High fish intake reduces diabetes risk in men

July 28, 2011

High fish intake reduces diabetes risk in men

By Springer
MedWire News: Results from a Japanese study suggest that eating fish can help men reduce their risk for Type 2 diabetes.

However, the investigators found no significant association between fish consumption and diabetes risk in women.

Some studies suggest that consumption of fish and omega-3 fatty acids can help prevent Type 2 diabetes, but other results have suggested that fish consumption might increase diabetes risk.
To investigate further, Akiko Nanri (National Center for Global Health and Medicine, Tokyo) and colleagues analyzed data from 22,921 men and 29,759 women who took part in the second survey of the Japan Public Health Center-based Prospective Study. The participants were aged between 45 and 75 years and had no previous history of diabetes.

Dietary information was obtained using a 147-item food frequency questionnaire at baseline and the participants were divided into quartiles for fish consumption, ranging from a median of 36.6 to 171.7 g/day for men and 35.3 to 163.1 g/day for women.

During 5 years of follow-up, 971 cases of Type 2 diabetes were reported (572 men, 399 women).
The team found that when compared with men in the lowest quartile for overall fish consumption, those in the highest quartile for consumption had a significant 27% reduced risk for developing Type 2 diabetes.

When only small and medium sized fish (mackerel, sardine, saury, and eel) were considered, the reduction in risk for diabetes in the top versus the bottom quartile of consumption was even greater, at 32%.

Men in the middle two quartiles also had a reduced risk for diabetes compared with men in the lowest quartile for total fish, and small and medium fish intake, but these reductions were not statistically significant.

Of note, fish consumption appeared to have no effect on risk for Type 2 diabetes in women.
Nanri and colleagues speculate that "the null finding in women in the current study may have been due to their relatively high proportion of body fat mass, which may have been responsible for higher levels of accumulation of fat-soluble chemicals, which negated the benefit of fish intake on glucose metabolism."

They also suggest: "The high consumption of nonfried fish in the Japanese might partly account for the inverse association between fish intake and Type 2 diabetes in the current study."
Preserving techniques such as salting and drying could also modify the association between fish intake and Type 2 diabetes risk, explain the authors. Excess salt intake can deteriorate insulin metabolism and drying may cause oxidation of polyunsaturated fatty acids in the fish, which can induce inflammation - a known risk factor for Type 2 diabetes.
Writing in the American Journal of Clinical Nutrition, Nanri et al conclude: "Biological mechanisms underlying the inverse association between fish intake and Type 2 diabetes need to be clarified."

MedWire (www.medwire-news.md ) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2011
By Helen Albert