Diabetes Nutrition - Vitamins
Vitamins do not supply energy but are essential for many vital functions of the body. Their requirement is extremely small, in terms of mg but their deficiency produces various diseases. Vitamins are traditionally classified into two groups, that is, fat soluble and water soluble. Fat soluble vitamins are vitamin A, D, E and K. Water soluble vitamins include those of the B Complex group and vitamin C.
FAT SOLUBLE VITAMINS
Retinol (Vitamin A)
This includes preformed vitamin A, retinoids and precursors of vitamin A, important of which is carotene. Vitamin A is essential for the healthy outer lining of skin and mucous membranes, growth, night vision and resistance against infection. Preformed vitamin A is present in milk, butter, ghee, curds, cheese, egg yolk, in some fatty fish and liver. Carotenes are abundant in the dark green leaves of vegetables like spinach, amaranth, coriander, drumstick leaves, curry leaves, mint, carrot, sweet potato, yellow fruits like tomatoes, yellow pumpkin, papaya, mangoes and oil of some palms. The daily requirement of retinol for adults, boys and girls is 600 micrograms and that of beta carotene is 2400 micrograms per day (1000 micrograms = 1 mg). Lack of vitamin A results in dry cornea and conjunctiva, opacity of the cornea and ultimately loss of vision. Vitamin A deficiency can produce night blindness, dry toad-like skin and repeated infections.
Vitamin D
This is essential for the absorption of calcium from the small intestine and for the development and mineralization of bones. It is formed in the skin by ultraviolet rays present in sunlight. Egg yolk, fatty fish, cod liver oil, milk and milk products and fortified vanaspati and margarine are good sources of vitamin D. Deficiency of vitamin D produces rickets in children and osteomalacia (softening of bones with deformity of pelvis and bending of spine) in adults.
Vitamin E (Tocopherol)
Vitamin E is a very effective antioxidant. By donating hydrogen to the free oxygen radicals, vitamin E protects cell membranes from the injurious effects of free radicals. Fats, oils like soya and palm oils, vegetables, poultry, fortified breakfast cereals and whole grain bread are good sources of vitamin E. Vegetable oils like wheatgerm, soya and palm, margarine, nuts and seeds are good sources of vitamin E. It is present in smaller amount in whole grain cereals, eggs, butter and some vegetables and fruits. Although vitamin E deficiency produces many diseases in animals, human deficiency disease is rare.
Vitamin K
This is essential for the clotting of blood. Green leafy vegetables, margarine, milk, tea and liver are good sources of vitamin K. Bacteria in the intestines produce vitamin K. Dietary requirement for adults is 1 microgram/kg body weight. Some babies who are solely breast-fed may have a tendency to bleed since human milk may have inadequate
WATER-SOLUBLE VITAMINS
Vitamin B1 (Thiamin)
It is essential for many reactions in carbohydrate metabolism. Its important sources are unrefined cereal grains, legumes, nuts, organ meats, pork flesh and yeast. Its daily requirement is 0.5 mg/1000 kcals. Lack of thiamin gives rise to beriberi which could be wet or dry. Enlargement and poor functioning of the heart and swelling of the body occur in wet beriberi. Dry beriberi which is often superimposed on wet beriberi, is characterised by marked muscle weakness and involvement of the nerves. Thiamin deficiency can also cause memory disturbances and paralysis of eye muscles.
Vitamin B2 (Riboflavin)
This is necessary for several oxidation processes inside the cells and plays a role in energy and protein metabolism. Milk and milk products, eggs, liver, kidney, green leafy vegetables are good sources of riboflavin. Wheat, millet and pulses are fair sources of this vitamin. Rice is poor in riboflavin, Its daily requirement is 0.6 mg/1000 kcals. Lack of riboflavin produces rash around the nose, cracking at the angles of mouth, severe burning of tongue and irritation of the scrotal skin.
Niacin
It plays a role in the metabolism of carbohydrates, proteins and fats and in tissue respiration. The body can convert tryptophan, an amino acid present in dietary proteins, to niacin. Meat, whole cereals, pulses and nuts for example, groundnuts are good sources of niacin. The daily requirement of this vitamin varies from 8 to 26 mg. Deficiency of niacin produces pellagra, a disease characterised by soreness of tongue, pigmentation of skin, diarrhoea and dementia.
Vitamin B6
This is necessary for several reactions related to the metabolism of proteins and fats. Poultry, fish, pork, eggs, liver, kidney, milk, banana, potatoes, vegetables, peanuts, walnuts and whole grain cereals are good sources of vitamin B6 The daily requirement is 0.6-2.5 mg. Its deficiency gives rise to soreness of tongue, cracking at the angles of lips and affection of nerves of the limbs.
Vitamin B12
This vitamin takes pan: in important biochemical reactions, necessary for deoxyribonucleic acid synthesis and maturation of cells. It is necessary for the formation of blood, normal functioning of the nervous system and metabolism of folic acid. It is synthesized by bacteria and is found in food of animal origin only. The daily requirement is about 1 microgram, and more in lactating women. Deficiency of vitamin B|2 gives rise to soreness of tongue, diarrhoea, anaemia, tingling and numbness of legs, unsteadiness and at times mental changes.
Folate
It is necessary for the multiplication and maturation of red cells. Extra folate reduces the plasma homocysteine level, a risk factor in diseases of heart and blood vessels. Green leafy vegetables, potatoes, pulses, nuts, grains and liver are good sources of folate. The daily requirement of folate is 50400 micrograms. Its requirement is increased to 300 micrograms during pregnancy and first six months of lactation. Extra folate in the beginning of pregnancy prevents neural tube defects and premature birth. Folate deficiency, common in the poor alcoholics produces anaemia.
Biotin
This is concerned with the metabolism of fatty acids, glucose and amino acids. Liver, egg yolk, soya flour, cereals and yeast are good sources of biotin. Human biotin deficiency is rare.
Pantothenic acid
It is essential for carbohydrate and fat metabolism. It is widely distributed in nature especially in animal products, whole grains and legumes. Recommended daily allowance for an adult is 3-7 mg. Deficiency of this vitamin gives rise to "burning feet".
Vitamin C
This is essential for synthesis of collagen and bone and teeth calcification. It helps absorption of iron in food. It is a powerful reducing agent and an antioxidant. Fresh raw vegetables, fruits and sprouted pulses and beans are good sources of vitamin C. Cheap fruits like amla and guava are rich sources of vitamin C. Besides, amla contains substances which protect vitamin C from destruction on heating and drying. The daily requirement of vitamin C in an adult is 60 mg. During pregnancy and lactation the intake should be increased by 10 mg and 40 mg respectively. Deficiency of vitamin C gives rise to scurvy. The claim that large doses of vitamin C reduces the likelihood of catching common cold has not been proved.
Antioxidants
Free radicals are produced during normal aerobic (requiring oxygen) metabolism. Free radicals are also present in cigarette smoke. Vitamin C and vitamin E, beta carotene, and selenium, a trace element are antioxidants which mop up the free radicals. Vegetables and fruits contain other antioxidants. Inclusion of vegetables and fruits in the diet leads to a reduced incidence of atherosclerosis and cancer.