Vitamins are organic micronutrients required by the body to perform a range of functions. They need to be obtained from our diet because our bodies are not able to produce them. Vitamins are generally classified as either fat soluble or water soluble. Fat-soluble vitamins are vitamin A, vitamin D, vitamin E, and vitamin K. These vitamins have the unique characteristic of dissolving in organic solvents such as fat, and tend to be stored in the body in large quantities.

On the other hand, water-soluble vitamins are vitamin C and the B-complex vitamins, they can only  be absorbed by the body in a solution of water, hence they cannot be stored. All unused or unabsorbed water-soluble vitamins are excreted from the body through urine. 

All vitamins are required in certain amounts by the body. Nutrient reference values, also known as dietary reference intakes (DRI) are developed and recommended by the National Academy of Medicine (NAM) in the United States. These DRIs form the scientific and medical basis for good nutrition and food guidelines in both the U.S. and Canada. DRIs may differ based on age, gender, health status, and stage of life. For most people, DRI for all vitamins can be obtained by eating a healthy, balanced diet. However, some others may require higher amounts of some vitamins due to their lifestyle or health conditions. These extra amounts of vitamins can be sourced from vitamin supplements in consultation with a health professional. 

Benefits and sources of Vitamins

Fat-soluble vitamins

Vitamin A: Vitamin A is essential for proper visual functions and for maintaining normal mucous membranes. It is naturally occurring in animal food including liver, milk, and eggs. Also, some processed foods such as margarines, and certain breakfast cereals are fortified with vitamin A.
Vitamin D: When converted to the active form in the liver, 1,25-dihydroxyvitamin D promotes the absorption of calcium and phosphorus in the intestines. Additionally, it positively influences bone mineralization and maintains blood concentrations of calcium and phosphate. Two forms of vitamin D are important in body functions, Vitamin D₂ (ergocalciferol) which is made by the ultraviolet (UV) irradiation of ergosterol, and vitamin D₃ (cholecalciferol) which is formed when sunlight acts on the skin. 

Vitamin E: Vitamin E acts as an antioxidant that protects polyunsaturated fatty acids from rupturing in cell membranes. The highest source of vitamin E is vegetable oils, others include nuts, whole grains, and wheat germ. Animal foods are not rich sources of Vitamin E.

Vitamin K: Vitamin K is essential for blood clotting factors in the liver. Like vitamin D, there are two derived forms, Vitamin K₁, (phylloquinone) which is synthesized by plants, and vitamin K₂ (menaquinones) which is synthesized by microflora of the gut. Dietary sources of vitamin K include dark-green leafy vegetables, cereals, meats, and fruits.

Water-soluble vitamins

Vitamin C: Also known as Ascorbic acid, vitamin C protects the body cells, maintains a healthy skin, and facilitates wound healing. Lack of, or below DRI levels of vitamin C causes scurvy while excess amounts (over 1,000mg per day) may cause stomach-ache, diarrhoea, and gassiness. Vitamin C is found in a wide variety of fruits and vegetables including oranges, peppers, and broccoli.

Vitamin B:

There are eight (8) types of vitamin B and they are thiamin (vitamin B1), riboflavin (vitamin B2), niacin (vitamin B3), pantothenic acid, vitamin B6, biotin (vitamin B7), folate and folic acid, and vitamin B12.

Thiamin (vitamin B1): Thiamin helps in the breakdown and release energy from food as well as in keeping the nervous system healthy. Sources are peas, liver, nuts, and bananas.

Riboflavin (vitamin B2): Riboflavin performs the same functions as thiamine by releasing energy from food and keeping the skin, eyes, and nervous system healthy. Sources are milk, eggs, mushrooms, and yoghurt.

Niacin (vitamin B3): Niacin maintains skin health, participates in energy release from food and preserves  the nervous system. Sources include meat, fish, and wheat flour.

Pantothenic acid: Pantothenic acid has several functions, such as helping the body to release energy from food. Sources of pantothenic acid are chicken, and eggs.

Pyridoxine (Vitamin B6): Pyridoxine facilitates the use and storage of energy from protein and carbohydrates in food. Sources are pork, peanuts, chicken, oats, and soya beans.

Biotin (vitamin B7): Biotin is needed in very small amounts to help the body make fatty acids. It is found at low levels in a wide range of foods. Sources include milk and fortified cereals.

Folate and folic acid: Folate helps the body make red blood cells and reduces the risk of neural tube defects in unborn babies. Folic acid is the synthesized form of folate and lack of folate causes anaemia. Sources include broccoli, leafy green veggies, Brussel sprouts and fortified cereals.

Vitamin B12: This vitamin plays a role in making red blood cells and keeping the nervous system stable. It also releases energy from food like many B vitamins. Lack of vitamin B12 may lead to vitamin B12 deficiency anaemia. Sources are meat, fish, milk, cheese, eggs.