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Most dietary supplements do not
protect against heart attack and stroke
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Fish oil and folate might help, but calcium plus vitamin D may cause harm, according to new research.
https://www.nbcnews.com/health/heart-health/most-dietary-supplements-do-not-protect-against-heart-attack-stroke-n1027366#anchor-Whataboutdietsforhearthealth
July 8, 2019
Most dietary supplements do nothing to protect against heart attacks, stroke or deaths from heart disease, and some may even cause harm, according to a newpaper published Monday in the Annals of Internal Medicine.
Researchers at West Virginia University analyzed data on the effects of dietary supplements and dietary approaches from 277 previous studies that included almost one million people in total.
They found scant evidence that supplements improve cardiovascular outcomes, and the evidence that they did find was lacking in quality.
"The majority of supplements have no effect on improving survival or reducing the risk of heart attack or stroke," said study author Dr. Safi Khan, an assistant clinical professor of internal medicine at West Virginia University.
Please stop spending money on these supplements for the sake of improving cardiovascular health. Because they don't.
Still, the findings may do little to shake Americans' strong faith in supplements and vitamins. An estimated 3 out of 4 people in the United States take at least one dietary supplement, and Americans are projected to spend $32 billion on them this year alone.
But, according to Khan's review of the available science, it's largely a waste of money - at least when it comes to heart health.
"Please stop spending money on these supplements for the sake of improving cardiovascular health. Because they don't," Khan told NBC News.
Little benefit, but may cause harm
Though the researchers did find that fish oil offered some benefit in reducing the risk of heart attack and overall heart disease, and that folic acid was associated with a lower risk of stroke, they said the majority of supplements analyzed offered no benefits at all.
For example, they said, there was no evidence that multivitamins, antioxidants, iron or vitamins A and B had any impact on heart health.
And some of the research suggested the potential for harm. Taking calcium plus vitamin D, the researchers found, was associated with an increased risk for stroke.
It's not clear whether this increased risk is due to the supplements on their own, or the add-on of the supplements to a diet already rich in calcium and vitamin D. The Western diet, for example, "already has significant dietary fortification with calcium plus vitamin D," researchers from the Scripps Research Translational Institute in La Jolla, California, wrote in an accompanying editorial.
But this isn't the first time scientists have identified a link between calcium and cardiovascular risk: An earlier study from Johns Hopkins University found people who took calcium pills were more likely to develop plaque in their arteries than people who did not take them.
Consistent findings
Outside experts said the overall findings on supplements were consistent with what they're already telling patients.
"Except to prevent or correct specific deficiencies, or in specific circumstances such as folic acid supplements in early pregnancy to prevent neural tube defects, there is generally good agreement that dietary supplements should not be recommended to the general population," Susan Jebb, a professor of diet and population health at the University of Oxford, wrote in an email.
You can't just eat a crummy diet and then pop a pill and assume that's going to solve all the problems.
Dr. Pieter Cohen, an associate professor of medicine at Harvard Medical School, who was not involved in the new research, noted that in general, it's better to get nutrients from foods, not supplements, to avoid any potential risks.
But Steve Mister, president of the Council for Responsible Nutrition, a lobbying group that represents the supplement industry, said that people turn to nutrients in a capsule to fill gaps in their diet, not prevent heart disease.
"Taking dietary supplements and practicing healthy dietary patterns are essential ways for consumers to assure they are getting the recommended levels of nutrients essential for overall health and wellness," Mister wrote in a statement to NBC News.
Nutrition experts maintained that a diet full of vegetables and fruit is sufficient to meet recommended nutrient levels for most people.
"There's no easy answer," said Dr. Alice Lichtenstein, director of the Cardiovascular Nutrition Laboratory at Tufts University.
"You can't just eat a crummy diet and then pop a pill and assume that's going to solve all the problems," she said.
What about diets for heart health?
Supplements aside, the new research also found very little high-quality evidence that diets widely touted as heart healthy - including the Mediterranean diet - had any impact on heart health. In fact, the only dietary intervention that seemed to be beneficial was reducing salt intake, but only in people with normal blood pressure.
Cardiologists readily acknowledge that the science behind how food may impact heart disease is lacking, and suggest this is where researchers should focus their attention, rather than on supplements.
"There's a little bit of data on blood pressure reduction. But the studies don't measure the effect on stroke and myocardial infarction (heart attack)," Dr. Steven Nissen, chair of cardiovascular medicine at the Cleveland Clinic, said.
"How can you make good scientific decisions in the absence of high-quality, randomized controlled evidence? You can't do it," Nissen said. "I wish we had better studies."
The most robust study of diet's potential effect on cardiovascular disease was a 2013 study called Predimed. It made international headlines at the time, claiming the Mediterranean diet - rich in olive oil, nuts, fruit and vegetables - cut the risk for heart disease by a third. The benefit was found to be so huge that the study was stopped early so everyone could be made aware of the dramatic findings.
But the study was later retracted because of minor flaws in the way it was conducted. Last year, the researchers released a watered down version of their findings, writing that "the incidence of major cardiovascular events was lower among those assigned to a Mediterranean diet supplemented with extra-virgin olive oil or nuts than among those assigned to a reduced-fat diet." In other words, they still found a link between the Mediterranean diet and a reduced risk of cardiovascular outcomes.
But because of the flaws in the study, the researchers could not prove cause-and-effect.
Still, cardiologists generally do recommend diets that mostly resemble the Mediterranean diet.
"I tell my patients the best evidence we have is for the Mediterranean diet. And that limiting calorie consumption is useful because you want to keep your weight down," Nissen said.
"The bottom line is we just need more evidence."
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Supplements and Diets for Heart Health Show Limited Proof of Benefit
Some supplements may actually be harmful for cardiovascular health.
