Chances are you've seen an old cartoon in which one of the characters is forced to down some cod liver oil. The comical face of disgust that quickly follows the dosing is not just a result of clever cartooning. One of the obvious negatives of cod liver oil is that it can smell, well, fishy. For those who take this dietary supplement as a gel capsule, pill or liquid, the scent may vary by brand and form, and be more than you've bargained for in your quest for improved health. Nasty breath, upset stomach and even vomiting can result after ingesting cod liver oil [source: O'Mathuna].
No one wants a medicine that's worse than the cure, and if nausea isn't bad enough, much like other dietary supplements, there have been reports of tainted products. For example, in 2002, two batches of cod liver oil supplements being sold in England contained hazardously high levels of dioxin and PCBs -- chemicals that have possible links cancer [source: BBC]. As our oceans become more polluted and the amount of junk that fish have to filter out of their systems increases, researchers have studied the links between fish consumption and serious illnesses, including cancer. Also, for people who might be susceptible to bleeding, including those who take anticoagulants, scientists are looking into a link between cod liver oil and a higher risk for bleeding [source: Bays].
As with any sort of supplement, it's important to weigh the side effects against any of the benefits. Speaking of benefits, there's one that deserves its own special section. Read on to find out the unique relationship between cod liver oil and your skin.