater the amount of information and experience, the brain extracts and ‘compartmentalizes’ (lateralizes) the information (Jensen 2000). Thereafter the brain creates patterns of meaning. The pattern making depends on past information or experience. According to Jensen (2000), ‘Learning is best when focused, diffused, and then focused again.’ Jensen (2000) explained that proper environment is important for learning to occur. Color, hydration, visual stimuli, psychological stimuli, seasons, temperatures, plants, music, noise and aromas can all influence learning. Learning engages the entire physiology, physical development (stress, diet, exercise ), personal comfort and emotional state will affect the brain. All learning involves our body, emotions, attitudes and physical well being.

Educational neuroscience

Education is about enhancing learning and neuroscience is about understanding the mental processes involved in learning (Report by the Royal Society, UK, 2011). The goal of educational neuroscience is to work out how all learners can be helped to achieve their learning potentials and to make learning more effective for all learners. Neuroscientists investigate the processes by which the brain learns and remembers from molecular and cellular processes right through to how brain systems function.
                             To make life and success easier,
                                Take better care of your brain.

“Brain is an apparatus with which we think that we think”.
                         –Ambrose Bierce, 1911.
“The human brain functions as a high speed internet system. 
 The quality of the brain’s connections is the key to its speed,
 bandwidth, fidelity and overall on-line capacity” (Dr.George Bartzokis).

Friday, August 22, 2014

Nutritional value and handling of fruits and vegetables

 Fruit and vegetable consumption is one element of a healthy diet. Fruits and vegetables provide excellent sources of nutrients such as fibre, complex carbohydrates and numerous vitamins, minerals as well as non-nutritive phytochemicals. The nutrient content of fruits and vegetables also vary greatly in quality and quantity. The phytochemicals present in fruits and vegetables are diverse, such as ascorbic acid, carotenoids and phenolic compounds and they function as antioxidants, phytoestrogens and anti-inflammatory as well as chemoprotective agents. The World Health Organization (2003) estimated that a low vegetable and fruit intake accounts for 2.7 million deaths annually. Insufficient  intake of fruits and vegetables is estimated to cause around 14% gastrointestinal cancer deaths, about 11% of ischemic heart disease deaths  and about 9% of stroke deaths worldwide (WHO 2009). The World Health Organization acknowledges that the global intake of vegetables is less than 20-50% of the recommended amount.

Types of fruits and vegetables

Vegetables can be categorized into 3 general types such as green leafy and cruciferous, low-glycemic and starchy. On the other hand fruits are mainly divided into sweet, sub-acid and acid fruits. Vegetables are derived from various parts of plants that include leaves, stems, shoots, flowers, roots, rhizomes, tubers, bulbs, seeds, pods and even fruits. Vegetables are often used for dietary variety, colour and taste and can be obtained in a range of processed state including fresh, frozen, canned and dried. The quality factors of vegetables include colour, flavour, nutritional composition and health – functionality. The content of individual fruits and vegetables is affected by factors such as variety, soil, climatic conditions, agricultural methods, physiological stress and degree of ripeness, storage conditions and length of storage before consumption.
Most fresh fruits and vegetables are high in water, low in protein and low in fat. The water content ranges from 70-85%, commonly protein content is no greater than 3.5% and fat content no greater than 0.5%. Legumes such as peas and certain beans are higher in protein; a few vegetables such as sweet corn are slightly higher in fat; and avocados are substantially higher in fat. The majority of proteins occurring in fruits and vegetables play enzymatic roles. Proteins are found mainly in the cytoplasmic layers. The lipids of fruits and vegetables are largely confined to the cytoplasmic layers, in which they are especially associated with the surface membranes. The total amount of mineral components in fruits and vegetables is in the range of 0.1% (in sweet potatoes) up to about 4.4% (in Kohlrabi). The most abundant mineral constituent in fruits and vegetables is potassium.

Nutrient composition

The water content in various foods ranges from about 15% in grains, about 16 to 18% in butter, 20% in honey, 35% in bread, 75% in meat to about 90% in many fruits and vegetables. The amount of carbohydrates in foods ranges from about 1% in meats and fish, 4.5% in milk, 18% in potatoes, and 15 to 21% in sugar beets to about 70% in cereal grains. The proteins constitutes from about 1% of the weight of fruits, and 2% of potatoes, 12% of eggs, 12 to 22% of wheat grains, about 20% of meat to 25 to 40% of various beans. Lipids makes up from less than 1% of the weight of fruits, vegetables and lean fish muscle, 3.5% of milk, 6% of beef meat and 32% of egg yolk to 85% of butter.

