Question: Name some benefits for older people eating oily fish.
About the article "Seafood", section "Health benefits".

Candidate passages:
Research over the past few decades has shown that the nutrients and minerals in seafood can make improvements in brain development and reproduction and has highlighted the role for seafood in the functions of the human body.
Doctors have known of strong links between fish and healthy hearts ever since they noticed that fish-eating Inuit populations in the Arctic had low levels of heart disease.
One study has suggested that adding one portion of fish a week to your diet can cut your chances of suffering a heart attack by half.
Fish is thought to protect the heart because eating less saturated fat and more Omega-3 can help to lower the amount of cholesterol and triglycerides in the blood – two fats that, in excess, increase the risk of heart disease.
Omega-3 fats also have natural built-in anti-oxidants, which are thought to stop the thickening and damaging of artery walls.
Regularly eating fish oils is also thought to reduce the risk of arrhythmia – irregular electrical activity in the heart which increases the risk of sudden heart attacks.10-12% of the human brain is composed of lipids, including the Omega-3 fat DHA.
Recent studies suggest that older people can boost their brain power by eating more oily fish, what with regular consumers being able to remember better and think faster than those who don't consume at all.
Other research has also suggested that adding more DHA to the diet of children with attention-deficit hyperactivity disorder can reduce their behavioural problems and improve their reading skills, while there have also been links suggested between DHA and better concentration.
Separate studies have suggested that older people who eat fish at least once a week could also have a lower chance of developing dementia and Alzheimer's disease.
Including fish as a regular part of a balanced diet has been shown to help the symptoms of rheumatoid arthritis – a painful condition that causes joints to swell up, reducing strength and mobility.
Studies also show that sufferers feel less stiff and sore in the morning if they keep their fish oil intake topped up.
Recent research has also found a link between Omega-3 fats and a slowing down in the wearing of cartilage that leads to osteoarthritis, opening the door for more research into whether eating more fish could help prevent the disease.
Fish is high in minerals such as zinc, iodine and selenium, which keep the body running smoothly.
Iodine is essential for the thyroid gland, which controls growth and metabolism, while selenium is used to make enzymes that protect cell walls from cancer-causing free radicals, and helps prevent DNA damage caused by radiation and some chemicals.
Fish is also a source of vitamin A, which is needed for healthy skin and eyes, and vitamin D, which is needed to help the body absorb calcium to strengthen teeth and bones.
In 1994, the UK Committee on Medical Aspects of Food and Nutrition Policy (COMA) recommended that people eat at least two portions of fish per week, one of which should be oily fish.
In 2004 the UK Food Standards Agency published advice on the recommended minimum and maximum quantities of oily fish to be eaten per week, to balance the beneficial qualities of the Omega 3 fatty acids against the potential dangers of ingesting polychlorinated biphenyls and dioxins.
It reiterated the 1994 guideline of two portions of fish per week including one portion of oily fish, but advised eating no more than four portions per week, and no more than two portions for people who are pregnant, may become pregnant or who are breastfeeding.
The United States Environmental Protection Agency's (EPA) Exposure Reference Dose (RfI) for MeHg is 0.1 micrograms per kg body weight per day.
The corresponding limit of blood mercury is 5.8 micrograms per liter.
The restrictions apply to certain oily fish – "marlin, swordfish, shark and, to a lesser extent, tuna" The recommendations on maximum consumption of oily fish were up to four portions (1 portion = 140g, or approx 4.9 ounces) a week for men, boys, and women past childbearing age, and up to two portions a week for women of childbearing age, including pregnant and breastfeeding women, and girls.
There is no recommended limit on the consumption of white fish.
The EPA and 2007 U.S. Department of Agriculture guidelines sets a limit only on consumption of fatty fish with greater than one part per million of methylmercury.
Specifically tilefish, king mackerel, shark and swordfish.
There are limits, however, for nursing/pregnant women and children under the age of six.
This population should completely avoid fish with high risk of Mercury contamination (those listed above) and limit consumption of moderate and low-Mercury fish to 12 ounces or fewer per week.
