High-quality fish oil capsules shouldn't taste like yesteryear's fish. If your pills smell rancid or cause nauseating burps, you might have an expired fish oil supplement. Fish oil that has oxidized can be harmful to your health.
While not a foolproof method, smelling and tasting fish oil is probably the best way to determine whether it's expired or safe for consumption.
Are Fish Oil Supplements Healthy?
Fish oil supplements contain polyunsaturated fats, such as omega-3 fatty acids. Omega-3s are components of the membranes that surround every cell in your body, especially those in the eyes, brain and sperm, according to the National Institutes of Health (NIH). Although many of the claimed benefits of omega-3s in supplement form appear to be inconclusive, these pills may have potential health benefits.
Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), two key nutrients in food and fish oil, do lower triglyceride levels, states the NIH, but this may not necessarily prevent cardiovascular problems. A January 2019 study in the New England Journal of Medicine has found that omega-3 supplements did not reduce heart attacks, strokes or cardiovascular mortality in people without any known risk factors for heart disease.
Fish oil may help during pregnancy and breastfeeding. As reported by the NIH, some studies indicate that taking omega-3 supplements while pregnant may slightly increase a baby's birth weight. These products may also help relieve the symptoms of rheumatoid arthritis, points out the National Center for Complementary and Integrative Health.
Rancid Fish Oil Effects
Like many other expired vitamins and supplements, expired fish oil can have a negative effect on your health because omega-3s are highly susceptible to oxidation. Improper storage or exposure to light, heat and oxygen may cause them to break down into lipid peroxides, which can further degrade and form aldehydes, according to an April 2013 study published in BioMed Research International.
Aldehydes have the potential to increase the frequency of mutations. They are toxic to your cells and have inflammatory properties that contribute to many ailments, including heart disease, reports an April 2019 study published in Nutrition. These compounds are toxic even when ingested in small doses.
The International Journal of Molecular Sciences published a study in September 2015, which has shown no adverse effects of the short-term intake of lightly oxidized fish oils in healthy people. However, the study reported that highly oxidized fish oils may have adverse effects on cholesterol levels.
Safe Fish Oil Consumption
If you're considering taking fish oil supplements, consult your doctor first to make sure the omega-3 softgels won't interact with any medications you may be taking. High doses of omega-3s may cause bleeding problems when combined with anticoagulant medicines, such as warfarin, warns the NIH. Fish oil supplements may also trigger mild side effects, including bad breath, nausea, stomach irritation, diarrhea and headaches.
Improperly storing fish oil can make it prone to early oxidation. Keep fish oil softgels away from heat, moisture and direct light. Some manufacturers recommend storing your softgels in the refrigerator. The BioMed Research International study found that fish oil may start to oxidize in as little as one month, even when stored in the dark at 39 degrees Fahrenheit.
Since fish oil, including cod liver oil, is highly prone to oxidation, it's best to get no more than a one-month supply at a time. Always check the expiration date. Products often sit on the drugstore shelf long before you purchase them.
In the end, the best indicator for whether your fish oil supplement is fresh or not is to use your nose. If you detect a rancid odor or taste, it's best to replace your fish oil softgels.
- BioMed Research International: "Oxidation of Marine Omega-3 Supplements and Human Health"
- National Institutes of Health: "Omega 3 Fatty Acids"
- New England Journal of Medicine: "Marine n−3 Fatty Acids and Prevention of Cardiovascular Disease and Cancer"
- National Center for Complementary and Integrative Health: "Omega-3 Supplements: In Depth"
- Nutrition: "Aldehydes Identified in Commercially Available ω-3 Supplements Via 1 H NMR Spectroscopy"
- International Journal of Molecular Sciences: "W-3 Fatty Acids and Cardiovascular Diseases: Effects, Mechanisms and Dietary Relevance"