Dietary recommendations

The World Cancer Society and the American Institute for Cancer Research suggest that mouth, stomach and colorectal cancers are less likely with high intakes of non-starchy foods like leafy green, broccoli and cabbage. The American Cancer Society advising at least five servings of fruits and vegetables per day for good health. The Harvard School of Public Health recommending nine servings of vegetables and fruits each day. The U.S. Department of Agriculture recommends filling half of one’s plate with fruits and vegetables at each meal. The USDA 2000 Dietary Guidelines (USDA, 2000) encourages people to: (1) enjoy five a day, i.e., eat at least 2 servings of fruits and at least 3 servings of vegetables each day.(2) choose fresh, frozen, dried or canned forms of a variety of colors and kinds, and (3) choose dark green leafy vegetables, orange fruits and vegetables  and cooked dry beans and peas often.The Dietary Guidelines for Americans 2010 has  recommended  that  every individual  should  make one-half of his/her plate with fruits and vegetables. The Expert Committee of the Indian Council of Medical Research has recommended that every individual should consume at least 300g of vegetables and 100g of fruits per day.

5 A DAY message

The '5 A DAY' message highlights the health benefits of consuming five 80 grams portions of fruits and vegetables every day. ‘5 A DAY’ is based on advice from the World Health Organization which recommends eating a minimum of 400g (80 x 5g) of fruits and vegetables a day to lower the risk of serious health problems such heart disease, stroke, type 2 diabetes and obesity.

Health benefits of fruits and vegetables

Hydrating effects –Drinking fruit and vegetable juices can contribute to the hydration of body  fluids and supply sugars and minerals e.g., water melon, celery, cucumber and lettuce.
Diuretic effects – Diuretics improve the rate of urination. The presence of potassium and magnesium help to accelerate the frequency of urination e.g., lemon, lime, cucumber, rose apples, peach and water melon.
Alkaline forming effects – Potassium, magnesium, calcium, copper, zinc and iron are alkaline minerals that are found in most fruits and vegetables. Citrus fruits, soybeans, carrots, lettuce, water cress and spinach are some examples of fruits and vegetables with alkalizing properties.
Mineralizing effects – Fruits and vegetables are a good source of mineral nutrients such as potassium, magnesium and calcium. E.g., bok choy, amaranth leaves, French beans, Brussels sprouts, dates, avocado and passion fruit.
Laxative effects –The dietary fibres in fruits and vegetables maintain healthy bowel function. High fibre fruits and vegetables act as natural laxatives e.g., psyllium, wheat bran, bananas, berries, apples, prunes, raisins, pineapple, and cabbage.
Tonic effects – Fruits and vegetables have curative properties which are useful in the treatment of certain diseases. Vegetables rich in potassium may help to maintain blood pressure e.g., sweet potatoes, white potatoes, white beans, tomato, soybeans, spinach and lentils. Fruits like apple, date and mango have a direct effect on the central nervous system.

