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

Should We Use Supplements For Cardiovascular Health?

Posted July 10, 2018 by Dr. Steve Chaney

Are You Just Wasting Your Money On Supplements?

Author: Dr. Stephen Chaney

 

supplements for cardiovascular health wast moneyYou’ve seen the headlines. “Recent Study Finds Vitamin and Mineral Supplements Don’t Lower Heart Disease Risk.”  You are being told that supplements are of no benefit to you. They are a waste of money. You should follow a healthy diet instead. Is all of this true?

If I were like most bloggers, I would give you a simple yes or no answer that would be only partially correct. Instead, I am going to put the study behind these headlines into perspective. I am going to give you a deeper understanding of supplementation, so you can make better choices for your health.

 Should we use supplements for cardiovascular health?

In today’s article I will give you a brief overview of the subject. Here are the topics I will cover today:

  • Is this fake news?
  • Did the study ask the right questions?
  • Is this a question of “Garbage In – Garbage Out?
  • Reducing Heart Disease Risk. What you need to know.

All these topics are covered in much more detail (with references) in my book “Slaying The Supplement Myths”, which will be published this fall.

 

How Was This Study Done?

supplements for cardiovascular healthThis study (D.J.A. Jenkins et al, Journal of the American College Of Cardiology, 71: 2540-2584, 2018 ) was a meta-analysis. Simply put, that means the authors combined the results of many previous studies into a single database to increase the statistical power of their conclusions. This study included 127 randomized control trials published between 2012 and December 2017. These were all studies that included supplementation and looked at cardiovascular end points, cancer end points or overall mortality.

Before looking at the results, it is instructive to look at the strengths and weaknesses of the study. Rather than giving you my interpretation, let me summarize what the authors said about strengths and weaknesses of their own study.

The strengths are obvious. Randomized control trials are considered the gold standard of evidence-based medicine, but they have their weaknesses. Here is what the authors said about the limitations of their study:

  • “Randomized control trials are of shorter duration, whereas longer duration studies might be required to fully capture chronic disease risk.”
  • “Dose-response data were not usually available [from the randomized control studies included in their analysis]. However, larger studies would allow the effect of dose to be assessed.”

There are some other limitations of this study, which I will point out below.

Is This Fake News?

supplements for cardiovascular health fake newsWhen I talk about “fake news” I am referring to the headlines, not to the study behind the headlines. The headlines were definitive: “Vitamin and Mineral Supplements Don’t Lower Heart Disease Risk.” However, when you read the study the reality is quite different:

  • In contrast to the negative headlines, the study reported:
    • Folic acid supplementation decreased stroke risk by 20% and overall heart disease risk by 17%.
    • B complex supplements containing folic acid, B6, and B12 decreased stroke risk by 10%.
    • That’s a big deal, but somehow the headlines forgot to mention it.
  • The supplements that had no significant effect on heart disease risk (multivitamins, vitamin D, calcium, and vitamin C) were ones that would not be expected to lower heart disease risk. There was little evidence from previous studies of decreased risk. Furthermore, there is no plausible mechanism for supposing they might decrease heart disease risk.
  • The study did not include vitamin E or omega-3 supplements, which are the ones most likely to prove effective in decreasing heart disease risk when the studies are done properly (see below).

Did The Study Ask The Right Question?

Most of the studies included in this meta-analysis were asking whether a supplement decreased heart disease risk or mortality for everyone. Simply put, the studies started with a group of generally healthy Americans and asked whether supplementation had a significant effect on disease risk for everyone in that population.

That is the wrong question. We should not expect supplementation to benefit everyone equally. Instead, we should be asking who is most likely to benefit from supplementation and design our clinical studies to test whether those people benefit from supplementation.

supplements for cardiovascular health diagramI have created the graphic on the right as a guide to help answer the question of “Who is most likely to benefit from supplementation?”. Let me summarize each of the points using folic acid as the example.

 

Poor Diet: It only makes sense that those people who are deficient in folate from foods are the most likely to benefit from folic acid supplementation. Think about it for a minute. Would you really expect people who are already getting plenty of folate from their diet to obtain additional benefits from folic acid supplementation?

The NIH estimates that around 20% of US women of childbearing age are deficient in folic acid. For other segments of our population, dietary folate insufficiency ranges from 5-10%. Yet, most studies of folic acid supplementation lump everyone together – even though 80-95% of the US population is already getting enough folate through foods, food fortification, and supplementation. It is no wonder most studies fail to find a beneficial effect of folic acid supplementation.

The authors of the meta-analysis I discussed above said that the beneficial effects of folic acid they saw might have been influenced by a very large Chinese study, because a much higher percentage of Chinese are deficient in folic acid. They went on to say that the Chinese study needed to be repeated in this country.

In fact, the US study has already been done. A large study called “The Heart Outcomes Prevention Evaluation (HOPE)” study reported that folic acid supplementation did not reduce heart disease risk in the whole population. However, when the study focused on the subgroup of subjects who were folate-deficient at the beginning of the study, folic acid supplementation significantly decreased their risk of heart attack and cardiovascular death.  This would seem to suggest using supplements for cardiovascular health is a good idea.

Increased Need: There are many factors that increase the need for certain nutrients. However, for the sake of simplicity, let’s only focus on medications. Medications that interfere with folic acid metabolism include anticonvulsants, metformin (used to treat diabetes), methotrexate and sulfasalazine (used to treat severe inflammation), birth control pills, and some diuretics. Use of these medications is not a concern when the diet is adequate. However, when you combine medication use with a folate-deficient diet, health risks are increased and supplementation with folic acid is more likely to be beneficial.

