While some research has shown these fats may help fight against type 2 diabetes, a review and meta-analysis published in August 2019 in the BMJ has found that increasing omega-3 intake — whether by consuming supplements or foods rich in this fat — does little or nothing to lower diabetes risk. “We found that despite over 58,000 participants being randomized into long-term trials, and 4 percent of those participants developing diabetes, the people who were randomized to consume more long-chain omega-3 fats — fish oils — had the same risk of diabetes diagnosis as the group who did not take more fish oil,” says the study author Lee Hooper, PhD, RD, an epidemiologist at the University of East Anglia in the United Kingdom. Because the review included only randomized controlled trials, the findings adjusted for potentially confounding factors that may affect diabetes risk, such as smoking status, physical activity level, overall diet, and genetics. “This is definitive: Taking fish oil supplements does not protect against diabetes, but neither is it harmful, except possibly at high doses,” Dr. Hooper says. RELATED: How Your Genes Can Affect Your Type 2 Diabetes Risk
How Eating Various Healthy Fats May Affect Type 2 Diabetes Risk
Hooper and her collaborators based their results on analyses of 83 trials that examined the effects of consuming more long-chain omega-3 (found in fatty fish), omega-6 (found in vegetable oils, nuts, and seeds, per the Mayo Clinic), alpha-linolenic acid (an omega-3 found in flaxseed and other plants, per a February 2015 review in BioMed Research International), or total polyunsaturated fatty acids (which include both omega-3 and omega-6 fat sources, according to MedlinePlus). Participants took the fats as supplements or via enriched or naturally rich foods. Study authors weighed how intake of the fatty acids affected new diabetes diagnoses and measures of glucose metabolism (how well the body processes carbohydrates). According to MedlinePlus, in type 2 diabetes, the body does not process glucose (blood sugar) as it should because of a condition called insulin resistance, so blood sugar levels remain high, increasing the risk of damage to the arteries, heart, and other organs. More than 100 million Americans live with diabetes or prediabetes, according to the Centers for Disease Control and Prevention. In their analysis, authors couldn’t determine the effects of alpha-linolenic acid, omega-6, and total polyunsaturated fats on type 2 risk because of insufficient evidence. “So we don’t know whether these fats are neutral, protective, or harmful as regards diabetes risk,” says Hooper. Yet information on long-chain omega-3 fats was significant enough to determine that increasing intake of these fats by an average of 2 grams (g) (.07 ounces) — during trials that lasted an average of 33 months — had little or no effect on the likelihood of participants’ diabetes diagnosis or on their glucose metabolism. Study authors point out that some evidence suggests that long-chain omega-3s may be effective at reducing blood triglycerides, a risk factor for heart disease per the Mayo Clinic, but high doses of 4.4 g per day or more could have negative effects on diabetes risk and glucose metabolism. RELATED: How Diabetes and Heart Disease Are Connected
The Importance of Practicing Caution With Fish Oil Supplements
Marilyn Tan, MD, the chief of the endocrinology clinic at Stanford Health Care in Palo Alto, California, who was not involved in the new study, did not find the results surprising. “We have not had any definitive evidence that any supplements can help reduce the risk of type 2 diabetes,” she says. “The only solid evidence we have for ‘natural’ ways to treat and prevent diabetes is aggressive lifestyle changes such as weight loss, diet changes, exercise, and avoiding sedentary time.” Dr. Tan cautions her patients about supplement use in particular because the U.S. Food and Drug Administration does not regulate them as tightly as it does traditional medication. “Many supplements will make claims about medical benefits even though the effects are not well studied,” she says. “That said, supplements such as omega-3 fats are generally recognized as safe.” In Hooper’s opinion, you may be better off focusing on other healthy habits, like following a nutritious diet and exercising, than reaching for supplements. “Patients don’t need to stop taking omega-3 supplements if they choose to take them, but neither should we be encouraging patients to start taking them,” she says. “Patients might choose to spend the money that would otherwise be spent on long-chain omega-3 supplements on other healthy choices, like physical activity they really enjoy or wonderful fruits and vegetables. These are more likely to be positively helpful as well as fun and delicious.” RELATED: 9 Tricks to Help You Start Working Out and Actually Stick to It
How Scientists Plan to Study Healthy Fats in the Future
For Hooper and her colleagues, the research on this topic will not stop with this review on fish oil pills. They are carrying out a set of studies for the World Health Organization (WHO) to assess the possible health effects of omega-3 and omega-6 fatty acids. The WHO is planning to update its dietary guidelines on fats in the near future, says Hooper. Hooper stresses that most trials included in this recent review focused on supplements, so “the effect of eating more oily fish on diabetes risk is unclear.” Oily fish are delicious and offer protein, selenium, calcium, vitamin D, and much more, she says. In general, she adds, fatty fish are also lower in saturated fat compared with meat and cheese. “For these reasons,” Hooper says, “I would encourage people to eat oily fish, but not to take fish oil supplements.”
