Posts Tagged vitamins

Vitamins and Cancer Risk

One of the greatest triumphs of marketing over evidence was the incredible rise of vitamin supplement use in the 20th century. Supplement makers successfully created a “health halo” around vitamins, and taking your vitamins became a virtue, something mothers told their children to do. The evidence, however, does not tell such a simple story.

In recent years it has become increasingly apparent that there are unintended consequences to taking vitamin supplements, and in fact there may be a net negative health effect. This is especially true for those who are healthy and don’t need vitamins, and for those who exceed the recommend dosages.

A recent review of the last 20 years of literature on the subject, presented at the American Association for Cancer Research 2015 meeting, found an overall increased risk of cancer among vitamin users. Dr. Tim Byers presented the study, which echoes the result of a 2012 review that he and others published. He specifically refers to two famous studies showing an increased risk of cancer from vitamins.

The 2011 SELECT trial found an overall increased risk of prostate cancer among men taking vitamin E. (more…)

Posted in: Herbs & Supplements, Nutrition

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Naturopathy vs. Science: Prenatal Vitamins


This is another post in the naturopathy versus science series, where a naturopath’s medical advice is assessed against the scientific evidence. Today’s topic is brought to you by Toronto naturopath Shawna Darou, who recently published her evaluation of prenatal vitamins.

Vitamin supplementation is unnecessary for the vast majority of people. You wouldn’t know this walking through a drug store, where you’ll usually find an entire aisle packed with supplements. Alternative health providers like naturopaths tend to be strong supporters of supplementation, but this advice seems to be based mainly on the belief that “vitamins are magic” rather than good science. The best research hasn’t established a strong evidence base for taking  supplements. We definitely need vitamins in our diet to live. But that’s where we should be getting those vitamins – from our food, instead of from pills. If you eat a reasonable and balanced diet, and have no medical conditions that require special consideration, vitamin supplementation won’t offer meaningful health benefits. In the absence of any deficiency, vitamin supplements seem to be useless at best and harmful at worst. (more…)

Posted in: Naturopathy

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More evidence that routine multivitamin use should be avoided

If scientific evidence guides our health decisions, we will look back at the vitamin craze of the last few decades with disbelief. Indiscriminate use is, in most cases, probably useless and potentially harmful. We are collectively throwing away billions of dollars into supplements, chasing the idea of benefits that have never materialized. Multivitamins are marketed with a veneer of science but that image is a mirage – rigorous testing doesn’t support the health claims. But I don’t think the routine use of vitamins will disappear anytime soon. It’s a skillfully-marketed panacea that about half of us buy into.

Not all vitamin and mineral supplementation is useless. They can be used appropriately, when our decisions are informed by scientific evidence: Folic acid prevents neural tube defects in the developing fetus. Vitamin B12 can reverse anemia. Vitamin D is recommended for breastfeeding babies to prevent deficiency. Vitamin K injections in newborns prevent potentially catastrophic bleeding events. But the most common reason for taking vitamins isn’t a clear need, but rather our desire to “improve overall health”. It’s deemed “primary prevention” – the belief that we’re just filling in the gaps in our diet. Others may believe that if vitamins are good, then more vitamins must be better. And there is no debate that we need dietary vitamins to live. The case for indiscriminate supplementation, however, has never been established. We’ve been led to believe, through very effective marketing, that taking vitamins is beneficial to our overall health – even if our health status is reasonably good. So if supplements truly provide real benefits, then we should be able to verify this claim by studying health effects in populations of people that consume vitamins for years at a time. Those studies have been done. Different endpoints, different study populations, and different combinations of vitamins. The evidence is clear. Routine multivitamin supplementation doesn’t offer any meaningful health benefits. The parrot is dead. (more…)

Posted in: Herbs & Supplements, Science and Medicine

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Do vitamins prevent cancer and heart disease?

It is a triumph of marketing over evidence that millions take supplements every day. There is no question we need vitamins in our diet to live. But do we need vitamin supplements? It’s not so clear. There is evidence that our diets, even in developed countries, can be deficient in some micronutrients. But there’s also a lack of evidence to demonstrate that routine supplementation is beneficial. And there’s no convincing evidence that supplementing vitamins in the absence of deficiency is beneficial. Studies of supplements suggest that most vitamins are useless at best and harmful at worst. Yet the sales of vitamins seem completely immune to negative publicity. One negative clinical trial can kill a drug, but vitamins retain an aura of wellness, even as the evidence accumulates that they may not offer any meaningful health benefits. So why do so many buy supplements? As I’ve said before, vitamins are magic. Or more accurately, we believe this to be the case.

There can be many reasons for taking vitamins but one of the most popular I hear is “insurance” which is effectively primary prevention – taking a supplement in the absence of a confirmed deficiency or medical need with the belief we’re better off for taking it. A survey backs this up – 48% reported “to improve overall health” as the primary reason for taking vitamins. Yes, there is some vitamin and supplement use that is appropriate and science-based: Vitamin D deficiencies can occur, particularly in northern climates. Folic acid supplements during pregnancy can reduce the risk of neural tube defects. Vitamin B12 supplementation is often justified in the elderly. But what about in the absence of any clear medical need? (more…)

Posted in: Herbs & Supplements, Nutrition, Science and Medicine

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Who takes dietary supplements, and why?

If you’re a regular reader of this blog, I’ll bet you’re not a regular consumer of vitamins or supplements. I’m in that group. Aside from sporadic vitamin D in winter, I don’t take any vitamins or supplements routinely, nor do I give any to my children. Your reasons may be close to mine: There is little to no evidence suggesting that dietary deficiencies are widespread, nor is there good evidence to suggest that vitamin supplements are beneficial in the absence of deficiency. I don’t have any need for an other supplements, nor am I confident in the scientific evidence for many of them.This position of “no supplements” is a cautious and conservative one, but is based on a consideration of the scientific evidence. I view decisions about healthcare as evaluations of risk and benefit, and then cost if necessary. Given supplementation (with some exceptions) has no demonstrable benefits and, in some cases, a little risk, the odds favour not supplementing in most cases. Add in costs, and it’s even less attractive as a routine health strategy.

