Q. I’ve heard that garlic supplements can boost heart health. Should I be taking them?
Garlic, known for its bold flavor and pungent aroma, has long been touted as a medicinal wonder, used in ancient cultures to prevent infections, improve athletic performance and even “cleanse” the arteries.
Today, garlic supplements are said to help reduce blood pressure and blood cholesterol levels and to slow plaque buildup in the arteries. Is that true?
There “are countless studies” suggesting that garlic supplements may provide cardiovascular benefits, said Dr. Donald D. Hensrud, a physician and associate professor of nutrition and preventive medicine at the Mayo Clinic. But the quality of those studies can vary, he said. And the data suggest that only certain people may benefit.
Here is what we know about what garlic supplements can do for you.
What the Research Suggests
Several meta-analyses conducted in recent years have found that garlic or its supplements may provide some heart benefits, especially for people with mild elevations in blood pressure and LDL (or “bad”) cholesterol.
In one meta-analysis published in January, for instance, researchers looked at data from 108 randomized controlled trials that involved more than 7,000 adults. They found that consuming raw, cooked or supplemental garlic improved cardiovascular risk factors like LDL cholesterol, triglycerides and blood pressure — especially in those with elevated cardiovascular risk.
The evidence, especially on the blood pressure and LDL cholesterol benefits, “is pretty compelling” said Dr. JoAnn Manson, a professor of medicine at Harvard Medical School who studies dietary supplements.
Other research on adults with cardiovascular risk has found that garlic supplements may slow or reduce the stiffening of artery walls, which can restrict blood flow and raise the risk of heart attack or stroke.
But as with many nutrition and supplement studies, the research has limitations, Dr. Hensrud said. Studying dietary supplements can be challenging because their composition varies across products. It’s also tricky to tease out whether the supplement was responsible for a participant’s improved health, or if it was another factor like their diet, lifestyle or genetics, said Dr. Linda Van Horn, a professor emeritus of preventive medicine at the Feinberg School of Medicine at Northwestern University.
Study results can also vary depending on the types and amounts of garlic used, and how long they were tested for. And many supplement studies receive industry support, calling their results into question, Dr. Van Horn said.
Dr. Matthew Budoff, a cardiologist and professor at the University of California, Los Angeles, has published several randomized clinical trials and meta-analyses that have found that garlic supplements can reduce cholesterol levels and plaque buildup in the arteries of people at cardiovascular risk.
Their results were consistent with other similar studies, although some of these studies (including Dr. Budoff’s) have received financial industry support. Still, he said, he recommends garlic supplements to his patients to help manage their plaque buildup, blood pressure and cholesterol.
Some studies have failed to demonstrate benefits of garlic supplements, including one from 2007 that found no significant effect of raw garlic or some of its supplements on LDL among about 200 participants with mildly elevated cholesterol; and another from 2004 that found no lipid- or cholesterol-lowering effects of dried garlic powder on 75 healthy, middle-aged adults.
The studies with negative results, however, are small and are “dwarfed” by the many clinical trials and meta-analyses that have shown positive results, Dr. Manson said.
That said, it’s still not clear whether garlic supplements prevent heart attacks, strokes or other chronic diseases like cancer. “We need long-term studies for those answers,” Dr. Manson said.
Who should take them?
Those who are likely to benefit most from garlic supplements appear to be people with mild cardiovascular risks “who want to nudge their numbers into a healthier range,” Dr. Manson said. This includes people who can’t tolerate higher doses of medications, like statins, because of their side effects, she said.
People with normal cholesterol or blood pressure levels seem less likely to benefit, Dr. Manson added. And the evidence is stronger for blood pressure benefits than for cholesterol-lowering ones, she added.
The standard dose is 600 milligrams, twice a day, of aged garlic extract, a type of supplement used in most of the research showing positive effects, Dr. Manson said.
Experts stressed, however, that it’s always best to get your nutrients from food. And that garlic supplements are not a substitute for proven strategies to treat or prevent heart disease like prescription medications, regular exercise, a heart-healthy diet and not smoking.
“I like to describe them as ‘complementary’” to standard medical care, Dr. Budoff said.
Both garlic and garlic supplements relax blood vessels and thin the blood, so those taking anticoagulants or aspirin should always consult a doctor before starting garlic supplements, Dr. Manson said. Surgeons also need to know if their patients take garlic supplements so they can be stopped about 10 days before surgery to prevent excessive bleeding, she added.
While not a panacea, the evidence for their cholesterol and blood pressure lowering effects is strong, Dr. Hensrud said. But, he added, “the jury is still out on whether they keep vampires away.”
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