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What scientists do and donít know about supplements (2018-04-11)

Harvard epidemiologist JoAnn Manson is working on two trials aimed at measuring the effectiveness of dietary supplements.
JoAnn Manson, Harvard Medical Schoolís Michael and Lee Bell Professor of Womenís Health, professor of epidemiology at the Harvard T.H. Chan School of Public Health, and chief of the Division of Preventive Medicine at Brigham and Womenís Hospital, has made a career of studying population health.

Research studies on vitamins have often had discrepant findings.
Thatís partly because some studies are randomized trials while others are observational.

Observational studies look at people who choose to take supplements, and examine their risk of heart disease, cancer, or other outcomes.

In contrast, in a randomized clinical trial, people agree to be assigned at random to take vitamins versus a placebo.

The different studies tend to provide different results for dietary supplements, but often the media does not make a distinction between the two.

Observational studies tend to show that people who choose to take supplements are healthier, but that may be because they are more health-conscious and also have healthier diets and healthier lifestyles.

There can be selection for more health-conscious people who are also compliant with taking supplements long-term, as well as confounding by other lifestyle practices, such as physical activity and diet.

The randomized clinical trials avoid bias from selection and confounding factors, and they tend to show little, if any, benefit of these supplements in healthy individuals.
And the randomized trials have also identified risks.

Randomized trials of beta-carotene show increased risk of lung cancer in smokers, randomized trials of vitamin E show increased risk of heart failure, bleeding-related strokes, prostate cancer, and even all-cause mortality in some studies.
Thereís also some concern about selenium in high doses.

So itís a very confusing literature because the observational studies and randomized trials have provided some discrepant results while the public is bombarded with hype about supplements in the media and advertising.

That said, the observational studies do have the advantage of being able to assess long-term use ó over decades ó while randomized trials tend to be shorter, often less than five years, due to their higher cost.

JoAnn Manson is now analyzing the data and finishing up the vitamin D and omega-3 trial VITAL.

Thatís a large-scale, randomized trial of vitamin D with and without omega-3 fatty acids, or fish oil.

There are four treatment groups, more than 25,000 participants nationwide, and researchers are looking at each of these interventions for prevention of cancer and cardiovascular disease.

They are also looking at cognitive function, diabetes, autoimmune diseases, and a number of other disorders.

So they are testing these very commonly used dietary supplements for their efficacy and safety over an average of five years.

They are also doing a large-scale, randomized trial of multivitamins and cocoa flavonol supplements, the COSMOS trial.

Thereís been only one previous large-scale, randomized trial of multivitamins.
That was in men, the Physiciansí Health Study II, and researchers are now testing it in both men and women.

Researchers are looking at what they think are promising supplements.
They are trying to identify dietary supplements that are effective and have a favorable benefit/risk profile.

People are generally encouraged to get vitamins and minerals from a healthy, well-balanced diet.

Micronutrients are better absorbed through the diet and a person will receive many other beneficial components besides these micronutrients.

And through the diet, you get the optimal biological ratio of vitamins and minerals as opposed to a mega-dose of a particular supplement that can cause harm and may interfere with the absorption or bioavailability of other vitamins and minerals.

If someone is really concerned about their diet, theyíre not having fruits and vegetables for whatever reason, theyíre eating a lot of processed foods ó which actually can strip foods of vitamins and minerals and healthful micronutrients ó and they donít think they can improve or modify their diet, then itís reasonable to take a multivitamin or other vitamin-mineral supplement as a form of insurance.

However, itís still not a substitute for a healthy diet.
Itís not going to be as good as having whole foods, avoiding processed foods, getting benefits like fiber, polyphenols, and phytochemicals from fruits and vegetables and whole grains.
Itís really important to have a healthful diet regardless.

Older adults often have a poorer diet. They may also have a problem with absorption of some vitamins and minerals.

The main ones to think about are B12, calcium, and vitamin D.

B12 deficiency can be a problem, especially with pernicious anemia.

With calcium and vitamin D, researchers encourage food sources, but supplements may be necessary ó some people are lactose-intolerant or donít eat dairy products.

Avoid excess amounts of calcium supplements because theyíve been linked to an increased risk of kidney stones.

Vitamin D has also been implicated in heart health, cognitive health, and reducing risk of cancer and diabetes.
Thereís no definitive evidence yet.

Itís very difficult for the public to separate fact from fiction, and understand what is just hype and marketing and promotion as opposed to actual evidence and facts.

For more information
Vitamin and Mineral SupplementsWhat Clinicians Need to Know
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The Harvard Gazette
Weíre in the dark on dietary supplements. Sheís working to change that.
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The Harvard Medical School
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The Harvard T.H. Chan School of Public Health
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Brigham and Women's Hospital
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MDN