The Mediterranean diet has become famous far beyond its namesake sea, as research increasingly backs up its longstanding reputation for improve health and longevity.
Studies have shown that people following the Mediterranean diet — which emphasizes plant-based foods and fish, and not so much red meat or dairy — tend to be healthier in many wayswith lower rates of heart disease, cancer, diabetes, dementiaAnd overall mortality.
But why? Despite strong evidence of health benefits, it’s unclear exactly how this blend of foods, at the cellular level, can extend lifespan.
That may change, however. A study by researchers at Stanford University in the United States revealed for the first time the cellular effects of the Mediterranean diet, based on how one of its healthy fats influences the lifespan of nematodes, also known as roundworms.
Finding that link is a big deal, say the study authors, offering new insights into the health effects of various fats and the role diet plays in longevity.
“Fats are generally considered harmful to health”, said Anne Brunet, geneticist at Stanford University. “But some studies have shown that specific types of fats, or lipids, can be beneficial.”
The Mediterranean diet is full of beneficial fats, also known as monounsaturated fatty acids (MUFAs), found in foods like nuts, fish, and olive oil. The new study focused on healthy fat, oleic acidwhich is the main MUFA in olive oil and some nuts.
Use of roundworm Caenorhabditis elegansBrunet and his colleagues discovered two benefits of oleic acid: it protects cell membranes from damage caused by lipid oxidation and it increases the amount of two key cellular components called organelles.
These effects make a significant difference, the researchers report, with roundworms fed oleic acid living about 35% longer than worms fed a more traditional diet.
One type of organelle, a reservoir of fat called a lipid droplet, allowed researchers to predict with surprising accuracy how many days a worm would survive.
“The number of lipid droplets in individual worms tells me the remaining lifespan of that animal,” said Katharina Papsdorf, biochemist at Stanford University. “Worms with more lipid droplets live longer than those with fewer droplets.”
The roundworms ate bacteria supplemented with oleic acid or elaidic acid, a monounsaturated trans fatty acid found in margarine and fried foods. The two acids have similar molecular structures but very different health effects.
trans fat like elaidic acid are considered unhealthy or “bad” fats because they increase the risk of heart disease, dementiaand other health issues.
“We saw that the number of lipid droplets in the gut cells of the worms increased if the worms were exposed to oleic acid, and that this was correlated with an extension of lifespan,” Brunet said. said.
Exposure to elaidic acid, on the other hand, did not increase the number of lipid droplets or the number of days of life of the worms.
Lipid droplets are important for cellular metabolism, the researchers note, because they help regulate the cells’ use of fat stores as energy. When researchers blocked a gene for proteins that help roundworm cells produce lipid droplets, the life-prolonging effect disappeared.
In addition to increased lipid droplets, roundworm intestinal cells also had more organelles called peroxisomeswhich contain enzymes involved in oxidation and metabolism.
Lipid droplets and peroxisomes were more abundant in cells from younger animals, the researchers report, naturally decreasing with age.
The number of these organelles also varies between individuals, and worms that naturally have more of them in their cells also tend to live longer, showing a similar effect to oleic acid-fed worms.
Along with its effects on organelles, oleic acid protects cells by limiting lipid oxidation, a chemical reaction that damages cell membranes. Elaidic acid had the opposite effect, increasing oxidation at the expense of cell integrity.
“Membrane oxidation is very bad news for an organism”, Brunet said. “Cell membranes can begin to leak and fail, which can cause a cascade of adverse biological effects.”
This is major insight into the links between diet and longevity, the researchers write, revealing key details about how specific components of the Mediterranean diet can extend lifespan.
This could improve dietary guidelines and could possibly inspire ways to combat the effects of aging by mimicking oleic acid’s defense against oxidation.
For now, however, the researchers note that this is an intriguing finding that warrants further research, including studies to determine if and how these findings apply to humans.
“For years, we’ve been very interested in how diet influences lifespan,” Brunet said. said. “It will be fascinating to see if we see a similar association between lipid droplets and longevity in mammals and humans. These results suggest that there may be a fat-based strategy to improve human health and longevity. “
The study was published in Cell Biology Nature.