Danger

Do Supplements Cause Cancer?

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

The Kernel of Truth Behind the Scary Headlines

Author: Dr. Stephen Chaney

DangerOnce again the sky is falling! Some of the recent headlines have been downright scary. You’ve probably seen headlines saying things like “The American Association for Cancer Research reports that dietary supplements increase cancer risk” and “A recent study shows that taking extra vitamins and minerals may do more harm than good”. You’re probably asking yourself if you should throw away those vitamin and mineral supplements that you have been taking.

Let me start by correcting some of the more misleading statements in the recent headlines:

•    This was not a position statement from the American Association for Cancer Research. It was a talk presented by a single scientist at the American Association for Cancer Research annual meeting.

•    This was not a new study. The talk was based on a paper published in 2012 (Martinez et al., Journal of the National Cancer Institute, 104: 732-739, 2012).

•    This was not even a study. It was a review of previously published studies.

•    When you read the paper you find that the majority of studies found no effect of supplementation on cancer risk, a few suggested that supplementation might decrease cancer risk, and a very few suggested that supplementation might increase cancer risk. However, the scientist giving the talk at the American Association for Cancer Research meeting choose to emphasize the few studies suggesting increased risk.

Should We Worry About A Few Studies Suggesting Increased Cancer Risk?

The important question is whether we should be concerned about even a few studies suggesting that supplementation increases cancer risk. As a mythsresearch scientist I am not particularly concerned. That’s because I realize that there is always some variability in the results of clinical trials.

•    Sometimes that’s because an individual clinical study was poorly designed. Those are studies that are easy to eliminate from consideration.

•    However, many times we do not know why an individual study is an “outlier”. We only know that it is different from all the other studies. Good scientists base their opinions on the weight of the evidence from all available clinical studies, not individual studies – particularly if the individual studies are outliers.

Unfortunately, that’s not the way it works in the “real world”. In the real world individual studies that support a particular viewpoint are often quoted over and over until they become “generally accepted as true” – even if multiple subsequent studies have come to the opposite conclusion. They become what I call “nutrition myths”.

In this issue of “Health Tips From the Professor” I will briefly debunk some of these nutrition myths about the cancer risk of supplementation by exposing the clinical studies that were poorly designed and/or have been contradicted by multiple subsequent studies.

However, there is often a “kernel of truth” buried in all the hype. This kernel of truth is the main focus of this issue because it should guide our decisions about supplementation – not the scary headlines.

Antioxidants & Cancer Risk – A Poorly Designed Study

One of the most widely quoted studies supporting the claim that antioxidant supplements increase the risk of cancer was a meta-analysis of 66 published clinical studies (American Journal of Clinical Nutrition, 297: 842-857, 2007). It came to the conclusion that consumption of extra vitamins A, E, and beta-carotene were associated with up to a 16% increased risk of cancer. However, that study included only those studies in which adverse outcomes were reported. 400 studies with no adverse outcomes were ignored.

More to the point, another group of scientists came back and re-analyzing the same data set a couple of years later (Nutrients, 2: 929-949, 2010). When they looked at same 66 studies included in the original meta-analysis, they reported that 60% of the studies showed no effect of supplementation; 36% of studies showed a benefit of supplementation; and only 4% showed an increased cancer risk.

You might ask yourself, “If only 4% of the studies showed any increase in cancer risk, how could the meta-analysis of all 66 studies report a 16% increase in cancer risk?” That’s because of a statistical quirk. In a meta-analysis the outcome of a single very large study can swamp the conclusions of multiple smaller studies. In this case, the increased cancer risk reported in the original meta-analysis was almost entirely due to a single study in which participants using vitamin E were also on hormone replacement therapy. That’s a concern because we now know that hormone replacement therapy significantly increases cancer risk.

In short, this was a flawed study, but it is cited over and over as “proof” that antioxidant supplementation may increase cancer risk.

Examples of Nutrition Myths Disproved by Subsequent Studies

Antioxidants & Cancer Risk

antioxidant supplementsI have covered this topic in a previous “Health Tips From the Professor” so I’ll just give you a brief summary here. In short, the flawed paper suggesting that antioxidants has been followed by several major studies that have come to the opposite conclusions. For example:

•    One study followed 24,000 adults in Germany for 11 years and found that those consuming antioxidant supplements at the beginning of the study had a 48% decrease in cancer mortality and a 42% decrease in overall mortality (European Journal of Nutrition, 51: 407-413, 2012).

•    A US study followed 15,000 male physicians for 10 years and found that multivitamin supplementation decreased cancer incidence by 8% (JAMA, 308: 1871-1880, 2012).

•    Another study with the same group of 15,000 physicians found that vitamin C and E supplements had no effect on cancer risk over an 8 year period. But, when the study was extended by an additional 3.8 years vitamin C supplementation decreased the risk of colon cancer by 46% (American Journal of Clinical Nutrition, 100: 915-923, 2014).

•    Finally, a study of 7,728 women with invasive breast cancer showed that multivitamin use increased breast cancer survival by 30% (Breast Cancer Research & Treatment, 141: 495-505, 2013).

Folic Acid & Cancer Risk

I have also covered this topic in a previous “Health Tips From the Professor”, so, once again, I will be brief.

•    The study (JAMA, 297: 2351-2359, 2007) that is widely quoted as suggesting that folic acid supplementation might increase the risk of developing colon cancer in people over 50 didn’t actually look at colon cancer. It looked at adenomas in the colon. That is an important distinction because adenomas are benign. They can develop into a cancerous lesion over time, but that is not inevitable.