Precautions for storing and cooking vegetables

Fresh fruits and vegetables are contaminated by pesticides, herbicides and fertilizers. Wash and scrub all fruits and vegetables thoroughly under running tap water before using them. Rinsing and rubbing is quite effective at removing tiny pathogens and surface deposits of pesticides. Do not use any chemicals for washing because fruits and vegetables are porous and they absorb the chemicals. Peel fruits and vegetables if possible and wash them before peeling. Trim only the inedible parts of the vegetable and cut the vegetables just before cooking. Washing, peeling and cooking fruits and vegetables reduces pesticide levels and eliminates the waxes.  Drying fruits and vegetables with a paper towel provides another measure of safety.
Do not buy or use produce that is moldy, badly bruised, shriveled or slimy. Discord the outer leaves of leafy vegetables because pesticides residues tend to accumulate there. Store fruits and vegetables in a cool dark place and use them as soon as possible after purchasing. Refrigerated fruits and vegetables should be kept in bags or containers, to minimize the chance of cross contamination between other foods and surfaces. Do not store fruits and greens together because fruits give off ethylene gas, which causes greens to decay. Frozen vegetables are often as healthy as fresh vegetables. Keep your fruits and vegetables separate from raw meats, poultry and sea-food. Store newly bought ones separate from old ones.
Dry and shelf –stable foods include flours, rice, and sugars should be stored in jars or containers in a cool, dry and well ventilated area. The food storage area should be regularly swept out and cleaned and any spit food should be cleaned up immediately. Onions should be stored away from other food in a cool, dry and well-ventilated area.
Water soluble vitamins are destroyed by cooking and are lost over time. Minerals and vitamins leach out into cooking water. Use minimum amount of water for cooking and avoid overcooking. Cover the pot when cooking vegetables to keep in steam and reduce cooking time.  Use vegetable water in stocks or gravies. Avoid frying vegetables. This will lead to loss of all valuable vitamins. Dulling of the greens can be minimized by keeping cooking times short. Do not use sodium bicarbonate, when cooking vegetables. Cook frozen vegetables without prior thawing and for as little time as possible. Eat food as soon as possible after cooking and avoid reheating.
Try to vary the intake of your vegetables. Because different pesticides are used on different crops, eating a variety of fruits and vegetables help ensure too much of any one pesticide. The best way to eat fruits and vegetables is without additional fat or sugar. Storage and cooking can lead to overall losses of up to half of the original nutrient content prior to consumption.
Choose cooking methods that minimize losses of vitamins and minerals. Since vegetables are very fragile,cook them as lightly as possible. Vegetables taste, keep their color and retain their nutrients better, when not overcooked. The best method is to steam the vegetables lightly and eat them while they are still crunchy.Fruits and vegetables should be eaten as far as possible in their natural state.

Tuesday, August 12, 2014

Cancer preventive dietary antioxidants

An antioxidant is a nutrient that helps inhibit or delay oxidation reactions caused by free radicals (free radical scavengers). Dietary antioxidants are compounds that reduce oxidative damage to the body by free radicals. Dietary antioxidants can safely interact with free radicals and terminate chain reaction of oxidation before vital molecules are damaged. Cell damage caused by free radicals appears to be a major contributor to aging and diseases like cancer and heart disease. Overall free radicals have been implicated in the pathogenesis of at least 50 diseases.  Antioxidants prevent the free radical damage to the delicate lining of one’s blood vessels, to the brain and nervous system and the DNA molecules. Antioxidants repair the cell damage associated with neurodegenerative conditions. They protect human body cells from the ravages of inflammation. Inflammation is known to be associated with increased levels of lipid peroxides and free radicals. Antioxidants play important roles as anti-disease agents and anti-aging agents.The dietary antioxidants such as vitamins A,C and E; carotenoids(i.e., beta-carotene, lutein and lycophene); polyphenols; the mineral selenium; and endogenous antioxidants such as glutathione-elevating agents (n-acetyl cysteine and alpha – lipoic acid), co enzyme Q10 and L-carnitine are essential for cancer prevention.

Definition of antioxidants

The USDA defined antioxidants as “compounds that protect biological systems against the potentially harmful effects of processes or reactions that can cause excessive oxidations.”
The Food and Nutrition Board of the Institute of Medicine (IOM) defined a dietary antioxidant as “a substance in foods that significantly decreases the adverse effects of reactive species such as reactive oxygen and nitrogen species, on normal physiological function in humans.”
The normal functioning of cells is dependent on a proper balance of pro-oxidants and antioxidants. The pro-oxidants promote the release of oxygen to provide energy needed for functioning of normal cells. However antioxidants protect the body from free radical damage. Antioxidants donate electrons to the free radicals and stop the chain reaction.

Reactive oxygen species (ROS)

Reactive oxygen species which encompasses all highly reactive oxygen molecules including free radicals. Free radicals are incomplete, highly unstable and reactive compounds or molecules. Free radicals contain one or more unbound or unpaired electrons. Due to the presence of unpaired electrons, free radicals show considerable degree of reactivity. Free radicals have the potential to attack critical molecules in the body by changing their chemical structures and affecting their functions. Free radicals are like robbers which are deficient in energy. Free radicals attack and snatch energy from other cells to satisfy them. The toxic of reactive oxygen species include the hydroxyl radical, hydrogen peroxide, the superoxide anion radical, nitric oxide radical, singlet oxygen, hypochlorite radical and various lipid peroxides. Reactive oxygen species and free radicals attack cells and lipoproteins to induce oxidation of lipids, proteins, sugars and DNA, which results in membrane damage, protein modification, enzyme deactivation, DNA strand breaks and base modification.

