Can the Keto Diet Mess With Your Cholesterol? Here's What Heart Doctors Had to Say

Short answer: potentially.

"There's a real mix of results when it comes to cholesterol and the ketogenic diet," said Nikki Stamp, MBBS(Hons), FRACS, a cardiothoracic surgeon based in Australia. That said, "there seems to be good science to suggest that total cholesterol, as well as low-density lipoprotein (also known as bad cholesterol), increases on the ketogenic diet."

Why? "In general, keto diets involve high intake of animal products, which contain a lot of saturated fat and animal protein," said Nicole Harkin, MD, a board-certified cardiologist and lipidologist and clinical instructor of cardiology at NYU Langone. Saturated fats are known to increase bad cholesterol, putting you at greater risk for cardiovascular disease.

The keto diet might help in this respect, according to cardiologist Jennifer Haythe, MD, codirector of the Women's Center for Cardiovascular Health at Columbia. "A 2010 study in The Archives of Internal Medicine found that patients on a low-carbohydrate (keto) diet showed a statistically significant reduction in blood pressure," Dr. Haythe said.

Why does this happen? "It has been postulated that by acting similarly to a diuretic, the keto diet reduces total body water, particularly at the beginning," she explained. "In addition, lower serum insulin levels seen on the keto diet may lead to less sodium retention and more vascular muscle relaxation, resulting in lower blood pressure."

Still, if you want to lower your blood pressure, Dr. Haythe suggests trying the DASH diet instead, which can help you cut back on your sodium intake.

It's still too early to know how the ketogenic diet might affect your heart, Dr. Stamp explained. "Unfortunately, these answers do take time." She's referring to research — the diet is still relatively new, and without many long-term studies, it's difficult to know its impact.

"At this stage, most research on ketogenic diets has looked at some of the illnesses that lead to or happen in conjunction with heart disease, such as diabetes and obesity," she continued. "Research is still ongoing, but some researchers believe that a ketogenic diet is a useful way to manage diabetes and aid in weight loss — but this is still very much under investigation."

Dr. Harkin expressed a warier viewpoint. "While ketogenic diets can lead to short-term weight loss, there is no scientific evidence that this type of diet results in improved health or longevity," she said. "In fact, what we currently know indicates otherwise, with many reviews demonstrating increased cardiovascular death and all-cause mortality."

A recent study from The Lancet found that both high- and low-carb diets are associated with increased mortality, with 50 to 55 percent carbohydrate intake being the sweet spot. "This adds to the growing body of research showing that plant-based fats should be chosen whenever possible compared to animal-based fats," Dr. Harkin told POPSUGAR. She cited a portion of the study that found that mortality increased when carbohydrates were replaced with animal-derived fat or protein and decreased when the substitutions were plant-based.

However, Dr. Harkin doesn't believe the study provides enough evidence to support limiting your consumption of high-quality carbohydrates, like fruits, vegetables, whole grains, and beans. "The type of carbohydrate was not accounted for, and the studies analyzed looked at various populations living in low-resource settings where, unfortunately, a large source of their diet relies on low-quality, refined carbohydrates," she said. "It makes sense that low-quality carbs (i.e. processed foods and refined grains), when replaced by high-quality, plant-derived fats and proteins, would result in improved morbidity and mortality."

Certified clinical nutritionist Autumn Bates, MS, agreed: "This study is by no means one to stake a claim on — there's no way to account for variables such as quality of the carbohydrates or fat eaten, as well as any other possible variables."

It's hard to say. The diet works well for some people, but doctors remain skeptical. Despite the warnings, it's not all bad, though. "Keto diets are low in refined grains, added sugar, and processed carbs — all good for cardiovascular health," Dr. Harkin said. However, she still believes that "a better alternative is a whole-food, plant-based diet, which may even reverse cardiovascular disease."

Dr. Stamp concurred, noting that "there isn't a lot of science to show that a ketogenic diet prolongs your life at the moment, although that can be hard to show in nutritional studies." She too believes that both the DASH diet and Mediterranean diet boast "the best evidence for protecting your heart."

"If someone has no history of high cholesterol or family history of cardiovascular disease, and they'd like to attempt the ketogenic diet in the short term to jump-start some weight loss, there are ways to make healthier choices," Dr. Harkin added. "Focus on the allowable low-carb veggies and fruits (like leafy greens, broccoli, avocado, and berries), nuts and seeds, and tofu."

Dr. Harkin noted that she still would not recommend the keto diet for long-term use. "For the best long-term diet, my advice is to ditch the processed carbs as the ketogenic diet recommends, but don't miss out on all of the antioxidants, fiber, and phytonutrients found in the whole range of fruits, legumes, whole grains, and starchy vegetables."

And though she believes it may be an effective way to lose weight when done correctly, Bates doesn't personally recommend the diet to her clients, either. "I'm not a keto promoter because I think it's very difficult to do well," she said.

If you plan to go keto for medical reasons, the experts had some tips for effectively managing your health while on this high-fat, low-carb diet.

"Anyone who is considering a low-carbohydrate diet that is ketogenic should definitely consult a registered dietitian to ensure there are no negative side effects of the diet," Dr. Stamp said. "It's also important to have your doctor check things like your blood pressure, blood glucose, and cholesterol to make sure these are not being harmed by what you're eating."

While it may seem daunting to make yet another appointment or hire a dietitian, it's worth it when it comes to something as risky as keto — particularly if you have an underlying condition that may be contraindicated. "Don't fly solo on this one if you have a heart condition, diabetes, or wish to lose weight for your health," Dr. Stamp said. "Make sure you're under the watchful eye of a dietitian and a doctor to ensure you're healthy when embarking on such a restrictive diet, or better yet, ensure this approach is actually the right one for you."

"If you choose to follow a keto diet, assessing the quality of your food is imperative to decrease inflammation and cholesterol," Bates said. "A problem I often see in those following a low-carb approach is the lack of attention toward the quality of fats. Low-quality fats such as trans fats or oxidized fats lead to increased inflammation," which can be damaging to the heart.

"When choosing the fats in your diet, you want to have a variety of high-quality fats with an emphasis on anti-inflammatory fats," she continued. "Coconut oil and grass-fed butter (rich in butyric acid) are great sources of healthy fats, but they shouldn't be your only source."

Bates cited a study in Evidence-Based Complementary and Alternative Medicine, which supports olive oil for heart health. "Olive oil is an amazing, anti-inflammatory oil that has been extensively studied to aid in heart disease reduction; the polyphenols and mono-unsaturated fats (MUFAs) in olives help to reduce the oxidation of cholesterol, which leads to decreased arterial damage," she said. "Other healthy fat sources include organic sprouted nuts, seeds, and avocado."

Bates noted there's mounting evidence of a connection between gut inflammation and heart health. She suggests pairing a keto diet with intermittent fasting, which can give your body the time it needs to "push food particles and bacteria out of the small intestine." (Intermittent fasting simply means tightening the window in which you eat, so you avoid late-night snacking.) By following these steps, "you'll help to heal the gut and further decrease inflammation and cholesterol levels while using a low-carb approach," she said.