Three months of a low-calorie vegetarian and a low-calorie Mediterranean diet were equally beneficial in reducing weight and improving cardiovascular risk profiles, in the first randomized crossover trial comparing the two directly.

The vegetarian diet was more effective in reducing LDL cholesterol, whereas the Mediterranean diet led to a greater reduction in triglycerides, which was not surprising, the researchers say.

These findings from the Cardiovascular Prevention With Vegetarian Diet (CARDIVEG) by Francesco Sofi, MD, PhD (University of Florence, Italy), and colleagues were published online February 26 in Circulation.

Participants received individual, in-person counseling from nutritionists on how to adhere to each of the two evidence-based healthy eating patterns. The vegetarian diet excluded meat and fish but included dairy and eggs.

This was the first “intervention study that follows the principles of evidence-based medicine, in a general population at low risk of cardiovascular disease, that compared these two beneficial diets,” Sofi told theheart.org | Medscape Cardiology.

“We can conclude that both diets are beneficial for heart health,” she said. The result was not surprising, she said, because both diets have a strong foundation of healthy foods, such as fruits and vegetables, whole grains, and legumes.

“We [now] have data on two strategies that might be helpful in reducing cardiovascular risk and promoting cardiovascular health,” Cheryl AM Anderson, PhD, MPH, MS, University of California, San Diego, author of an accompanying editorial, told theheart.org | Medscape Cardiology.

“This is a study that provides some evidence base on which you can begin to feel reasonably reassured in counseling patients that there’s not necessarily one path to Rome, but multiple strategies can be helpful.”

“It’s easy to focus on meat vs no meat, but what’s really important is the rest of the diet,” Anderson stressed.

A healthy diet should be “nutrient dense; rich in vegetables and fruits, whole grains, legumes and nuts; low in refined grains and commercially processed foods with added sugars, saturated fats, and sodium; sustainable; culturally relevant; and enjoyable.”

There is helpful information and tools online at ChooseMyPlate.gov, she noted, which are based on the most recent US guidelines.

Two Healthy Diets

The Mediterranean diet is widely reported to be one of the healthiest eating patterns to prevent cardiovascular disease, Sofi and colleagues note. In an earlier meta-analysis, the researchers reported that a vegetarian eating pattern was associated with improvements in cardiovascular risk factors.

To compare the two diets, the CARDIVEG trial randomly assigned 118 participants (78% women) living in Florence in 2014 to 2015 who were age 18 to 75 years and overweight (BMI ≥ 25 kg/m²).

The participants also had one or more of the following risk factors for cardiovascular disease, as defined by the European Society of Cardiology (ESC) guidelines: total cholesterol greater than 190 mg/dL, LDL cholesterol greater than 115 mg/dL, triglycerides greater than 150 mg/dL, and glucose greater than 110 but less than 126 mg/dL.

On average, they were 51 years of age, weighed 84 kg, and had a BMI of 31 kg/m². Close to half (48%) were obese (BMI > 30 kg/m²).

All participants received in-person, individual counseling as well as a detailed, 1-week menu plan for each diet and recipes for the vegetarian diet.

After a run-in period, they ate a vegetarian or Mediterranean diet for 3 months and then switched diets for another 3 months. A total of 85% of the participants (50 for each intervention) completed the study.

Both diets had similar low calories and consisted of 50% to 55% carbohydrates, 25% to 30% fat, and 15% to 20% protein.

The participants ate a similar number of servings of cereals, fruits and vegetables, potatoes, sweets, and olive oil on both diets, but on the vegetarian diet they ate more legumes, nuts, eggs, and dairy products, as well as flaxseed and avocado (to compensate for the lack of essential fatty acids from fish).

Both diets were similarly effective for weight loss. After 3 months, the participants lost a mean of 1.88 kg and 1.77 kg while on the vegetarian and Mediterranean diets, respectively.

They also lost a similar amount of fat mass (about 1.3 kg) and lowered their BMI by a similar amount (about 0.65 kg/m²).

During the vegetarian diet, 46 participants (44%) modified their cardiovascular risk category by reaching ESC-recommended target levels: Sixteen reached the target for total cholesterol, 17 for LDL cholesterol, 6 for triglycerides, and 14 for BMI.

During the Mediterranean diet, 35 participants (34%) modified their cardiovascular risk category: Seven reached the target for total cholesterol, 6 for LDL cholesterol, 8 for triglycerides, and 10 for BMI.

The vegetarian diet is low in cholesterol, total fat, and saturated fatty acid, leading to lower rates of cholesterol in the bloodstream, whereas the Mediterranean diet “can reduce triglyceride levels through its beneficial components, including olive oil, dietary fiber, and many phytonutrients,” Sofi and colleagues explain.

Vitamin B12 levels were significantly lower with the vegetarian diet.

However, there were no significant differences in levels of oxidative stress markers or inflammatory cytokines after 3 months of each diet.

The study shows that “if a person would like to follow a lacto-ovo-vegetarian diet he/she can obtain a beneficial effect as well as with the Mediterranean diet, or probably in a greater extent as for cholesterol and lipid variables,” Sofi said. “The most important thing is that he/she needs to be followed and instructed by an expert nutritionist in order to avoid possible deficiencies.”

Although these diets should be investigated in larger studies in other populations, this research suggests that “a low-calorie healthy vegetarian or Mediterranean diet pattern may offer a possible solution to the ongoing challenges to prevent and manage obesity and cardiovascular diseases,” Anderson said.

The researchers are continuing to follow the study participants, Sofi said, and “a considerable portion of them declared that they learned how to eat without meat, at least in part and for a short period. In my opinion, this is already a good result.”