- These diets and supplements may not really protect the heart
- Heart Health and Multivitamins
- Who needs multivitamins?
- So what should you do to stay healthy?
- Past evidence on multivitamins
- Vitamin D is good for the bones, but what about the heart?
- Effects of Nutritional Supplements and Dietary Interventions on Cardiovascular Outcomes
- Do multivitamins make you healthier?
- What we know about multivitamins so far
These diets and supplements may not really protect the heart
Doctors often recommend certain dietary interventions — such as following a Mediterranean-type diet or cutting salt intake — in the interest of protecting heart health. On top of this, many individuals believe that dietary supplements will help them stay healthy.
Share on PinterestCan supplements and dietary interventions protect the heart? Not according to a new meta-analysis.
Common knowledge has it that diet and lifestyle play an important role in supporting a person’s physical health and overall well-being.
That is why doctors may advise their patients to modify their diets and lifestyle habits by making them more conducive to good health.
In particular, dietary interventions can allegedly help individuals safeguard their cardiovascular health, preventing heart disease and events such as strokes.
Dietary guidelines for people in the United States advise that people adhere to healthful diets, such as a vegetarian diet or the Mediterranean diet, which is rich in vegetables, legumes, and lean meat.
On a related note, many individuals believe that taking dietary supplements can enhance different aspects of their health, including heart health, although recent studies have contradicted this assumption.
Now, a meta-analysis by researchers from different collaborating institutions — including The Johns Hopkins School of Medicine in Baltimore, MD, West Virginia University in Morgantown, and Mayo Clinic in Rochester, MN — suggests that many interventions and even more supplements may have no protective effect for the heart, and some may even harm cardiovascular health.
The review — the first author of which is Dr. Safi Khan from West Virginia University — appears in Annals of Internal Medicine.
In their research, Dr. Khan and team analyzed the data from 277 randomized controlled trials that had involved almost 1 million participants between them. They looked at the effects of 16 nutritional supplements and eight dietary interventions on cardiovascular health and mortality.
The supplements that they took into consideration were: selenium, multivitamins, iron, folic acid, calcium, calcium plus vitamin D, beta carotene, antioxidants, omega-3 long-chain polyunsaturated fatty acids, and vitamins A, B complex, B-3, B-6, C, D, and E.
The dietary interventions included: modified dietary fat, reduced salt (in people with normal and high blood pressure), reduced saturated fat, Mediterranean diet, reduced dietary fat, higher intake of omega-6 polyunsaturated fatty acids, and higher intake of omega-3 alpha-linolenic acid.
Dr. Khan and colleagues did find that some of these interventions had a positive effect. For instance, eating less salt may reduce the risk of premature death in people with a normal blood pressure, although only with moderate certainty.
Moreover, they concluded that omega-3 long-chain polyunsaturated fatty acids protected against heart attacks and coronary heart disease and that there was an association between folic acid intake and a slightly lower risk of stroke, but all with only low certainty.
At the same time, however, other supplements and interventions seemed to either have no effect or be downright harmful.
The researchers found that taking multivitamins, selenium, vitamin A, vitamin B-6, vitamin C, vitamin D, vitamin E, calcium, folic acid, and iron did not significantly protect against cardiovascular problems and early death. They also noted that following a Mediterranean diet, reducing saturated fat intake, modifying fat intake, reducing dietary fat intake, and increasing the quantity of dietary omega-3 and omega-6 were not beneficial.
In fact, people who took calcium and vitamin D supplements together actually had a higher risk of experiencing a stroke, although only with moderate certainty.
However, in their paper, the investigators admit that “these findings are limited by suboptimal quality of the evidence.
” They are referring to the fact that, due to the different methodologies of the studies that they assessed, they “could not analyze interventions according to important subgroups, such as sex, body mass index [BMI], lipid values, blood pressure thresholds, diabetes, and history of [cardiovascular disease].”
Yet, they argue that their current review paves the way to better care and stronger research into the helpfulness and value of different dietary interventions:
“This study can help those who create professional cardiovascular and dietary guidelines modify their recommendations, provide the evidence base for clinicians to discuss dietary supplements with their patients, and guide new studies to fulfill the evidence gap.”
