Selenium in diet

The role of selenium in the diet has been much interest in recent times. Reduced consumption of this element in Europe is worrying given that its deficiency can lead to an increased risk of chronic diseases such as cancer or cardiovascular disease. Is this true? What can be done?

A vital role in the body.

Selenium is found in a number of vital proteins in our body, selenium proteins calls, of which twenty-five have been identified so far, including: I) peroxides, which have significant anti-inflammatory properties and protect cell membranes from damage by free radicals, ii) the deiodinasas, involved in the production of active thyroid hormones, and iii) proteins involved in breeding and in DNA repair.

Sources of selenium.

Selenium is found in soil and rocks, accumulates in plants and thus enters the food chain. It is present in most foods and nuts (especially Brazil nuts) and fish, shellfish, organ meats (kidney, liver) and meat are rich in this element. Cereals, vegetables and other plant-derived foods contain selenium, but the amount varies depending on the land where grown. The European soil contains a relatively small amount of selenium in comparison with areas of North America, Canada and China.

Decreased consumption.

In recent decades, consumption of selenium in northern Europe has declined significantly. In the ’70s, consumption was about 60-70 mg per day, while today is estimated at about 30 micrograms per day for women and 40 micrograms in men 1, representing half the amount recommended 2 . It is believed that the reason may be the increased consumption of local wheat instead of imported from Canada and America, which contains up to 50 times more selenium than its European counterpart. In the ’80s, Finland introduced selenium in fertilizers and their levels have increased proportionately (see chart).

Weakened defenses.

Although selenium intake has been reduced in Europe, yet there has been no obvious signs of deficiency. However, suboptimal intake of this element can reduce the production of selenium proteins, which in turn affect DNA repair, reduced immune and inflammatory responses, and reduce the protection against diseases like cancer and cardiovascular disease.

Selenium and cancer.

Recently, it has extensively analyzed the role of selenium in cancer development 3. Although there are plausible mechanisms by which selenium proteins could reduce cancer risk (for example, by eliminating free radicals that damage DNA), has concluded that there is little evidence that foods containing selenium protect against the risk of developing any cancer, except for prostate cancer since the selenium proteins involved in the production of testosterone, which is an important regulator of normal and abnormal growth of the prostate.

Cardiovascular Disease.

A meta-analysis of thirteen observational studies that examined the role of selenium in cardiovascular disease has found a moderate inverse relationship between the state of the markers of selenium and the risk of cardiovascular disease. However, studies conducted in populations with an adequate intake of selenium found no evidence of cardiovascular protection and additional studies are inconclusive 4.

Safety Margin.

In Europe, the maximum consumption of selenium without risk to health has been fixed at 300 mg / day for adults, a figure that gradually decreases to 60 mg / day for children 1-3 years 2. Overcoming these levels can cause skin damage or loss of hair and nails. The long-term consumption of large doses (more than 900 mg / day) can cause neurological changes including numbness, convulsions and paralysis. Excessive intake of selenium from food sources is rare, although there have been cases of poisoning in children in Sweden by accidental ingestion of high doses of selenium tablets 5.

It is best to moderate consumption.

Although selenium consumption in Europe has diminished, is still sufficient to prevent any hint of lack and remains at the same level as in many other areas of the world (see table) 1. Selenium proteins levels reach their maximum levels with relative ease by following a normal diet, and do not increase to take supplements of selenium 3. These data are consistent with a recent study of antioxidant supplements did not attribute any clear benefit to the additional consumption of selenium from dietary sources 6. With a balanced diet, most people obtain the necessary selenium through foods.

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