For the next few weeks we are going to use the rubric More Info Mondays here on the blog to talk about some nutrients that can be critical for our health and that deserve a special atention, not only on a vegan or vegetarian diet, but for any kind of regimen.
Today we are talking about selenium.
Selenium is an essential mineral. It is a micronutrient (as well as vitamins and water are, contrary to proteins, carbohydrates and lipids, which belong to the macronutrient group) and it is considered a trace mineral since we only need a very little amount of it (contrary to, for instance, calcium or iron from which we need in bigger amounts and are called major minerals).
Main functions of selenium:
- Selenium has been identified to take part of more than 50 proteins in our bodies, having for that reason several functions (antioxidant defense, fertility, thyroid hormone metabolism, immune response and central nervous system functions).
- It is an essential component of two amino acids - selenomethionine (a methionine derivative) and selenocysteine (a cysteine derivative) - and it is in these amino acids that most our our selenium is used. Selenomethionine function as storage component of selenium in our bodies and selenocysteine corresponds to the active form of selenium and integrates proteins with antioxidant function and proteins that take a role on thyroid hormone metabolism.
- It is a co-factor of the enzyme family glutathione peroxidases, an enzyme family with antioxidant function and that protect cellular membranes from free radical damages.
- It is important for the good function of the immune system and for its action against viral infections and other conditions that depend on the immune system health, as the development of cancer.
- It plays a role on the good functioning of the central nervous system, being essential for a good motor performance, coordination, memory and cognitive capacity.
Selenium deficiency can be manifested as:
- Hypothyroidism development.
- Weak defense against viral infections or long and frequent viral infections.
- Brittle hair and nails, hair loss, nail discoloration.
- Infertility issues.
- Heart conditions, such as the Keshan Syndrome (described for the first time in Chinese children from the region of Keshan).
- Low levels of Selenium seem to be involved in the development of Alzheimer's disease, Parkinson's disease, lateral amiothrophic sclerosis, infertility and propensity to develop cancer.
The recommended daily allowence (RDA) for both men and women has recently been increased from 55 to 70 micrograms per day (European Food Safety Authority, ESFA) and its tolerable upper limit (UL) is currently 400 micrograms.
Food Sources of Selenium
Seafood, meat and fish are generally recommended as good sources of Selenium but the richer food on Selenium are Brazil Nuts. One single Brasil nut has about 129 % of the RDA. As so, one Brazil nut every other day should provide the needed amount of selenium.
Indeed, Brazil nuts are so high in selenium that eating 4 nuts per day systematically can make us go beyond the tolerable upper limit of selenium.
Selenium is also present in other plant foods, such as seeds, other nuts, mushrooms, cereals, beans and vegetables (broccoli, cauliflower, spinach).
- Brazil Nuts: 1 Brazil nut provides around 129 % of the RDA (90,6 ug in 31 Kcal)
- Shiitake Mushrooms: 1 cup provides about 51 % if the RDA (36 ug in 80 Kcal)
- Pinto Beans: 1 cup provides about 15 % of the RDA (11 ug in 245 Kcal)
- Chia Seeds: 2 tbsp provide about 15 % of the RDA (11 ug in 97 Kcal)
- Brown Rice: 1 cup provides around 27 % of the RDA (19 ug in 215 Kcal)
- Broccoli: 1 cup provides around 4 % of the RDA (2.5 ug in 55 Kcal)
Excess selenium can be toxic
Excess selenium can be toxic and its supplementation is not recommended. Hair loss and brittle nails are symptoms of both selenium deficiency or toxicity.
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