Oxidative stress

Oxidative stress is caused by the imbalance between pro-oxidants and antioxidant mechanisms. Oxidant exposure and antioxidant depletion are general phenomena that together are described as “oxidative stress.” Oxidants occur in various forms.Both chronic and natural and both acute and catastrophic events contribute oxidative stress.  Normal cells maintain a balance between reactive oxygen species (ROS) generation and antioxidant defense mechanism. Any disturbance of this balance produces oxidative stress which damage cellular components and even leads to cell death. Oxidative damage to DNA, proteins and other macromolecules may lead to a wide range of human diseases. The excessive oxidative stress can be due to the impact of several environmental factors such as exposure to pollutants, alcohol, medications, infections, poor diet, toxins, radiation etc.

Types of natural antioxidants

Natural antioxidants may be classified according to their nutritive value or their solubility. The hydrophobic (water hating/ lipid soluble e.g., vitamin E) and the hydrophilic (water loving/ water soluble e.g., vitamin C) is important both as nutrients and as antioxidants. The nutrient antioxidants include vitamins A,C and E, minerals copper, zinc and selenium. The non-nutritive antioxidants can subdivided into lipid soluble (e.g., carotenoids) and water soluble antioxidants (e.g., polyphenols). The examples of lipid-soluble antioxidants are vitamins A and E, carotenoids and lipoic acid. Water -soluble antioxidants include vitamin C, polyphenols and glutathione.  The antioxidants, which can be produced by human body include glutathione, alpha-lipoic acid and CoQ10 (ubiquinone).  
Antioxidant –rich phytochemicals are micro-constituents in plants and agriproducts. They differ from proteins, carbohydrates and lipids, which are macronutrients that are abundant in plants and food products. The type and quantity of antioxidant phytochemicals vary significantly from source to source. The antioxidant capacity of fruits and vegetables depends on the total concentrations of phytochemicals mainly ascorbic acid, phenolic compounds and carotenoids.

Physiologic mechanism of antioxidant activity

The physiologic activity of antioxidants may be divided into 3 categories: preventive antioxidants, chain breaking antioxidants and repair and de novo compounds. The preventive antioxidants are those compounds that reduce the rate of initiation of free radical chain reaction e.g., the selenium – dependent enzyme glutathione peroxidise. Chain – breaking antioxidants interact rapidly with the free radicals after the chain reaction is initiated, converting free radicals to stable forms e.g., vitamin C and E. Vitamin E has been referred to as Nature’s best chain – breaking antioxidants. Vitamin C can be a double-edged sword, where on one edge it is essential for health and acts as an antioxidant and the other edge it promoted pro-oxidant reactions. Repair and de novo compounds include enzymes that directly restore altered molecules to their original state or degrade them to non-functional compounds (catabolic reactions). Β-carotene is an important singlet oxygen and free radical scavenger.

Antioxidant Vitamins

Vitamin A and beta-carotene -Diets high in vitamin A and beta-carotene, the plant form of vitamin A that the body converts to vitamin A, appear to have cancer preventive properties. Those who have diets low in vitamin A and beta-carotene seem to have an increased risk of developing cancer. Both smokers and chewers of tobacco have low levels of vitamin A and increased precancerous cells in the tissues of mouth, throat and lungs. According to the Academy of nutrition and Dietics , carotenoids – rich foods may help prevent prostate cancer.
Vitamin C – Vitamin C has the ability to render harmful free radicals harmless. Vitamin C seems to block the conversion of nitrites in processed foods to nitrosamines, which are thought to be carcinogenic to the stomach, colon and bladder. Vitamin C helps in the formation of collagen and it also takes part in the formation of interferon, a naturally occurring antiviral agent. It regenerates damaged vitamin E to an active form of vitamin E.
Vitamin E – Vitamin E has been promoted as a cancer preventive vitamin because of its apparent ability to stabilize cell membranes and reduce free radicals. Its derivative vitamin E succinate exhibits potent anticancer activity. Vitamin E reduces inflammation and stimulates immune function.
Alpha –lipoic acid – it is a more potent antioxidant than vitamin C or E. It is soluble in both water and lipid; therefore it protects cell membranes and water soluble compounds. It regenerates tissue levels of vitamins C and E and markedly elevates glutathione levels.

