Health kick? = Nuts

JVL has decided that we need more selenium in our diets, because apparently it will help our prostates. Or something. I don’t think I *have* a prostate. Anyway. We have begun eating a brazil nut a day, to “keep the doctor away”.

In an attempt to do some research of my own on this mysterious nut-flesh we’re consuming, I appealed to the mighty Internet. Apparently, by eating just one ounce of brazil nut meat, we are getting 780% of our recommended daily intake of selenium.

In case you missed it, that was SEVEN HUNDRED AND EIGHTY PERCENT. I think maybe, just maybe, we should cut back to one brazil nut each, per week.

What IS the health risk of too much selenium?
High blood levels of selenium (greater than 100 μg/dL) can result in a condition called selenosis. Symptoms of selenosis include gastrointestinal upsets, hair loss, white blotchy nails, garlic breath odor, fatigue, irritability, and mild nerve damage.

Selenium toxicity is rare in the U.S. The few reported cases have been associated with industrial accidents and a manufacturing error that led to an excessively high dose of selenium in a supplement. The Institute of Medicine of the National Academy of Sciences has set a tolerable upper intake level (UL) for selenium at 400 micrograms per day for adults to prevent the risk of developing selenosis.

I think my goal is avoiding selenosis. Sounds too much like halitosis (and causes it, apparently).

FYI, here’s what I got from Googling ‘Brazil Nut’

The tough-shelled, triangular Brazil nut is the seed of a tropical evergreen tree, Bertholletia excelsa, family Lecythidaceae, that grows in large forests in the Amazon River basin of South America. The trees, which can reach a height of 45 m (150 ft), are not cultivated; propagation is entirely by the chance sowing of the seeds, usually by animals. The fruits of the tree are melon-size–10-20 cm (4-8 in) in diameter–thick-walled pods, each of which contains some 18-30 nuts. The pods are gathered when they have fallen from the trees and must be chopped open to obtain the nuts. They can be shipped only during the rainy season, when stream and river waters are navigable. Belem, a port in the Brazilian state of Para, is a center for Brazil nut export, and the nuts are often called Para nuts. Brazil nut kernels are sweet tasting and an excellent source of protein. They are also rich in an oil that is used for lubricating and lighting.

…and here’s what came up for ‘selenium’

Selenium is a trace mineral that is essential to good health but required only in small amounts. Selenium is incorporated into proteins to make selenoproteins, which are important antioxidant enzymes. The antioxidant properties of selenoproteins help prevent cellular damage from free radicals. Free radicals are natural by-products of oxygen metabolism that may contribute to the development of chronic diseases such as cancer and heart disease. Other selenoproteins help regulate thyroid function and play a role in the immune system.

Plant foods are the major dietary sources of selenium in most countries throughout the world. The content of selenium in food depends on the selenium content of the soil where plants are grown or animals are raised. For example, researchers know that soils in the high plains of northern Nebraska and the Dakotas have very high levels of selenium. People living in those regions generally have the highest selenium intakes in the United States (U.S.). In the U.S., food distribution patterns across the country help prevent people living in low-selenium geographic areas from having low dietary selenium intakes. Soils in some parts of China and Russia have very low amounts of selenium. Selenium deficiency is often reported in those regions because most food in those areas is grown and eaten locally.

Selenium also can be found in some meats and seafood. Animals that eat grains or plants that were grown in selenium-rich soil have higher levels of selenium in their muscle. In the U.S., meats and bread are common sources of dietary selenium. Some nuts are also sources of selenium.

Selenium content of foods can vary. For example, Brazil nuts may contain as much as 544 micrograms of selenium per ounce. They also may contain far less selenium. It is wise to eat Brazil nuts only occasionally because of their unusually high intake of selenium. Selected food sources of selenium are provided in Table 1.

Table 1: Selected food sources of selenium
Food – Micrograms (μg) – Percent Daily Value (%)
Brazil nuts, dried, unblanched, 1 ounce 544 780
Tuna, light, canned in oil, drained, 3 ounces 63 95
Beef, cooked, 3½ ounces 35 50
Spaghetti w/ meat sauce, frozen entrée, 1 serving 34 50
Cod, cooked, 3 ounces 32 45
Turkey, light meat, roasted, 3½ ounces 32 45
Beef chuck roast, lean only, roasted, 3 ounces 23 35
Chicken Breast, meat only, roasted, 3½ ounces 20 30
Noodles, enriched, boiled, 1/2 cup 17 25
Macaroni, elbow, enriched, boiled, 1/2 cup 15 20
Egg, whole, 1 medium 14 20
Cottage cheese, low fat 2%, 1/2 cup 12 15
Oatmeal, instant, fortified, cooked, 1 cup 12 15
Rice, white, enriched, long grain, cooked, 1/2 cup 12 15
Rice, brown, long-grained, cooked, 1/2 cup 10 15
Bread, enriched, whole wheat, commercially prepared, 1 slice 10 15
Walnuts, black, dried, 1 ounce 5 8
Bread, enriched, white, commercially prepared, 1 slice 4 6
Cheddar cheese, 1 ounce 4 6

