Can Antioxidant Supplements Cause Cancer?

Written by Dr. Steve Chaney on . Posted in current health articles, Drugs and Health, Supplements and Health

The Truth About Vitamins C & E

Author: Dr. Stephen Chaney

mythsI am always amazed at how certain nutrition myths take on a life of their own. A single study gets sensationalized. The study may not be very good, but some nutrition guru publicizes it even though it may be contradicted by other studies that come to the opposite conclusion.

Other blogs and news feeds pick it up. It gets repeated over and over until it becomes generally accepted as true. It becomes what I call an “urban nutrition myth”. Once these myths become well established they are hard to correct. When contrary information is published, it is ignored because everyone already knows the “truth”.

Can Antioxidant Supplements Cause Cancer?

The risks of antioxidant supplements are a perfect example. Most web sites and health experts warn that you should be careful about using antioxidant supplements. You are told that they may just increase your risk of cancer. They may just kill you!

The antioxidant vitamins C and E have generated the most scrutiny in recent years. There were a number of reasons to suspect that they might decrease cancer risk:

1) They destroy free radicals.
2) They decrease cancer risk in animal studies.
3) Increase consumption of vitamins C & E is associated with decreased risk of cancer in human population studies.

Because there was so much circumstantial evidence that vitamins C & E might decrease cancer risk, there have been a number of double-blind, placebo controlled human clinical trials to test that hypothesis.

• 6 clinical studies showed no effect of vitamin C and/or E on cancer incidence.
• 1 study suggested that vitamin E might decrease prostate cancer risk, and another study suggested that vitamin E might decrease colon cancer risk.
• 1 study (Kristal et al, Journal of the National Cancer Institute, doi: 10.1093/jnci/djt456, 2014) suggested that vitamin E alone might increase prostate cancer risk, but when vitamin E was combined with selenium there was no increased risk. I have discussed a likely explanation of those confusing results in a previous “Health Tips From the Professor” (https://healthtipsfromtheprofessor.com/selenium-vitamin-e-increase-prostate-cancer-risk/).

That’s it. Six clinical studies show no effect of vitamins C & E on cancer risk, two studies suggest that vitamin E decreases cancer risk and one study suggests that vitamin E increases cancer risk. Yet all the “experts” are warning that antioxidant supplements might increase your cancer risk. It has become an urban nutrition myth.

You may remember that I said that the final characteristic of an urban nutrition myth is that when contrary information is published, it is ignored. In fact, an excellent study showing no effect of vitamins C and E on cancer risk has just been published – and it is being ignored because it doesn’t fit the “truth” that most experts have come to believe.

What Does the Latest Study Show?

antioxidant supplementsThe study in question (Wang et al, American Journal of Clinical Nutrition, 2014; doi: 10.3945/ajcn.114.085480) was a post-trial follow-up to the Physicians’ Health Study II. It followed 14,641 US male physicians (average age 64 at the beginning of the trial) for 10.3 years. The subjects were randomly assigned to receive 400 IU of vitamin E every other day, 500 mg of vitamin C daily, or their respective placebos.

The investigators in charge of the study recognized that cancer takes many years to develop and that the effects of supplementation might not be recognized until years later. Because of that, the subjects were followed for an additional 2.8 years after the close of the trial to allow additional time for cancers to develop.

The results were clear cut:

• Vitamin E supplementation had no effect on the incidence of prostate cancer or total cancers.
• Vitamin C supplementation also had no effect on the incidence of prostate cancer or total cancers.
• Vitamin C supplementation decreased the incidence of colon cancer during the post-trial period by 46%, which was marginally significant.

The Bottom Line:

1) Can antioxidant supplements cause cancer?  You can ignore the dire warnings that antioxidant supplements may increase your risk of cancer. The only case where this appears to be true is for high dose beta-carotene supplements in smokers. The weight of evidence for vitamins C and E suggests that they are unlikely to increase your risk of cancer.

2) As I have said previously if there is any risk of antioxidant supplements, it is most likely to arise from using high purity individual antioxidant supplements. I recommend vitamin E supplements containing the full spectrum of tocopherols and tocotrienols, carotenoid supplements containing all the naturally occurring carotenoids, and supplements that combine complementary antioxidant nutrients – vitamin E and selenium, for example.

3) That doesn’t mean that you should run out and stock up on antioxidant supplements in the hope that they will prevent cancer. The same clinical studies that showed no harm from vitamin C and E supplementation also showed no consistent benefit.

4) This is also consistent with my comments in previous “Health Tips from the Professor”. For example:

• It is very difficult to prove, and unreasonable to expect, that supplementation will have a measurable effect on risk of a particular disease like cancer for everyone. People who are healthy and have very low risk of cancer, may experience other benefits from supplementation but are unlikely to experience a measurable decrease in cancer risk.

• Supplementation is most likely to be advantageous in select populations, generally populations with increased need for a particular nutrient or at highest risk of disease. It is clinical studies looking at the effect of supplementation in these select populations that often show the greatest benefit of supplementation.

• Supplementation is just one component of a holistic approach for reducing disease risk. Diet, weight control, exercise, adequate rest and stress reduction all play a major role as well. You can’t weigh 250 pounds and eat all your meals at McDonalds and expect supplementation to save you from disease.

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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