Higher Fish Intakes Linked to Better Endothelial Function and Lower Inflammatory Markers in Healthy Adults
Blood vessels are lined with a single layer of endothelial cells that actively contribute to healthy heart function, blood flow and immune responses. They release substances that affect blood clotting, fight inflammation and maintain healthy blood pressure. When their function is disturbed, as in atherosclerosis, hypertension, diabetes and inflammation, these cells become highly active by producing an array of substances to handle the challenges. Endothelial function is sensitive to an individual’s dietary pattern, fish intake and long-chain omega-3 fatty acids (omega-3s). Studies have reported that individuals with severe heart failure, type 2 diabetes, abnormal blood lipids or obesity experience improved endothelial function when treated with long-chain omega-3s. A common factor in these conditions is sub-clinical or low-grade inflammation and omega-3s have been frequently shown to decrease the markers of underlying inflammation. What is less clear is whether these fatty acids modify endothelial function in healthy individuals with no symptoms of disease. A limited amount of evidence suggests that Mediterranean-style diets may be associated with improved endothelial function compared with diets rich in saturated fatty acids or a low-fat diet enriched with alpha-linolenic acid, an omega-3 fatty acid found in some plants. To learn more about the effect of diet on endothelial function in healthy adults, investigators in the Netherlands examined the dietary patterns of participants in the Amsterdam Growth and Health Longitudinal Study established in 1976. Dietary data and blood samples were collected at baseline and 6 years later. An array of markers for endothelial function and inflammation were analyzed in the blood samples and the relationships between the consumption of different food categories and the biological markers were determined. Changes in these parameters over the 6-year follow-up were used to assess the relationships studied. Of all the food groups examined, only fish consumption was related to the scores for endothelial function and inflammation. Individuals who ate no fish were nearly 3 times more likely to have higher scores for endothelial dysfunction compared with those who ate 200 grams (7 oz) or more of fish per week. Among all study participants, the median consumption of fish was 75 grams (2.6 oz) per week, but this level was also associated with nearly twice the risk of increased endothelial dysfunction. Similar findings for improved endothelial function were observed for the consumption of long-chain omega-3s, which are found mainly in fish. Likewise, the investigators observed that participants with the highest intakes of fish or long-chain omega-3s had significantly lower scores for the markers of inflammation compared with those who did not eat fish. No other food group was associated with inflammatory markers. A reduction in inflammatory markers would be expected to reduce the risk of heart disease. When the researchers examined the type of fish consumed they found that only the consumption of fatty fish was associated with the lowest scores for endothelial dysfunction. This observation, while expected, helps solidify the interpretation that the most active components in fish for heart health are its long-chain omega-3s. Fatty fish have much more of these fatty acids than lean fish. Taken together, these findings suggest that two ways long-chain omega-3s may protect heart health are through improved endothelial function and reduced inflammation. That these observations occurred in healthy adults without heart disease points to the preventive effects of eating fish regularly.