Five Top Tips on Selenium

What are the best food sources of Selenium?

Selenium is a trace element naturally present in many foods.  Selenium is nutritionally essential for humans, and is a constituent of more than two dozen 'selenoproteins' that play critical roles in reproduction, thyroid hormone metabolism and DNA synthesis. Some also act as antioxidants and have an antiviral function. Low selenium has been associated with higher risk of mortality, poor immune function, and cognitive decline (1), although more research is needed to determine the exact health role selenium plays in cancer, cardiovascular disease, cognitive function and thyroid disease. 

TOP TIP # 1 - Supplementation

Most people obtain adequate selenium through their diet.  There appears to be a U-shaped curve with selenium status; whereas additional selenium intake may benefit people with low status, those with adequate-to-high status might be affected adversely, and there is a possible increased risk of developing Diabetes (2 - 4).  More research is required in this area as most studies have confounding factors, but currently the studies indicate supplementation in people with adequate diets can increase the risk of developing Type 2 Diabetes (3).  The NHANES study (4) in 2009 – 10 found that the average daily selenium intake in Americans aged 2 years and older is 108.5 micrograms daily from foods, and 120.8 micrograms from both food and supplements.

TOP TIP # 2 - Recommended intakes

Recommended Daily Allowances (RDA) for healthy adults (19 – 50 years) is about 55 mcg daily (6).  Requirements gradually increase from birth to 19 years, and also for pregnant and breastfeeding women.  See the table below.

Recommended Dietary Allowances (RDA) for Selenium daily (6)

TOP TIP # 3 - Food Sources

Seafood and organ meats are the richest food sources of selenium, and a vegan alternative is brazil nuts. Typically, brazil nuts' macronutrient profile is 11% carbohydrate, 67% fats, and 14% protein. One single brazil nut provides 160% of the US Recommended Daily Allowance (RDA) of selenium – perhaps the best source of selenium from plant-based foods. One serving of brazil nuts (6 – 8 nuts or about 30 g) provides over 700% of RDA for selenium, or over 1900 micrograms. The amount of selenium in a plant-based food depends on the soil pH, the amount of organic matter in the soil, and whether the type of selenium is best for plants uptake.  Therefore, the selenium levels in the meat of the animals that eat the plants will also vary, depending on the uptake from the plants.

TOP TIP # 4 - Who is at risk of low selenium status?

At risk groups include people living in selenium-deficient regions, people undergoing kidney dialysis (as the hemodialysis process removes some of the selenium from the blood)(7), in addition to anorexia resulting from uremia, and possible dietary restrictions, and people with diseases that cause diarrhea and malabsorption.  Toxicity may occur from over-supplementation or occupational exposure.

TOP TIP # 5 - How do you know if you lack selenium?

Common symptoms of low selenium are hair loss, skin and fingernail discoloration, low immunity, tiredness, difficulty concentrating, reproductive problems, hypothyroidism. Don't forget that high levels can also be toxic and some symptoms are severe gastrointestinal and neurological symptoms, acute respiratory distress syndrome, myocardial infarction, hair loss, muscle tenderness, tremors, light-headedness, facial flushing, kidney failure, cardiac failure, and, in rare cases, death (6). To check your selenium status,you will need to see your doctor to arrange a blood test, and a nutritional review with a Registered Dietitian or Registered Nutritionist could also be beneficial.

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References

1.  Sunde 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

2.  Rayman, M. P. (2012). Selenium and human health. The Lancet, 379(9822), 1256-1268.

3.  Stranges, S., Marshall, J. R., Natarajan, R., Donahue, R. P., Trevisan, M., Combs, G. F., ... & Reid, M. E. (2007). Effects of long-term selenium supplementation on the incidence of type 2 diabetes: a randomized trial. Annals of internal medicine, 147(4), 217-223.

4.  Stranges, S., Sieri, S., Vinceti, M., Grioni, S., Guallar, E., Laclaustra, M., ... & Krogh, V. (2010). A prospective study of dietary selenium intake and risk of type 2 diabetes. BMC Public Health, 10(1), 564.

5.  U.S. Department of Agriculture, Agricultural Research     Service. What We Eat in America, 2009-2010.

6.  Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes: Vitamin C, Vitamin E, Selenium, and Carotenoids. National Academy Press, Washington, DC, 2000.

7.  Tonelli M, Wiebe N, Hemmelgarn B, Klarenbach S, Field C, Manns B, et al. Trace elements in hemodialysis patients: a systematic review and meta-analysis. BMC Med 2009;7:25.

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