CNN — In one corner: the medically renowned Mediterranean diet, a perennial favorite among nutritionists. The competitor: the popular ketogenic diet, known for restricting carbohydrates to a few per day.
Keto proponents claim that the diet reduces appetite, melts belly fat, and increases mental acuity, once a person gets past the first few days of “keto flu,” a feeling of malaise, fatigue, and mental fogginess. Studies have shown at least short-term improvement in blood sugar in people also taking keto.
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. For the first four weeks of each diet, participants received healthy keto- or Mediterranean-based meal deliveries, 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. What diet was still standing at the final bell?
“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, a professor of epidemiology and nutrition in the School of Public Health TH Chan of Harvard and professor of medicine. at Harvard Medical School. He was not involved in the study.
However, when 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 “bad” cholesterol, and triglycerides, which are a different type of fat in the blood that also contributes to hardening of the arteries.
“The ketogenic diet significantly increased LDL cholesterol by 10 percent, while the Mediterranean diet lowered LDL cholesterol by 5 percent,” said Dr. Frank Hu, chair of the department of nutrition at the TH Chan School of Public Health in Harvard, who was not involved in the study. the study.
“The difference between the two diets is quite large, and this could have long-term consequences on cardiovascular disease,” Hu said.
While both diets lowered triglycerides, the ketogenic diet did so more significantly, the study found. 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 sides were quite effective in short-term glycemic 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 success, advocates 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 to 50 grams per day. (A cup of cooked rice equals about 50 grams). Eating extra carbs knocks you out of ketosis.
The typical American’s daily diet is 50% carbohydrate, Hu said, so reducing that intake to less than 50 grams is “a big reduction. That’s hard for people to maintain.”
People often view the ketogenic diet as a “meat” diet and fill their plates with full-fat dairy, sausage, bacon, and other meats with saturated fats, all of 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 make it bad keto and good Mediterranean or bad Mediterranean and good keto,” said Gardner, who is also director of clinical and translational research. at the Stanford Diabetes Research Center.
The ketogenic 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 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 an advantage to ditching fruit, whole grains, and beans on keto, after doing the things that everyone agrees on.”
In addition to the increase in bad cholesterol, people in the ketogenic phase had a “decreased intake of thiamin, vitamins B6, C, D, and E, and phosphorous,” as well as an “unbelievably low amount of fiber,” said Dr. Shivam. Joshi, clinical assistant professor of medicine at New York University Grossman School of Medicine. He was not involved in the study.
“Whole grains and fruits have positive health benefits, and their exclusion from the ketogenic group raises some concern about long-term health impacts,” Willett said. Additionally, she said, “many people find long-term adherence to a ketogenic diet difficult.”
In fact, the study found that most people ditched the ketogenic diet after the research ended.
“They were on keto at home. They had a health educator helping them,” Gardner said. “Boom though! Most people stopped following the ketogenic diet almost immediately (when that part of the study ended), while many of those on the Mediterranean diet were still eating that way when the study ended.” .
What is the key message of the study?
“The main message for me is that severe restriction of some healthy carbohydrates is not necessary to improve glycemic control and cardiovascular metabolic 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.”
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