Genetic Predisposition: The best known genetic defect affecting folic acid metabolism is MTHFR. MTHFR deficiency does not mean you have a specific need for methylfolate. However, it does increase your need for folic acid. Again, this is not a concern when the diet is adequate. However, when you combine MTHFR deficiency with a folate-deficient diet, health risks are increased and supplementation with folic acid is more likely to be beneficial. I cover this topic in great detail in my upcoming book, “Slaying The Supplement Myths”. In the meantime, you might wish to view my video, “The Truth About Methyl Folate.”

Diseases: An underlying disease or predisposition to disease often increases the need for one or more nutrients that help reduce disease risk. The best examples of this are two major studies on the effect of vitamin E on heart disease risk in women. Both studies found no effect of vitamin E on heart disease risk in the whole population. However, one study reported that vitamin E reduced heart disease risk in the subgroup of women who were post-menopausal (when the risk of heart disease skyrockets). The other study found that vitamin E reduced heart attack risk in the subgroup of women who had pre-existing heart disease at the beginning of the study.

Finally, if you look at the diagram closely, you will notice a red circle in the middle. When two or three of these factors overlap, that is the “sweet spot” where supplementation is almost certain to make a difference and it may be a good idea to use supplements for cardiovascular health.

Is This A Question Of “Garbage In, Garbage Out”?

supplements for cardiovascular health garbage in outUnfortunately, most clinical studies focus on the “Does everyone benefit from supplementation question?” rather than the “Who benefits from supplementation?” question.

In addition, most clinical studies of supplementation are based on the drug model. They are studying supplementation with a single vitamin or mineral, as if it were a drug. That’s unfortunate, because vitamins and minerals work together synergistically. What we need are more studies of holistic supplementation approaches.

Until these two things change, most supplement studies are doomed to failure. They are doomed to give negative results. In addition, meta-analyses based on these faulty supplement studies will fall victim to what computer programmers refer to as “Garbage In, Garbage Out”. If the data going into the analysis is faulty, the data coming out of the study will be equally faulty. It won’t be worth the paper it is written on. If you are looking for personal guidance on supplementation, this study falls into that category.

 

Should We Use Supplements For Cardiovascular Health?

 

If you want to know whether supplements decrease heart disease risk for everyone, this meta-analysis is clear. Folic acid may decrease the risk of stroke and heart disease. A B complex supplement may decrease the risk of stroke. All the other supplements they included in their analysis did not decrease heart disease risk, but the analysis did not include vitamin E and/or omega-3s.

However, if you want to know whether supplements decrease heart disease risk for you, this study provides no guidance. It did not ask the right questions.

I would be remiss, however, if I failed to point out that we know healthy diets can decrease heart disease risk. In the words of the authors: “The recent science-based report of the U.S. Dietary Guidelines Advisory Committee, also concerned with [heart disease] risk reduction, recommended 3 dietary patterns: 1) a healthy American diet low in saturated fat, trans fat, and meat, but high in fruits and vegetables; 2) a Mediterranean diet; and 3) a vegetarian diet. These diets, with their accompanying recommendations, continue the move towards more plant-based diets…” I cover the effect of diet on heart disease risk in detail in my book, “Slaying The Food Myths”.

 

The Bottom Line

 

You have probably seen the recent headlines proclaiming: “Vitamin and Mineral Supplements Don’t Lower Heart Disease Risk.” The study behind the headlines was a meta-analysis of 127 randomized control trials looking at the effect of supplementation on heart disease risk and mortality.

  • The headlines qualify as “fake news” because:
    • The study found that folic acid decreased stroke and heart disease risk, and B vitamins decreased stroke risk. Somehow the headlines forgot to mention that.
    • The study found that multivitamins, vitamin D, calcium, and vitamin C had no effect on heart disease risk. These are nutrients that were unlikely to decrease heart disease risk to begin with.
    • The study did not include vitamin E and omega-3s. These are nutrients that are likely to decrease heart disease risk when the studies are done properly.
  • The authors of the study stated that a major weakness of their study was that that randomized control studies included in their analysis were short term, whereas longer duration studies might be required to fully capture chronic disease risk.
  • The study behind the headlines is of little use for you as an individual because it asked the wrong question.
  • Most clinical studies focus on the “Does everyone benefit from supplementation question?” That is the wrong question. Instead we need more clinical studies focused on the “Who benefits from supplementation?” question. I discuss that question in more detail in the article above.
  • In addition, most clinical studies of supplementation are based on the drug model. They are studying supplementation with a single vitamin or mineral, as if it were a drug. That’s unfortunate, because vitamins and minerals work together synergistically. What we need are more studies of holistic supplementation approaches.
  • Until these two things change, most supplement studies are doomed to failure. They are doomed to give negative results. In addition, meta-analyses based on these faulty supplement studies will fall victim to what computer programmers refer to as “Garbage In, Garbage Out”. If the data going into the analysis is faulty, the data coming out of the study will be equally faulty. It won’t be worth the paper it is written on. If you are looking for personal guidance on supplementation, this study falls into that category.
  • If you want to know whether supplements decrease heart disease risk for everyone, this study is clear. Folic acid may decrease the risk of stroke and heart disease. A B-complex supplement may decrease the risk of stroke. All the other supplements they included in their analysis did not decrease heart disease risk, but they did not include vitamin E and/or omega-3s in their analysis.
  • If you want to know whether supplements decrease heart disease risk for you, this study provides no guidance. It did not ask the right questions.
  • However, we do know that healthy, plant-based diets can decrease heart disease risk. I cover heart healthy diets in detail in my book, “Slaying The Food Myths.”

 

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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