(CNN) — In one corner: the Mediterranean diet, of great medical prestige and eternal favorite of nutritionists. The contender: The popular keto, or ketogenic, diet, known for restricting carbs to a precious few a day.
Proponents of the keto diet claim that it reduces appetite, melts belly fat, and increases mental acuity once a person gets over the first few days of “keto flu,” a feeling of malaise, fatigue, and brain fog. The studies have shown at least one short-term improvement in blood sugar in people following the ketogenic diet.
Research has linked the Mediterranean diet to reduced risk of diabetes, high cholesterol, dementia, memory loss, depression, and breast cancer, as well as weight loss, stronger bones, a healthier heart, and a longer life. long.
A new controlled clinical trial conducted during the pandemic compared the two diets by asking 33 people with prediabetes or diabetes to do both diets, one after the other, for three months. During the first four weeks of each diet, the participants received deliveries of healthy, keto-friendly or Mediterranean diet meals, and then followed the meal plans on their own.
The researchers monitored the participants’ weight, blood sugar (glucose) levels, cardiovascular risk factors, and dietary compliance. Which diet was still standing at the end?
“Both diets improved blood glucose control to a similar degree, and both groups lost a similar amount of weight,” said lead nutrition researcher Dr. Walter Willett, professor of epidemiology and nutrition in the School of Public Health. TH Chan of Harvard and professor of medicine at Harvard Medical School. He did not participate in the study.
However, when the researchers examined the impact of the two diets on levels of blood fats that contribute to heart disease, the Mediterranean diet was the clear winner, according to the study published Friday in The American Journal of Clinical Nutrition.
The study tracked low-density lipoprotein, or LDL, known as the “bad” cholesterol, and triglycerides, which are a different type of fat in the blood that also contributes to hardening of the arteries.
“The keto diet significantly increased LDL cholesterol by 10%, while the Mediterranean diet decreased LDL cholesterol by 5%,” said Dr. Frank Hu, head of the department of nutrition at the TH Chan School of Public Health in Harvard, which was not involved in the study.
“The difference between the two diets is quite large, and this may have long-term consequences for cardiovascular disease,” Hu said.
Although both diets lowered triglycerides, the keto diet did so more significantly, according to the study.
However, lowering triglycerides is not as important as raising bad cholesterol, Hu said.
“High LDL cholesterol is a much more powerful and important risk factor for cardiovascular disease than triglyceride levels,” he said. “So while both parts were quite effective in short-term glycemic control, I think the main question is the possible long-term effects of the keto diet on cardiovascular disease.”
“I tried to give each diet the best chance”
Keto dieters achieve rapid weight loss success, they say, by putting people into ketosis, a state in which the body begins to burn stored fat for fuel. But to get to that point, carbohydrates are drastically reduced to 20 or 50 grams a day. (A cup of cooked rice contains about 50 grams). Eating more carbs kicks you out of ketosis.
The typical American’s daily diet is 50% carbohydrate, Hu said, so reducing intake to less than 50 grams is “a big reduction. That’s hard for people to maintain.”
People often view the keto diet as a “meat” diet and fill their plates with full-fat dairy, sausage, bacon, and other meats with saturated fats, which can contribute to inflammation and chronic disease.
However, the study used a “well-formulated ketogenic diet,” which limited high-protein intake and emphasized nonstarchy vegetables, said study author Christopher Gardner, a research professor of medicine at the Stanford Prevention Research Center. .
“I tried to give each diet the best shot. I didn’t try to do a lacking keto diet and a good Mediterranean diet or a bad Mediterranean diet and a good keto diet,” said Gardner, who is also the director of the Nutrition Studies Research Group at Stanford. .
The keto diet bans grains, legumes, and fruit, except for a handful of berries. The Mediterranean diet, however, emphasizes filling your plate with fruits, vegetables, beans, lentils, whole grains, nuts, and seeds.
Both diets agree that “we eat too many added sugars and refined grains, and we don’t eat enough vegetables,” Gardner said. “So the whole study was set up to see if there’s an advantage to getting rid of fruits, whole grains and beans on the keto diet, after doing the things that everyone agrees on.”
In addition to the increase in bad cholesterol, people in the ketogenic phase had “lower intakes of thiamin, vitamins B6, C, D, and E, and phosphorous,” as well as an “incredibly low amount of fiber,” Dr. Shivam said. Joshi, clinical assistant professor of medicine at New York University Grossman School of Medicine. He did not participate in the study.
“Whole grains and fruits have positive health benefits, and their exclusion from the keto group raises some concern about long-term health impacts,” Willett said. Additionally, she said, “many people find long-term adherence to a keto diet difficult.”
In fact, the study found that most people went off the keto diet after the research was over.
“They brought the diet to their house. They had a health educator to help them,” Gardner said. “But, boom! Most people stopped following the keto diet almost immediately (when that part of the study ended), while many of those on the Mediterranean diet continued to eat that way after the study ended.” .
What is the key message of the study?
“The No. 1 take-home message is that severe restriction of some healthy carbohydrates is not necessary to improve glycemic control and cardiometabolic health,” Hu said.
“You can do a healthy Mediterranean diet or a moderate low-carb diet or a very healthy vegetarian diet. There are different options for people with different food preferences.”