Studies have shown that regular fish intake -- about once a week -- can significantly reduce the risk of heart disease. In a 1998 study, researchers found that men who ate fish at least once a week reduced their risk of sudden cardiac death by 52 percent, compared to men who ate fish less than once a month. The American Heart Association recommends at least two servings of fish per week.
Johns Hopkins University's Dr. Lawrence J. Appel found that omega-3 fatty acids, the kind found in salmon and mackerel, can help lower blood pressure in people with untreated high blood pressure. There have also been numerous studies confirming the benefits of dietary fish intake combined with weight loss to lower blood pressure.
A study by Brigham and Women's Hospital in Boston found that fish oil may help reduce the pain and inflammation of rheumatoid arthritis. Especially helpful are cold-water fish like salmon, cod and even sardines. Shellfish weren't proven to be very effective.
There is some evidence to indicate that fish intake may protect against breast cancer, and, based on animal models, fish oil seems to have inhibitory effects against several other types as well -- including cancer of the colon, skin, pancreas, prostate, lung and larynx.
Several studies have found the correlation between regular fish intake, in addition to a healthy diet, and weight loss. Fish rich in omega-3 fatty acids, such as tuna or salmon, can help in weight loss, lower cholesterol and improve overall health, according to researchers and dieticians.
Though several studies have confirmed the link between fish intake and depression risk, it is unclear exactly what causes the lowered depression risk. Some experts think that fish oil blocks the abnormal signaling in the brain that is present in mania and depression.
Studies show that a moderate intake of fish -- one to three servings a month -- may protect against age-related macular degeneration (AMD), the leading cause of irreversible blindness in the United States. AMD usually affects people over age 60 and affects central vision -- so although victims of the disease don't usually go blind, the condition complicates daily activities such as reading and driving.