Oily fish has been linked to a number of health benefits, including a lower risk of heart disease, improved mental ability, and protection from cancer, alcohol-related dementia, and rheumatoid arthritis.
Fish oil contains the two fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These are believed to benefit the cardiovascular system.
The American Heart Association (AHA) suggests consuming at least two servings of fish, and especially oily fish, each week. A serving is 3.5 ounces of cooked fish, or about three quarters of a cup of flaked fish.
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Health benefits of oily fish
Oily fish offers a range of health benefits.
Both white and oily fish are good sources of lean protein. White fish contains fatty acids, but only in the liver, and in smaller quantities.
Omega-3 oils have been linked to higher levels of high density lipoprotein (HDL) and lower levels of triglycerides in the blood.
Cholesterol is mainly produced by the liver. It is involved in strengthening cell walls and in hormone production. Low density lipoproteins (LDL) carry the cholesterol to the cells, while HDL takes the excess cholesterol back to the liver for recycling or removal.
Consuming oily fish can help to protect against cardiovascular disease, according to the AHA. A study published by the American Physiological Society suggests that fatty fish oils can protect the heart during times of mental stress.
A study published in Annals of the Rheumatic Diseases linked an average daily intake of at least 0.21 grams a day of omega-3 with a 52 percent lower risk of developing rheumatoid arthritis (RA). Other research suggests that omega-3 fatty acids might protect against the future development of RA.
Among people who abuse alcohol, fish oil may offer protection from dementia. Brain cells that were exposed to a mix of fish oil and alcohol had 95 percent less neuroinflammation and neuronal death compared with brain cells that were only exposed to alcohol.
Mouth and skin cancers
Oily fish consumption may protect from early- and late-stage oral and skin cancers. Omega-3 fatty acid has been found to target and selectively inhibit the growth of malignant and pre-malignant cells at doses that do not affect the normal cells.
Sensory, cognitive and motor development
Consuming oily fish during the last months of pregnancy can have positive effects on a child's sensory, cognitive, and motor development, research suggests. The same study did not find that breastfeeding offered the same benefits.
Eating salmon during pregnancy can benefit offspring.
Protecting vision and memory
DHA can protect against vision loss. Scientists have identified a link between oily fish consumption and a lower risk of vision loss in older people. A study published in PLOS One indicates that eating oily fish may improve working memory.
Breast and prostate cancer
One meta-analysis of nearly 900,000 women has linked a higher consumption of oily fish with a lower risk of breast cancer. However, another team found that men with high quantities of omega-3 oil in their blood had a higher risk of prostate cancer.
Which fish, and how much?
Oily fish contain significant amounts of oil throughout their body tissues and in their belly cavity. Examples of oily fish include trout, salmon, sardines, pilchards, kippers, eels, whitebait, mackerel, herring, and tuna.
All these fish, except for tuna, are rich in omega-3 fatty acids, whether canned, fresh or frozen. Tuna is rich in omega-3 when it is fresh, but not when canned.
How much oily fish is healthy?
Although eating oily fish promotes many aspects of good health, overconsumption may be not be beneficial.
What about the pollutants?
The United States Food and Drug Administration (FDA) note that nearly all fish and shellfish contain traces of mercury.
This is because oily fish contain pollutants called polychlorinated biphenyls (PCBs) and dioxins. These pollutants do not have an immediate effect on health, but long term exposure can be harmful.
Dioxins are highly toxic compounds. Humans are exposed to them through animal products, including fish. High exposure can cause skin lesions, and impairment of the immune and reproductive systems.
Fish is not the only source of omega-3.
Despite these concerns, oily fish is recommended while pregnant or breastfeeding, because it will benefit the fetus or the infant, as long as the maximum limits are adhered to.
The FDA and Environmental Protection Agency (EPA) suggest a maximum of 12 ounces a week for young children and pregnant women, or two average meals.
Suitable options are shrimp, canned light tuna, salmon, pollock, and catfish, which are low in mercury. The FDA and EPA recommend avoiding shark, swordfish, king mackerel, and tilefish.
If fish is caught locally and there is no information about pollutants, the maximum intake should be 6 ounces a week.
A number of hygiene rules must be followed.
All fish should be stored in a fridge or freezer. Hands should be thoroughly washed before and after handling fish. Fish should be thawed in a fridge overnight. Raw fish should not come into contact with cooked fish or other foods.
In view of the rapidly declining fish stocks worldwide, people are encouraged to look for sustainable sources of fish.