Selenium is one of many important dietary minerals, and we require a small amount of selenium in our daily diet. Selenium is incorporated in a small cluster of important proteins, each of which plays a critical role in our health. Scientists named these selenium-containing proteins "selenoproteins."
Selenium has received publicity over the past couple decades based on some confusing and contradictory research about whether low-selenium diets are implicated in cancer risk. To date, this is still a question without a clear answer. Regardless of whether selenium deficiency is associated with increased risk of cancer, it is clear that good selenium nutrition is important for antioxidant protection and for other health reasons as well.
The selenium content of plant foods is often closely related to selenium content of soil in which the plants have been grown. Selenium content of soils can vary widely, including in the U.S. However, poor soil content of selenium is not typically a factor in the average U.S. diet, and the U.S. population 2 years and older averages over 100 micrograms of selenium per day. (This amount easily exceeds all common public health recommendations.)
Most of our food groups at WHFoods provide valuable amounts of selenium. Fish, grass-fed and pasture-raised meats, whole grains, and nuts and seeds are either good, very good, or excellent food sources of selenium.
We rate nine of the World's Healthiest Foods as excellent sources of selenium. We also have eight very good sources and ten good sources of this important mineral.
Selenium is required for the proper activity of a group of enzymes called glutathione peroxidases. (You'll sometimes see the abbreviation "GPO" or "GPx" for a glutathione peroxidase enzyme.) These enzymes play a key role in the body's detoxification system and they also provide protection against oxidative stress. (Oxidative stress is physiological circumstance in which there is excessive risk of oxygen-related damage to the body.) Of the eight known glutathione peroxidase enzymes, five of them require selenium.
In addition to the activity of glutathione peroxidase, selenium-containing enzymes are involved in recycling of vitamin C from its spent form back to its active one, allowing for greater antioxidant protection.
A selenium-containing enzyme is responsible for transforming a less active thyroid hormone called T4 into the more active T3. As you'll see below in the Relationship with Other Nutrients section, selenium and iodine work together to keep thyroid function strong and consistent.
Like the antioxidant protection issue, this is not just an esoteric concern. Researchers have been able to induce problems with the thyroid gland in just two months of a low-selenium diet.
Probably, if you've read about food sources of selenium, you've read about Brazil nuts as a strong source of the mineral. Depending on where they are grown, this is likely to be true—one ounce of Brazil nuts may contain as much as 10 times the Dietary Reference Intake (DRI) recommendation for selenium intake. Other exceptionally selenium-rich foods include oysters, clams, liver, and kidney. Each of these foods is likely to contain double to triple the DRI in a serving. These foods are the exception, however, and not the rule.
As a more general rule of thumb, we can identify the best sources of selenium by food group. Fish and shellfish make up an outsized proportion of our excellent and very good sources. After these come other animal meats, many of which fall in the very good category. Close behind are whole grains and seeds, both of which are well-represented in our good selenium sources category.
Almost all the World's Healthiest Foods contain at least some selenium. Because of this widespread availability, we believe that selenium is a mineral you'll have little trouble getting from our recipes.
|World's Healthiest Foods ranked as quality sources of|
|Mushrooms, Crimini||1 cup||15.8||18.72||34||38.7||excellent|
|Mushrooms, Shiitake||0.50 cup||40.6||17.98||33||14.5||excellent|
|Mustard Seeds||2 tsp||20.3||8.32||15||13.4||excellent|
|Turkey||4 oz||166.7||34.25||62||6.7||very good|
|Chicken||4 oz||187.1||31.30||57||5.5||very good|
|Lamb||4 oz||310.4||27.90||51||2.9||very good|
|Scallops||4 oz||125.9||24.61||45||6.4||very good|
|Beef||4 oz||175.0||23.93||44||4.5||very good|
|Barley||0.33 cup||217.1||23.12||42||3.5||very good|
|Tofu||4 oz||164.4||19.73||36||3.9||very good|
|Eggs||1 each||77.5||15.40||28||6.5||very good|
|Brown Rice||1 cup||216.4||19.11||35||2.9||good|
|Sunflower Seeds||0.25 cup||204.4||18.55||34||3.0||good|
|Sesame Seeds||0.25 cup||206.3||12.38||23||2.0||good|
|Cow's milk||4 oz||74.4||4.51||8||2.0||good|
|Swiss Chard||1 cup||35.0||1.57||3||1.5||good|
Density>=7.6 AND DRI/DV>=10%
Density>=3.4 AND DRI/DV>=5%
Density>=1.5 AND DRI/DV>=2.5%
Like other minerals, selenium content of foods tends to be stable during storage. Consult each specific World's Healthiest Food profile for tips on how to best select and store for optimal nutrient content.
