Foods high in saturated fats have been demonized for some time now, with high intake linked to heart disease and a variety of other health conditions, including obesity. But slowly we seem to be realizing that perhaps their “unhealthy” label has been prematurely and unfairly slapped on, and avoiding them could actually be leading to unforeseen problems.

Adding to this growing body of evidence, scientists have now discovered that one particular saturated fat may actually protect against metabolic syndrome, a cluster of risk factors – elevated blood pressure, high blood sugar, abnormal cholesterol levels and excess belly fat – that can lead to diabetes. And how did they come to this conclusion? Studying dolphins.

That may sound strange at first glance, but there is method behind the madness. Bottlenose dolphins can also develop metabolic syndrome, so researchers from the National Marine Mammal Foundation (NMMF) reasoned that we may be able to learn something about this subclinical condition by examining their diet. More specifically, they wanted to see if they could identify potential protective factors that could translate to our own diet.

Since these animals predominantly eat fish, and humans are encouraged to eat oily fish as a source of healthful omega-3 fatty acids, the researchers began their investigation by examining fatty acid levels in both bottlenose dolphins and their dietary fish. Two groups of dolphins were studied: one with higher insulin levels, the other with lower. As described in PLoS One, they found that out of all the fatty acids investigated, one in particular – heptadecanoic acid – seemed to be associated with beneficial effects on their metabolism.

Those in the higher insulin group had increased amounts of a type of fat found in the blood called triglycerides, too much of which is associated with a raised risk of heart disease, and also a molecule called ferritin, which has been previously linked to metabolic syndrome, lead author Stephanie Venn-Watson tells IFLScience. In addition to this, these animals also had lower levels of heptadecanoic acid in their blood.

Examination of their diet revealed that the amount of heptadecanoic acid varied between different species of fish, so the researchers decided to investigate the effects of feeding dolphins with low levels of heptadecanoic acid a diet enriched in fish with high levels of this fat. Over six months, signs of metabolic syndrome fell towards normal levels, including ferritin, triglyceride, insulin and glucose levels.

According to Venn-Watson, high ferritin, or hyperferritinemia, is thought to be a possible underlying cause of metabolic syndrome because of the damage ferritin can cause to cells and tissues. “Thus, we believe that [heptadecanoic acid] may work in decreasing high ferritin, resulting in less cell damage and reduced indicators of metabolic syndrome,” she tells IFLScience.

To relate this to humans, the researchers examined various food products for heptadecanoic acid levels, which is known to be present in things like dairy fat, rye and certain fish. They found that butter, whole milk and yoghurt contained the highest amounts, whereas it was undetectable in nonfat dairy products.

“We hypothesize that widespread movement away from whole fat dairy products in human populations may have created unanticipated heptadecanoic acid deficiencies,” Venn-Watson said in a statement, “and, in turn, this dietary deficiency may be playing a role in the global diabetes pandemic.”

Obviously, human studies would be needed to confirm this idea, but Venn-Watson tells IFLScience that human studies are already planned to determine the optimal level of heptadecanoic acid blood levels. But there already exists some supportive evidence, as large-scale studies in Japan and Europe have linked higher blood heptadecanoic acid levels to a lower risk of metabolic syndrome and type-2 diabetes, she adds.