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The UK government Food Standards Agency (FSA) has published advice recommending maximum consumption levels of oily fish for different groups according to age and reproductive status. Expert advisors examined the benefits of eating oily fish against the possible risks from consuming pollutants such as dioxins. The Agency's recommendation is that men and boys, and women past childbearing age can eat up to four portions of oily fish a week. Women of childbearing age, including pregnant and breastfeeding women, and girls, can eat up to two portions of oily fish a week.
The FSA report says that there is good evidence that eating oily fish reduces the risk of death from heart disease. Some oily fish contain chemicals such as dioxins and polychlorinated biphenyls (PCBs), which accumulate over time in the body and could have adverse health effects if consumed over long periods at high levels. The levels of dioxins in oily fish vary, and some types of fish tend to have higher levels than others. The FSA recommendations are based on people eating different types of oily fish: people should eat at least two portions of fish a week, one of which should be oily. A portion = 140 g (5 oz)
White fish: no limit
Girls (under 16), breastfeeding or pregnant women and those who may become pregnant: Up to 2 portions a week
Boys (under 16), men, and women who are not intending to, or can't become pregnant: Up to 4 portions a week
Marlin, shark, swordfish (heavily contaminated due to being at the top of the food chain):
Girls and boys (under 16), pregnant women and those who may become pregnant, breastfeeding women: do not eat
Men, and women who are not intending to, or can't become pregnant: Up to 1 portion a week.
Fresh tuna counts as oily fish, but tinned tuna counts as white because the oils are lost in the canning process. There is no consumption limit for tinned tuna, except for pregnant women and those who may become pregnant: Up to 4 medium-sized cans per week [presumably the canning process also destroys the PCBs and dioxins in the tuna].
The full report can be downloaded as a PDF from the FSA web site
It also lists the types of fish considered oily, and white (non-oily) fish.
The UK Vegetarian & Vegan Foundation have, not surprisingly, produced a response to the claim that eating oily fish is healthy in a report on their web site.
Plant sources of essential fatty acids (EFAs) as an alternative to those from fish are listed in the report.
The report says to ensure an adequate intake of alpha linolenic acid, good plant sources should be included in the daily diet, including green leafy vegetables, seeds, whole grains, beans and nuts, and flaxseed oil, Minimising consumption of omega-6 rich vegetable oils (especially corn oil, sunflower oil and safflower oil) and commercial oil-based processed foods will also help increase the omega 3 to omega 6 dietary ratio. The best way to buy and store nuts, seeds and their oils is in very small quantities and to keep them in the fridge for freshness. These oils are not suitable for heating as it destroys the beneficial fatty acids. They are best used as a cold salad dressing.
The report also notes that farmed salmon can contain two to three times less omega-3 fats as well as 15% less protein. Farmed fish can also contain chemical pesticide residues as well as dangerous levels of PCBs.
Of course neither of these reports take individuality into account when examining the health benefits of EFAs in oils. Those who have a genetic tendency to cardiovascular disease are people with blood group A, who will get the benefit from eating fish instead of meat.
The potential human health effects of dioxins and PCBs may also include damage to the immune system, infertility, birth defects, and altered levels of sex hormones. These are not yet known to have blood group specificity [although the next IfHI conference may enlighten us on this].
This is an example of how difficult it is to decide whether a basic food product such as fish is going to be healthy to eat. The FSA guidelines advise those who are likely to become pregnant to avoid swordfish, for example. Should restaurants therefore restrict the sale of meals containing this popular seafood to girls and young women unless they confirm that they are not intending to have children?
The only answer is to keep as healthy as possible while avoiding industrial processes that contaminate the sea, and encouraging environmentally friendly alternatives to polluting practices. It may take generations to clean up the damage that has already been done, but at the very least we should stop making it worse.
The book Eat Right for Your Baby contains detailed information on which food to avoid before and during pregnancy according to ABO blood type, including certain types of fish high in mercury.
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