Antioxidant mineral

Selenium is the only mineral that functions as an antioxidant.Selenium is a component of the enzyme glutathione peroxidase and is involved in the removal of harmful peroxides. It converts  hydrogen peroxide in the body into water.The sites of action include the blood vessels (endothelium), kidney, liver and erythrocytes.   According to the Academy of Nutrition and Dietics, selenium may reduce cancer risk and promote heart health. The richest sources of selenium include Brazil nuts, meat (particularly liver and kidney), mushrooms, seafood and other protein foods. The RNI for selenium is 75 μg/day for men and 60µg/day for women.

Antioxidant endogenous enzymes

The endogenous antioxidant enzymes include catalase, glutathione peroxidase, and superoxide dismutase. The minerals that are critical components of antioxidant enzymes include copper (as superoxide dismutase), zinc (as superoxide dismutase) and iron (as catalase).

Antioxidant amino acids

There are three amino acids which have antioxidant activity include cysteine, glutathione and methionine. Vegetable sources of proteins such as  nuts, beans and grains are not only provide amino acids but additional nutrients such as fibre, vitamin A and C.

Antioxidant phytochemicals

Antioxidant phytochemicals generally possess one or more hydroxylated aromatic or phenolics rings which contribute to their antioxidant activity e.g., phenolic phytochemicals. More than 800 phenolic substances have been detected in plants.   Protocatechuic, Caffeic, coumaric and chlorogenic acids are phenolic acids found in abundance in fruits and vegetables. Ferulic acid is a phenolic acid commonly found in grains especially in grain bran.Polyphenols are a group of flavonoids, which are divided into anthocyanins, Isoflavones, flavones, flavonols, flavanols and flavanones. Anthocyanins are present in high levels in berries (e.g.,blue berries, black berries, straw berries) and Isoflavones are abundant in beans. The flavonol quercetin is largely present in apples, while catechin, a flavanols, is found in teas and coffees. Grapefruits are rich in flavanones such as naringenin. Tannins are a group of polymerized polyphenolic antioxidants present in berries and red wines. Some antioxidant phytochemicals in grain germ and bran such as tocols and oryzanols are lipid soluble.

Antioxidant mechanism of flavonoids

  1. Direct radical scavenging – Flavonoids may act at any stage of free radical formation. They may trap hydroxyl free radicals.
  2. Down –regulation of radical generation – Flavonoids react with peroxy radicals to slow their propagation and delay the onset of lipid peroxidation.
  3. Elimination of radical precursors – Flavonoids proactively work to eliminate the precursors to free radicals such as hydrogen peroxide thus eliminating them before the initiation of a problem.
  4. Metal chelation – Flavonoids prevent radical formation by chelation of transition metals such as iron, preventing iron-induced lipid peroxidation.
  5. Inhibition of xanthine oxidase – Flavonoids inhibit pro-peroxidant enzyme xanthine oxidase which prevent the formation of superoxide radicals.
  6. Elevation of endogenous antioxidants – Flavonoids elevate body concentration of endogenous antioxidant such as SOD (superoxide dismutase) which themselves eliminate free radicals or their precursors. 

Food sources of antioxidant phytochemicals

Fruits and vegetables are rich in antioxidant nutrients. They are recognized  as important sources of vitamins and mineral micro-nutrients.The green leafy vegetables like spinach, kale and collard beans are loaded with antioxidants such as vitamins C,E,A and selenium. Nuts like almonds, cashews and walnuts are rich in fibre, phytonutrients and antioxidants vitamin E and selenium. Olive oil is very high in phenolic compounds which act as powerful antioxidants. Red wine contains polyphenols that reduce cholesterol, prevent blood colts and lower blood pressure. Turmeric has antioxidant, anti-inflammatory and cholesterol- lowering properties.

Health advice

For optimum health, people should consume on a daily basis at least five portions (80g/portion) of fruits and vegetables (World Cancer Research Fund 1997; Department of Health 1998) or a pound of vegetables a day (World Health Organization).

Some anti-cancer foods

Berries, Beans, Onions, garlic, Cauliflower, Broccoli, Carrots, mushrooms, Grasses like wheat grass, barley grass and fruits like Durian, cranberries.

