In the first part of this series we deviated from normal discussions by opening a topic directly related to our own personal nutrition. The beef industry has, fortunately, taken a position that we must be able to show the healthfulness of our product if we are to continue to sell to a consumer base that is increasingly aware of the effects diet and nutrition play on their quality of life. We have long known the value of beef in our diets as a source of protein and energy, as well as minerals such as iron, copper and zinc. We have learned that certain fatty acids inherent to beef products can also be beneficial in our diets. More recent data has shown that the trace mineral selenium is critical to our long term health and that improved status of Se in our bodies can dramatically reduce the incidence of many diseases including cancer and those heart related. Beef can be a significant source of Se in our diets. The Se level in the beef product can also be manipulated through proper feeding and supplementation. Long term it is possible to increase the nutritional value of beef through manipulation of the animal's diet but this will require extensive research to determine where we can go with the concept.
Selenium and Cancer
A variety of observational research has shown that incidence of a number of types of cancer is lower among people with higher blood levels or intake of selenium as shown in a variety of studies as well as demographic analysis. In addition, the incidence of nonmelanoma skin cancer is significantly higher in areas of the United States with low soil selenium content which is, frankly a fairly large area including much of the eastern, southern and western states. 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 ìg 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. First, as an anti oxidant, selenium can help protect the body from damaging effects of free radicals. Remember that free radicals are compounds that are essentially the by products of a well functioning immune system. The immune system generates a variety of cells and compounds that are designed to fight off and kill agents and micro organisms that would otherwise cause sickness and infection in the body. The role of an anti oxidant is to "turn off" these compounds and either destroy or neutralize them so that they do not attack or damage body tissues. Secondly, 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.
Observational studies indicate that death from cancer, including lung, colorectal, and prostate cancers, show that people who have low serum selenium levels are more vulnerable. Selenium's main role in health care is regarded as being an important antioxidant - a precursor of the antioxidant enzyme called 'glutathionperoxidase' (GSHpx) which protects cells from free radical damage. The evidence linking lack of selenium with cancer is found not only in epidemiological studies, but also from clinical studies. In
fact, low dietary selenium levels have become an accurate way of predicting future
cancer rates. An American study, published in the Journal of the American Medical Association (JAMA) showed that selenium supplementation led to a 50 percent reduction in cancer mortality. This was the first double blind, placebocontrolled study to show such a drastic effect of selenium supplementation to the diet. The study was carried out on 1,312 patients aged between 18 80 years and diagnosed with skin carcinoma from seven dermatological clinics in the USA. The aim of the study was to determine whether daily selenium supplementation could prevent skin cancer from recurring, and although the results did not support this contention, the researchers did discover that cancer rates (including colorectal, prostate and lung) were significantly lower in the patients taking selenium supplements than in the placebo group.
The results revealed that there were 63 percent fewer cases of colon cancer, 58 percent fewer cases of colorectal cancer and 46 percent fewer cases of breast cancer. The total reduction in cancer mortality was found to be 50 percent, and there was a 37 percent decrease in cancer in general (all types).
Two important long term studies, one 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. If these are consistent with other clinical research they are very likely to show a positive correlation. The French 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 ìg selenium. This study, which began in 1994, has followed more than 12,000 adult men and women.
The SELECT study, a longterm 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 ìg 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 ìg 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 as noted above are natural by products of a functioning immune system and 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. Currently there is insufficient evidence available to recommend selenium supplements for the prevention of coronary heart disease; however, the French study mentioned earlier is looking at the effects of antioxidant nutrients such as selenium on heart disease as well as cancer.
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.
As discussed previously, 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 HIVpositive 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.
A Preventative, Not a Therapy
One thing that should be emphasized is that increasing Se intake and improving our overall Se status is a preventative measure, not a therapy. The vast majority of the data shows that increasing Se levels will help reduce the incidence or onset of various diseases such as cancer and possibly heart disease or arthritis. It has not been proven that increasing Se intake after the disease is present is significantly useful at reducing the effects or in mortality rates. However, it should also be noted that once an illness is present, it is increasingly important to adopt a proper nutrition program to help support the immune system platform.
Is There a Health Risk From Too Much Selenium?
It is always risky to recommend a given product or nutrient as providing health benefits. The main reason being that many people with make the assumption "if a little is good, more must be better." High blood levels of selenium (greater than 100 ìg/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. For this reason it is necessary to follow the directions on supplements and not over consume ANY type of product or preventative or therapeutic nutrient.
Secondly, the form of Se may be important. Some research is showing that while organic Se, in the form of Selenomethionine is more available it is also safer and less problematic at higher intake levels.
Selenium toxicity in humans is very uncommon 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. Table 1 lists upper intake limits for selenium, in micrograms per day, for infants, children, and adults.
Science is learning more about the importance of nutrition and intake of specific nutrients on health. If we are to assume that the data is correct, increasing selenium intake and selenium status in your diet can prove very beneficial and may have a significant effect on reducing a number of serious health problems.
Finally, while the focus of this article has been on the health benefits of improving our Se intake, to take a full 360, remember that significant levels of Se can be delivered through beef products. By improving Se intake in cattle we can improve animal reproduction, health and growth and subsequently produce a more nutritious product for the consumer.
Dr. Steve Blezinger is a management and nutritional consultant with an office in Sulphur Springs, TX. He can be reached at 667 CR 4711 Sulphur Springs, TX 75482, by phone at (903) 8857992 or by e mail at email@example.com