Do Selenium & Vitamin E Increase Prostate Cancer Risk?

Written by Dr. Steve Chaney on . Posted in Issues, Supplements and Health

Should Men Avoid Those Supplements?

 Author: Dr. Stephen Chaney

Vitamin EYou’ve probably seen the headlines saying “Supplementation with selenium and vitamin E increases the risk of prostate cancer.” The authors of the study even said “Men aged greater than 55 should avoid supplements with either vitamin E or Se (selenium) at doses that exceed recommended dietary intakes.”

In a recent “Health Tips From The Professor” I debunked the headlines saying “Omega-3 fatty acids increase prostate cancer risk“.

What about vitamin E and selenium? Is it true that they increase prostate cancer risk? If you are a man over 55, should you be concerned? Should you stop using supplements containing vitamin E and selenium?

Do Selenium & Vitamin E Increase Prostate Cancer Risk?

Previous Studies On Selenium, Vitamin E And Prostate Cancer Risk

The study that generated the initial excitement in the field was the Nutrition Prevention of Cancer (NPC) Trial that ended in 1998 (Clark et al, British Journal of Urology, 81: 730-734, 1998; Duffield-Lillico et al, British Journal of Urology, 91: 608-612, 2003).

That study showed that supplementing men who had low blood levels of selenium with 200 ug/day of selenium decreased their prostate cancer risk by 65%.

It was followed by a second, much larger trial called the Selenium and Vitamin E Cancer Prevention Trial (SELECT) (Lipmann et al, JAMA, 301: 39-51, 2009). It looked at supplementation with 200 ug/day of selenium and/or 400 IU/day of synthetic alpha-tocopherol.

The SELECT study found no protective effect of either selenium or vitamin E on prostate cancer risk, but did suggest that vitamin E might actually cause a slight increase in prostate cancer risk.

The Study That Generated The Headlines

The authors of the study that generated the recent headlines (Kristal et al, Journal of the National Cancer Institute, doi: 10.1093/jnci/djt456, 2014) were attempting to find a simple explanation for the unexpected results of the SELECT study.

They hypothesized that the baseline selenium status at the beginning of the study might have influenced the outcome of supplementation. Kristal et al reanalyzed the data from the SELECT trial, comparing the effect of selenium and vitamin E supplementation in men with low selenium status and men with high selenium status.

However, at face value their data were confusing rather simplifying. They found:

  • Supplementation with selenium had no effect on prostate cancer risk in men with low selenium status, but increased prostate cancer risk by 91% in men with high selenium status.
  • Conversely, supplementation with 400 IU of vitamin E had no effect on prostate cancer risk in men with high selenium status, but increased prostate cancer risk by 63% in men with low selenium status.

Based on this hodge-podge of data, they concluded that “Men aged greater than 55 should avoid supplements with either vitamin E or Se (selenium) at doses that exceed recommended dietary intakes.” That was the statement that generated the headlines. Was that recommendation justified?

What Do Other Experts Say?

There was an editorial evaluation of the paper by some of the top expects in the field in the same journal (Frankel et al, Journal of the National Cancer Institute, doi: 10.1093/jnci/dju005, 2014) that provided thoughtful explanations of the confusing data in the paper by Kristal et al. They examined three questions:

1)     Why did the SELECT study find no effect of selenium supplementation in men with low selenium status, while the earlier NPC trial found a 65% decrease in prostate cancer risk?

  • The authors of the editorial pointed out that the lowest baseline selenium status in the SELECT trial was much higher than the lowest baseline selenium status in the previous NPC trial. In fact the baseline selenium status in the SELECT trial was at a level in which no effect of selenium supplementation would have been expected based on the results from the NPC trial.

The authors speculated that the addition of selenized yeast to animal feed has improved selenium status in the US population to the point where selenium supplementation can no longer be expected to reduce prostate cancer risk.

2)     Why did selenium supplementation increase prostate cancer risk in men with high selenium status, but not in men with low selenium status?