Animal foods tend to lose little selenium in cooking or processing. For example, the amount of selenium lost in the canning process of common seafood was marginal—less than 10% of the total pre-cooking amount. Similarly, broiling beef does not lead to significant loss of the rich selenium content.
Processing whole grains is much more detrimental to selenium content. Making 60% extraction wheat flour from 100% whole wheat robs it of just shy of half of the selenium content. (It is 60% extraction wheat flour that is the most common type used in production of breads in the U.S. where the bran and the germ of the grain have been removed and the flour has become lighter in color.)
According to the third National Health and Nutrition Study (NHANES III), the risk of selenium deficiency is very low. The average U.S. adult eats about 106 mcg of dietary selenium per day. This is well above the Dietary Reference Intake (DRI) recommendation of 55 mcg.
Looking deeper into national eating patterns, we do not see any age or gender group at significant risk of selenium deficiency. Even small children in the United States average above the adult DRI intake recommendation.
We are not aware of common risk factors for deficiency of selenium in the United States. As mentioned earlier, the average U.S. diet exceeds all common public health recommendations for intake of this mineral. For this reason, is it not common to find research studies showing other reasons for selenium deficiency in the U.S.
When we have come across selenium deficiency studies related to the U.S. population, non-dietary factors tend to be medical. For example, we have seen bowel surgeries—especially weight loss surgeries—associated with symptomatic deficiency of selenium. Also, malabsorption problems can lead to selenium deficiency. These need to be severe, however, and again are uncommon and would be associated with deficiency of many nutrients in addition to selenium.
In otherwise well-nourished individuals, selenium deficiency is a relatively silent condition. In fact, maybe uniquely among nutrients, a deficiency of other vitamins or minerals is probably required for overt symptoms to emerge.
If a person is also deficient in other key antioxidants, particularly vitamin C and vitamin E , the problems related to disruptions in antioxidant protection can be amplified. Many of our recipes—such as Steamed Salmon and Asparagus —combine strong sources of multiple antioxidant nutrients. .
A deficiency of both selenium and iodine can make thyroid disorders more severe than a deficiency of iodine alone. Thankfully, the level of selenium deficiency needed to create this combined effect is severe, and not common in the U.S. . This Huevos Rancheros recipe is a good source of both selenium and iodine.
The National Academy of Sciences has set the Tolerable Upper Intake Level (UL) of selenium intake at 400 mcg per day. Based on data from the National Health and Nutrition Study, it doesn't appear that we eat more than this amount very frequently.
In practical terms, most of our excellent and very good sources of selenium contain from 25 to 60 mcg. To routinely go above the UL for selenium intake, you would need to have about 5 or more servings of these high-selenium foods on top of a number of more moderate selenium sources every day.
Reflecting this set of relationships, our Healthiest Way of Eating Plan averages about one fourth of this UL level. From our perspective, this amount gives you plenty of room for remaining well below the UL level while still meeting the recommended daily amount.
In the year 2000, the National Academy of Sciences established Dietary Reference Intakes (DRI) for selenium that included Recommended Daily Allowance (RDA) recommendations by age. These DRI recommendations are used as the reference standard for the charts on this page. (The only exceptions here are the recommendations for infants 12 months and under. Those recommendation levels are not RDAs but rather Adequate Intake, or AI levels.)
The DRI report also established a Tolerable Upper Intake Level (UL) for selenium intake of 400 mcg. This UL is for all selenium intake from foods and supplements and it is established as an amount not be exceeded on any routine basis.
The Daily Value (DV) for selenium intake is 70 mcg per day. This is the standard you'll see on food labels.
As our WHFoods standard, we adopted the DRI value for males and non-pregnant females ages 14 and older of 55 micrograms.