Outside of developing countries, pronounced vitamin deficiency diseases, e.g., beriberi, pellagra and scurvy are rare today. Even with depleted foods, processing, storage, genetic selection, age, drug interactions, poor food choices and chronic stress, our diet is still adequate to avoid these deficiency syndromes.
On the other hand, does our modern diet really provide us with enough nutrients to optimize health and prevent age-related diseases like cancer, heart disease, diabetes and Alzheimer’s? Doubtful. There is abundant evidence that various vitamins, minerals, amino acids, herbs and plant extracts can be used to judiciously supplement our diet to reduce risk to chronic diseases. Food is still our best medicine, but supplements can definitely provide significant complementary benefits.
In the next two posts, I’ll just focus on two essential nutrients, selenium and folate, as examples of the benefits of supplementation.
Selenium is an essential trace mineral that plays an important role in antioxidant defense and thyroid function. Through clinical trials, laboratory experiments and population studies, it has been linked to the prevention of a wide variety of degenerative conditions including cancer, infertility, cardiovascular disease, neurological disease and impaired immune function.
Selenium’s anticancer effects, especially with regard to the prevention of prostate cancer, has been getting a great deal of attention in recent years. While the evidence to support the anticancer activity of selenium is overwhelming, the Selenium and Vitamin E Cancer Prevention Trial (SELECT), published in 2009, showed that neither 200 mcg/day of selenium from L-selenomethionine nor 400 IU/day of synthetic alpha tocopherol, nor both together could reduce prostate cancer risk. In a more recent examination of the SELECT data using toenail selenium as an index of tissue stores, selenium supplementation did not benefit men with low selenium status and actually increased the risk of high-grade prostate cancer among men with high selenium status.
With regard to the lack of benefit from Vitamin E, this can be explained by the use of only synthetic alpha tocopherol which suppresses cancer-protective gamma tocopherol.
This major flaw has been addressed in a recent editorial in the Journal of the National Cancer Institute, as well as by Life Extension.
The issue with selenium is more complex. Are selenium supplements ineffective, and, more importantly, are they harmful? Highly unlikely.
Let’s look at some of important limitations of the SELECT study:
1. The major flaw is the use of only one form of selenium – L-selenomethionine. The form of selenium does matter. Our diet provides us with different forms of selenium with different anticancer mechanisms that complement one another. The National Prevention of Cancer study (NPC) demonstrated that 200 mcg/day of selenium from high-selenium Brewer’s yeast reduced prostate cancer risk by 63%. Yeast fed with selenium creates secondary compounds, or byproducts, that have chemopreventive effects. It is possible that these secondary metabolites or forms of selenium other than selenomethionine could account, at least in part, for the positive results in the NPC trial.
This topic, as well as the various mechanisms for the cancer prevention effects of selenium, are extensively covered with supporting references by Life Extension.`
2. Prostate cancer is usually initiated many years before it is clinically diagnosed in older men ( highest risk for ages 50 and >). According to Dr. Gerhard Schrauzer, a pioneer in selenium research, selenium supplementation should start early in life and be maintained over the entire lifespan for optimal utilization of its anticancer effects. The participants in the SELECT study were on the trial dose of 200 mcg/day of selenium for only seven years.
3. The SELECT study subjects, including the placebo group, had a high baseline serum selenium content that was estimated to equate to a selenium intake of 200-250 mcg/day. This amount is already within the range of 200-300 mcg/day that’s estimated to be optimal for cancer protection. The addition of 200 mcg/day of supplemental selenium would therefore not be expected to render any further protective effects against the placebo group.
4. This a correlational study, i.e., it does not prove causation. In 2007, it was reported that high plasma selenium levels were found in diabetics. Does this mean selenium causes diabetes? Of course not. Dr. Schruazer notes that the high selenium levels are due to disease-related changes of the plasma proteins of diabetics. The preponderance of evidence suggests that selenium protects against type 2 diabetes.
Who knows what else can be correlated with high toenail selenium?
5. Other variables not accounted for: (1) Exposure to selenium-antagonistic toxic elements such as cadmium, lead and mercury that inhibit selenium-dependent enzymes. Cadmium exposure has been linked to increased risk to prostate cancer.
Dietary mercury, a possible cancer-causing metal, was moderately correlated with toenail selenium. (2) Vitamin D protects against prostate cancer. Vitamin D status was not reported. (3) Intake of other antioxidants. Investigating a single nutrient presents many problems. Selenium and vitamin E tend to spare one another. Thyoredoxin reductase, a selenium-dependent enzyme, helps regenerate several antioxidants, including vitamin C. In a study investigating toenail selenium as an indicator of selenium intake, dietary beta-carotene intake was positively associated with toenail selenium. Interestingly, the study’s authors suggest that beta-carotene spares selenium in antioxidant-type reactions leaving more selenium to accumulate in toenails. So what else can drive selenium into toenails? Who knows!
6. The use of toenail selenium to measure tissue stores has been questioned for individuals that are not selenium deficient. It does not measure the functional activity of about a dozen important selenium-dependent proteins.
Conclusion and Suggestions
Relative to other nutrients, there is a narrow range of selenium intake between toxicity (>900 mcg/day) and deficiency (<30 mcg/day). The Food and Nutrition Board (FNB) has set the tolerable upper intake level for selenium at 400 mcg/day in adults. The first reversible toxicity symtoms appear at intakes of 2,400-3,000 mcg per day for several months.The average dietary intake of US adults is around 100 mcg/day. However, since there is great variation in the soil content of selenium, and plants do not need selenium, this number becomes a very rough estimate. Brazil nuts have the most selenium of any food, but the amount can vary tenfold!!
Nevertheless, a varied diet can easily provide the US RDA of 55 mcg/day to prevent selenium deficiency diseases such as cardiomyopathy. For maximal protection against cancer, however, a total intake of 200-300 mcg/day is probably necessary.
A supplement of 100-200 additional mcg of selenium is perfectly safe, and far from being toxic. Best option is to include all three forms of selenium: L-selenomethionine, sodium selenite and selenium –Methyl L-Selenocysteine.
It’s unfortunate that research money, time, and effort is wasted on investigating non-toxic amounts of a critical nutrient as it relates to prostate cancer, while poor diet, heavy metal and other oxidant exposures, along with chronic stress and micronutrient deficiencies should be the focus of prostate disease prevention.
If you’re still hesitant about selenium supplementation, consider the revolutionary Triage Theory of micronutrients recently put forth by Dr. Bruce Ames, a prominent scientist best known for the invention of the Ames Tests that test for mutagenicity (potentially cancer-causing) of compounds.
In medicine, triage is the process of deciding which patients should be treated first based on how sick or injured they are. In this instance, the Triage Theory means short-term survival at the expense of long-term survival. A moderate shortage of a single micronutrient, though enough (RDA amounts) to avoid noticeable symptoms, will impair functions essential for long-term health. Over time, the body will accumulate DNA damage that accelerates aging and increases the risk of chronic diseases such as cancer.
In other words, from an evolutionary perspective, the body prioritizes nutrients to survive for reproduction at the expense of longevity.
Dr. Ames and his research team demonstrated his theory with none other than selenium (as well as vitamin K). They found that with “moderate” selenium deficiency the activity and levels of non-essential selenium-dependent proteins declined. These selenoproteins are needed only for long-term health.
A strong case for sensible selenium supplementation.
Robert Iafelice, MS, RDN