(CNN) – In a corner: the medically renowned Mediterranean diet, a perennial favorite among nutritionists. The contender: the popular keto diet, known for limiting carbs to a precious few a day.
Keto proponents claim the diet reduces appetite, melts abdominal fat, and boosts mental acuity, once a person gets past the early days of the “keto flu,” feeling sick, tired and brain fog. Studies showed at least short-term improvement in blood sugar in people on keto as well.
Research has linked the Mediterranean diet to a 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.
A new controlled clinical trial conducted during the pandemic compared the two diets by asking 33 people with prediabetes or diabetes to follow the two diets, one after the other, for three months. During the first four weeks of each diet, participants received healthy meal deliveries based on keto or Mediterranean cuisine, then followed meal plans on their own.
The researchers monitored the participants’ weight, blood sugar (glucose) levels, cardiovascular risk factors and adherence to the diet. Which regime was still standing at the final bell?
“Both diets improved blood sugar 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 at Harvard TH Chan School of Public Health and Professor of Medicine. at Harvard Medical School. He did not participate in the study.
However, when researchers looked at 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 on Friday in the American Journal of Clinical Nutrition.
The study tracked low-density lipoproteins, or LDL, known as “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, chair of the nutrition department at Harvard TH Chan School of Public Health. , who was not involved in the study.
“The difference between the two diets is quite large, and it may have long-term consequences for cardiovascular disease,” Hu said.
While both diets lowered triglycerides, the keto diet did so more significantly, according to the study. However, lowering triglycerides isn’t as significant as raising bad cholesterol, Hu said.
“High LDL cholesterol is a much more potent and important risk factor for cardiovascular disease than triglyceride levels,” he said. “So while both sides were quite effective at short-term blood sugar control, I think the main issue is the potential long-term effects of keto on cardiovascular disease.”
“I tried to give each diet the best chance”
Keto achieves rapid weight loss, proponents say, by putting people into ketosis, a state in which the body begins to burn stored fat for fuel. But to get into ketosis, carbs are drastically reduced to 20-50 grams per day. (A cup of cooked rice weighs about 50 grams.) Eating extra carbs kicks you out of ketosis.
The typical American’s daily diet is 50% carbohydrates, Hu said, so reducing that intake to less than 50 grams is “a huge reduction. It’s hard for people to maintain.
People often think of keto as a “meat-based” diet and fill their plates with whole dairy products, sausages, bacon, and other meats that contain saturated fat, all of which can contribute to inflammation and disease. chronicles.
However, the study used a “well-formulated ketogenic diet,” which limited high protein intake and emphasized non-starchy vegetables, said study author Christopher Gardner, a research professor in medicine at the Stanford Prevention Research Center.
“I tried to give each diet the best chance. I didn’t try to make it crappy keto and good mediterranean or crappy mediterranean and good keto,” said Gardner, who is also director of the nutritional studies research group at Stanford.
The keto diet prohibits all grains, legumes, and fruits except for a handful of berries. The Mediterranean diet, however, emphasizes packing your plate with fruits, vegetables, beans, lentils, whole grains, nuts, and seeds.
Both diets agree that “we eat way too much added sugar and refined grains, and we don’t eat enough vegetables,” Gardner said. “So the whole study was set up to see if there’s any benefit to getting rid of fruits, whole grains, and beans on keto — after doing the things that everyone agrees on. .”
In addition to increased bad cholesterol, people on keto had “decreased intake of thiamin, vitamins B6, C, D, and E, and phosphorus” as well as an “incredibly low amount of fiber” , said Dr. Shivam. 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 effects, and excluding them from the keto group raises concerns about long-term health effects,” Willett said. Also, he said, “Many people find it hard to stick to a keto diet long-term.”
Indeed, the study found that most people quit the keto diet after the research ended.
“They had keto delivered to their house. They had a health educator to help them,” Gardner said. “Yet boom! Most people stopped following the keto diet almost immediately (when this part of the study ended), while many who followed the Mediterranean diet continued to eat this way at the end of the study. .
What is the key message of the study?
“The No. 1 take-home message for me is that severe restriction of certain healthy carbs is not necessary to improve glycemic control and cardio-metabolic health,” Hu said.
“You can do a healthy Mediterranean diet or a moderately low carb diet or a very healthy vegetarian diet. There are different options for people with different food preferences.