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Fish

Although a forkful of fish is a gold mine of concentrated nutrients, North Americans consume an average of only 15 lb (6.8 kg) a year, compared to the annual per capita intake of beef and chicken of close to 100 lb (45 kg). While these statistics seem to indicate a clear culinary preference for beef and chicken, there are important health benefits to be gained from eating more fish and less meat.

 

The average Western diet provides about twice as much protein as necessary; in itself, this might not be a problem except that our typical protein choices with large quantities of saturated fats. in contrast, fish and shellfish are rich in protein with fewer calories, and less fat per serving than most meats. The fats in fish are particularly high in polyunsaturates, which remain liquid even when chilled. (If fish had a lot of saturated fat, it would congeal into a solid mass and prevent them from moving in their cold-water habitat.) And although some shellfish do contain cholesterol, they are low in saturated fats and are no more likely to increase blood cholesterol than skinless poultry.

 

HEALTH BENEFITS

Eating fish three times a week has been associated with a significant decrease in the rate of heart disease. This became apparent when scientists noted that coronary artery disease a leading cause o death in North America was almost nonexistent among the indigenous people of Greenland, Japanese fishermen, and First Nations of the Pacific Northwest. The one factor that these three groups had in common was a diet that relied heavily on fish for protein. When researchers looked at the effects of diets in other populations, they found that men who ate fish regularly two or three times a week were much less likely to suffer heart attacks than men who shunned fish.

 

In the recent Physicians Health Study, the male participants who ate fish at least once a week were 52 percent less likely to die of a heart attack than men who are fish once a month or less. It's not yet known whether the effect is due to one factor or many, but evidence so far points to the beneficial action of fish oils. Fish oils are rich in a type of unsaturated fatty acid known as omega-3. These fatty acids decrease the stickiness of blood platelets, making it less likely that they will clump together to form clots. They also increase the flexibility of red blood cells, enabling them to pass more readily through tiny vessels, reduce inflammation of the artery walls, and lower levels of triglycerides in your blood.

 

A study of more than 43,000 men, published in 2003, showed that men who ate about 3 to 5 oz (85-140 g) of fish one to three times a month were 43 percent less likely to have an ischemic stroke, the most common type of stroke, which is caused by blood clots.

 

The human body uses omega-3 fatty acids to manufacture prostaglandins, chemicals that play a role in many processes, including inflammation and other functions of the immune system. Several studies have found that a diet that includes fish oil equivalent to the amount in an 8-oz (230-g) daily serving of fish could relieve the painful symptoms of rheumatoid arthritis. Researchers believe that the beneficial effect was due to omega-3 fats, especially eicosapentaenoic acid (EPA). This fatty acid seems to promote the production of forms of prostaglandins and other substances that are less active in inflammation than those derived from saturated and polyunsaturated fats. The anti-inflammatory effects of omega-3 fats are being studied as a possible treatment for Crohn's disease and ulcerative colitis.

 

Some studies also suggest that people whose at fish regularly (especially varieties rich in omega-3s) are less likely to suffer from a decline in age-related thinking skills such as memory. Other studies slink low levels of omega-3s to higher rates of depression.

 

A study from Australia involving more than 3,500 older adults found that eating fish just one to three times per month appeared to protect participants against age-related macular degeneration, the leading cause of blindness in older adults.

 

NUTRITIONAL VALUE

All fish are rich in nutrients, especially protein, niacin, vitamin B12, zinc, magnesium, and more. Oily fish are particularly rich in vitamins A and D. In addition, the bones in canned salmon and sardines are an excellent source of calcium.

 

Fish are high in protein because they carry a massive bulk of muscle on a much more spindly skeleton than land animals do. Contrary to popular belief, it's not necessarily true that the darker the flesh, the oilier the fish; the dark color is, in fact, due to the presence of myoglobin, a pigment that stores oxygen in the muscles. The flesh of salmon and trout gets its appealing pink color from astaxanthin, a carotenoid pigment derived from the crustaceans and insects the fish feed on. the diet of farmed fish is often fortified with carotenoids to enhance the pink color of the flesh.

 

There is no difference in nutrient content between fish that are farmed and those caught in the wild. However, some farmed fish, such as salmon and trout, have a texture that is mealier than that of their wild counterparts. There is some concern that farmed fish may contain PCBs since these substances are more likely to be found as contaminants in coastal waters.

 

HOW MUCH IS ENOUGH ?

The mounting evidence about fish-linked cardiovascular benefits led the American Heart Association to include eating two servings of fish a week in its updated dietary recommendations. Some experts suggest up to three servings of fish a week are needed to provide the benefits attributed to omega-3 fatty acids.

 

Fish oil supplements may be advisable for some people, but check with your doctor first since they can "thin" the blood. Look for a product with a combination of DHA and EPA (two omega-3 fatty acids). Avoid fish liver oil capsules, which are a concentrated source of vitamins A and D. These vitamins can be toxic when taken in large amounts for long periods.

 

HEALTH RISKS

Some raw fish preparations, particularly sushi, can harbor parasites. Dutch "green" herring and Scandinavian gravlax (picked salmon) are also raw, but the pickling process used in herring and properly made gravlax eliminates worms and eggs.

 

Oily fish, like fresh herring and mackerel, must be cooked or processed soon after they are netted. If kept too long before cooking they are susceptible to bacterial growth, which can cause scombroid poisoning, characterized by a rash and stomach upset.

 

Shellfish from waters polluted by human waste bring a threat of viral hepatitis as well as bacterial infections that can cause severe gastrointestinal upset. Shellfish farms are required to meet strict health standards to ensure that their products are safe, but bacterial contamination still occurs. The old rule of eating raw oysters only in the "R" months does have some validity since bacteria are more likely to survive in warmer waters. thorough cooking destroys the bacteria that can contaminate oysters.

 

Coastal waters are, at times, tinged red by a species of algae (Karenia brevis) in a phenomenon known as "red tide." Shellfish from red tide areas should not be eaten because they concentrate a toxin produced by the algae. eating contaminated shellfish brings on symptoms of poisoning within 30 minutes: facial numbness, breathing difficulty, muscle weakness, and sometimes partial paralysis. Ciguatera poisoning is similar, and is caused by a toxin produced by a species of plankton. the plankton are consumed by fish, which then pass the poison on to the humans. In some cases, the effects of this toxin have lasted more than 20 years.

 

Large, long-lived fish, such as tuna, shark, king mackerel, and swordfish, may accumulate heavy-metal contaminants especially mercury which are toxic to the human nervous system and can be dangerous for unborn babies. Because of this potential hazard, women should either avoid these fish completely during pregnancy or eat them no more than once a month. In terms of canned tuna, albacore tends to be higher in mercury than light tuna. Some consumer groups recommend that pregnant women eat no more than 6 oz (170 g) of light tuna every 4 days 10 days for albacore.

 

Some species of fish caught in certain areas may show high levels of PCBs and other industrial pollutants; they are best avoided. Pregnant women are advised not to eat striped bass, especially from the northeastern regions, which may accumulate oil residues. Check with your local health department before eating fish caught in local streams and lakes. They may contain pollutants that are harmful.

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