Table 2: Recommended Dietary Allowances (RDA) for selenium for children and adults
Age(years)- Males and Females – Pregnancy – Lactation
1-3 y ============ 20 =============N/A======== N/A
4-8 y ============ 30 =============N/A======== N/A
9-13 y =========== 40 =============N/A======== N/A
14-18 y ========== 55 ==============60======== 70
19 y + =========== 55 ==============60======== 70

Human selenium deficiency is rare in the U.S. but is seen in other countries, most notably China, where soil concentration of selenium is low. There is evidence that selenium deficiency may contribute to development of a form of heart disease, hypothyroidism, and a weakened immune system. There is also evidence that selenium deficiency does not usually cause illness by itself. Rather, it can make the body more susceptible to illnesses caused by other nutritional, biochemical or infectious stresses.

Three specific diseases have been associated with selenium deficiency:
Keshan Disease, which results in an enlarged heart and poor heart function, occurs in selenium deficient children.
Kashin-Beck Disease, which results in osteoarthropathy
Myxedematous Endemic Cretinism, which results in mental retardation

Keshan disease was first described in the early 1930s in China, and is still seen in large areas of the Chinese countryside with selenium poor soil. Dietary intake in these areas is less than 19 micrograms per day for men and less than 13 micrograms per day for women, significantly lower than the current RDA for selenium. Researchers believe that selenium deficient people infected with a specific virus are most likely to develop Keshan disease.

Selenium deficiency has also been seen in people who rely on total parenteral nutrition (TPN) as their sole source of nutrition [20,21]. TPN is a method of feeding nutrients through an intravenous (IV) line to people whose digestive systems do not function. Forms of nutrients that do not require digestion are dissolved in liquid and infused through the IV line. It is important for TPN solutions to provide selenium in order to prevent a deficiency. Physicians can monitor the selenium status of individuals receiving TPN to make sure they are receiving adequate amounts.

Severe gastrointestinal disorders may decrease the absorption of selenium, resulting in selenium depletion or deficiency. Gastrointestinal problems that impair selenium absorption usually affect absorption of other nutrients as well, and require routine monitoring of nutritional status so that appropriate medical and nutritional treatment can be provided.

Most cases of selenium depletion or deficiency are associated with severe gastrointestinal problems, such as Crohn’s disease, or with surgical removal of part of the stomach. These and other gastrointestinal disorders can impair selenium absorption. People with iodine deficiency may also benefit from selenium supplementation. Researchers believe that selenium deficiency may worsen the effects of iodine deficiency on thyroid function, and that adequate selenium nutritional status may help protect against some of the neurological effects of iodine deficiency.

Current issues and controversies about selenium

Selenium and cancer
Observational studies indicate that death from cancer, including lung, colorectal, and prostate cancers, is lower among people with higher blood levels or intake of selenium. In addition, the incidence of nonmelanoma skin cancer is significantly higher in areas of the United States with low soil selenium content. The effect of selenium supplementation on the recurrence of different types of skin cancers was studied in seven dermatology clinics in the U.S. from 1983 through the early 1990s. Taking a daily supplement containing 200 μg of selenium did not affect recurrence of skin cancer, but significantly reduced the occurrence and death from total cancers. The incidence of prostate cancer, colorectal cancer, and lung cancer was notably lower in the group given selenium supplements.

Research suggests that selenium affects cancer risk in two ways. As an anti-oxidant, selenium can help protect the body from damaging effects of free radicals. Selenium may also prevent or slow tumor growth. Certain breakdown products of selenium are believed to prevent tumor growth by enhancing immune cell activity and suppressing development of blood vessels to the tumor.

However, not all studies have shown a relationship between selenium status and cancer. In 1982, over 60,000 participants of the Nurse’s Health Study with no history of cancer submitted toenail clippings for selenium analysis. Toenails are thought to reflect selenium status over the previous year. After three and a half years of data collection, researchers compared toenail selenium levels of nurses with and without cancer. Those nurses with higher levels of selenium in their toenails did not have a reduced risk of cancer.

