Selenium And Your Thyroid Gland
Selenium is required for the production, activation and metabolism of thyroid hormone. A healthy thyroid gland contains more selenium per gram than any other tissue in the body. Selenium is required by the enzyme that converts T4 thyroid hormone into its active form, T3. If you are deficient in selenium you will not be able to manufacture sufficient T3 and you may experience the symptoms of an under active thyroid gland, such as fatigue, muscle weakness, easy weight gain, depression and scalp hair loss. A selenium deficiency can contribute to the development of autoimmune thyroid conditions, such as Hashimoto’s disease and Graves’ disease.
How to get enough selenium for good health
The selenium content of food is directly related to how much selenium was in the soil where the food was grown. Many areas of the world have selenium deficient soils, including most of Australia and New Zealand.
Normally selenium is found in organ meats, seafood, Brazil nuts, whole grains, brewer’s yeast, garlic, kelp, molasses, onions and medicinal mushrooms (reishi and shitake). However, because selenium levels in the soil are unreliable, it is virtually impossible to obtain enough selenium through diet alone.
Food processing, antacid drugs and digestive disorders, such as gluten intolerance, can greatly reduce the absorption of minerals. For these reasons, mineral deficiencies are a common contributor to disease states.
Selenium supplements come in organic and inorganic form. Organic supplements are in the form selenomethionine; inorganic selenium comes as selenite and sodium selenite. Selenomethionine is better absorbed by the body with reports of up to twice the bio-availability of selenite.
How do you know if you are low in selenium?
It can be very difficult to know if you have optimal or even adequate levels of selenium in your body. This is because selenium is concentrated in the deepest parts of our cells and not in our blood stream. Thus blood and urinary selenium levels only show the tip of the iceberg; in other words they can show “normal” but you can still be deficient. The most accurate test would be a tissue biopsy but that’s expensive and hurts a little!
The amount of selenium in a person can be measured by selenium plasma and urine levels and the selenium content of a hair sample. Human plasma should not contain less than 100 to 150 or more than 2,800 nanograms of selenium per millilitre of plasma. Urine levels should be 50 to 100 nanograms of selenium per millilitre of urine. Hair selenium levels should be more than 27 micrograms per gram of hair.
A far more accurate measure of a person’s long term selenium status is found by assessing the amount of selenium in their toe nails. This requires clippings of toe nails and is not a commonly performed laboratory test, except in research studies. It is however, a valuable test.
Can selenium become toxic?
Generally speaking, selenium is very safe, as it is an essential nutrient for all animals. Just because it’s good for you, however, does not mean the more you take the better off you will be! Like all nutrients we do not need to overdose and if you overdose on selenium, you can get side effects.
The effects of selenium overdose include - brittle hair and nails, gastro-intestinal upset, skin rashes, fatigue and irritability.
The toxic dose is considered to be over 800mcg daily for several months. There is no reason to take these huge amounts and, generally speaking, overdose comes from industrial pollution. A beneficial and safe daily dose of selenium in adults is 100mcg to 300mcg and it’s always good to get professional advice.
Children with a weak immune system who are always catching new viral infections may be low in selenium and iodine as well as vitamin D and vitamin C. Doses of selenium for children are shown in the table below.
Recommended Dietary Intake (RDI) for Selenium
Life Stage Age Females (mcg/day) Males (mcg/day)
Infants 0-6 months 12 12
Infants 7-12 months 15 15
Children 1-3 years 25 25
Children 4-8 years 30 30
Children 9-13 years 50 50
Adolescents 14-18 years 60 70
These are minimum amounts and, in my opinion, are not necessarily optimal in children with a weak immune system.
Tolerable Upper Intake Level for Selenium
Life Stage Age Mcg/day
Infants 0-6 months 45
Infants 7-12 months 60
Children 1-3 years 90
Children 4-8 years 150
Children 9-13 years 280
Adolescents 14-18 years 400
Adults 19 years plus 400
Some people will need to take more than 100mcg of selenium everyday to get the best results, and many of the studies done on selenium used a daily dose of 200mcg to achieve good outcomes. If you are going to take more than 300mcg daily, do this under the supervision of your health care practitioner. For more advice call my naturopath, Christine, for Liver Advisory Service on 623 334 3232.
If you are an adult, you may need to take 300mcg daily for several months to build up your body’s stores to optimal levels and then reduce to a maintenance dose of 800mcg every week. It is safe to take the weekly dose at one time.
The Food and Nutrition Board (FNB) sets the tolerable upper level for selenium at 400mcg daily in adults – this upper limit includes selenium obtained from food, which averages around 100mcg/day for adults in the USA, as well as from supplements. At this stage there is insufficient data to estimate average selenium intake in Australians, however studies done in New Zealand show intakes as low as 28mcg/day. New Zealand and Australian soils are similarly selenium deficient.
Problems with our immune system
Basically our immune system cannot function efficiently if it does not have the correct nutrients in our blood stream. The most important nutrients for the immune system are antioxidant minerals and vitamins and essential fatty acids.
Today many people find that their immune system lets them down and this can manifest as:
• Frequent or severe infections
• Excess inflammation causing arthritic pain or autoimmune disease
Why are these problems so common?
- Modern diets –these contain processed foods, excess sugar and hydrogenated fat
- Low vitamin D - we spend too much time indoors working too hard!
- Our environment - it is overloaded with toxic chemicals and exposure to environmental toxins and heavy metals increases your requirement for selenium
- Stress – this has increased with overpopulation and poverty and the struggle for survival
- Our bodies easily become depleted of protective minerals and vitamins and very few people get enough in their daily diet. I know this because I have done extensive surveys at my seminars all over Australia and the USA. Generally speaking, whenever I ask the audience “Who takes vitamin C?, Who takes selenium?, Who takes fish oil?, Who drinks raw juices?”, only 10% of the audience is taking these protective nutrients and many of them suffer with sub-clinical scurvy!
The basic cause of many different types of diseases is chronic uncontrolled inflammation.
I still find it amazing that most people are unaware of the huge protective effect that can be achieved by taking specific nutrients. Whether they do this on a daily, or if that’s too hard, a weekly basis, there is a wealth of scientific research that has been published about their benefits.
The sad thing, however, is that many folks leave it until it is too late – especially when the power of nutritional medicine has the ability to regenerate diseased cells in our body and to restore a damaged immune system.
Take it from me, a doctor who has practiced nutritional medicine for over 30 years, don’t wait till you get really sick; start using nutritional medicine as part of your regular routine.
Sharda B. Free Radicals: emerging challenge in environmental health research in childhood and neonatal disorders. International Journal of Environmental Research and Public Health, 2006 Sep;3(3):286-91
Linus Pauling Institute: Micronutrient Research for Optimum Health, Oregon State University.
Hurwitz BE, Klaus JR, Llabre MM, et al. Suppression of human immunodeficiency virus type 1 viral load with selenium supplementation: a randomized controlled trial. Archives Internal Med. 2007 Jan 22; 167(2):148-54.
Beck MA et al, Selenium deficiency & viral infection. J Nutr 2003; 133 (5 Suppl 1):1463S
Selenium as a chemo preventative agent in human primary hepatocellular carcinoma
Yu SY, Zhu YJ, Li WG. Cancer Institute, Chinese Academy of Medical Sciences, Beijing 100021 and Qidong Liver Cancer Institute, Jiangsu, PR China.