The authors of the accompanying editorial, doctors Amitabh Pandey and Eric Topol, both from the Scripps Research Translational Institute in La Jolla, CA, also emphasize that the quality of the data in many studies assessing the effects of dietary interventions and supplements on heart health can be questionable.
“[D]ifferences in geography, dose, and preparation — most studies rely on food diaries, which are a person’s memory of what they consumed — raise questions about the veracity of the data,” they write.
“Perhaps, however, the biggest difference that needs to be considered in the future is the individual,” they add, advising that future research should pay more attention to the differences among participants.
Heart Health and Multivitamins
A new study on multivitamins and heart health reinforces what medical experts have been saying for years: They don’t do much to prevent cardiovascular disease.
The report is a meta-analysis of previous research. It looked at 18 different studies that spanned more than 16 years. In all, about 2 million people were involved. In some of the studies, the participants were followed for 12 years.
Researchers from the University of Alabama at Birmingham (UAB) published their report in the journal Circulation: Cardiovascular Quality and Outcomes. The authors say their report confirms previous findings on the role that vitamins play in improving heart health.
Who needs multivitamins?
The general concept that multivitamins and supplements in the form of pills are beneficial to your health isn’t wrong per se. For example, pregnant women, children, and specific adult populations, such as people with cancer, should take certain types of vitamins. At issue here is whether multivitamins can reduce the risk of cardiovascular disease.
“I hope our study findings help decrease the hype around multivitamin and mineral supplements and encourage people to use proven methods to reduce their risk of cardiovascular diseases,” said study lead author Dr. Joonseok Kim, assistant professor of medicine/cardiology in the Department of Medicine at UAB, in a press release.
So what should you do to stay healthy?
The best defense for good heart health is a healthy lifestyle, according to Dr. Stephen Kopecky, a cardiologist at the Mayo Clinic in Rochester, Minnesota. That includes consistent exercise, adequate sleep, and a diet that relies on whole foods, with an emphasis on fruits and vegetable.
The misperception that multivitamins can mitigate unhealthy eating, in particular, continues to exist in the public consciousness. Kopecky hopes this new meta-analysis can better educate the public about multivitamins and heart heath.
“I’m in full agreement with the study,” he told Healthline.
Kopecky said the reason people view multivitamins and supplements as a means to improve their heart health is simple — people want convenience.
“We want to take a pill that will negate our lifestyle shortcomings,” Kopecky said.
Dr. Zhaoping Li, director at the UCLA Center for Human Nutrition, agrees. She said someone who has heart disease but still has a sedentary lifestyle, and a diet filled with lots of fat, salt, and sugar, won’t see an improvement in their heart health because they take a daily multivitamin.
“I’m not sure vitamins are going to reverse that,” she told Healthline.
There is one exception that both Kopecky and Li point to. In the instance of cardiovascular disease, they do support taking omega-3 fatty acids in the form of fish oil supplements.
This type of unsaturated fatty acid may decrease triglycerides, lower blood pressure, reduce blood clotting, decrease the risk for stroke and heart failure, and reduce irregular heartbeats.
This new report didn’t focus on studies that included fish oil. It only looked at the studies that revolved around multivitamins, vitamins D and C, and calcium. It’s not the first time a study has shown multivitamins don’t improve heart health.
Past evidence on multivitamins
A 2012 study on nearly 2,000 men showed no evidence that a daily multivitamin could reduce a major cardiovascular event. A U.S. taskforce also said there is insufficient evidence to conclude that multivitamins can prevent cardiovascular disease and cancer.
Even the country’s leading health institutions such as the Mayo Clinic and Johns Hopkins Hospital have devoted pages on their websites to dispute the notion that multivitamins can boost heart health. But despite the attempts of medical organizations and the U.S. government to counter this misinformation, their words continue to go unheeded.
Around 76 percent of Americans take a dietary supplements, according to a 2017 survey by the Council for Responsible Nutrition.
Roughly 42 percent said they were taking supplements for overall health and about 26 percent said it was to improve heart health. According to the National Institutes of Health (NIH), in 2014 Americans spent $36.