Yet a decision not to take vitamins or supplements regularly is becoming a minority position. Supplement use has grown over the past 40 years among Americans, with the National Health and Nutrition Examination Survey (NHANES) showing steadily increasing utilization among younger and older adults:

Posted in: Herbs & Supplements, Nutrition, Science and Medicine

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Andrew Weil/AAFP Article Rejected by Slate

I was asked to write an article for Slate, the on-line magazine, about Andrew Weil’s selection as the keynote speaker for the 2012 AAFP annual scientific assembly. The science and health editor, Laura Helmuth, was initially enthusiastic about what I wrote, but eventually decided not to publish it. Here is the initial draft of my article. My comments follow.

Original Draft of Article for Slate

The American Academy of Family Physicians picked Andrew Weil to be the keynote speaker at its annual scientific assembly October 16-20 in Philadelphia. What were they thinking? That’s like having an astrologer give the keynote speech at an astronomy meeting.

The AAFP stands for the best in conventional medicine, for the standard of care as determined by physicians and scientists. Weil doesn’t. The AAFP stands for evidence-based medicine. Weil doesn’t. (more…)

Posted in: Herbs & Supplements, Science and Medicine

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Antioxidants and Exercise: More Harm Than Good?

Multivitamin supplementation has been getting a rough ride in the literature, as evidence emerges that routine supplementation for most is, at best, unnecessary. Some individual vitamins are earning their own unattractive risk/benefit profiles: Products like folic acid, calcium, and beta-carotene all seem inadvisable for routine supplementation in the absence of deficiency or medical indication. Vitamin E, already on the watch list,  looks increasingly problematic, with data recently published confirming the suspected association of supplementation with an elevated risk of prostate cancer.

Reading through the vitamin posts here at SBM, one issue comes through repeatedly: The danger of assuming therapeutic benefits in the absence of confirmatory evidence. Vitamin supplement have the patina of safety and of health, a feature that’s reinforced when you purchase them: You don’t need a prescription, you don’t get counseled on their use, and there isn’t a long list of frightening potential side effects to accompany the product. You can pull a bottle off the shelf, and take any dose you want. After all, how harmful can vitamins be when you can buy 5 pounds of vitamin C at a time, or vitamin E capsules in a 1000-pack?  But the research signals seem to be getting stronger, and most are pointing in the same direction: what we though we knew about antioxidants was based on simplistic hypotheses about nutrition and health. And while we thought we were doing ourselves good with antioxidant supplements, we may have been doing harm. (more…)

Posted in: Herbs & Supplements, Science and Medicine

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Vitamins and Mortality

The discovery of various vitamins – essential micronutrients that cause disease when deficient – was one of the great advances of modern scientific medicine. This knowledge also led to several highly successful public health campaigns, such as vitamin-D supplementation to prevent rickets.

Today vitamins have a deserved reputation for being an important part of overall health. However, their reputation has gone beyond the science and taken on almost mythical proportions. Perhaps it is due to aggressive marketing from the supplement industry, perhaps recent generations have grown up being told by their parents thousands of times how important it is to take their vitamins, or eat vitamin-rich food. Culture also plays a role – Popeye eating spinach to make himself super strong is an example this pervasive message.

Regardless of the cause, the general feeling is that vitamins are all good – they are not only important for health, they promote health. Many people take vitamin supplements on the idea that more is better, or for nutritional “insurance” to make sure they are getting enough of every vitamin.


Posted in: Nutrition

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Autism and Prenatal Vitamins

Science has found no evidence that vaccines cause autism; but the true cause(s) of autism have not yet been determined. So far the available evidence has pointed towards a largely genetic cause with possible interaction with environmental factors. A new study supports that interpretation. It also supports previous evidence that autism is triggered prior to birth, rather than at the time of vaccinations.

Schmidt et al. published a study in Epidemiology on May 23, 2011, entitled “Prenatal Vitamins, One-carbon Metabolism Gene Variants, and Risk for Autism.” It was a population-based case control study of 566 subjects comparing a group of autistic children to a matched control group of children with normal development. They looked at maternal intake of prenatal vitamins in the 3 months before conception and the first month of pregnancy, and they looked for genotypes associated with autism. They found that mothers who didn’t take prenatal vitamins were at greater risk of having an autistic child, and certain genetic markers markedly increased the risk. There was a dose/response relationship: the more prenatal vitamins a woman took, the less likely she would have an autistic child. There was no association with other types of multivitamins, and no association with prenatal vitamin intake during months 2-9 of pregnancy. (more…)

Posted in: Neuroscience/Mental Health, Nutrition

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Antioxidant Supplements for Macular Degeneration

Age-related macular degeneration (AMD) is one of the major causes of visual impairment in the elderly: it affects central vision, impairing the ability to read and recognize faces while preserving some peripheral vision. It comes in two forms: wet and dry. Dry macular degeneration is by far more common, but wet macular degeneration, involving the proliferation of blood vessels, is more severe. 

There is evidence that antioxidant vitamin supplementation may slow the progression of the dry type when it is already established and moderately severe, but the published evidence does not support the use of these supplements for prevention or for patients with early stages of the disease. Some people are using it for prevention, but there is concern that the risks might exceed any benefit. Of more concern, it appears that a manufacturer’s (Bausch & Lomb’s) advertising has gone way beyond the available evidence.  (more…)

Posted in: Herbs & Supplements, Ophthalmology

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