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

A Low Carb Diet and Weight Loss

Posted January 15, 2019 by Dr. Steve Chaney

Do Low-Carb Diets Help Maintain Weight Loss?

Author: Dr. Stephen Chaney

 

low carb dietTraditional diets have been based on counting calories, but are all calories equal? Low-carb enthusiasts have long claimed that diets high in sugar and refined carbs cause obesity. Their hypothesis is based on the fact that high blood sugar levels cause a spike in insulin levels, and insulin promotes fat storage.

The problem is that there has been scant evidence to support that hypothesis. In fact, a recent meta-analysis of 32 published clinical studies (KD Hall and J Guo, Gastroenterology, 152: 1718-1727, 2017 ) concluded that low-fat diets resulted in a higher metabolic rate and greater fat loss than isocaloric low-carbohydrate diets.

However, low-carb enthusiasts persisted. They argued that the studies included in the meta-analysis were too short to adequately measure the metabolic effects of a low-carb diet. Recently, a study has been published in the British Medical Journal (CB Ebbeling et al, BMJ 2018, 363:k4583 ) that appears to vindicate their position.

Are low carb diets best for long term weight loss?

Low-carb enthusiasts claim the study conclusively shows that low-carb diets are best for losing weight and for keeping it off once you have lost it. They are saying that it is time to shift away from counting calories and from promoting low-fat diets and focus on low-carb diets instead if we wish to solve the obesity epidemic. In this article I will focus on three issues:

  • How good was the study?
  • What were its limitations?
  • Are the claims justified?

 

How Was The Study Designed?

low carb diet studyThe investigators started with 234 overweight adults (30% male, 78% white, average age 40, BMI 32) recruited from the campus of Framingham State University in Massachusetts. All participants were put on a diet that restricted calories to 60% of estimated needs for 10 weeks. The diet consisted of 45% of calories from carbohydrate, 30% from fat, and 25% from protein. [So much for the claim that the study showed low-carb diets were more effective for weight loss. The diet used for the weight loss portion of the diet was not low-carb.]

During the initial phase of the study 161 of the participants achieved 10% weight loss. These participants were randomly divided into 3 groups for the weight maintenance phase of the study.

  • The diet composition of the high-carb group was 60% carbohydrate, 20% fat, and 20% protein.
  • The diet composition of the moderate-carb group was 40% carbohydrate, 40% fat, and 20% protein.
  • The diet composition of the low-carb group was 20% carbohydrate, 60% fat, and 20% protein.

Other important characteristics of the study were:

  • The weight maintenance portion of the study lasted 5 months – much longer than any previous study.
  • All meals were designed by dietitians and prepared by a commercial food service. The meals were either served in a cafeteria or packaged to be taken home by the participants.
  • The caloric content of the meals was individually adjusted on a weekly basis so that weight was kept within a ± 4-pound range during the 5-month maintenance phase.
  • Sugar, saturated fat, and sodium were limited and kept relatively constant among the 3 diets.

120 participants made it through the 5-month maintenance phase.

 

Do Low-Carb Diets Help Maintain Weight Loss?

low carb diet maintain weight lossThe results were striking:

  • The low-carb group burned an additional 278 calories/day compared to the high-carb group and 131 calories/day more than the moderate-carbohydrate group.
  • These differences were even higher for those individuals with higher insulin secretion at the beginning of the maintenance phase of the study.
  • These differences lead the authors to hypothesize that low-carb diets might be more effective for weight maintenance than other diets.

 

What Are The Pros And Cons Of This Study?

low carb diet pros and consThis was a very well-done study. In fact, it is the most ambitious and well-controlled study of its kind. However, like any other clinical study, it has its limitations. It also needs to be repeated.

The pros of the study are obvious. It was a long study and the dietary intake of the participants was tightly controlled.

As for cons, here are the three limitations of the study listed by the authors:

#1: Potential Measurement Error: This section of the paper was a highly technical consideration of the method used to measure energy expenditure. Suffice it to say that the method they used to measure calories burned per day may overestimate calories burned in the low-carb group. That, of course, would invalidate the major findings of the study. It is unlikely, but it is why the study needs to be repeated using a different measure of energy expenditure.

#2: Compliance: Although the participants were provided with all their meals, there was no way of being sure they ate them. There was also no way of knowing whether they may have eaten other foods in addition to the food they were provided. Again, this is unlikely, but cannot be eliminated from consideration.