  • The authors pointed out that for selenium there is a very narrow range between sufficient intake and toxicity. The daily value (DV) for selenium is 90 ug/day and the recommended upper limit (UL) for selenium intake is 400 ug/day.

The average selenium intake for adult men in this country is 151 ug/day. That’s just the average. It’s not hard to imagine that adding 200ug/day of selenium to men at the highest selenium intake could move them into the toxic range.

3)     Why did vitamin E supplementation increase prostate cancer risk in men with low selenium status, but not in men with high selenium status?

  • In part, the authors felt that the pure alpha-tocopherol used in the SELECT trial was not optimal. Pure alpha-tocopherol interferes with the absorption of the other naturally occurring forms of vitamin E, such as gamma-tocopherol – which is the form of vitamin E that decreases prostate cancer risk in animal studies.
  • The authors also noted that vitamin E and selenium work together to inactivate free radicals in cell membranes. Vitamin E reduces the free radicals to a chemically unstable intermediate that still has the potential to damage membranes. A selenium-containing enzyme is required to convert that unstable intermediate into a completely harmless compound.

So when vitamin E is present in much higher levels than selenium, as it was in the group with low baseline selenium status, unstable radicals can accumulate and membrane damage can occur. The authors felt that this was the most likely explanation of the increased prostate cancer risk when men with low selenium status were supplemented with high dose vitamin E.

The authors of the editorial had a much more nuanced interpretation of the data reported by Kristal et al. If you read their evaluation carefully you would likely conclude that you should avoid high dose selenium supplements. However, rather than simply avoiding vitamin E supplements, you should choose vitamin E supplements that contain all of the naturally occurring vitamin E forms and contain near DV amounts of selenium.

These recommendations would be a much better fit to the data, but don’t lend themselves to dramatic headlines – so the editorial has been largely ignored by the press.

The Bottom Line:

1)     Ignore the scary headlines about selenium and vitamin E causing prostate cancer. You can continue to use your supplements as long as you choose ones that are well balanced.

2)     Conversely, if you are at risk of prostate cancer, there is no good evidence that supplementation with either selenium or vitamin E will reduce your risk.

3)     The results of this study are fully consistent with my longstanding recommendation to follow a holistic approach to supplementation and to avoid high dose single nutrient supplements.

4)     There is no reason to supplement with 200 ug/day of selenium. If you are already getting good amounts of selenium from your diet, that dosage could be toxic and may actually increase your risk of cancer. Make sure that your supplements have no more than the DV (70 ug) of selenium.

5)     Avoid high purity alpha-tocopherol supplements. Look for vitamin E supplements containing the full spectrum of tocopherols and tocotrienols in addition to alpha-tocopherol. In addition, make sure that your vitamin E supplement also contains selenium at near DV levels.

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

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Latest Article

Can Plant-based Diets Be Unhealthy?

Posted September 10, 2019 by Dr. Steve Chaney

Do Plant-Based Diets Reduce Heart Disease Deaths?

Author: Dr. Stephen Chaney

 

plant-based diets vegetablesPlant-based diets have become the “Golden Boys” of the diet world. They are the diets most often recommended by knowledgeable health and nutrition professionals. I’m not talking about all the “Dr. Strangeloves” who pitch weird diets in books and the internet. I am talking legitimate experts who have spent their life studying the impact of nutrition on our health.

Certainly, there is an overwhelming body of evidence supporting the claim that plant-based diets are healthy. Going on a plant-based diet can help you lower blood pressure, inflammation, cholesterol and triglycerides. People who consume a plant-based diet for a lifetime weigh less and have decreased risk of heart disease, diabetes, and cancer.

But, can a plant-based diet be unhealthy? Some people consider a plant-based diet to simply be the absence of meat and other animal foods. Is just replacing animal foods with plant-based foods enough to make a diet healthy?

