Vitamins like minerals are also known as micronutrients as they are only required by the body in small amounts. Vitamins are not direct fuels for energy metabolism but enable many important biochemical processes to take place, whether for energy or sustaining healthy and active tissue. For example, the B group vitamins are needed to help release energy from the food we eat and vitamin C helps in bone formation. Eating a wide range of foods in a well-balanced diet, (especially fresh fruit and vegetables) ensures that a sufficient supply of vitamins is provided. Indeed, vitamin supplementation is very rarely required in the Western World and can be avoided through eating a diet containing many types of fresh and good quality produce.
Vitamins are classified as either fat-soluble (stored in body's fatty tissues) or water-soluble (dispersed in body fluids). A checklist summary of the Recommended Daily Intake (RDA), dietary sources, functions in the body, problems due to deficiency and what can happen if an excess amount is consumed are listed below.
| Fat-soluble vitamins | ||||||
|
Vitamin
|
RDA(mg)
M
|
RDA(mg)
W
|
Dietary Sources | Body Functions | Deficiency | Excess |
| Vitamin A | 1.0 | 0.8 |
Liver,
oily fish, |
Essential for vision in dim light, skin and growth & the maintenance of mucous membranes | Can lead to blindness | Headache, vomiting, anorexia, swelling of long bones |
| Vitamin D | 0.01 (0.005mg for adults 25+) |
0.01 | Cod-liver oil, oily fish, eggs, margarine, dairy products, fortified cereals | Promotes absorption of calcium & phosphate for bones & teeth | Rickets - bone deformities in children, Osteomalacia in adults | Vomiting, diarrhoea, weight loss, kidney damage |
| Vitamin E | 10.0 | 8.0 | Vegetable oils, eggs, leafy green vegetables, whole grain cereals | An antioxidant, protects cell membranes | Possibility of anaemia | Relatively non-toxic |
| Vitamin K | 0.08 | 0.06 | Whole grain cereals, green leafy vegetables, small amount in fruit, cereals, meat | Essential for blood clotting by helping form prothrombin | Severe bleeding problems, internal haemorrhages | Relatively non-toxic, may lead to jaundice, thrombosis & haemorrhage |
| Water-soluble vitamins | ||||||
|
Vitamin
|
RDA
(mg) W
|
RDA
(mg) M
|
Dietary Sources | Body Functions | Deficiency | Excess |
| Vitamin B1 | 1.5 | 1.1 | Cereals, nuts, pulses, green vegetables, pork, fortified breakfast cereal | Involved in energy production from carbohydrate, important for central nervous system | Beriberi, mental depression, apathy | Unlikely |
| Vitamin B2 | 1.7 | 1.3 | Widely distributed in foods | Involved in energy metabolism | Sore lips, mouth, eye lesions, | Unlikely |
| Niacin | 19 | 15 | Liver, beef, pork, mutton, fish, fortified breakfast cereals, grains, legumes | Involved in energy release from carbohydrates & fats | Pellagra (skin & gastrointestinal lesions, nervous & mental disorders | Headaches, nausea, burning & itching of skin |
| Vitamin B6 | 2.0 | 1.6 | Protein foods, liver, lean meat, fish, legumes, green leafy vegetables | Involved in amino acid & glycogen metabolism | Irritability, convulsions, kidney stones, dermatitis | Loss of nervous sensation |
| Pantothenic acid | 4-7 | 4-7 | Liver, lean meat, milk, eggs, legumes, most vegetables | Involved in energy metabolism | Fatigue, sleep disturbances, impaired coordination & nausea | Unlikely |
| Folic acid | 0.2 | 0.2 | Legumes, green vegetables, whole wheat products | Formation of blood cells and nerve fibres | Anaemia, fatigue, diarrhoea | Unlikely |
| Vitamin B12 | 0.002 | 0.002 | Offal, meat, eggs, milk, fortified breakfast cereals (not found in plant foods) | Formation of blood cells and nerve fibres | Pernicious anaemia, nerve damage | Unlikely |
| Biotin | 0.03 | 0.1 | Meats, milk, eggs, grains & vegetables | Fat, carbohydrate & protein metabolism | Fatigue, depression, nausea, dermatitis, muscular pains | Unlikely |
| Vitamin C | 60 | 60 | Fresh fruit especially citrus, green vegetables, potatoes, broccoli, peppers, salad greens | Wound healing, iron absorption & formation of collagen for connective tissues and bones | Scurvy, weakness, slow wound healing, bleeding gums | Diarrhoea, kidney stones |
These are recommended values (revised 1994) from the Food & Nutrition Board, National Academy of Sciences-National Research Council, Washington D.C for Men (M) and Women (W).
From an exercise point of view, a dietary deficiency in at least some of the above vitamins will impair athletic performance although scientific evidence demonstrates that supplementation does not improve performance in individuals eating a well-balanced diet, whatever their age and physical activity level. Supplementation only seems necessary in athletes if there is a dietary deficiency. Exercise can increase the demand for vitamins but again, well-balanced meals will provide an adequate quantity of vitamins. Athletes eating low-energy foods or who do not eat properly (lack of time or motivation), may find benefit from vitamin supplements but should always consult their doctor beforehand for correct medical advice. For more information on vitamin and general nutritional supplements click here.
Click here to visit the nutritional advice section of Soccer Performance.
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