#3: Generalizability: This is simply an acknowledgement that the greatest strength of this study is also its greatest weakness. The authors acknowledged that their study was conducted in such a tightly controlled manner it is difficult to translate their findings to the real world. For example:

  • Sugar and saturated fat were restricted and were at very similar levels in all 3 diets. In the real world, people consuming a high-carb diet are likely to consume more sugar than people in the other diet groups. Similarly, people consuming the low-carb diet are likely to consume more saturated fat than people in the other diet groups.
  • Weight was kept constant in the weight maintenance phase by constantly adjusting caloric intake. Unfortunately, this seldom happens in the real world. Most people gain weight once they go off their diet – and this is just as true with low-carb diets as with other diets.
  • The participants had access to dietitian-designed prepared meals 3 times a day for 5 months. This almost never happens in the real world. The authors said “…these results [their data] must be reconciled with the long-term weight loss trials relying on nutrition education and behavioral counseling that find only a small advantage for low carbohydrate compared with low fat diets according to several recent meta-analyses.” [I would add that in the real world, people do not even have access to nutritional education and behavioral modification.]

 

low carb diet and youWhat Does This Study Mean For You?

  • This study shows that under very tightly controlled conditions (dietitian-prepared meals, sugar and saturated fat limited to healthy levels, calories continually adjusted so that weight remains constant) a low-carb diet burns more calories per day than a moderate-carb or high-carb diet. These findings show that it is theoretically possible to increase your metabolic weight and successfully maintain a healthy weight on a low-carb diet. These are the headlines you probably saw. However, a careful reading of the study provides a much more nuanced viewpoint. For example, the fact that the study conditions were so tightly controlled makes it difficult to translate these findings to the real world.
  • In fact, the authors of the study acknowledged that multiple clinical studies show this almost never happens in the real world. These studies show that most people regain the weight they have lost on low-carb diets. More importantly, the rate of weight regain is virtually identical on low-carb and low-fat diets. Consequently, the authors of the current study concluded “…translation [of their results to the real world] requires exploration in future mechanistic oriented research.” Simply put, the authors are saying that more research is needed to provide a mechanistic explanation for this discrepancy before one can make recommendations that are relevant to weight loss and weight maintenance in the real world.
  • The authors also discussed the results of their study in light of a recent, well-designed 12-month study (CD Gardener et al, JAMA, 319: 667-669, 2018 ) that showed no difference in weight change between a healthy low-fat versus a healthy low-carbohydrate diet. That study also reported that the results were unaffected by insulin secretion at baseline. The authors of the current study noted that “…[in the previous study] participants were instructed to minimize or eliminate refined grains and added sugars and maximize intake of vegetables. Probably for this reason, the reported glycemic load [effect of the diet on blood sugar levels] of the low-fat diet was very low…and similar to [the low-carb diet].” In short, the authors of the current study were acknowledging that diets which focus on healthy, plant-based carbohydrates and eliminate sugar, refined grains, and processed foods may be as effective as low-carb diets for helping maintain a healthy weight.
  • This would also be consistent with previous studies showing that primarily plant-based, low-carb diets are more effective at maintaining a healthy weight and better health outcomes long-term than the typical American version of the low-fat diet, which is high in sugar and refined grains. In contrast, meat-based, low-carb diets are no more effective than the American version of the low-fat diet at preventing weight gain and poor health outcomes. I have covered these studies in detail in my book “Slaying The Food Myths.”

Consequently, the lead author of the most recent study has said: “The findings [of this study] do not impugn whole fruits, beans and other unprocessed carbohydrates. Rather, the study suggests that reducing foods with added sugar, flour, and other refined carbohydrates could help people maintain weight loss….” This is something we all can agree on, but strangely this is not reflected in the headlines you may have seen in the media.

The Bottom Line

 

  • A recent study compared the calories burned per day on a low-carb, moderate-carb, and high-carb diet. The study concluded that the low-carb diet burned significantly more calories per day than the other two diets and might be suitable for long-term weight control. If confirmed by subsequent studies, this would be the first real evidence that low-carb diets are superior for maintaining a healthy weight.
  • However, the study has some major limitations. For example, it used a methodology that may overestimate the benefits of a low-carb diet, and it was performed under tightly controlled conditions that can never be duplicated in the real world. As acknowledged by the authors, this study is also contradicted by multiple previous studies. Further studies will be required to confirm the results of this study and show how it can be applied in the real world.
  • In addition, the kind of carbohydrate in the diet is every bit as important as the amount of carbohydrate. The authors acknowledge that the differences seen in their study apply mainly to carbohydrates from sugar, refined grains, and processed foods. They advocate diets with low glycemic load (small effects on blood sugar and insulin levels) and acknowledge this can also be achieved by incorporating low-glycemic load, plant-based carbohydrates into your diet. This is something we all can agree on, but strangely this is not reflected in the headlines you may have seen in the media.
  • Finally, clinical studies report averages, but none of us are average. When you examine the data from the current study, it is evident that some participants burned more calories per hour on the high-carb diet than other participants did on the low carb diet. That reinforces the observation that some people lose weight more effectively on low-carb diets while others lose weight more effectively on low-fat diets. If you are someone who does better on a low-carb diet, the best available evidence suggests you will have better long-term health outcomes on a primarily plant-based, low-carb diet such as the low-carb version of the Mediterranean diet.

For more details 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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