Why the Mediterranean diet is actually as beneficial as everyone says

The Mediterranean diet -- inspired by the cuisines of Spain, Italy and Greece -- has been named the best overall diet by U.S. News & World Report for the fourth consecutive year. With its focus on fish, healthy fats and unprocessed grains, there's good evidence that sticking to this diet can lead to a longer life. But now, evidence is mounting that the Mediterranean diet may have benefits even beyond life longevity.

“When people think of the Mediterranean diet, they think of a heart-healthy diet,” said Dr. Timothy Harlan, editor-in-chief of Health meets Food: the Culinary Medicine Curriculum. “But really, the Mediterranean diet has been shown to prevent Alzheimer’s disease, macular degeneration and cancer as well.”

Jen Bruning, registered dietitian and spokesperson for the Academy of Nutrition & Dietetics, agreed. There is evidence to support that the diet does help reduce blood pressure and improve cholesterol levels and overall cardiac outcomes, she said.

“When it comes to the Mediterranean diet and weight, switching to a Mediterranean diet doesn't necessarily guaranteed there's going to be weight loss,” Bruning said. “However, the high satiety factor of these higher fiber foods may naturally decrease the amount of calories that you eat in a day, which could result in weight loss or weight maintenance.”

Dr. Joel Kahn, a cardiologist and director of the Kahn Center for Cardiac Longevity, said the diet has been studied for decades because countries such as Italy and Greece had low levels of heart disease and cancers, while western countries had exceedingly high rates.

“With years of research the question was asked: Is this a magical place, and what might be the reason why that pocket of the world is not experiencing an illness like heart disease?” he said.

Some studies also indicate the Mediterranean diet may have benefits on a cellular level, including decreased free radical damage that is linked to aging, as well as a reduced anti-inflammatory response in the body.

Extra virgin olive oil, the primary source of fat in the Mediterranean diet, has been shown to reduce inflammation because it is rich in compounds such as phenols and mono-unsaturated fat. One study found increased phenol content reduced the level of fat in the blood and increased the amount of HDL, the “good” cholesterol that can help lower your risk of heart disease.

Meanwhile, a landmark study showed that people who previously experienced a heart attack who switched to the diet were 50% to 70% less likely to have a second.

Some studies have demonstrated a link between the diet and cancer rates, though research is ongoing to better understand this association. Cancer doctors like Dr. Justin Gregg, an assistant professor of urology at the University of Texas MD Anderson Cancer Center, have also wondered whether this diet would show benefit to their patients.

Initial results of Gregg's study, published in Cancer, show that men diagnosed with prostate cancer, in its early stage not requiring treatment, who adhere to elements consistent with the Mediterranean diet, may have a slower rate of cancer progression, meaning they may not need invasive cancer therapy.

“There may be a component of inflammation [in prostate cancer] that's actually associated with disease progression,” he said. “That prompted our hypothesis that generally eating a diet that's consistent with principles of the Mediterranean diet may be associated with decreased rates of [cancer] progression.”

For many patients, it's difficult to stick with a new diet plan, but Bruning has had success with a step-by-step approach.

“I recommend starting with small changes,” she explained. “Try switching out your refined grains (white bread and pasta) for their whole grain counterpart or even switching out the source of fat in a recipe. It is really about making small changes, one or two at a time.”

Despite his practice being framed around a plant-based Mediterranean diet, Kahn said he first assesses whether patients are amenable to changing their diet. If he sees resistance, he will initially emphasize sleep and fitness.

“People are more open-minded about sleeping better and getting moving, while there's some resistance about changing their diet," Kahn said. “If sleep is a problem, then I will provide some tips on how to improve it or get a sleep study. In regards to fitness, I ask patients to walk 25 to 30 minutes a day and follow up on diet changes during the next visit.”

Harlan agreed with these approaches, but he said with his program he teaches patients they do not have to specifically adhere to Mediterranean foods to receive the overall health benefits. Instead, practicing the diet means taking the elements of it and translating them into similar American dishes.

Regardless of the approach in making these lifestyle changes, Harlan said even small steps in the direction of the Mediterranean diet might help prevent cancer and heart disease.

Lily Nedda Dastmalchi, D.O., M.A., an internal medicine resident physician at The George Washington University, is a contributor to the ABC News Medical Unit.