Maybe not. After all, sugar and white flour are plant-based food ingredients. Fake meats of all kinds abound in our grocery stores. Some are very wholesome, but others are little more than vegetarian junk food. If you replace animal foods with plant-based sweets, desserts, and junk food, is your diet really healthier?

While the answer to that question seems obvious, very few studies have asked that question. Most studies on the benefits of plant-based diets have compared population groups that eat a strictly plant-based diet (Seventh-Day Adventists, vegans, or vegetarians) with the general public. They have not looked at variations in plant food consumption within the general public. Nor have they compared people who consume healthy and unhealthy plant foods.

This study (H Kim et al, Journal of the American Heart Association, 8:e012865, 2019) was designed to fill that void.

 

How Was The Study Done?

plant-based diets studyThis study used data collected from 12,168 middle aged adults in the ARIC (Atherosclerosis Risk in Communities) study between 1987 and 2016.

The participant’s usual intake of foods and beverages was assessed by trained interviewers using a food frequency questionnaire at the time of entry into the study and again 6 years later.

Participants were asked to indicate the frequency with which they consumed 66 foods and beverages of a defined serving size in the previous year. Visual guides were provided to help participants estimate portion sizes.

The participant’s adherence to a plant-based diet was assessed using four different well-established plant-based diet scores. For the sake of simplicity, I will include 3 of them in this review.

  • The PDI (Plant-Based Diet Index) categorizes foods as either plant foods or animal foods. A high PDI score means that the participant’s diet contains more plant foods than animal foods. A low PDI score means the participant’s diet contains more animal foods than plant foods.
  • The hPDI (healthy plant-based diet index) is based on the PDI but emphasizes “healthy” plant foods. A high hPDI score means that the participant’s diet is high in healthy plant foods (whole grains, fruits, vegetables, nuts, legumes, coffee and tea) and low in animal foods.
  • The uPDI (unhealthy plant-based diet index) is based on the PDI but emphasizes “unhealthy” plant foods. A high uPDI score means that the participant’s diet is high in unhealthy plant foods (refined grains, fruit juices, French fries and chips, sugar sweetened and artificially sweetened beverages, sweets and desserts) and low in animal foods.

For statistical analysis the scores from the various plant-based diet indices were divided into 5 equal groups. In each case, the group with the highest score consumed the most plant foods and least animal foods. The group with the lowest score consumed the least plant foods and the most animal foods.

The health outcomes measured in this study were heart disease events, heart disease deaths, and all-cause deaths. Again, for the sake of simplicity, I will only include 2 of these outcomes (heart disease deaths and all-cause deaths) in this review. The data on deaths were obtained from state death records and the National Death Index. (Yes, your personal information is available on the web even after you die.)

 

Do Plant-Based Diets Reduce Heart Disease Deaths?

plant-based diets reduce heart deathsThe participants in this study were followed for an average of 25 years.

The investigators looked at heart disease deaths over the 25 years and compared people with the highest intake of plant foods to people with the highest intake of red meat and other animal foods. The results were:

  • People with the highest intake of plant foods and the highest intake of healthy plant foods (whole grains, fruits, vegetables, nuts, legumes, coffee and tea) had a 19-32% lower risk of dying from heart disease than people with the highest intake of red meat and other animal foods.
  • People with the highest intake of unhealthy plant foods (refined grains, fruit juices, French fries and chips, sugar sweetened and artificially sweetened beverages, sweets and desserts) had the same risk of dying from heart disease as people with the highest intake of red meat and other animal foods.

When the investigators looked at all-cause deaths over the 25 years:

  • People with the highest intake of plant foods and the highest intake of healthy plant foods had an 11-25% lower risk of dying from any cause than people with the highest intake of red meat and other animal foods.
  • People with the highest intake of unhealthy plant foods had the same risk of dying from heart disease as people with the highest intake of red meat and other animal foods.

What Else Did The Study Show?

