Predicting the risk

By the time hardening of the arteries (atherosclerosis) develops, full-blown heart disease could be right around the corner. A test called flow-mediated dilation can help measure blood vessel health (endothelial function) and predict a person's heart disease risk, giving them time to make changes to head off heart disease before it takes hold.

Several studies have examined the effect of omega-3 fatty acids on blood vessel health, as measured by flow-mediated dilation. To summarize these findings, researchers from Beijing, China, looked at 16 different studies including 901 people who took omega-3 supplements made from fish or walnut oil. The people took from 0.5 to almost 5 grams per day of EPA (eicosapentaenoic acid), DHA (docosahexaenoic acid), or ALA (alpha linolenic acid) for an average of 56 days. Here's what they found:

• Omega-3 fatty acids significantly increased flow-mediated dilation compared with placebo.
• Omega-3 supplementation seemed to improve flow-mediated dilation in those with poorer health (people with heart disease or with other risk factors for it) more so than in healthy people.
• Higher omega-3 consumption improved flow-mediated dilation to a greater extent than lower amounts.

Should you take an omega-3 supplement?

"Although a positive association was identified between omega-3s and endothelial function, the evidence for a clinical efficacy is not strong enough to make final recommendations concerning specific doses or the durations of intakes for different populations," concluded the researchers.

While flow-mediated dilation can help predict heart disease risk, improving it doesn't necessarily prevent heart disease. The studies included in the review showed that omega-3s improved flow-mediated dilation, but they didn't go on to follow the people to see if they actually developed heart disease. Nevertheless, this kind of information is helpful when making decisions about using omega-3 supplements.

Eating your omega-3s

Cold-water fish like salmon, halibut, mackerel, trout, sardines, and scallops are all terrific sources of omega-3 fatty acids. And walnuts have so much ALA that they've earned the right to bear a qualified health claim from the FDA for their heart health benefits.

Eating fish is the preferred way to boost your omega-3 intake, since non-fish sources of omega-3s have to go through a series of steps in the body to be converted to DHA and EPA, and the process isn't perfect. This means that the pathways leading from ALA to DHA and EPA can become maxed out, limiting the amount of DHA and EPA that's available from plant sources.

(Atherosclerosis 2012; 221:536-43)