July 8, 2019
https://www.nytimes.com/2019/07/08/well/eat/supplements-and-diets-for-heart-health-show-limited-proof-of-benefit.html
Millions of Americans use dietary supplements and a variety of diets to protect their heart health. But a large new analysis found that there was strikingly little proof from rigorous studies that supplements and some widely recommended diets have the power to prevent heart disease.
The new research, published in the Annals of Internal Medicine, reviewed data from hundreds of clinical trials involving almost a million people and found that only a few of 16 popular supplements and just one of the eight diets evaluated had any noticeable effect on cardiovascular outcomes.
Folic acid, reduced salt diets and omega-3 fatty acids, the kind found in fish oil, showed some benefits. But the evidence was fairly weak. And at least one showed evidence of harm: Taking calcium with vitamin D increased the risk of stroke, possibly because it increases blood clotting and hardening of the arteries.
The findings are likely to elicit controversy and continued debate. But the researchers said one clear message from their analysis was that the more than half of Americans who use dietary supplements should be wary of claims that multivitamins and other supplements will improve their heart health.
"People who are taking these supplements for the sake of improving their cardiovascular health are wasting their money," said Dr. Safi U. Khan, an assistant professor at West Virginia University School of Medicine and the lead author of the new study.
The findings regarding supplements dovetail with the conclusions of a report by the United States Preventive Services Task Force, an influential group of health experts that reviewed vitamin and mineral supplements in 2013 and found little proof that they promote cardiovascular health. "This has been shown very consistently," Dr. Khan said.
The new study was exhaustive. The authors examined 24 supplements and diets by analyzing data from 277 trials of cardiovascular prevention involving a total of 992,000 people. To get conclusive answers, they selected only randomized controlled trials, in which people are randomly assigned to various interventions for a set period of time and which are considered the "gold standard" for testing treatments. Weaker data from observational studies, which can show only correlations and not cause and effect, were excluded.
Ultimately the researchers found a surprising lack of tangible benefits for almost everything they looked at, both supplements and diets.
Among the supplements that showed no evidence of cardiovascular protection were vitamins A, B, C, D and E, as well as beta-carotene, calcium, iron, antioxidants and multivitamins. While two supplements were found to have some benefit, folic acid and omega-3 fatty acids, there were important caveats.
Taking folic acid was found to lower the risk of stroke. But the finding was largely driven by research from China, where deficiencies of the vitamin are common. The researchers said it was not clear that people who take folic acid in America, where foods are fortified with it, will get the same benefit.
Fish oil, one of the most popular supplements in America, is widely used for its omega-3 fatty acids, which are anti-inflammatory. A recent clinical trial found that high-risk patients who took very large doses of Vascepa, a purified form of omega-3 that is available by prescription only, had a reduction in cardiovascular events. Another study found that supplementing with fish oil could benefit people who eat very little seafood. But the majority of trials involving fish oil have been disappointing. Dr. Khan and his colleagues concluded that there was only weak evidence at best that taking fish oil could prevent heart disease.
"This just reinforces that the supplement story is so shaky," said Dr. Eric Topol, a cardiologist and the founder of the Scripps Research Translational Institute, who wrote an editorial accompanying the new review. "Not only is there the potential for harm, but there's also no hard evidence for good."
When Dr. Khan and his co-authors looked at various diets recommended for cardiovascular prevention, they found a similar lack of solid evidence.
That was certainly the case for low-fat diets, which health authorities have recommended for decades as a way to lower cholesterol and heart disease risk.
Dr. Khan and his colleagues found that the most rigorous randomized trials provided no evidence that eating less fat, including saturated fat, had an impact on mortality or cardiovascular outcomes. Low-fat diets have largely fallen out of favor among health authorities in recent years, though the federal government's dietary guidelines still encourage people to limit their intake of foods rich in saturated fat, such as butter, meat and cheese.
One diet that remains highly touted by health authorities is the Mediterranean diet, with its abundance of whole grains, beans, nuts, fruits and vegetables and olive oil. While clinical trials have found that it reduces cardiovascular risk, some of the major ones have been flawed, and experts who have scrutinized the evidence for the diet have urged caution.
One of the largest and most publicized Mediterranean diet trials, called Predimed and published in 2013, found that it reduced heart attacks and strokes. But last year it was retracted because of methodological problems. The Predimed authors published a new analysis of their data, claiming their conclusions had not changed. But other Mediterranean diet trials have been embroiled in similar controversies. After analyzing data from all the relevant trials, Dr. Khan and his colleagues found that "the totality of evidence did not favor the Mediterranean diet for cardiovascular outcomes."
"It's not favorable or harmful," he added. "It's just a neutral diet from a cardiovascular perspective."
The one dietary intervention that seemed to have the most support from randomized trials was lowering salt intake, though the researchers graded the evidence only as having "moderate certainty." And there was nuance. Low-salt diets reduced mortality from all causes only in people with normal blood pressure. Among people with hypertension, lowering salt intake reduced deaths from heart disease but not from other causes.
Dr. Topol said that in his own clinic he sees a wide range of responses to salt intake. Some people are very sensitive to salt: A small increase in salty foods can have a pronounced effect on their blood pressure. But others can eat salt-laden meals and their blood pressure will hardly budge.
Dr. Topol said he finds diet studies hard to interpret because they rarely take into account the unique way that different people can have markedly different responses to dietary changes, whether it is cutting back on salt or avoiding fat or carbohydrates.
"The problem we have here is that all these studies essentially treat all people as one," he said. "I think that all these things are going to turn out to be quite heterogeneous. Maybe salt restriction really is beneficial for some, but we haven't defined the people yet that would drive that."
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