Atlantic fish improves glucose and fat metabolism

By Sally Robertson, B.Sc.Aug 2 2012

Eating saury, a type of fish common to the Atlantic, has immediate beneficial effects on glucose and fat metabolism, show findings from a Japanese study.

Consuming 150 g of grilled saury significantly increased postprandial insulin levels in Asian individuals, while it decreased their plasma levels of glucose and free fatty acids (FFAs).

The meal contained an abundant source of long-chain n-3 polyunsaturated fatty acids (PUFAs) and long-chain monounsaturated fatty acids (MUFAs), both of which have previously been shown to reduce the risk for metabolic syndrome in animal studies.

"To our knowledge, this is the first report evaluating the effect of a single ingestion of saury on postprandial fatty acid composition and in plasma of healthy human subjects," say Zhi-Hong Yang (Tokyo Innovation Center, Japan) and colleagues.

After a 12-hour fast, one Chinese and four Japanese individuals consumed the meal, which contained approximately 6 g of the n-3 PUFAs eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and approximately 12 g of MUFA isomers, C20:1 and C22:1.

No further meals containing the fatty acids were consumed over the following 24 hours and blood samples were obtained at 2, 6, and 24 hours.

As reported in Lipids in Health and Disease, mean levels of EPA, DHA, and total n-3 PUFA peaked 6 hours after saury ingestion. At 24 hours, the respective percentage increases in these values were 196%, 25%, and 65%.

In addition, the mean level of total long-chain MUFAs increased from 0.17% before ingestion to 2.38% at 2 hours after ingestion and then declined sharply, although the level at 24 hours was still 2.14-fold higher than the basal value.

The mean plasma glucose level also dropped significantly 2 hours after saury ingestion, while the mean insulin concentration increased significantly, rising more than fivefold.

At 6 hours, mean insulin was still 4 times higher than the basal value, but returned to the pre-ingestion value by 24 hours. Conversely, mean plasma FFA concentration was significantly reduced 6 hours after saury ingestion and returned to basal level by 24 hours.

"It has been reported that dietary fats of varying degree of unsaturation exert different effects on postprandial glucose/lipid homeostasis, and a MUFA-rich diet improves insulin sensitivity acutely," says the team.

"To clarify the effectiveness of saury on mitigating the postprandial insulin response, it is necessary to directly compare the saury oil and other dietary fats," they conclude.

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