Vitamins and minerals (I)

Micronutrients are essential substances for the body, but are required only in very small amounts. They include vitamins and minerals, both of which essentially have a regulatory function, as they help in the metabolization of other nutrients (e.g., they are necessary for glucose to be burned and produce energy). 

At this point we will refer to vitamins, leaving minerals for a later article.

The vitamins are classified into fat-soluble (vitamins A, D, E, K) and water-soluble, which are the rest: vitamins B1 or thiamine, B2 or riboflavin, B3 or niacin, B5 or pantothenic acid, B6 or pyridoxine, B12 or cyanocobalamin, folic acid and vitamin C.

Vitamin C is related to cellular oxidation-reduction processes, in which it plays an antioxidant role. 

Vitamin A has both an antioxidant and an epithelial and mucosal maintenance function. 

B vitamins act mainly as regulators of intermediary carbohydrate and protein metabolism. 

Vitamin B12 is related to the synthesis of red blood cells and brain function. It is found in foods of animal origin, and therefore deficiency may occur in strict vegetarians. There is also a certain risk of vitamin B12 deficiency in the elderly and in people who continuously (for years) take certain drugs such as metformin (for diabetes) and omeprazole (for the stomach); the clinical picture is one of megaloblastic anemia (so called because the red blood cells are larger than normal) and impaired brain function (dementia), and even paralysis of the limbs.

Vitamin D is formed in the skin by the action of the sun's ultraviolet rays. It is involved in phospho-calcium metabolism: it promotes calcium absorption and helps form and maintain strong bones. 

It also has other functions. For example, it is important for muscles to function properly and thus helps reduce falls in the elderly; and some studies suggest that it may help prevent diabetes mellitus, hypertension and many cancers. 

It is also involved in immune function, and is capable of destroying the tuberculosis bacillus. Perhaps this is the reason why tuberculosis patients, before the antibiotic era, were exposed to the sun. Nevertheless, about 35 % of young adults and up to 60 % of older adults are deficient in this vitamin. Lack of exposure to sunlight in the winter months (even though we are in a country as sunny as ours!), the use of creams with a very high protection factor and diets low in vitamin D contribute to this. 

Finally, vitamin E is an important antioxidant, and vitamin K is involved in coagulation processes.

The food sources of the main vitamins are shown below:

• Vitamin A: found in butter, egg yolk, whole milk and fruits;
• Vitamin D: ingested with fish oils, salmon, herring, eggs, fortified milk and cod liver oil; it can also be formed in the skin by the action of ultraviolet rays;
• Vitamin E: provided by vegetable oils, nuts and vegetables;
• Vitamin K: contained in vegetables, cereals, meat and milk;
• Vitamin C: provided by fruits (mainly citrus fruits) and vegetables;
• B group vitamins: found in legumes, eggs, cereals, brewer's yeast;
• Folic acid: vegetables, meat, eggs;
• Vitamin B12: meat, eggs, fish, milk.