Two newly published systematic reviews from a team of UK researchers have concluded omega-3 supplements confer little to no protective benefit against either cardiovascular disease or cancer. The research builds on prior evidence suggesting fish oil supplements are mostly useless when taken by otherwise healthy individuals.
The two studies were produced by a team called the Polyunsaturated Fats and Health group (PUFAH) from the University of East Anglia, and funded by a World Health Organization nutrition advisory group.
The first new study updates a previously published meta-analysis from 2018, expanding its dataset to comprise 86 randomized, controlled trials including over 160,000 subjects, investigating the relationship between omega-3 fatty acid supplements and cardiovascular disease. All trials included in the review ran for no less than 12 months.
The results confirmed the 2018 findings, verifying with “high-certainty” omega-3 supplements have “little or no effect on deaths and cardiovascular events.” With “moderate-certainty,” the review suggests supplements have little to no effect on stroke, cardiovascular death or heart irregularities. A very slight reduction in risk of coronary death was identified.
The second study examined the relationship between omega-3 supplements and cancer risk. This analysis included 47 randomized controlled trials including over 100,000 subjects. In general, the supplements had little to no effect on risk of cancer diagnosis or cancer death.
“Our previous research has shown that long-chain omega 3 supplements, including fish oils, do not protect against conditions such as anxiety, depression, stroke, diabetes or death,” says Lee Hooper, lead author on the new research. “These large systematic reviews included information from many thousands of people over long periods. This large amount of information has clarified that if we take omega 3 supplements for several years we may very slightly reduce our risk of heart disease, but balance this with very slightly increasing our risk of some cancers. The overall effects on our health are minimal.”
The meta-analysis did detect a slight increase in prostate cancer risk associated with omega-3 supplementation. This observation is not novel, but instead has been the source of great debate over the past few years due to a number of studies reaching inconsistent conclusions regarding whether increased omega-3 levels do directly correlate with higher prostate cancer risk.
Hooper suggests any potential small increase in prostate cancer risk from omega-3 supplements would most likely be offset by a tiny decrease in cardiovascular disease risk. Plus, he makes a distinction between omega-3 fish oil supplements and simply adding oily fish to a diet, noting a balanced, healthy diet is the better option than taking supplements.
“The evidence on omega 3 mostly comes from trials of fish oil supplements, so health effects of oily fish, a rich source of long-chain omega 3, are unclear,” says Hooper. “Oily fish is a very nutritious food as part of a balanced diet, rich in protein and energy as well as important micronutrients such as selenium, iodine, vitamin D and calcium – it is much more than an omega 3 source. But we found that there is no demonstrable value in people taking omega 3 oil supplements for the prevention or treatment of cancer.”
As well as implicitly pointing out the lack of health benefits from omega-3 supplementation in otherwise healthy individuals, Hooper notes the potential environmental impact on fish stocks of this multi-billion dollar fish oil industry.
“Considering the environmental concerns about industrial fishing and the impact it is having on fish stocks and plastic pollution in the oceans, it seems unhelpful to continue to take fish oil tablets that give little or no benefit,” says Hooper.