7 billion on dietary supplements, of which $5.7 billion dollars went toward multivitamins.
The multivitamin and supplement industry is regulated by the Dietary Supplement Health and Education Act passed by Congress in 1994. The FDA is the governing body. The act states that makers can’t make a claim that specific supplements can reduce pain or improve heart health, according to the agency’s website.
However, the act doesn’t require manufacturers to demonstrate the safety of a given supplement before bringing it to market. Additionally, the FDA can only ban a supplement if it finds proof that it’s dangerous.
Both Kopecky and Li said they usually don’t encourage their patients to take multivitamins. The only exception for both doctors is if a patient with heart disease has difficulty making their diet nutritionally diverse.
“If they’re already healthy, I don’t necessarily,” Li said. “For people who don’t take in adequate fruits and vegetables, I do recommend it.”
Kopecky noted that he does take the time to consult his patients about the importance diet plays in their overall health.
He encourages his patients to eat oat bran in the form of oatmeal, which has been proven to lower cholesterol.
He also recommends his patients take a daily dose of soluble fiber, which also helps to keep cholesterol from getting absorbed into the blood stream. But Kopecky added that the hard part is making all of the information stick.
“It’s hard to meet someone and in 20 or 30 minutes change their lifestyle,” he said.
Vitamin D is good for the bones, but what about the heart?
(BrianAJackson, Getty Images)
Vitamin D plays an important role in overall health, but if you've been taking supplements to strengthen your heart, recent research may disappoint you.
Although vitamin D is best known for its role in developing strong bones, low blood levels have been linked to an increased risk of heart attacks and strokes. But recent studies found vitamin D supplements did not bolster heart health.
“Initially there was a lot of enthusiasm for vitamin D treatment for cardiovascular disease, and this was observational data,” said Dr. Erin Michos, an associate professor of medicine at Johns Hopkins School of Medicine in Baltimore.
“The link was that individuals who have low blood levels of vitamin D have increased risk of a lot of bad things,” she said, “including increased risk of heart attacks, stroke, heart failure and even increased risk of death. It was a really strong association.”
But associations don't always mean causation. In June, an analysis in JAMA Cardiology that included 21 clinical trials showed vitamin D supplements do not reduce the risk of having or dying from a heart attack or stroke.
A highly publicized 2018 study called VITAL was part of that analysis. Researchers studied more than 25,000 people across the United States taking either a daily vitamin D supplement of 2,000 IUs or a placebo.
“The key question is, do you need more vitamin D than what is required for bone health in order to have optimal heart health?” said Dr. JoAnn Manson, the lead author of VITAL, published in the New England Journal of Medicine. “And the answer, available research, seems to be no.”
Manson, a professor of medicine at Harvard Medical School and chief of preventive medicine at Brigham and Women's Hospital in Boston, said even study participants with lower levels of vitamin D at the start of the study did not see a decreased risk of heart attack or stroke from supplementation.
“There is some promising research that vitamin D may reduce the risk of heart failure, and that requires additional research,” Manson said. “However, the evidence to date is that moderate to high vitamin D supplementation does not appear to reduce the risk of heart attacks or strokes.”
VITAL researchers soon will report results on other outcomes, including heart failure, diabetes, cognition and autoimmune disorders, she said.
Vitamin D is created when people are exposed to sunlight and can also be found in a handful of foods, including fatty fish such as salmon and fortified dairy products. It helps the body absorb calcium and phosphorous and protects against bone loss.
Because vitamin D is primarily produced through skin synthesis after exposure to sunlight, the VITAL study also focused on the effect of supplements on people with darker skin pigmentation; more than 5,000 of the 25,871 participants in the study were African American.
“We had a very strong interest in determining whether vitamin D might have a greater benefit in African Americans,” Manson said. “We did see some signals that there might be some benefit in terms of cancer reduction – it was not statistically significant – but for heart health, we did not see an added benefit race or ethnicity.”
Manson said these latest findings also are important because people who take megadoses of vitamin D supplements, such as more than 10,000 IUs a day, without a true medical need may be doing themselves harm.
