Omega-3 fatty acids, long praised for their ability to reduce inflammation and promote heart and brain health, may not be as simple as once believed.
A surprising new study from researchers at the University of Bristol and The University of Queensland has found that omega-3s may actually increase certain markers of inflammation in the body. These findings challenge decades of public belief and scientific assumptions about these popular nutrients.
The research, published in the International Journal of Epidemiology, was led by Dr. Daisy Crick during her Ph.D. studies at the Medical Research Council (MRC) Integrative Epidemiology Unit.
The team looked at the effects of both omega-3 and omega-6 fatty acids in the body, using data from a long-term study in the UK called the Avon Longitudinal Study of Parents and Children. This study has tracked thousands of people from birth into adulthood for more than 30 years.
Omega-3s are commonly found in oily fish such as salmon, mackerel, and sardines, and are also widely available in supplement form. They’ve become popular due to their reputation for lowering inflammation, which is believed to play a role in many chronic illnesses, including heart disease, arthritis, and dementia.
On the other hand, omega-6 fats—found in vegetable oils and processed foods—are often thought to have the opposite effect, increasing inflammation.
But Dr. Crick’s study showed that the story isn’t so black and white. The researchers found that higher levels of omega-3s in the blood were linked to increased levels of inflammation markers. This relationship remained even after adjusting for other factors like triglycerides and LDL cholesterol (often called “bad” cholesterol).
In addition, people with a high ratio of omega-6 to omega-3 fats also had higher levels of inflammation in their bodies. This suggests that not only can omega-3s raise inflammation in some cases, but an imbalance between the two types of fats could make things worse.
To make sure their findings were reliable, the team also looked at another massive dataset—the UK Biobank—which contains health information from nearly 500,000 people.
They used a scientific method called Mendelian randomization, which uses people’s genetic data to better understand cause-and-effect relationships, similar to what a randomized trial would do. This method supported the same result: omega-3s and omega-6s can both be linked to higher inflammation in certain ways.
Dr. Crick said this goes against the usual belief that omega-3s are purely anti-inflammatory. “Our findings suggest the relationship between dietary fats and inflammation is more complex than previously thought,” she said. “Rather than focusing only on increasing omega-3s, it might be more helpful to pay attention to the balance between omega-6 and omega-3 in the diet.”
The study’s senior author, Dr. Hannah Jones, added that while some inflammation markers went up, this doesn’t mean omega-3s are bad for you overall. “There may still be other benefits to these fats,” she said. “Inflammation is complicated, and more research is needed to fully understand how omega-3s work in the body.”
In short, this research doesn’t mean you should stop eating fish or taking omega-3 supplements altogether. Instead, it highlights that nutrition is rarely one-size-fits-all. It may be time to think less about “good” and “bad” fats, and more about keeping the right balance between different types of fats in your diet.
Future studies will hopefully uncover more about how omega-3s truly affect our health, and whether they’re helpful, harmful, or a bit of both depending on the situation.
If you care about nutrition, please read studies that whole grain foods could help increase longevity, and vitamin D supplements strongly reduce cancer death.
For more information about nutrition, please see recent studies about natural coconut sugar that could help reduce blood pressure and artery stiffness, and whey and soy protein may reduce inflammation in older people.
The study findings can be found in International Journal of Epidemiology.
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