The word ‘vitamin’ comes from the latin word vita meaning life. And this is exactly what they are: vitamins are micronutrients which are absolutely essential for growth, development and well being. They boost immunity and fight infections. They play a vital role in many functions of the body and vitamin deficiency leads to several diseases.
What are the different kinds of vitamins, their food sources and daily intake levels?
What is the role of vitamin D?
Why vitamins should not be consumed in excess?
We produce a few vitamins: vitamin K is produced by the bacteria present in our intestines, vitamin D is synthesized in the skin when exposed to sunlight and vitamin B3 (Niacin) is manufactured from amino acid tryptophan. We have to acquire all the other vitamins from food.
Vitamins are naturally present in the food and beverages that we consume and our daily requirement of vitamins is easily met by eating a well balanced healthy diet. Most of us do not need to take vitamin supplements.
The vitamins contained in food are natural vitamins: they are strong and effective. On the other hand, the vitamins in a vitamin supplement (e.g. tablet or syrup) are mostly synthetic, prepared from chemicals, and their effectiveness (bio-availability) is uncertain.
|VITAMINS||FOOD SOURCES||RECOMMENDED DAILY INTAKE|
|Vitamin A||carrots, pumpkins, oranges, milk, soya milk, fish, liver||3000 IU|
|Vitamin C||fruits, vegetables, liver||75 mg|
|Vitamin D||fish, eggs, liver, mushrooms||600 IU|
|Vitamin E||fruits, vegetables, nuts, seeds, wheat germ||15 mg|
|Vitamin K||green leafy vegetables, eggs, liver||60 micrograms|
|Vitamin B1 (Thiamine)||potatoes, brown rice, oat, liver, eggs, pork||1 mg|
|Vitamin B2 (Riboflavin)||dairy products, bananas, green beans||1.1 mg|
|Vitamin B3 (Niacin)||vegetables, nuts, meat, fish, eggs||15 mg|
|Vitamin B5 (Pantothenic acid)||meat, broccoli, mushroom||5 mg|
|Vitamin B6 (Pyridoxine)||vegetables, pistachio, banana, meat||1.5 mg|
|Vitamin B7 (Biotin)||eggs, peanuts, green leafy vegetables, liver||30 micrograms|
|Vitamin B9 (Folic acid)||green leafy vegetables, cereal, liver||400 micrograms|
|Vitamin B12||fish, meat, soya milk||2.5 micrograms|
|Choline||egg, beef, soya, cauliflower||500 mg|
Vitamins B and C are water soluble and are eliminated from the body in the urine. Toxicity due to excessive intake vitamin Bs is rare because the excess gets excreted out through the urine, giving urine a deep yellow color. Vitamin Bs help convert carbs into glucose which is used to produce energy. Vitamin B6 plays a vital role in helping absorb vitamin B12 from the intestine.
Vitamins A, D, E, K are fat soluble. The fat in the diet helps absorb them from the intestine, and they are then transported to the liver and other sites in the body. When the fat soluble vitamins are consumed in excess, they accumulate in the liver and other sites in the body. Excessive accumulation is toxic and produces harmful effects including heart disease and cancer.
Many people erroneously believe that taking vitamin supplements is healthful, that they improve the overall energy level of the body, and that excess vitamins are beneficial and do no harm. There is strong scientific evidence that people who consume certain vitamins (such as vitamins A and E) in excess.
There is a reason why this happens. Vitamins are powerful anti-oxidants and they neutralize the harmful free-radicals in our bodies. When free-radicals are present in rich abundance, they accelerate the process of aging and cause a number of diseases. However, bad as they are, we still need some free-radicals because they kill cancer cells and other harmful cells like bacteria. When certain vitamins are taken in excess, all the free-radicals are neutralized, and none are left to kill cancer and other harmful cells. This is the reason why excessive vitamin supplements lead to cancer, heart disease, and early death.
Eating a varied and nutritious diet supplies all the vitamins in their natural and health-promoting form – such as a diet would include fruits, vegetables, whole grains, seeds and nuts, legumes (dal), milk and milk products, meat, fish and eggs. There is hardly ever any need to take vitamin supplements, but there are certain exceptions. Folic acid deficiency if present during pregnancy can lead to birth-defect in the child. Therefore, it is prudent for all women to take a small dose of vitamin folic acid during the course of pregnancy. Strict vegetarians are likely to develop vitamin B12 deficiency and require a vitamin B12 supplement to combat the deficiency. Another deficiency frequently seen is that of vitamin D.
Exposing our body to the sun for just 15 minutes each day will produce all the vitamin D that is required. Unfortunately, our current life-style, with virtually no exposure to sun, especially in the cities, leads to vitamin D deficiency. Regular exposure to sun is highly desirable, but if that is not possible, a small dose of vitamin D needs to taken daily.
The FDA issues permits for the manufacture and sale of medicines in USA. Based on concrete scientific evidence, the FDA was deeply concerned that people were consuming large quantities of multivitamin supplements which were actually increasing their risk of cancer and heart disease and shortening their lives. In December 1972, the FDA announced a plan to control the sale of vitamin supplements. The pharmaceutical industry naturally saw this as a threat to their windfall income from the sale of vitamins and got a bill passed in the US senate preventing the FDA from regulating the manufacture and sale of multivitamins. In 1976 it became law and the production and sale of multivitamins has continued unhindered since! So much for the state caring for the health and well-being of its citizens! Peter Barton Hutt, chief counsel to the FDA acknowledged this crushing defeat and wrote “it was the most humiliating defeat in the FDA’s history”.