“There has been some concern that very high doses of supplementation could increase the risk of blood vessel calcification and could actually have adverse effects,” she said. “So, an important principle is that more is not necessarily better, and in fact, mega-dosing on vitamin D can have some harmful effects.”
Michos said people who take vitamin supplements despite not having a diagnosed deficiency – the “worried well” – would be better served by focusing on living a healthier lifestyle instead.
“People are just wasting their money on supplements, hoping for this panacea benefit,” Michos said. “Really, for most things, you can get all the nutrients you need from a heart-healthy diet … and from getting normal physical activity and maintaining a healthy body weight.
“People are trying to find a magic bullet in a pill form, and it's just not there.”
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Effects of Nutritional Supplements and Dietary Interventions on Cardiovascular Outcomes
Current U.S. dietary guidelines recommend several healthy eating patterns, including U.S., Mediterranean, and vegetarian diets (1).
Although the guidelines recognize the occasional need for nutritional supplementation or food fortification for specific nutrients that may be consumed in inadequate amounts, they do not recommend routine use of any dietary supplement to reduce risk for cardiovascular disease (CVD) or other chronic diseases.
Despite these recommendations, most U.S. adults use supplements to enhance their diets, with uncertain health benefits (2, 3). From 1999 to 2012, the NHANES (National Health and Nutrition Examination Survey) reported that 52% of participants used at least 1 and 10% used at least 4 dietary supplements (4).
From 2011 to 2014, the NHANES reported that among participants aged 60 years or older, 70% used at least 1 and 29% used at least 4 supplements, and 41% of supplement takers reported that they did so to improve their overall health (5).
In 2013, the U.S. Preventive Services Task Force conducted a systematic review of the utility of vitamin and mineral supplements for CVD prevention and found little evidence to support use (6). More recently, Jenkins and colleagues published a meta-analysis of randomized controlled trials (RCTs) of dietary supplements published through October 2017 (7).
They found some stroke benefit conferred by folate; no CVD benefit for multivitamins, vitamin C, vitamin D, or calcium; and evidence for mortality harm for niacin and antioxidants. Since then, several landmark RCTs evaluating the efficacy of fish oils (8–10) and vitamin D (11, 12) for CVD prevention have been published, which add to the evidence level.
In addition, the quality of the evidence base of these various nutritional supplements and dietary interventions still needs to be evaluated to ascertain the confidence in their efficacy.
Thus, we performed a systematic review of existing meta-analyses of RCTs and generated an evidence map for efficacy of nutritional supplements and dietary interventions for CVD prevention.
We used PubMed, CINAHL, and the Cochrane Library from inception to March 2019 to find meta-analyses published in the English language about vitamins, minerals, dietary supplements or products, and dietary interventions using the following search terms: (*minerals OR *vitamins OR *diet AND *cardiovascular outcomes) and (meta-analy* OR metaanaly* OR systematic review*). After selecting systematic reviews on the basis of a priori criteria, the search timelines of the systematic reviews were reviewed for recency and an updated search for RCTs published in English was performed starting from the end date of searches from selected systematic reviews until March 2019 (Supplement Table 1). Additional sources included Web sites of major cardiovascular and medicine journals (www.onlinejacc.org; https://academic.oup.com/eurheartj; www.ahajournals.org/journal/circ; www.nejm.org; https://jamanetwork.com; and http://annals.org/aim) and bibliographies of relevant studies. We also searched ClinicalTrials.gov (10 March 2019) to check for publication bias and to identify any new or ongoing trials (Supplement Table 2).
The prespecified inclusion criteria were meta-analyses of RCTs assessing efficacy of nutritional supplements (vitamins, minerals, dietary supplements) or dietary interventions in adult participants (≥18 years) that report effect estimates for all-cause mortality and cardiovascular outcomes of interest and were written in English. Because the nutritional and dietary recommendations are universal, there were no restrictions on baseline health status, race, or sex of the participants.
Meta-analyses of observational studies or those reporting efficacy of interventions on surrogate or other outcomes, such as blood pressure, lipid values, inflammatory markers, electrolytes, renal values, or quality-of-life indicators, were excluded.