Benefits of antioxidants

Antioxidants protect our genetic material (DNA) from the attacks of free radicals.  Some antioxidants stop cancer growth or induce cancer cell death (apoptosis). Antioxidants can regulate your body’s gene expression and increase your natural immunity. Certain antioxidants prevent metal radical chelation and toxification (e.g., mercury, arsenic). Antioxidants can repair damaged biomolecules like DNA.


Polyphenols scavenge carcinogens and mutagens. Carotenoids and ascorbic acids (vitamin C) quench free radicals. Sulphur – containing phytochemicals stimulate DNA repair.  Antioxidants do not have a long half-life in the body and should be maintained and replaced daily. Antioxidants work synergistically in giving protection against free radical damage, so it is better to take smaller doses of several different antioxidants than a large amount of only one.  Antioxidant nutrients work best when they are used consistently and preventively. Antioxidants are naturally occurring in fresh fruits, vegetables and certain spices.

Friday, August 8, 2014

The Glycemic Index ranking of dietary carbohydrates

High carbohydrate foods are the basis of diets around the world. Both the quantity and quality of carbohydrate intake are important in optimal nutrition. In Asia, where rice is a staple food, carbohydrates provide as much as 80% of the fuel in the diet. Carbohydrate makes up more than 50% of the energy in a typical American’s diet. Carbohydrate provides energy for the brain, central nervous system and muscle cells. The sugar glucose is the most important carbohydrate. It is as glucose that dietary carbohydrate is absorbed into blood stream. Normal blood glucose levels are about 80 to 120 mg per 100 ml of blood. This level is regulated primarily by the hormones Insulin and glucagon.  Controlling carbohydrate intake plays a central role in maintaining normal glucose level (normoglycemia). Eating too much carbohydrate at one time can raise blood glucose too high stressing the insulin – producing cells. Eating too little carbohydrate can lead to abnormally low blood sugar (hypoglycemia). The diets high in carbohydrates have been blamed for everything from obesity to diabetes. The reason for this is related to the types and sources of dietary carbohydrates.

The glycemic response

A rise in blood glucose levels can be detected shortly after eating carbohydrate – rich foods. The impact of different foods on the magnitude and duration of the rise in blood glucose after a meal is called glycemic response. A rating system known as the glycemic index (GI) is developed to classify foods according to their relative glycemic response.

The glycemic index (GI)

The glycemic index (also glycaemic index, GI) is a measure of the extent of the change in blood glucose content (glycemic response) following consumption of digestible carbohydrate, relative to a standard such as glucose. The glycemic index was developed by David Jenkins, Thomas Wolever and colleagues at the University of Toronto in 1981. GI ranks the quality of individual carbohydrate – rich foods on a scale of 1-100 by measuring how glucose levels rise in blood after someone eats an amount of that food containing 50grams of carbohydrate.

The GI measurement

The glycemic index is a numerical index that ranks carbohydrates based on their rate of glycemic response. In the first step about 50 grams of available carbohydrates have been consumed and the blood sugar levels are measured over a period of 2 hours. The changes in blood glucose over time are plotted as a curve (glucose response curve). In the second step about 50 grams of two control foods, either white bread or pure glucose have been consumed. Once again blood sugar levels are measured over a period of two hours. Another curve is plotted and the glucose AUCs or “area under the curves” are compared.  The glycemic index is calculated as the area under the glucose curve after the test food is eaten, divided by the corresponding area after the control food is eaten. The value is multiplied by 100 to represent a percentage of the control food. For example, if a person consumes a starchy vegetable like green peas and the glucose AUC is 48%. In this case the GI for green peas would be calculated at 48% of 100 or simply 48. Glycemic index uses a scale of 1 to 100 with high values given to foods that cause the most rapid rise in blood sugar. The glycaemic index is influenced by the amount of carbohydrate, nature of the sugar components, and nature of starch, cooking / food processing and other food components such as fats, proteins, dietary fibres, anti-nutrients and organic acids.

Definition of Glycemic index

For a given food, glycemic index is defined as the incremental area under the glucose response curve 2 hours after consumption of 50 grams of carbohydrate from a test food relative to the same amount of available carbohydrate from a control food (either white bread or pure glucose). It reflects the rate at which the carbohydrate in the food is digested and absorbed into the blood stream.

