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Vitamins and minerals (and II)

There is a widespread perception that it is advisable to take vitamin and mineral supplements in any case. Is this true? In particular, what are the dietary functions of minerals and where are they found?

Pilar Riobó-April 11, 2017-Reading time: 3 minutes

The minerals are, like vitamins, micronutrients that participate as coenzymes in the metabolism of nutrients, have structural functions (such as calcium and phosphorus, constituents of the skeleton), participate in the transport of oxygen to the tissues (such as iron, essential for the formation of red blood cells), or intervene as constituents of muscle proteins (as in the case of iron) or thyroid hormones (iodine). Calcium is also involved in nerve signal transmission functions in the brain and muscle. Other minerals, such as sodium (a constituent of common salt), control water balance and blood pressure levels.

Potassium is the main ion found in cells. Together with sodium and chlorine, it is involved in the hydration of the organism and in neuromuscular transmission. Because of their physiological importance, they are all subject to fine regulation in the body, mainly through the action of the kidney, so there are usually no major variations in their level in the body, unless there is an underlying pathology.

In the body, 65 % of iron is found as part of hemoglobin. This protein, contained in red blood cells, is responsible for transporting oxygen from the lung to the tissues. The rest of the iron is part of myoglobin, a protein found in muscle, which gives up oxygen when needed, and is also stored in the liver or spleen. From these stores, iron is mobilized to form more hemoglobin when needed.

Iron deficiency prevents hemoglobin from being synthesized. This is what is called iron deficiency anemia. Iron deficiency is very frequent especially in adolescents and women of childbearing age, and in pregnant women, who have higher requirements. In the elderly, the most frequent reason for iron deficiency anemia is chronic losses, especially at the gastrointestinal level, even if they are small, and the cause should always be sought.

Some micronutrients (vitamins A and E, selenium, and zinc) have antioxidant capacity, thus preventing the formation of free radicals (which have been linked to aging, tumor genesis, cataract formation, atherosclerosis, and myocardial infarction). 

Calcium and phosphorus play an essential role in bone formation. Due to the Western and hyperproteic diet we eat, there are not usually deficiencies of phosphorus, although it is frequent that the calcium intake does not cover the requirements. Specifically, these are high in children and adolescents, a time when bone is being formed and the so-called "peak bone mass" is reached. From this moment on, when the bone is stronger, bone will be lost very slowly. The loss of bone mass is accelerated at the time of menopause, when the female sex hormones are absent, so that the requirements are also high around those years. It has been shown that high calcium intake at this time of life attenuates the loss; if it is accelerated, or if the peak bone mass reached in adolescence is not adequate, osteopenia appears more easily and then osteoporosis ("porous bone", which breaks easily with small traumas), with its dreaded consequences (hip fractures, vertebral fractures, radius fractures...).

So, is it necessary to take pharmacological vitamin and mineral supplements? If you eat a plentiful and varied diet and do not suffer from diseases, it is generally not necessary: vitamins are contained in food. There are specific cases, such as those mentioned above (iron deficiency anemia, sun deficiency, calcium intake during menopause, vitamin B12 in the elderly, malabsorption problems...) in which vitamin supplements may be of interest, always after consulting your doctor.  

The main minerals and their dietary sources are shown below:

  • Iron: meat, blood sausage, eggs, legumes;
  • Calcium: dairy products, fish scrapings;
  • Phosphorus: meat, fish, dairy products, eggs;
  • Magnesium: vegetables, legumes, nuts, meat, chocolate, seafood;
  • Sodium: common salt;
  • Potassium: fruits, vegetables;
  • Iodine: iodized salt, fish;
  • Selenium: seafood, kidneys, liver and meat;
  • Zinc: oysters, meat, liver, eggs, milk.
The authorPilar Riobó

Medical specialist in Endocrinology and Nutrition.

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