Albacore tuna should be limited to 6 oz or less per week. 
Oily fish have oil in their tissues and in the belly cavity around the gut.
Their fillets contain up to 30 percent oil, although this figure varies both within and between species.
Examples include small forage fish, such as sardines, herring and anchovies, and other larger pelagic fish, such as salmon, trout, and mackerel.
Oily fish can be contrasted with whitefish, which contain oil only in the liver, and much less overall than oily fish.
Examples of whitefish are cod, haddock and flatfish.
Whitefish are usually demersal fish which live on or near the seafloor, whereas oily fish are pelagic, living in the water column away from the bottom.
Oily fish are a good source of vitamins A and D, and are rich in omega-3 fatty acids (whitefish contain the same nutrients but at a much lower level).
For this reason the consumption of oily fish rather than whitefish can be more beneficial to humans, particularly concerning cardiovascular diseases; however, oily fish are known to carry higher levels of contaminants (such as mercury or dioxin) than whitefish.
Among other benefits, studies suggest that the omega-3 fatty acids in oily fish may help improve inflammatory conditions such as arthritis. 
Salmon is a popular food.
Classified as an oily fish, salmon is considered to be healthy due to the fish's high protein, high omega-3 fatty acids, and high vitamin D content.
Salmon is also a source of cholesterol, with a range of 23–214 mg/100 g depending on the species.
According to reports in the journal "Science", however, farmed salmon may contain high levels of dioxins.
PCB (polychlorinated biphenyl) levels may be up to eight times higher in farmed salmon than in wild salmon, but still well below levels considered dangerous.
Nonetheless, according to a 2006 study published in the Journal of the American Medical Association, the benefits of eating even farmed salmon still outweigh any risks imposed by contaminants.
The type of omega-3 present may not be a factor for other important health functions.
Salmon flesh is generally orange to red, although white-fleshed wild salmon occurs.
The natural colour of salmon results from carotenoid pigments, largely astaxanthin, but also canthaxanthin, in the flesh.
Wild salmon get these carotenoids from eating krill and other tiny shellfish.
The vast majority of Atlantic salmon available around the world are farmed (almost 99%), whereas the majority of Pacific salmon are wild-caught (greater than 80%).
Canned salmon in the US is usually wild Pacific catch, though some farmed salmon is available in canned form.
Smoked salmon is another popular preparation method, and can either be hot or cold smoked.
Lox can refer to either cold-smoked salmon or salmon cured in a brine solution (also called gravlax).
Traditional canned salmon includes some skin (which is harmless) and bone (which adds calcium).
Skinless and boneless canned salmon is also available.
Raw salmon flesh may contain "Anisakis" nematodes, marine parasites that cause anisakiasis.
Before the availability of refrigeration, the Japanese did not consume raw salmon.
Salmon and salmon roe have only recently come into use in making sashimi (raw fish) and sushi. 
As described by early visitors (e.g., Jesuit cartographers on the Ussury River in 1709), the economy of the people living there (who would be classified as Nanai, or possible Udege people, today) was based on fishing.
The people would live in villages along the banks of the Ussuri, and would spend their entire summers fishing, eating fresh fish in the summer (particularly appreciating the sturgeon), and drying more fish for eating in winter.
Fish would be used as fodder for those few domestic animals they had (which made the flesh of a locally raised pig almost inedible by visitors with European tastes).
The traditional clothing was made out of fish skins.
These skins were left to dry.
Once dry, they were struck repeatedly with a mallet to leave them completely smooth.
Finally they were sewn together.
The fish chosen to be used were those weighing more than 50 kilograms.
In the past centuries, this distinct practice earned the Nanai the name "Fish-skin Tartars" (, "Yupi Dazi").
This name has also been applied, more generically, to other aboriginal groups of he lower Sungari and lower Amur basins.
Agriculture entered the Nanai lands only slowly.
Practically the only crop grown by the "Yupi" villagers on the Ussuri River shores in 1709 was some tobacco.