The investigators made a couple of other interesting observations:

  • The association of the overall diet with heart disease and all-cause deaths was stronger than the association of individual food components. This underscores the importance of looking at the effect of the whole diet on health outcomes rather than the “magic” foods you hear about on Dr. Strangelove’s Health Blog.
  • Diets with the highest amount of healthy plant foods were associated with higher intake of carbohydrates, plant protein, fiber, and micronutrients, including potassium, magnesium, iron, vitamin A, vitamin C, folate, and lower intake of saturated fat and cholesterol.
  • Diets with the highest amount of unhealthy plant foods were associated with higher intake of calories and carbohydrates and lower intake of fiber and micronutrients.

The last two observations may help explain some of the health benefits of plant-based diets.

 

Can Plant-Based Diets Be Unhealthy?

plant-based diets unhealthy cookiesNow, let’s return to the question I asked at the beginning of this article: “Can plant-based diets be unhealthy?” Although some previous studies have suggested that unhealthy plant-based diets might increase the risk of heart disease, this study did not show that.

What this study did show was that an unhealthy plant-based diet was no better for you than a diet containing lots of red meat and other animal foods.

If this were the only conclusion from this study, it might be considered a neutral result. However, this result clearly contrasts with the data from this study and many others showing that both plant-based diets in general and healthy plant-based diets reduce the risk of heart disease deaths and all-cause deaths compared to animal-based diets.

The main message from this study is clear.

  • Replacing red meat and other animal foods with plant foods can be a healthier choice, but only if they are whole, minimally processed plant foods like whole grains, fruits, vegetables, nuts, legumes, coffee and tea.
  • If the plant foods are refined grains, fruit juices, French fries and chips, sugar sweetened and artificially sweetened beverages, sweets and desserts, all bets are off. You may be just as unhealthy as if you kept eating a diet high in red meat and other animal foods.

There is one other subtle message from this study. This study did not compare vegans with the general public. Everyone in the study was the general public. Nobody in the study was consuming a 100% plant-based diet.

For example:

  • The group with the highest intake of plant foods consumed 9 servings per day of plant foods and 3.6 servings per day of animal foods.
  • The group with the lowest intake of plant foods consumed 5.4 servings per day of plant foods and 5.6 servings per day of animal foods.

In other words, you don’t need to be a vegan purist to experience health benefits from adding more whole, minimally processed plant foods to your diet.

 

The Bottom Line

A recent study analyzed the effect of consuming plant foods on heart disease deaths and all-cause deaths over a 25-year period.

When the investigators looked at heart disease deaths over the 25 years:

  • People with the highest intake of plant foods and the highest intake of healthy plant foods had a 19-32% lower risk of dying from heart disease than people with the highest intake of red meat and other animal foods.
  • People with the highest intake of unhealthy plant foods had the same risk of dying from heart disease as people with the highest intake of red meat and other animal foods.

When the investigators looked at all-cause deaths over the 25 years:

  • People with the highest intake of plant foods and the highest intake of healthy plant foods had an 11-25% lower risk of dying from any cause than people with the highest intake of red meat and other animal foods.
  • People with the highest intake of unhealthy plant foods had the same risk of dying from heart disease as people with the highest intake of red meat and other animal foods.

The main message from this study is clear.

  • Replacing red meat and other animal foods with plant foods can be a healthier choice, but only if they are whole, minimally processed plant foods like whole grains, fruits, vegetables, nuts, legumes, coffee and tea.
  • If the plant foods are refined grains, fruit juices, French fries and chips, sugar sweetened and artificially sweetened beverages, sweets and desserts, all bets are off. You may be just as unhealthy as if you kept eating a diet high in red meat and other animal foods.

A more subtle message from the study is that you don’t need to be a vegan purist to experience health benefits from adding more whole, minimally processed plant foods to your diet. The people in this study were not following some special diet. The only difference was that some of the people in this study ate more plant foods and others more animal foods.

For more details on the study, read the article above.

 

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

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