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Selenium
Assessment and Plan: Selenium
The benefits of selenium intake in the conditions described here are derived mainly from observational studies and some randomized placebo controlled trials. The dose of greatest benefit of selenium will likely be seen when taking an amount between the recommended daily allowance and up to one half the intake limit. For adults as an example, this would be a dose of somewhere between 55 and 200 mcg oral daily. The greatest benefit is also most likely to occur from the intake of selenium from food sources rather than a supplement since standards for the supplements are not thoroughly regulated and because of the benefit seen in the intake of additional nutrients that food sources contain.
Preventive Health Advisor recommends that dietary selenium intake including the amount contained within the diet plus that contained in supplements should not exceed 200 mcg daily.
Selenium dietary allowance for both males and females by age: Birth to 6 months: 15 mcg per day, 7–12 months: 20 mcg per day, 1–3 years: 20 mcg per day, 4–8 years: 30 mcg per day, 9–13 years: 40 mcg per day, 14–18 years: 55 mcg per day, 19–50 years: 55 mcg per day, 51+ years: 55 mcg per day, Pregnancy: 60 mcg per day, Lactation: 70 mcg per day.
Selenium intake limits and toxicity:
Toxicity may occur over the following intake limits for males and females: Birth to 6 months: 45 mcg, 7–12 months: 60 mcg, 1–3 years: 90 mcg, 4–8 years: 150 mcg, 9–13 years: 280 mcg, 14 years and older including pregnant or lactating women: 400 mcg.
Symptoms of toxicity may include loss of, or brittle hair or nails, skin rash, fatigue, nausea, diarrhea, irritability and peripheral neuropathy.
For cancers,
A higher selenium intake from diet or supplements was associated with a 31% lower risk of cancer (OR 0.69, 95% CI 0.53 to 0.91 ) and a 45% lower risk of mortality (OR 0.55, 95% CI 0.36 to 0.83) and the risk reduction of cancer was greater in men than women 34% vs 10% (4). No protective benefit by selenium was seen in non-melanoma skin cancer and prostate cancer (4).
For breast cancer, patients with high risk breast cancer on standard treatment plus 387 mcg selenium, 2850 mg vitamin C, 2,500 IU vitamin E, 32.5 IU ß-carotene, 1.2 g gamma-linolenic acid, 3.5 g omega-3 fatty acids from fish oil, and 90 mg CoQ10 were found to survive at least 18 months, had no further evidence of metastasis, less pain medication, no weight loss and remission resulted in 6/32 (5).
For prostate cancer, when subjects in the highest 20 percent for selenium status were compared with those in the lowest 20 percent, those with the highest selenium status were half as likely to get prostate cancer as those with the lowest levels (6).
For skin cancer, selenium taken by patients with a history of basal cell cancers or squamous cell cancers for about 6.4 years showed that 200 mcg of selenium did not lower risk of skin cancer and actually may increase the risk of BCC (by 10%) and SCC (by 14%) compared to placebo, but total cancer incidence was decreased by 37%, cancer mortality was decreased 50%, and prostate cancer incidence was decreased by approximately 50% compared to placebo (7).
Nutritional Prevention of Cancer Study Group also performed a study in 1312 patients to test whether or not 200 mcg of selenium would prevent non-melanoma skin cancer in a randomized, double-blind, placebo controlled trial, but it was found that squamous cell skin cancer risk was increased by 25%, and non-melanoma skin cancer by 17% by calculating a hazard ratio (19).
For gastrointestinal cancers, a daily vitamin and mineral supplements of 50 mcg of selenium, 30 mg of vitamin E, and 15 mg of beta-carotene given to 29,584 adults at high risk of esophageal and stomach cancers found the treatment resulted in lower mortality from all causes, cancer overall, and gastric cancer (8).
In coronary heart disease, a meta-analysis of observational studies by Flores-Mateo G found that higher selenium levels were associated with a lower risk of coronary heart disease the author related that there is a lack of randomized controlled trials and selenium should not be offered as a preventive agent for cardiovascular disease (10).
In thyroid disease, the most common dose of selenium used in research mentioned was 100 mcg oral twice daily. Supplementation with selenium appears to have benefit for thyroid disease over placebo resulting in improved clinical status of autoimmune thyroiditis (Hashimoto’s thyroiditis), Graves’ disease, prevents goiter, and reduces autoimmune antibody titers(11). Toulis KA noted in a systematic review and a meta-analysis that selenium taken over a period of 3 months resulted in significant reduction of thyroid peroxidase autoantibodies in Hashimoto’s thyroiditis, and 3 studies showed better mood (12). Selenium taken for 6 months was found to improve quality of life, was associated with less eye involvement and slowed progression better than placebo and pentoxifylline for Graves’ ophthalmopathy (13).
In depression, a selenium rich diet of 240 mcg per day compared to 28 mcg of selenium per day studied in men was found to result in a better mood after being asked about six different states of mood (14).
In Alzheimer’s disease, Loef M et al reviewed 9 placebo controlled clinical trials which showed lack of consistent benefit of selenium supplements for use in treatment of Alzheimer’s disease (15).
In infertility, a double-blind, placebo controlled, randomized study by Safarinejad MR and Safarinejad S. found that a selenium supplement at dose of 200 mcg per day for 26 weeks improved semen function significantly (16).
