Selenium is a trace mineral required for good health. We should not be complacent about the small amount of this essential nutrient needed because not having enough of it has serious consequences.
Selenium is required for antioxidant protection, DNA repair, thyroid hormone activation, immune system enhancement, production of prostaglandins, muscle function and protection against cancer.
In the body, selenium is incorporated into proteins to make important antioxidant enzymes called selenoproteins. The antioxidant properties of selenoproteins help prevent cellular damage from free radicals.
Free radicals are natural by-products of oxygen metabolism that can damage just about any tissue, such as artery walls or skin cells. Some free radicals result as byproducts when our bodies metabolize nutrients. Others enter our bodies from the air we breathe and the food we eat. Free radicals may contribute to the development of chronic diseases such as cancer and heart disease.
Antioxidants protect us from free radical damage, scavenging them and reducing them to water and other harmless molecules. Other selenoproteins help regulate thyroid function and play a role in the immune system.
There is evidence that selenium acts as a component of the enzyme responsible for converting the thyroxin to triiodothyronine (T3); thus it is possible that the systemic utilization of iodine is impaired in people who are deficient in selenium (Arthur and Beckett, 1989; Arthur, Nicol and Beckett, 1990).
Thyroxin is one of the principal hormones secreted by the thyroid gland that increases the use of all food types for energy production and increases the rate of protein synthesis in most tissues. (Taber’s Cyclopedic Medical Dictionary.)
Selenium plays a necessary role in muscle activity, promoting strength. In addition, this mineral is vitally necessary for production of prostaglandins (cell hormones) from omega-6 fatty acids. Prostaglandins are involved in many various activities. One is their rapid formation in response to injury, resulting in inflammation.
Selenium is absorbed in the upper segment of the small intestine. It is excreted in the urine.
In the general population, deficiency of selenium is considered rare despite a wide range of intake, yet it has an increased frequency in untreated celiac disease that results from malabsorption in the upper small intestine.
A study investigating selenium in whole blood, plasma, and white blood cells in patients with biopsy-confirmed celiac disease on gluten-free diet demonstrated significantly lower concentrations of selenium than controls.
A study investigating serum levels of free carnitine and selenium in children with celiac disease having type 3 duodenal lesions demonstrated that selenium and carnitine levels are decreased in children with celiac disease, with and without diarrhea.
In general, mild to moderate depletion make us feel run down because deficiency results in low energy and fatigue.
Other symptoms include:
· Muscle weakness, pain and tenderness
· Loss of vitality
· Thyroid disorders
· Lowered resistance to infections
· Elevated liver enzymes
· Predisposition to cancer
Food Sources of Selenium
The quantity of selenium in foods is directly dependent on selenium in the soil where plants grow and animals pasture. States lowest in selenium are: California, Oregon, Washington, Wisconsin, Michigan, Illinois, Indiana, Ohio, Pennsylvania, West Virginia, New York, New Hampshire, Massachusetts, Vermont, Maine, Rhode Island, New Jersey, Delaware, and Florida.
Unless otherwise indicated, following foods are in amount of 100 grams:
Food Micrograms (μg) of Selenium
Brazil nuts ¼ cup 380
Pork kidneys 311.5
Lamb kidneys 218.8
Beef kidneys 168
Pacific oysters 154
Turkey giblets 142
Snapper, baked 3 oz. 148
Lamb liver 111
Halibut, baked 3 oz. 113
Chicken giblets 104
Mussels, blue 89.6
Chicken liver 82.2
Tuna, canned 75.2
Salmon, baked 3 oz. 70
Scallops, cooked 3 oz. 70
Bacon, cooked 65
Pork liver 55.7
Crimini mushrooms raw 26
Sunflower seeds, ¼ cup 25
Shitake mushrooms, ckd 24.8
Oyster mushrooms 18.4
Corn bran 16.5
Rice bran 15.6
Corn flour 15.4
White rice flour 15.1
Recommended Dietary Allowances for Selenium
The adult RDA is 70 μg (micrograms) for adult males and 55 μg for adult females.
Children 1 to 10 years require 20 μg each day.
Boys 11 to 14 need 40 μg and those 15 to 18 need 50 μg.
Girls 11 to 14 need 45 μg, those 15 to 18 need 50 μg.
Pregnant women need 65 μg and lactating women need 75 μg.
Getting Your Daily Intake
· Make foods rich in selenium a part of your diet, especially if you feel weak, have low energy, and catch every bug that comes along.
· If you like seafood, eat oysters, clams, fish and shrimp! The richest animal source is kidney, then liver and dark turkey meat. A rich plant source is sunflower seeds, but nothing comes close to Brazil nuts.
· Enjoy these spices and herbs for flavoring: in descending order – mustard seed, ginger, garlic, chervil, coriander, parsley, curry, caraway, celery, dill, pumpkin spice, bay leaf, horseradish, mace, nutmeg, cinnamon, and basil.
Form in Dietary Supplements
Dietary supplements of selenium may be needed to correct a deficiency, but should not exceed 100% of RDA without blood monitoring.
Toxicity from supplements may easily develop. Symptoms include brittle hair and nails, dizziness, fatigue, nausea, diarrhea, liver disease, neurological abnormalities, and tooth decay.
Impact of Storage, Processing, and Cooking
Selenium is minimally affected by storage, processing or cooking.
Krause’s Food, Nutrition, and Diet Therapy, Mahon and Escott-Stump. 10th edition.