A growing body of evidence shows distinct differences in the ways that heart disease manifests in men and women.
by Craig Weatherby
When people experience chest pain, doctors usually look for signs of the fatty, calcified arterial plaque called atherosclerosis, which is a key risk factor for cardiovascular disease.
But in many women, problems in two other areas—the lining of coronary arteries and tiny blood vessels within the heart itself—combine to rob the heart's muscles of oxygen: a phenomenon called “diffuse atherosclerosis.”
Although diffuse atherosclerosis is not apparent on the coronary angiograms normally used to look for arterial clogs, it still results in dangerously reduced blood flow to the heart tissues.
And absent evidence of a blocked artery, a woman's symptoms are likely to be dismissed as signs of something unknown and far less dangerous than heart disease (Mercuro G et al. 2010; Leuzzi C et al. 2010).
Now, a new clinical study shows that when it comes to the “stickiness” of their blood, men and women react differently to the two key omega-3s in marine (fish or krill) oils, called EPA and DHA.
This distinction may explain part of researchers' persistent confusion about the overlapping but not identical roles that EPA and DHA play in preventing heart disease and adverse heart events.
Fish and fish oils are known to lower blood triglyceride levels, improve people's cholesterol profiles, and reduce the risk of “sudden cardiac death” …which accounts for half of all heart-related fatalities, and is usually triggered by an arrhythmia.
There is an unfortunate misperception that of the two omega-3s, EPA is the more important omega-3 for heart health.
But DHA exerts overlapping effects and is probably more important for reducing certain cardiovascular risk factors.
The results of a new clinical trial suggest that this confusing picture may stem from a previously unproven difference in the effects of EPA and DHA in men and women.
Trial detects gender differences in responses to two key omega-3s
Researchers in Australia report that the omega-3 fatty acids EPA and DHA may have gender-specific effects on blood platelet aggregation (Phang M et al. 2010).
Platelets are critical for blood clotting and wound healing. But they can become overactive and promote an unhealthy tendency toward formation of unneeded clots, and can contribute to blood vessel blockage.
Because the synthetic drugs prescribed to people with excessive platelet aggregation can have adverse side effects, researchers have been looking for safer alternatives, with some of that search focused on omega-3 EPA and DHA.
The majority of studies on omega-3 supplements use fish oil containing both EPA and DHA, making it hard to tell which exerts the greatest beneficial effect on a given aspect of health.
But recent lab research by the same Australian team behind the new clinical trial suggested that EPA and DHA exert different, gender-specific effects on platelet aggregation, with regard to human blood cells in a test tube (Phang M et al. 2009).
The Aussie team decided to conduct a clinical trial to test the validity of those indications.
For the new trial, 30 healthy participants were given a single dose of EPA-rich fish oil, DHA-rich fish oil, or a placebo, and their blood chemistry was tested before and after taking the capsules.
Both EPA and DHA reduced platelet aggregation, but the results showed a sharp gender difference:
EPA was significantly more effective in men, compared to DHA or placebo capsules.
DHA was significantly more effective in women, compared with EPA or placebo capsules.
The researchers proposed that the observed gender differences could be caused by differing interactions between the two omega-3s and male and female sex hormones.
As the Aussie team wrote, “…males may benefit more from EPA supplementation while females are more responsive to DHA.”
The results hold obvious implications for how omega-3 supplements intended to specifically reduce excessive platelet aggregation are formulated.
However, while platelet aggregation is considered a risk factor for heart attacks, it is not considered a particularly critical factor in the development of cardiovascular disease.
It's likely that EPA and DHA also play gender-specific roles in other, more important cardiovascular risk factors such as cholesterol profile, inflammation, triglyceride levels, arrhythmias, arterial plaque… and the less obvious factors associated with heightened risk for women.
Given that most of the evidence that omega-3s aid heart health comes from population studies that find fish consumption helpful, it seems wise for both sexes to continue taking a “whole food” approach to cardiovascular health.
In other words, eat fatty fish regularly and take whole fish or krill oil supplements that provide both EPA and DHA.
Phang M, Sinclair AJ, Lincz LF, Garg ML. Gender-specific inhibition of platelet aggregation following omega-3 fatty acid supplementation. Nutr Metab Cardiovasc Dis. 2010 Aug 11. [Epub ahead of print]
Phang M, Garg ML, Sinclair AJ. Inhibition of platelet aggregation by omega-3 polyunsaturated fatty acids is gender specific-Redefining platelet response to fish oils. Prostaglandins Leukot Essent Fatty Acids. 2009 Jul;81(1):35-40. Epub 2009 May 29.
Leuzzi C, Sangiorgi GM, Modena MG. Gender-specific aspects in the clinical presentation of cardiovascular disease. Fundam Clin Pharmacol. 2010 Sep 14. doi: 10.1111/j.1472-8206.2010.00873.x. [Epub ahead of print]
Mercuro G, Deidda M, Piras A, Dessalvi CC, Maffei S, Rosano GM. Gender determinants of cardiovascular risk factors and diseases. J Cardiovasc Med (Hagerstown). 2010 Mar;11(3):207-20.