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What Are the Possible Heart-Healthy Benefits of the Keto Diet?

The heart’s scourge is inflammation, which injures arteries, says Audrey Fleck, RDN, an integrative and functional nutritionist and certified diabetes care and education specialist in Perkasie, Pennsylvania. “Many times, the cause of inflammation is elevated blood sugar,” she says. What’s more, a keto diet may help lower blood sugar and improve insulin function, and can be anti-inflammatory, she says. Insulin is a hormone that helps regulate blood sugar levels. A June 2020 review published in The American Journal of Medicine acknowledges that diet changes are critical for lowering risk of cardiovascular disease. But because of anecdotal reports (e.g., that coworker who swears by keto) and social media, the authors wanted to clear up confusion about the influence of popular diets, including keto, on heart health. The keto diet, they conclude, is effective for weight loss in people who have obesity, and it may lower blood pressure and blood sugar, favorably affect lipid levels, and reduce insulin resistance — in the short term. However, they have major reservations about the fact that saturated fats and animal products are allowed, which are known to increase heart disease risk, and a restrictive diet like keto may prompt people to overconsume these foods. As such, there may be a small set of dieters who would be advised to go on keto: “Therefore, the recommendation to start the ketogenic diet for patients must be made prudently, as this dietary approach will likely not be appropriate for most people. In patients who are meticulous, disciplined, and motivated, the ketogenic diet might be a reasonable approach to employ for cardiovascular disease prevention.” Indeed, the specific foods you choose on keto matter, too. In past research conducted on women and men who followed a low-carb diet, those who heavily relied on animal sources of fat and protein, such as cheese and meat, had a 23 percent higher risk of early death compared with those who emphasized vegetable sources, such as avocado and nuts, for those nutrients. Those in the veggie low-carb group had a 20 and 23 percent lower risk of early death and heart disease, respectively. A review in the May 2017 issue of the journal Nutrients examined the effects of keto on the heart by looking at both rodent and human studies. In humans, the authors noted, research has shown that total cholesterol, triglycerides, and LDL (“bad”) cholesterol often decrease on keto, while protective HDL (“good”) cholesterol may increase. Blood sugar and HbA1C (which is a two- to three-month average of blood sugar levels) also tend to go down, possibly offering protection against prediabetes and type 2 diabetes. However, the authors cautioned that, while research is mixed, following a keto diet long-term may be linked to an increase in mortality rate after 10 years. But human studies have shown mixed results about whether the keto diet increases or decreases insulin resistance or insulin sensitivity. And while people may lose weight on keto, the key is maintaining that loss, and that’s not a given. The researchers also note that there isn’t a strict definition of keto across the board that studies are using, so it’s tough to even know if the participants reached ketosis in the first place. Last, a study published in May 2018 in Cardiovascular Diabetology looked at people with type 2 diabetes. One group received standard care, while another was guided in nutritional recommendations to get into ketosis, and they received professional advice for mitigating keto side effects, such as headaches, which could make the experience unpleasant. After one year, while the usual-care group had no changes, those in the ketosis group benefited from reduced cardiovascular risk factors, including decreases in triglycerides, blood pressure, and inflammation, and improved lipid profiles. There’s a connection between heart disease and diabetes: Those with diabetes are about two times more likely to have heart disease or stroke than those without the disease, according to the Centers for Disease Control and Prevention (CDC). But the aforementioned research doesn’t prove keto is the best diet for everyone with diabetes. If you’re managing diabetes, check with your healthcare team before making any dramatic changes to your diet. RELATED: What Are the Possible Benefits and Risks of the Keto Diet?

What to Know About Keto if You Want to Help Prevent Heart Disease

There is a lot of talk about the dangers of eating sugar when it comes to your heart. (By “sugar,” we’re talking simple, processed carbs and added sugars.) Indeed, “eating a diet high in sugars can lead to insulin resistance, weight gain, and (down the line) metabolic syndrome,” which increases the risk of heart disease, says Suzanne Steinbaum, DO, a national spokesperson for the Go Red for Women campaign with the American Heart Association in New York City. It was in the ’80s and ’90s that some touted going low or no fat, she says, but then a funny thing happened: “People gained weight [because they were] eating more carbs and sugar.” Today, with the popularity of keto, the pendulum has swung in the other extreme direction, into high fat and very low carb. If there’s anything to be learned there — and this is what Dr. Steinbaum wants everyone to hear if they’re looking to reduce their risk of heart disease — it’s this: “I promise, there is a place that lies in between low fat and high fat. And that’s a Mediterranean diet filled with good fats like omega-3s from fish and unsaturated fats from avocado and nuts but also fiber-rich whole grains,” she says. RELATED: What Are the Best and Worst Fats to Eat on the Ketogenic Diet?

