Swedish researchers examined data on more than 61,000 women who participated in the Swedish Mammography Cohort study beginning in 1987. The women were all between the ages of 40 and 76. Researchers found that after 15 years of follow-up, those who ate one or more servings of fatty fish per week reduced their risk of kidney cancer by 44 to 74 percent over those who did not eat fatty fish.
The healthy varieties of fish in the study included salmon, herring, sardines and mackerel. However, the researchers note that not all types of fish protect against kidney cancer. For example, less fatty varieties of fish such as cod, tuna and fresh water fish, as well as shellfish such as shrimp and lobster, did not protect against cancer.
The researchers believe that high levels of omega-3 fatty acids and vitamin D found in fish oil may be responsible for the cancer protection. Omega-3s and vitamin D have been shown in laboratory studies to prevent cancer cells from reproducing, hindering the cancer's ability to spread.
Consumer advocate Mike Adams, author of "The Seven Laws of Nutrition," says healthy fish oils can be used to treat a wide range of health problems, from heart disease and osteoporosis to asthma and ADHD. Adams says fish oils have also proven effective at treating and helping to prevent other types of cancer, such as prostate cancer.
Scientists are calling for more research to discover whether fish oil or vitamin D is responsible for the cancer protection, as well as to strengthen the link between consuming oily fish and preventing kidney cancer.