In the news: Fish Omega-3 Linked to Kidney Health; Vitamin D May Help in Prediabetes

Study Links Seafood Based Omega-3 with Lower Risk of Chronic Kidney Disease

A new study published in the British Medical Journal(1), found an 8-13% lower risk of chronic kidney disease and a slower decline in kidney function with a higher intake of omega-3 fatty acids from seafood sources.

Although the associations were relatively modest, the findings suggest a beneficial role of omega-3 intake in preventing and managing chronic kidney disease – a condition affecting about 700 million people worldwide, or about one in eleven people in the general global population.

This large study is important because while animal studies suggest omega 3 fatty acids have beneficial effects on kidney function, the evidence from human studies is limited.

To assess the relationship between omega-3 fatty acid intake and chronic kidney disease, a team of international researchers analyzed data from 19 studies conducted in 12 countries that included over 25,500 participants who were followed an average 11 years.

Omega-3 biomarkers indicate that these fatty acids can improve artery stiffness, lower blood pressure and reduce plasma triglycerides – all of which could help protect against the development of chronic kidney disease. The researchers found that those in the top 20% of omega-3 biomarkers had a 13% lower risk of the disease compared to those in the bottom 20% of biomarkers (which reflect intake).

Higher levels of seafood omega-3 biomarkers were not only associated with a lower risk of the disease but also a slower decline in kidney function. Seafood omega-3 included the fatty acids eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA).

On the other hand, omega-3 fatty acids from plant sources – namely alpha linolenic acid from oils such as flaxseed, canola, soy, perilla, and walnut oil – were not associated with a lower risk of kidney disease or kidney function. This highlights the need to include seafood as part of a healthy diet.

Vitamin D May Help Control Pre-Diabetes

People with prediabetes – estimated at 1 out of 3 Americans – have blood sugar levels higher than normal, but not high enough to be diagnosed as type 2 diabetes. Prediabetes, however, does raise the risk for developing type 2.

A new systemic review and meta-analysis(2), from researchers at Tufts Medical Center has found that a higher vitamin D intake by individuals with prediabetes is associated with a 15% reduced risk of going on to develop type 2 diabetes.

While previous studies have suggested a benefit of vitamin D to those with prediabetes, none of the studies were large enough to show statistical significance. Because these studies were conducted in different countries, different doses and forms of vitamin D were tested: 20,000 IU cholecalciferol weekly, 4,000 IU cholecalciferol daily, and 0.75 mcg of eldecalcitol (an analogue of D used in Japan).

Cholecalciferol reduced the risk for diabetes significantly among those who maintained a higher vitamin D blood level during follow-up. There were no apparent safety issues, with no difference in adverse events (including kidney stones, high blood or urine calcium levels) between those taking vitamin D and placebo takers.

The authors point out that there are other strategies to combat prediabetes: Intensive lifestyle modification has resulted in a 58% lower risk, and taking the drug metformin has been shown to lower risk by 31%.

References

1. Ong KL, et al. Association of omega 3 poly-unsaturated fatty acids with incident chronic kidney disease: pooled analysis of 19 cohorts. BMJ. 380:e072909, 2023.
2. Pittas AG, et al. Vitamin D and risk for type 2 diabetes in people with prediabetes. A systematic review and meta-analysis of individual participant data from 3 randomized clinical trials. Ann Intern Med. Epub Feb 7, 2023.