Ask The Doctors: September 2019
Q: I am getting mixed messages about fish oil to prevent heart disease. Should I be taking supplements or not?
A: Since 2002 the American Heart Association (AHA) has promoted the benefits of omega-3 fatty acids (also called long chain n-3 polyunsaturated fatty acids, or PUFA) and recommended regular consumption of seafood rich in these substances.
Whether taking supplemental fish oil capsules can prevent heart disease remains controversial. The role of fish oil in triglyceride (TG) treatment also is unclear, although analyses from several fibrate studies suggest they may be beneficial in treating TG levels greater than 200 mg/dL.
In the VITAL trial, supplementation with 1 gram of n-3 fatty acids per day over a five-year period was not effective for the primary prevention of cardiovascular disease (CVD) in healthy middle-aged adults. Perhaps higher doses in those most likely to benefit-adults with high CVD risk and elevated TG levels-might prove beneficial.
Such a group was studied in REDUCE-IT. This trial involved 8,179 patients with CVD or diabetes plus other risk factors and LDL levels of 40-100 mg/dL on statin therapy. Over five years, 4 grams a day of the fish oil icosapent ethyl reduced both first and subsequent heart attacks and strokes as well as CVD deaths by 25%. Although icosapent ethyl is a TG-lowering agent, the results appeared to be independent of patients' baseline TG levels. This suggests some benefit was due to independent actions, such as potent plaque-stabilizing properties. This fish oil product is currently FDA-approved only for treating TG levels above 500 mg/dL.
If you are at low risk of CVD, stick to dietary sources of omega-3s. If you have CVD or diabetes, and your TGs remain elevated on statin therapy, high-dose fish oil may improve your long-term outlook. A recent analysis of veterans whose LDL levels were controlled on statins found that about 30% had a similar profile to the subjects in REDUCE-IT. Therefore, it appears many people might benefit from this type of therapy. However, we await confirmation from studies using other fish oil products and an FDA review of the results to expand the indication for icosapent ethyl use.
Q: I am 65 and have high blood pressure. Should I take daily aspirin?
A: The efficacy of aspirin (ASA) for the secondary prevention of CVD events has been confirmed. However, its value in primary prevention is unclear.
Three 2018 clinical trials added insight into this issue. They found reductions in CVD events with ASA were modest at best and offset by similar or greater bleeding risks, particularly in the elderly. Only the trial conducted in patients with diabetes found benefit with ASA, but with similar increased absolute bleeding risk.
A recent meta-analysis combining these three trials with 10 earlier primary prevention trials reported an overall benefit of 11%, with a 43% increase in bleeding. Major heart associations responded that low-dose ASA should not be used for primary prevention of CVD in adults of any age who are at increased risk for bleeding, or anyone age 70 or older. It may be considered in selected adults ages 40 to 70 at higher risk for CV events but not at increased risk for bleeding.
Your decision to start ASA should be based on a discussion with your doctor that includes an assessment of your CVD risk and potential harm versus benefit. ASA would be reasonable for a combination of high CVD risk, high colorectal cancer risk and low bleeding risk. Use caution if you are over 70. Stop taking ASA or don't start if you have low CVD risk (a 10-year risk less than 5%), high risk of bleeding or a clear preference to avoid bleeding.