Two important long-term studies, the SU.VI.MAX study in France and the Selenium and Vitamin E Cancer Prevention Trial (SELECT) study in the U.S., are now underway to further investigate the selenium/cancer prevention link.

The SU.VI.MAX Study is a prevention trial looking at the effects of antioxidant vitamins and minerals on chronic diseases such as cancer and cardiovascular disease. Doses of the nutrients provided in the study are one to three times higher than recommended intakes, including a daily supplement of 100 μg selenium. The SU.VI.MAX study, which began in 1994, has followed more than 12,000 adult men and women. This study was designed to continue for eight years, and the research community is eagerly awaiting the results of this study.

The SELECT study, a long-term study sponsored by the NIH, is investigating whether supplemental selenium and/or vitamin E can decrease the risk of prostate cancer in healthy men. Past evidence as well as pre-clinical trials for the SELECT study suggests that these two nutrients may be effective in preventing prostate cancer. A daily supplement containing 200 μg of selenium will be given to individuals in the selenium-only study group, while men in the combined-nutrients group will receive a daily supplement containing 200 μg selenium and 400 mg vitamin E. The study, which will span from 2001 to 2013, will include 32,400 healthy adult men.

Selenium and heart disease
Some population surveys have suggested an association between lower antioxidant intake and a greater incidence of heart disease. Evidence also suggests that oxidative stress from free radicals, which are natural by-products of oxygen metabolism, may promote heart disease. For example, it is the oxidized form of low-density lipoproteins (LDL, often called “bad” cholesterol) that promotes plaque build-up in coronary arteries. Selenium is one of a group of antioxidants that may help limit the oxidation of LDL cholesterol and thereby help to prevent coronary artery disease [47-49]. Currently there is insufficient evidence available to recommend selenium supplements for the prevention of coronary heart disease; however, the SU.VI.MAX study mentioned earlier is looking at the effects of antioxidant nutrients such as selenium on heart disease.

Selenium and arthritis
Surveys indicate that individuals with rheumatoid arthritis, a chronic disease that causes pain, stiffness, swelling, and loss of function in joints, have reduced selenium levels in their blood. In addition, some individuals with arthritis have a low selenium intake.

The body’s immune system naturally makes free radicals that can help destroy invading organisms and damaged tissue, but that can also harm healthy tissue. Selenium, as an antioxidant, may help to relieve symptoms of arthritis by controlling levels of free radicals. Current findings are considered preliminary, and further research is needed before selenium supplements can be recommended for individuals with arthritis.

Selenium and HIV
HIV/AIDS malabsorption can deplete levels of many nutrients, including selenium. Selenium deficiency is associated with decreased immune cell counts, increased disease progression, and high risk of death in the HIV/AIDS population. HIV/AIDS gradually destroys the immune system, and oxidative stress may contribute to further damage of immune cells. Antioxidant nutrients such as selenium help protect cells from oxidative stress, thus potentially slowing progression of the disease. Selenium also may be needed for the replication of the HIV virus, which could further deplete levels of selenium.

An examination of 125 HIV-positive men and women linked selenium deficiency with a higher rate of death from HIV. In a small study of 24 children with HIV who were observed for five years, those with low selenium levels died at a younger age, which may indicate faster disease progression. Results of research studies have led experts to suggest that selenium status may be a significant predictor of survival for those infected with HIV.

Researchers continue to investigate the relationship between selenium and HIV/AIDS, including the effect of selenium levels on disease progression and mortality. There is insufficient evidence to routinely recommend selenium supplements for individuals with HIV/AIDS, but physicians may prescribe such supplements as part of an overall treatment plan. It is also important for HIV-positive individuals to consume recommended amounts of selenium in their diet.

3 thoughts on “Health kick? = Nuts

  1. I thought selenium was the anti-gravitional mineral they used to get to the moon in that H.G. Wells story.

  2. Selenium is a trace element (less than 100mg is needed per day) so I seriously doubt you (or rather, Justin) should be worried about how much you’re getting a day…and yeh, I’d cut back to like, a teeny tiny piece of brazil nut a week… or better yet, none at all? 🙂
    (And btw, you shouldn’t have a prostate)

  3. …could you overdose on brazil nuts? I’m pretty sure I’ve never seen any kind of “health risk” label on a jar of brazil nuts. If you sit down with a bowl of them…yikes! Heh

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