We hear and read about many elements, minerals and vitamins, needed for our bodies to be healthy. What is selenium and why do we need it?
Selenium is a trace element naturally present in many foods, added to others and available as a dietary supplement. This element is essential for human nutrition and is comprised of more than two dozen selenoproteins important for reproduction, thyroid hormone metabolism, DNA synthesis and protection from oxidative damage and infection.1
How Much Do We Need?
The amount of selenium recommended by the US Food and Nutrition Board varies by age and gender and recommends an average daily level sufficient to meet the requirements of nearly all healthy individuals without causing any adverse health effects. Recommendations start with 15 micrograms per day for newborns to 6 months of age, but nursing babies receive an adequate intake through their mother’s milk. From 7 months to 3 years of age 20 micrograms per day is recommended and intake is gradually increased up to age 50 plus to 55 micrograms per day. Pregnant women and nursing mothers require slightly more – 60 to 70 micrograms daily.
Most North American diets contain adequate amounts of selenium. Seafood and organ meats are the richest food sources of selenium. At the top of the selenium rich food list is Brazil nuts. One Brazil nut daily is enough to provide a more than adequate amount of selenium as 1 ounce of Brazil nuts (6 to 8 nuts) contains 544 micrograms. Brazil nuts contain very high amounts of selenium (68–91 mcg per nut) and could cause selenium toxicity if consumed regularly. Yellowfin tuna is next on the list at 92 micrograms per 3 ounce serving, with halibut (47mcg), sardines canned in oil (45mcg), roasted ham (42mcg) and canned shrimp (40mcg) following as the top few food items. Other sources include muscle meats, cereals and grains and dairy products. The amount of selenium in drinking water is not nutritionally significant in most geographic regions. 2,3
Selenium concentration is higher in the thyroid gland than in any other organ in the body. Like iodine, selenium has important functions in thyroid hormone synthesis and metabolism.
Some experts have suggested that selenium could reduce the risk of cardiovascular disease as it would appear to reduce inflammation and prevent blood platelets from clumping together. Conflicting data from other studies have found the opposite so further studies are ongoing.
Because of its effects on DNA repair, apoptosis (normal death of cells) and the endocrine and immune systems, as well as other mechanisms, including its antioxidant properties, selenium might play a role in the prevention of cancer.4
As selenium concentrations decline with age, marginal or deficient selenium concentrations might be associated with age-related declines in brain function, possibly due to decreases in selenium’s antioxidant activity.5
Selenium deficiencies are uncommon among healthy people, but some health conditions – such as HIV, Crohn’s disease and others – are associated with low selenium levels. People who are fed intravenously are also at risk for low selenium and in some cases those who are on kidney dialysis. Health practitioners sometimes suggest that people with these conditions use selenium supplements.
Health Risks from Excessive Selenium:
Continual use of either organic or inorganic forms of selenium have similar effects. Early indicators of excess intake are a garlic odor in the breath and a metallic taste in the mouth. Common signs of chronically high selenium intakes, or selenosis, are hair and nail loss or brittleness. Other symptoms include lesions of the skin and nervous system, nausea, diarrhea, skin rashes, mottled teeth, fatigue, irritability and nervous system abnormalities.
It is imperative to be watchful for over-the-counter products containing very large amounts of selenium as it can cause gastrointestinal and neurological problems, respiratory distress, muscle tenderness, tremors, lightheadedness, kidney and cardiac failure and in rare cases even death.
A healthy body also includes a healthy spine, which in turn means a healthy nervous system, muscles, tendons and organs. Regular check-ups by your chiropractor should always be a part of your wellness regime.
- de RA. Selenium. In: Ross AC, Caballero B, Cousins RJ, Tucker KL, Ziegler TR, eds. Modern Nutrition in Health and Disease.11th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2012:225-37
- Sunde RA. Selenium. In: Bowman B, Russell R, eds. Present Knowledge in Nutrition. 9th ed. Washington, DC: International Life Sciences Institute; 2006:480-97
- Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes: Vitamin C, Vitamin E, Selenium, and Carotenoids. National Academy Press, Washington, DC, 2000.
- Rayman MP. Selenium and human health. Lancet 2012;379:1256-68. [PubMed abstract]
- Akbaraly TN, Hininger-Favier I, Carriere I, Arnaud J, Gourlet V, Roussel AM, et al. Plasma selenium over time and cognitive decline in the elderly. Epidemiology 2007;18:52-8. [PubMed abstract]