•    Two major studies since then (American Journal of Clinical Nutrition, 94: 1053-1062, 2011 and Gastroenterology, 141: 98-105, 2011) have reported that folic acid supplementation does not increase the risk of colon cancer.

•    In fact, the second study showed that people with the highest intake of both folic acid from supplementation and folates from food significantly decreased their risk of developing colon cancer.

The Kernel of Truth Behind the Headlines

While the scary headlines about supplements causing cancer are clearly misleading, I would be doing my readers a disservice if I didn’t discuss the Newspaper Headlineskernel of truth behind the headlines.

Let me start by saying that I am not a big fan of high dose, high purity individual supplements. In foods vitamins and minerals tend to occur in a natural balance. When we take individual nutrients in high doses, they often interfere with our body’s ability to absorb and utilize similar nutrients from the foods we eat. We create an imbalance.

That is the “kernel of truth” behind the headlines. High dose, high purity supplements have the potential to create nutritional imbalances. They have the potential to cause harm. Let me give you some examples in the context of cancer risk.

•    Alpha-tocopherol is the most abundant form of vitamin E in foods. However, there are many other forms of vitamin E in foods and high dose, pure alpha-tocopherol suppresses their absorption. This is a potential concern because some of them – gamma-tocopherol and the tocotrienols, for example – are more effective than alpha-tocopherol at reducing the risk of certain cancers in animal studies. This selective anticancer effect has not yet been demonstrated in humans, but it does raise some concern about the use of high dose, high purity alpha-tocopherol supplements.

•    Antioxidants are generally found in combination in foods, not as isolated nutrients. This is important because antioxidants work together. For example, vitamin E reduces free radicals to chemically unstable intermediates that have the potential to damage cells and cause cancer. A selenium-containing enzyme is required to convert these unstable intermediates into completely harmless compounds. This is thought to be the reason why a recent study found that high dose alpha-tocopherol increased prostate cancer risk in men with low selenium status, but not in men with high selenium status (Journal of the National Cancer Institute, doi: 10.1093/jnci/djt456, 2014).

•    Beta-carotene is the most abundant carotenoid in foods, but there are many other naturally occurring carotenoids – some of which appear to have unique anticancer activity in animal studies. This has been suggested as the reason why several studies have shown that diets high in carotenoids decrease the risk of lung cancer in smokers, but high dose beta-carotene alone appears to increase the risk of lung cancer in smokers.

•    B vitamins are best utilized in balance. That is especially true for folic acid, B12 and B6, which probably explains a recent study that suggested high dose B6 and folic acid supplements were associated with an increased risk of mortality, but a B complex supplement containing the same doses of both folic acid and B6 was not associated with increased mortality (Archives of Internal Medicine, 171: 1625-1633, 2011).

Do Supplements Cause Cancer?

Now that you understand the “kernel of truth” behind the headlines you can better understand why some experts recommend getting our vitamins and minerals from foods rather than supplements. While I understand the logic behind that recommendation, I consider it an imperfect solution to the problem for three reasons:

#1: Most of us don’t eat the way that we should. The USDA tells us that only 3-5% of Americans eat a healthy diet on a daily basis.

#2: Most of us don’t eat enough variety of foods. Even if we eat some healthy foods, we won’t get the balance of essential nutrients we need unless we eat a wide variety of healthy foods.

#3: Some of us have increased nutritional needs. Poor diet, genetic predisposition and poor health can all increase our needs for certain essential nutrients – and we may not know about those increased needs until it is too late.

Supplementation to fill nutritional gaps is still a good choice for many Americans, but I recommend avoiding the high dose, high purity individual supplements. For example:

•    Choose a supplement that contains all the naturally occurring forms of vitamin E and selenium in addition to alpha-tocopherol.

•    Choose a supplement that contains a variety of carotenoids, not just pure beta-carotene.

•    Choose a supplement that contains the B vitamins in balance, not just high dose individual B vitamins like folic acid or vitamin B6.

I could go on, but I think you get the idea. If you take individual high purity, high dose supplements you might actually increase your cancer risk. For the most part, the increased cancer risk has not been proven, but it is theoretically possible. A better approach is to choose supplements that are designed to mimic the balance of vitamins and minerals found in the foods we eat.

The Bottom Line

•    Ignore the scary headlines warning that supplement use may increase your risk of cancer. For the most part, those headlines are based on a few flawed studies that have been refuted by multiple subsequent studies which have come to the opposite conclusion.

•    However, there is a kernel of truth behind the idea that certain supplements might have the potential to increase cancer risk. High dose, high purity individual supplements such as alpha-tocopherol, beta-carotene and folic can interfere with our body’s ability to absorb or utilize related nutrients that are important for cancer prevention. In short, high dose, high purity supplements can create nutrient imbalances that have the potential to increase cancer risk.

•    That doesn’t mean that we need to avoid supplements entirely. It does mean that we need to make wise choices about the supplements we use. My recommendations are:

o    Choose a supplement that contains all the naturally occurring forms of vitamin E and selenium in addition to alpha-tocopherol.

o    Choose a supplement that contains a variety of carotenoids, not just pure beta-carotene.

o    Choose a supplement that contains the B vitamins in balance, not just high dose individual B vitamins like folic acid or vitamin B6.

o    I could go on, but you get the idea. You want to choose supplements that are designed to mimic the balance of nutrients we find in nature.

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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