The effectiveness of the Mediterranean diet isn’t really up for debate anymore—at this point, it’s more a question of how to tweak it, and home in on what the active ingredients are. (For example, the MIND diet is a science-based variant of the Mediterranean diet, developed purely from what the research has shown.)
Now, a new study looks at whether olive oil or nuts do more for cholesterol in people at high risk of heart disease, since both have been shown to have significant heart benefits in the past, and both contain healthy fats. The short answer is that olive oil seems to do more for cholesterol, but nuts are not without their own benefit.
High-density lipoprotein (HDL) cholesterol is considered the “good” cholesterol, since it clears less healthy forms of cholesterol from the blood.
But it hasn’t been shown to function so well in people who are at higher risk of heart disease. “At the same time, small-scale trials have shown that consuming antioxidant-rich foods like virgin olive oil, tomatoes and berries improved HDL function in humans,” said study author Montserrat Fitó in a news release.
“We wanted to test those findings in a larger, controlled study.” The authors underline that how well HDL functions is at least as important as how much of it you have.
The team randomly assigned people to eat a Mediterranean diet—which included higher amounts of vegetables, fruits, legumes and whole grains, and low to moderate amounts of fish and poultry—or a still-healthy low-fat diet, which stressed cutting back on sweets, meat, high-fat dairy and processed foods.
But those eating the Mediterranean diet were further divided into two groups: People in one group were instructed to have four teaspoons of olive oil as part of their daily diet, and one group asked to have a “fistful” of nuts every day. Cholesterol and other markers were measured at the beginning and end of the one-year study period.
None of the groups had higher HDL levels in the end, but people in the Mediterranean diet groups had improved HDL function, and this was particularly true for those in the olive oil group. The difference was borne out in a few different ways.
They had better movement of cholesterol into the liver where it can be broken down or eliminated from the body; better antioxidant protection (whereby HDL prevents LDL from getting oxidized and triggering plaques to develop); and better function of the blood vessels.
Oddly, people in the control group (the low-fat diet) had better LDL and total cholesterol numbers (a good thing), but the anti-inflammatory action of HDL was lower in this group, too, which is not so good.
This suggests that there’s something intrinsic about olive oil that benefits cholesterol function. Of course this isn’t the first study to suggest that certain fats are good for the heart, and nuts have certainly been shown to have an effect. One study a few years ago found that a Mediterranean diet supplemented with either olive oil or nuts was linked to a reduced risk of major cardiovascular events (i.e., heart attack and stroke) over time.
And research has often shown how olive oil added to a healthy diet (especially if it’s paired with greens) benefits the heart. Eating fish once a week has been linked to heart health, presumably for its abundance of omega-3 fatty acids.
Finally, other studies have found that nuts are linked to reduced risk of death from a number of causes (although peanut butter does not, and there was an upper limit to nut intake).
So we may not need more convincing that a Mediterranean diet, including a dose of healthy oils, is good for the heart. Another body of work has shown that it’s also very good for the brain—which isn’t surprising, since brain and heart health generally go hand-in-hand.
But we are learning more and more why each component does what it does. So grab some greens and oils and whole grains. Have a little fish and red wine, if you like, and finish it off with a little dark chocolate. The benefit of the Mediterranean diet is not just that it’s good for you, but it’s also just really good.