An Italian study comparing a Mediterranean diet with a lacto-ovo-vegetarian diet for weight control and overall health was published in Circulation in February 2018. The Mediterranean diet focused on fruits, vegetables, beans, and whole grains as well as poultry, fish, dairy, and some red meat. The most common type of vegetarian diet, the lacto-ovo-vegetarian diet included dairy and eggs but no meat or fish. Both diets are widely promoted as being healthful, and previous research has shown that each can improve aspects of cardiovascular health and help with weight control, but no clinical trial has compared them until now.
The study was smaller and shorter than the recent Stanford study comparing low-fat and low-carb diets. It involved 107 relatively healthy but overweight or obese omnivores, ages 18 to 75, who were randomly assigned either a low-calorie lacto-ovo-vegetarian diet or a low-calorie Mediterranean diet for three months. Then the participants switched diets for another three months. They received individual dietary counseling as well as weekly menu plans and detailed instructions about food selection, but no weight-loss goals. The two diets ended up supplying about the same number of calories and had similar levels ofcarbs (supplying about 53 percent of daily calories), fat (about 30 percent), and protein (about 17 percent). They were told not to change their exercise habits.
Both diets led to a loss of about four pounds. And both reduced cardiovascular risk, but in different ways: The vegetarian diet (like the low-fat diet in the Stanford study) led to a slightly greater reduction in LDL (“bad”) cholesterol, while the Mediterranean diet (like the low-carb diet in the Stanford study) led to a modestly larger reduction in triglycerides. Triglycerides rose slightly on the vegetarian diet.Markers for inflammation and oxidative stress improved on both diets.
It’s not surprising that overall the diets had “equally effective results,” since they were alike in many ways, except in terms of meat. The diets were similar to those in the Stanford study in their focus on “high-quality,” wholesome foods. Both emphasized nutrient-dense foods such as vegetables, fruits, legumes, whole grains, and nuts, and both limited saturated fats. This being Italy, the vegetarian diet had a Mediterranean slant (thus, both groups averaged about 10 tablespoons of olive oil a week).
Bottom line: There is no “best diet” for everyone. This study along with the Stanford study show that Mediterranean, vegetarian, healthy low-fat, and healthy low-carb are all dietary patterns that can be good for your heart as well as your waistline. Healthful versions of other traditional diets from around the world may well be just as beneficial.
A version of this article first appeared in the UC Berkeley Wellness Letter.