The Glycemic index ranking system

The glycemic index is a ratio of the blood glucose response to a given food compared to a standard (pure glucose or white bread).Glycemic index uses pure glucose as its control food and rates all other carbohydrates in relation to it. It measures the rate and degree of blood sugar elevation following the consumption of a single food carbohydrate. It provides a numerical, evidence -based index of postprandial (post-meal) glycemic response. The glycemic index’s ranking system is only for carbohydrates and not for fats or proteins.
Carbohydrates are broadly categorized by the glycemic index as high (70 or greater), medium(56 to 69)  and low glycemic (0 to 55) rating system. High glycemic carbohydrates enter the blood stream quickly and readily available for the body. Low glycemic carbohydrates enter the blood stream slowly and help maintain stable blood sugar levels in an extended period of time. Lower glycemic eating  improves overall health, maintain lean body mass and reduces the risk of cardiovascular disease, type 2 diabetes, metabolic syndrome, stroke, depression, chronic kidney disease, formation of gall stones and cancers of the breast, colon, prostate and pancreas.  The glycemic index helps as a useful guide for persons with diabetes to help keep their blood sugar levels in the healthy range. The GI index is also used for weight loss and weight management.

GI classification of food carbohydrates

High GI foods such as white breads, white rice, cornflakes, baked potatoes, chips, rice crackers, muffins doughnuts and popcorn score between 70 and 100. Medium GI foods scoring between 55 and 70 include whole-grain cereals, brown rice, quick oats, some cakes and cookies, table sugar and energy bars.  Low GI foods scoring between 0 and 55 include all vegetables, most fruits, oatmeal, barley, nuts and seeds and most whole-grain products. Eating food with a glycemic index of 75 or above causes irritability, mood swings and excess weight gain. Eating foods with a glycemic index below 60 tends to conserve insulin, energy and moods, balances hormones and adds to our anabolic capacity.  We should select our daily foods with a glycemic index of 60 and below.

The Glycemic load, GL

Walter Willett and colleagues at the Harvard School of Public Health created the concept of glycemic load (GL). Glycemic load combines both quality and quantity of a carbohydrate in one number. It is an excellent way to predict blood glucose values of different types and amounts of food.
Glycemic load = (Glycemic index value X no. of grams of carbohydrates per serving)/100.
The glycemic load of a food is calculated by multiplying the glycemic index by the amount of carbohydrate in grams provided by a food and dividing the total by 100. Dietary glycemic load is the sum of the glycemic loads for all foods consumed in the diet. The average range in the glycemic load is lower than the glycemic index.
High Glycemic load = 20 or more; Medium Glycemic Load = 11 – 19; Low Glycemic load = 10 or less.
A glycemic load of 0-10 is considered low (slow, steady conversion to blood sugar), whereas a high glycemic load is 20 and more (sudden spike in blood glucose, tough on health and body homeostasis).

How to follow glycemic index diet

The glycemic index of foods is of primary importance for keeping blood glucose under control. Our management of blood glucose over time appears to depend on our regular food choice and life style. Try to start the day with a great breakfast of low glycemic index foods. Eat a balanced diet with a variety of nutrient – dense foods every day. Try to choose whole – grain foods over processed foods. Try  to have at least one food from the lower glycemic index list at every meal. Do choose foods that are high in fibre to prolong your digestion time. Do choose a diet rich in fresh vegetables, fruits and beans. Don’t mix too many foods together. Don’t over-eat or take too large portions. Over eating encourages insulin resistance, which leads to weight gain. Choose foods with little added sugar or calorific sweeteners. Be cautious of the types of fats that you choose. Use in moderation of unhealthy items such as salt, caffeine or alcohol. Try your best to make small changes in your dietary habits. Remember even the small changes are still changes.

Benefits of GI awareness

Glycemic index helps anyone making the best choices of low glycemic foods.Knowing the glycemic index foods, one can virtually eliminate the risk of contracting diabetes. Eating   low glycemic foods protects our insulin response from becoming overtaxed, which in turn keeps our heart, brain and other organs healthier. Over consumption of high glycemic index foods encourages the risk of heart disease and strokes. Focusing on food from low glycemic index list will significantly improve one’s heart health. By following the glycemic index, one can choose low glycemic foods which helps to lose weight and reduce the risk of developing diabetes, will also help to lower one’s level of blood cholesterol, which in turn will eliminate the risk of several chronic diseases. The low glycemic index eating is life – style friendly and keeps our sugar and insulin levels on a healthy and constant plateau.