There is a significant protective benefit of fish consumption in people with cardiovascular disease, as well as with significant improvements in multiple other health outcomes.
An umbrella review of meta-analyses found that increased fish consumption also improved rates of cardiovascular and all-cause mortality. However, fish consumption had no significant effects on rates of hypertension, atrial fibrillation, or type 2 diabetes.
Although not directly reflected in the findings, modest fish consumption also appears to be was associated with significant improvements in multiple health outcomes, including the risks for myocardial infarction, stroke and heart failure to have cardiac benefits, according to a Journal of the American Medical Association commentary.
Medscape Medical News reports that researchers Jayedi and Shab-Bidar examined 34 meta-analyses of prospective observational studies, which featured a total of 40 different outcomes. Greater fish consumption of 100 g/day was associated with significant improvements in multiple health outcomes, including the risks for myocardial infarction, stroke and heart failure.
Medscape Medical News comments that there is a lack of large studies that have differentiated the effects of fish consumption among adults with and without a history of cardiovascular disease (CVD). The current study addresses this gap.
People with CVD who regularly ate fish had significantly fewer major CVD events and there were fewer total deaths compared with similar individuals who did not eat fish, but there was no beneficial link from eating fish among the general population in prospective data collected from more than 191 000 people from 58 countries.
Despite the neutral finding among people without CVD, the finding that eating fish was associated with significant benefit for those with CVD or who were at high risk for CVD confirms the public health importance of regular fish or fish oil consumption, says one expert.
A little more than a quarter of those included in the new study had a history of CVD or were at high risk for CVD. In this subgroup of more than 51 000 people, those who consumed on average at least two servings of fish weekly (at least 175 g, or about 6.2 ounces per week) had a significant 16% lower rate of major CVD events during a median follow up of about 7.5 years.
The rate of all-cause death was a significant 18% lower among people who ate two or more fish portions weekly compared with those who did not, say Dr Deepa Mohan and associates. The researchers saw no additional benefit when people regularly ate greater amounts of fish.
‘There is a significant protective benefit of fish consumption in people with cardiovascular disease,’ summed up Dr Andrew Mente, a senior investigator on the study and an epidemiologist at McMaster University in Hamilton, Canada. ‘This study has important implications for guidelines on fish intake globally. It indicates that increasing fish consumption, and particularly oily fish, in vascular patients may produce a modest cardiovascular benefit,’ he said in a statement released by McMaster.
The neutral finding of no significant benefit (as well as no harm) regarding either CVD events or total mortality among people without CVD ‘does not alter the large body of prior observational evidence supporting the cardiac benefits of fish intake in general populations,’ notes Dr Dariush Mozaffarian, in a commentary that accompanies the report.
Although the new analysis failed to show a significant association between regular fish consumption and fewer CVD events for people without established CVD or CVD risk, ‘based on the cumulative evidence from prospective observational studies, randomised clinical trials, and mechanistic and experimental studies, modest fish consumption appears to have some cardiac benefits,’ he adds.
‘Adults should aim to consume about two servings of fish per week, and larger benefits may accrue from non-fried oily (dark meat) fish,’ writes Mozaffarian, a professor of medicine and nutrition at Tufts University School of Medicine,
Boston, Massachusetts. Oily, dark fishes include salmon, tuna steak, mackerel, herring and sardines. Species such as these contain the highest levels of long-chain omega- 3 fatty acids, eicosapentanoic and docosapentanoic acid; these nutrients likely underlie the CVD benefits from fish, Mozaffarian says.
‘Fish oil lowers heart rate, blood pressure and triglycerides (at high dosages), increases adiponectin, improves endothelial function, and in some studies improves oxygen consumption in myocardium. If there is benefit from fish, it’s from the omega-3s, and all in all the evidence supports this,’ but because the evidence is primarily observational, it can only show linkage and cannot prove causation, he explains.
Given the potential benefit and limited risk: ‘I think everyone should aim to eat two servings of fish each week, preferentially oily fish. That’s very solid,’ says Mozaffarian, who is also a cardiologist and dean of the Gerald J and Dorothy R Friedman School of Nutrition Science and Policy, Boston, Massachusetts. The investigators did not have adequate data to compare the associations between outcomes and a diet with oily fish versus less oily fish.
For people who either can’t consume two fish meals a week or want to ensure their omega-3intake is adequate, ‘it’s very reasonable for the average person to take one [over-thecounter] fish oil capsule a day,’ Mozaffarian adds.
He acknowledges that several studies of fish-oil supplements failed to show benefit, but several others have. ‘It’s a confusing field, but the evidence supports benefit from omega-3s,’ he concludes.
He discounts the new finding that only people with established CVD or who are at high risk benefit. ‘’m not sure we should make too much of this, because many prior studies showed a lower CVD risk in fish-eating people without prevalent CVD,’ he said. The new study ‘provides important information, given its worldwide breadth,’ he added.
The new report used data regarding 191 558 people enrolled prospectively in any of four studies. The average age of the participants was 54 years, and 52% were women.
During follow up, death from any cause occurred in 6% of those without CVD or CVD risk and in 13% of those with these factors. Major CVD events occurred in 5 and 17% of these two subgroups, respectively. To calculate the relative risks between those who ate fish and those who did not, the investigators used standard multivariate adjustment for potential confounders and adjusted for several dietary variables, Mente says.
References
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