Systematic reviews reporting meta-analyses of both clinical trials and observational studies were reviewed for data related to RCTs only. In case of multiple meta-analyses of the same intervention and outcome, we preferred the most recent, largest, and updated meta-analysis.
However, the competing meta-analyses were screened for any additional trials not included in the selected meta-analysis.
After removing duplicates and following the selection criteria, we screened the retrieved articles at the title and abstract level and then at the methods level.
The search, selection, and abstraction processes were performed independently by 2 authors (M.U.K. and S.V.).
Any discrepancies were resolved by discussion and mutual consensus, referring to the original study or third-party review (S.U.K.).
We first extracted information from eligible meta-analyses on first author, journal, year of publication, interventions, outcomes of interest, number of trials, whether an appropriate study search and selection criteria was reported, method of pooling estimates (fixed or random effects), methods of detecting publication bias, measure of heterogeneity, and risk-of-bias assessment.
Second, we generated the pool of clinical trials by identifying trials contained in the selected meta-analyses and screening competing meta-analyses for additional trials and trials published after the selected meta-analyses (Supplement Table 3).
Among new clinical trials for omega-3 long-chain polyunsaturated fatty acid (LC-PUFA) (8–10), we excluded REDUCE-IT (Reduction of Cardiovascular Events With EPA-Intervention Trial) (9) because icosapent ethyl, a highly purified form of eicosapentaenoic acid (EPA), does not qualify as a dietary supplement according to the Dietary Supplement Health and Education Act of 1994 (13).
Third, after removing duplicates, we abstracted data on trial name, first author, year, intervention, outcomes, raw events, and sample sizes for each group.
The main outcome of interest was all-cause mortality. The secondary outcomes were cardiovascular mortality, myocardial infarction (MI), stroke, and coronary heart disease (CHD).
Two independent reviewers (V.O. and M.S.K.
) assessed the methodological quality of meta-analyses on specific potential factors that may affect the validity of summary estimates—that is, appropriate search and selection criteria, number of trials and participants included, risk-of-bias assessment of included trials, method of pooling the estimates, assessment of publication bias, and degree of heterogeneity (Supplement Table 4).
We created an evidence map that displays the plausible benefits of each intervention and the certainty of the evidence (14).
The certainty of the evidence was evaluated using the GRADE (Grading of Recommendations Assessment, Development and Evaluation) approach (GRADEpro GDT) (https://gdt.gradepro.
org/app/) (14) and was classified as high, moderate, low, or very low (Supplement Table 5). Two reviewers (V.O. and M.S.K.) performed these assessments under the supervision of a third reviewer (S.U.K.).
Estimates were pooled according to Mantel–Haenszel random-effects model. The Paule–Mandel method was used for reestimating outcomes. Hartung–Knapp/Sidik–Jonkman (HKSJ) small-sample adjustments were applied when the number of studies was less than 10 (15).
We used the modified HKSJ when meta-analyses only included 2 to 4 studies and tau2 = 0 because some of these meta-analyses produced abnormally narrow CIs. Effect sizes were reported as risk ratios (RRs) with 95% CIs. We used I2 statistics to estimate the extent of unexplained heterogeneity; I2 greater than 50% was considered a high degree of between-study heterogeneity.
We calculated the Egger regression test as an estimate of publication bias for any reanalysis that included at least 10 studies (16).
Statistical analyses were conducted using “meta,” version 4.9-4 (R Project for Statistical Computing), and “meta” commands from Stata, version 16 (Stata Corp). Statistical significance was set at 0.05 for all analyses except for the Egger regression test, which had a threshold less than 0.10 because of the test's limited statistical power.
The study received no funding.
Of 942 citations, after removing duplicates and screening at the title and abstract level we reviewed 140 full-text articles for eligibility.
