Vitamins are essential substances needed by the body in small amounts for normal growth, function and maintenance of healthy tissues. Since the body is not able to synthesize vitamins, they must be supplied from foods-plant or animal. Vitamins don’t supply the body directly with energy. Instead they participate in metabolic processes (chemical reactions) that generate energy for the body. Out of total 13 vitamins, some are fat soluble, which are not readily excreted from the body, while others dissolve in water which are easily lost from the body.

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Following are the fat-soluble vitamins

1. Vitamin A: The most common dietary form of vitamin A is retinol.  It plays key role

in maintaining vision- light sensing cells and formation of tear fluid.  It supports cell growth and development, maintains healthy skin, hair, nails, bones and teeth. It supports the immune system and protects from infections. Vitamin A also maintains fertility and is vital for fetal development. Vitamin A is found preformed in certain animal foods and also is derived from plant foods that contain beta-carotene (provitamin A).

Once consumed, beta-carotene is converted to vitamin A by the liver. Beta-carotene may prevent heart-disease, cataracts, macular degeneration and possibly lung cancer. Vegans may be at risk as vitamin A is only found in animal-sourced foods. Studies suggest that vitamin A supplements suppress the measles virus and protect against measles- associated pneumonia and reduce the risk of death by 50-80%. 

The best sources of vitamin A are liver, fish liver oil, milk, cheese, butter and egg yolks. Beta-carotene is found in orange and dark produce such as carrots, sweet potato, winter squash, broccoli, kale, spinach, apricots, cantaloupe, peaches, nectarines, mango and papaya.

2. Vitamin D: Commonly known as sunshine vitamin, vitamin D is produced when skin is exposed to sunlight. It is also known as calciferol. Vitamin D is a collective term and comes in two main dietary forms- vitamin D2 (ergocalciferol) and vitamin D3 (chloecalciferol). Once absorbed into blood stream, liver and kidney change calciferol into calcitriol which is the biologically active form of vitamin D. Vitamin D3 is more actively converted into calcitriol than vitamin D2.

Vitamin D is regulates circulating body calcium and phosphorus levels which are the most important minerals for bone growth and maintenance. It promotes the absorption of these minerals from diet. It helps to prevent osteoporosis. Vitamin D also regulates and strengthens immune system function.

Most of our vitamin D comes from sunlight through skin- exposure. When ultra-violet hits the skin, it forms vitamin D3. This compound then makes its way to liver and kidneys where it transform into active vitamin D. The dietary forms are found mushrooms, eggs, chicken and pork livers, fish oil, fatty fish shrimp, butter, margarine, milk, fortified rice and soy beverages.

3. Vitamin E (Alpha Tocopherol): Alpha-tocopherol is the most common form of vitamin E and makes up around 90% of the vitamin E. As a strong antioxidant, it protects cell membranes against premature aging and damage by free radicals. This antioxidant property is enhanced by other nutrients such as vitamin C, vitamin B3 (niacin) and selenium. Vitamin E also enhances the body’s immune system. It is also necessary for iron metabolism and protects polyunsaturated fat and vitamin A from oxidation. Research suggests that vitamin E may prevent heart-disease and prostate cancer and slow the progression of Alzheimer’s disease. In high amount, vitamin E also acts as a blood thinner, reducing the blood’s ability to clot.

The good sources of vitamin E are vegetable oils, almonds, peanuts, soybeans, whole grains, wheat germ, wheat germ oil, avocado and green leafy vegetables.

4. Vitamin K: This is essential for blood clotting. It also plays an important role in the formation of new bone and may help prevent osteoporosis. Studies show that high dietary intake of vitamin K are associated with lower risk of hip fractures. Vitamin K also helps to prevent the calcification of blood vessels, reducing the risk of heart disease. Vitamin is divide into two main groups-vitamin K1 (phylloquinone) and vitamin K2 (menaquinone). 

The best sources of vitamin K are green peas, broccoli, spinach, leafy green vegetables, Brussels sprouts, romaine lettuce, cabbage, fermented soy foods, butter, egg yolks and liver.  Vitamin K1 found in plant foods and vitamin K2 found is animal derived foods and soy foods.