Halibut is a dietary source of selenium and vitamin D, and also contains the marine omega-3 fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), both of which have been associated with lower risk of certain cancers, including breast cancer. However, unlike low-mercury fish such as herring, halibut is considered to contain "moderate" amounts of mercury, and should not be consumed more than six times per month for that reason.
Cancer-related effects of eating halibut
There is no epidemiological evidence to suggest that consumption of halibut influences risk of breast cancer. Pan frying fish has been shown to release carcinogenic heterocyclic amines (HCAs) in concentrations high enough to affect human health. Population studies have found that consumption of fried fish is associated with increased risk of breast cancer.
Halibut are found in the North Pacific and North Atlantic Oceans. The major species are Pacific halibut, Atlantic halibut and Greenland halibut. Most halibut sold to consumers in the U.S. is Pacific halibut, which has less than one-quarter of the omega-3 fat content as wild salmon. Atlantic halibut is more likely to be the product of fish farming. Halibut raised in fish farms tend to have less favorable omega-6/omega-3 fatty acid ratios since vegetable oils and other non-fish foods are used, in part, to feed them. When used for sushi or sashimi in the U.S., Pacific halibut is often termed hirame (although, technically it should be called ohyo).
Halibut consumption should be avoided by pregnant women and nursing mothers due to its mercury content.
Note that while we are continually searching for new evidence specifically concerning this food, there is not much interest in it among breast cancer researchers, so few studies are available.