Warnings About the Keto Diet if You’re at Risk for Heart Disease

If you’re at risk for heart disease (factors include having high blood pressure, high cholesterol, or prediabetes or type 2 diabetes, or if you are overweight or obese, according to the National Heart, Lung, and Blood Institute), one overarching factor to consider is that the keto diet is restrictive, and it’s tough to stick to a restrictive diet, says Steinbaum. “People go on keto and in the short term lose a lot of weight, but it’s not sustainable. So when they go off it, they gain the weight back — and maybe even more,” she says. Yo-yo dieting can put stress on the heart. One large study in the October 2018 issue of the journal Circulation found that people who have the greatest variability in measures like fasting blood glucose, cholesterol, blood pressure, and body weight are 2.3 times more likely to die from any cause and more than 40 percent more likely to suffer a heart attack or stroke compared with those who stay more stable. Staying stable in these measurements is healthier than constantly going up and down. (Of course, this doesn’t mean that you shouldn’t try to reach a healthy weight, only that restrictive diets that lead to loss and regain can make you worse off than when you began.) “Ultimately what you’re doing [with yo-yo dieting] is setting yourself up for developing metabolic syndrome,” says Steinbaum. RELATED: Yo-Yo Dieting Associated With Early Death, Study Finds What’s more, lifestyle factors aren’t the only thing that affects your likelihood of developing heart disease. There’s a genetic component, too. Particularly for people with a family history of the disease, genes may affect their ability to metabolize fats. “If you’re one of those people, a keto diet can make the situation significantly worse. This isn’t just about weight loss. It’s about your metabolism on a cellular level, and you can be doing yourself much more harm than good.” Translation: Keto may increase your risk for heart disease if the condition runs in your family. One concern is the effect a keto diet has on cholesterol levels. As an article in the Harvard Health Blog explains, data shows that cholesterol may spike when you first start a keto diet but then decrease after a few months of ketosis. The author points out something critical: There isn’t long-term research showing what happens to cholesterol levels. And that uncertainty matters — especially when we’re talking about your heart health. RELATED: 10 Surprising Facts About Cholesterol

Is the Keto Diet a Good Choice if You’re Living With Heart Disease?

If you have heart disease, you need to be working closely with your cardiologist to make the best heart-healthy lifestyle changes for you. In terms of your diet, your doctor may recommend the Mediterranean diet — not keto. One study published in April 2016 in the European Heart Journal looked at 15,482 patients with stable heart disease and asked them questions about their diets. After a four-year follow-up, those who more closely followed the Mediterranean diet had a lower risk of a heart attack or stroke compared with those on a Western diet (higher in refined grains and sugars and fried foods). The researchers concluded that adding these healthier foods, which include sources of carbs banned on keto — fruit, veggies, legumes, and whole grains — rather than avoiding unhealthy foods (sweets, for instance) was the most important factor in preventing another heart problem. In an analysis for the American College of Cardiology in May 2016, which was geared toward an audience of cardiologists, Dariush Mozaffarian, MD, a cardiologist and professor of nutrition at Tufts University in Boston, advised doctors to wade through the trendy diets, including low-carb diets, noting that these have a “minor or uncertain influence on health.” He adds that the Mediterranean diet comes the closest to an evidence-based diet that hits the mark. RELATED: 10 Easy Mediterranean Diet Swaps to Make Today

The Bottom Line on the Relationship Between Keto and Heart Disease

Heart disease development is based on multiple factors, including blood pressure, cholesterol, blood sugar, family history, smoking, and stress, says Steinbaum. Your diet, while important, “is just a piece of the story,” she says. “Ultimately, it’s not about keto. It’s not about eating sugar. People may want to follow this diet because it makes them feel in control, but nothing is such a quick fix. It’s just not that simple,” she says. Don’t rely on keto to prevent heart disease or treat existing heart disease. If you’re at risk, go on a keto diet only under the supervision of your doctor or cardiologist, especially if you have a family history of the disease, which, in that case, may mean a keto diet could be dangerous.