Vitamins: Essential Substances with Zero Calories

They are indispensable compounds for our organism, necessary for growth, structural integrity of cells, and for all metabolic processes to occur regularly.

Vitamins are essential substances devoid of energy value and act in minimal doses, belonging to the category of micronutrients.

They are divided into fat-soluble (A, D, E, K) and water-soluble (B-complex and C); most of them are sensitive to heat, therefore to cooking: it is advisable to consume them through fresh and minimally processed foods. The heat-resistant vitamins include vitamin K, some B-group vitamins (B2, B3, B8, B12).

The requirement for each of them varies according to age, sex, and particular physiological states. A balanced, healthy, and varied diet is sufficient to meet these needs (except for some cases, such as vitamin D). Any deficiencies are usually secondary or due to inadequate diets.

Therefore, the use of vitamin supplements must necessarily be limited to the period of life when it is believed that nutrition is not sufficient to meet the need. In any case, it is always preferable to seek advice or prescription from a specialist.

Fat-soluble vitamins (A, D, E, K) easily oxidize when exposed to light, heat, oxygen; they can be stored in tissues. If taken in excess, they can cause hypervitaminosis problems (headaches, dizziness, vomiting, nausea).

Vitamin A, or retinol, is found in animal-derived foods, among the richest are fish liver oil, milk, butter, cheese, eggs. Carotenoids, precursors of vitamin A, are also found in leafy vegetables, carrots, apricots, and butter. In recent decades, carotenoids (lycopene, beta-carotene, lutein) have generated great interest in the field of human nutrition, as they act as biological antioxidants, contributing to the body's defense; they also play a protective role in pathological conditions such as diabetes and cardiovascular diseases and also seem to have a protective effect against some forms of cancer.

Vitamin E (alpha-tocopherol) is well known as an effective antioxidant, protecting membranes from oxidation initiated by free radicals. Vitamin E is one of the most effective antioxidants in removing free radicals, and is therefore used in cosmetics, functional foods, and many other applications. It has a protective function against cardiovascular diseases, cataracts and other eye diseases, aging, atmospheric pollution, smoking damage, diabetic vascular complications, and skin diseases.

Sources (mg/100g of product):

Sunflower oil 44 mg

Sunflower seeds 31.2 mg

Almonds 24.6 mg

Hazelnuts 21 mg

Wheat 3.4 mg

Vitamin D regulates calcium metabolism, so deficiency leads to deficient bone mineralization (causing rickets in children, osteomalacia in adults). Dietary sources are scarce, in fact, few foods contain appreciable amounts of vitamin D: it is found in fish liver oil, in fatty fish such as salmon and herring, and in oily fish in general, in milk and butter, and in eggs. Exposure to light and sun can contribute to endogenous intake, but unfortunately in a minimal and insufficient way for the minimum daily requirement.

B-group vitamins and vitamin C are water-soluble, not stored, so there is a need for daily intake through diet. B-group vitamins are involved in various metabolic reactions related to energy production, while vitamin C is a potent antioxidant.

Thiamine (B1) is widely distributed in foods, both of plant and animal origin. It is found in raw foods, legumes and cereals, green vegetables, nuts, egg yolk, and pork. Conversely, it is not present in refined foods, such as sugar, fats, or alcohol, nor in foods heated for a long time or at high temperature. One of its fundamental functions is to directly intervene in the transmission of nerve impulses.

Riboflavin (B2), an essential part of two coenzymes, is also widespread in foods. The main sources are the bran and germ of cereals, milk, eggs, meat, fish. Vitamin B2 deficiency in humans is rare. Vitamin B6 or Pyridoxine is particularly present in yeast, but also in cereals, meat, and eggs, meat, fish, vegetables, and fruits. Vitamin B6 deficiency can cause asthenia, apathy, neurological alterations. Also included in this group are folic acid and Vitamin B12 (cobalamin).

The main dietary sources of folic acid are yeast, leafy vegetables (spinach, broccoli), and cereals. The bioavailability of dietary folates depends on the activity of an enzyme that can be limited by zinc deficiency, some inhibitors present in foods (cabbages, oranges, beans, lentils), or some drugs such as aspirin or contraceptives. Folic acid deficiency can cause anemia. Vitamin B12 is a fundamental coenzyme in our metabolism. It is exclusively present in foods of animal origin, so much so that its integration is recommended in vegan diets (devoid of any animal food, including derivatives). Deficiency can cause serious disorders such as nervous problems, anemia.

Vitamin C or ascorbic acid is an essential substance to be introduced through nutrition, as we are not able to produce it. It is widely present in fresh vegetables, fruits, especially kiwi and citrus fruits, and to a lesser extent also in some foods of animal origin. It is absent in eggs, fish, cheeses, cereals. It is involved in various metabolic processes and has numerous functions:

It protects the body from the damaging action of free radicals, through an antioxidant action

It enhances and modulates the immune response

It has a detoxifying action by favoring the degradation of exogenous substances and drugs

It has a protective role against some forms of cancer (stomach and esophagus)

Below are the reference intake levels for the Italian population for VITAMINS (source: LARN - Italian Society of Human Nutrition - SINU, 2014)