We excluded 131 articles because they focused on nonrandomized studies, were not relevant, or were outdated, as well as 5 systematic reviews that assessed intake of nuts (17), fruits and vegetables (18), fiber (19), and green or black tea (20) and those focusing on low-carbohydrate and low-fat diets (21) that did not report cardiovascular outcomes of interest. Ultimately, we included 9 systematic reviews and 4 new RCTs for a total of 105 meta-analyses of 24 interventions (277 RCTs, 992 129 participants) (7, 22–29) (Figure 1). The interventions evaluated in the meta-analyses included 16 types of supplements (antioxidants, β-carotene, vitamin B complex, multivitamins, selenium, vitamin A, vitamin B3 or niacin, vitamin B6, vitamin C, vitamin E, vitamin D, calcium plus vitamin D, calcium, folic acid, iron, and omega-3 LC-PUFA) and 8 types of dietary interventions (Mediterranean diet and intake of reduced saturated fat, modified dietary fat, reduced dietary fat, reduced salt among hypertensive and normotensive participations, increased omega-3 α-linolenic acid [ALA], and increased omega-6 PUFA) (Supplement Table 6).
Figure 1. Evidence search and selection.
RCT = randomized controlled trial.
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All included studies were trial-level meta-analyses (7, 22–28), except the study by Mente and colleagues, which was a patient-level analysis of 4 studies (29) (Supplement Table 4).
All trial-level systematic reviews reported comprehensive search and selection criteria as well as quality assessment of studies by using the Cochrane Risk of Bias Tool (30).
Six systematic reviews primarily used random-effects models for meta-analyses, of which 4 used fixed-effects models for sensitivity analyses.
Two studies primarily used fixed-effects models, of which 1 selected a random-effects model only for estimates with an I2 greater than 50%. all trial-level analyses, only 2 did not assess publication bias, and 1 did not evaluate between-study variance because of the limited number of trials (
Do multivitamins make you healthier?
Harvard Men's Health Watch
Some experts say it's time to give up on daily multivitamins to preserve health, but others disagree. What should you do?
If you take a multivitamin, it's probably because you want to do everything you can to protect your health. But there is still limited evidence that a daily cocktail of essential vitamins and minerals actually delivers what you expect. Most studies find no benefit from multivitamins in protecting the brain or heart. But some Harvard experts think there is still hope.
“There are potential benefits and there are no known risks at this time,” says Dr. Howard Sesso, an associate professor of epidemiology at the Harvard School of Public Health. “It is worth considering a multivitamin as part of a healthy lifestyle.”
Caught between expert opinions, what do you do? Start with asking yourself why you would consider taking a multivitamin. If you suspect your diet is nutritionally lax, focus your efforts there.
What we know about multivitamins so far
Despite all the research on vitamins and health, we have only a handful of rigorous scientific studies on the benefits of what Dr. Sesso calls a “true” multivitamin: a pill that provides essential vitamins and minerals at the relatively low levels that the body normally requires.
The Physicians' Health Study II is the best study completed so far. It was the first and only large-scale randomized clinical trial to test a commonly taken multivitamin the ones most people take, containing the daily requirements of 31 vitamins and minerals essential for good health.
A large group of male physicians took either a multivitamin or a placebo pill for more than a decade. The results have been mixed, with modest reductions in cancer and cataracts, but no protective effect against cardiovascular disease or declining mental function. Is it safe?
Multivitamin advocates point to the lack of any strong proof that taking a multivitamin for many years is dangerous. “While I agree that the lihood of harm is small, the lihood of a clear health benefit is also very small—and also we have no clear proof yet of such benefit,” says Dr. Guallar, a scientist at the Johns Hopkins Bloomberg School of Public Health.
Dr. Sesso speaks for the optimists, who urge a wait-and-see approach. “Multivitamin supplementation is low risk and low cost, and it helps to fill potential gaps in the diet that people might have,” Dr. Sesso says. “These are compelling reasons to consider taking a multivitamin for cancer and eye disease that should be discussed with your physician.”
For now, you can take certain steps:
- Ask your doctor if you really need to take a multivitamin. Could you have a vitamin deficiency?
- Assess your diet. Do you eat as healthy as you could? Is anything lacking?
- Do you want expert nutritional advice? See a dietician. Also, Medicare beneficiaries get an annual “wellness” visit with their primary care providers.
- Do not take high doses of specific vitamins, especially A and E. These may actually be harmful.
Physicians' Health Study II
Researchers looked at the effect of long-term multivitamin use in healthy men on various aspects of health. Here is what they found:
Image: Yakobchuk/Getty Images
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