Essentials of Nutrition for Sports

Contaminants Fish

Some species of fish may contain significant levels of

methylmercury, polychlorinated biphenyls (PCBs), or other environmental contaminants.

In general, older, larger, predat

ory fish, including swordfish, tend

to contain the highest levels of these contaminants.

Removing the skin, fat, and internal organs of the fish prior to

cooking, and allowing the fat to drain from the fish while it cooks will decrease exposure to a number of fat-soluble pollutants, including PCBs.

However, methylmercury is found throughout the muscle of fish,

so these cooking precautions will not reduce exposure to methylmercury. Methylmercury

Organic mercury compounds are toxic and excessive exposure

can cause brain and kidney damage.

Unborn children, infants, and young children are especially

vulnerable to the toxic effects of mercury on the brain.

The FDA recommends women who may become pregnant,

pregnant and breastfeeding women, and young children: 1.^

Do not eat shark, swordfish, or king mackerel; they contain levels near 1 part per million.

2.^

Limit the consumption of other fish to 12 ounces per week. Read the advisory at:

http://www.fda.gov/oc/opacom/mehgadvisory1208.html

.

For others, the FDA recommends eating no more than 7 ounces

per week of fish with methylmercury levels near 1 part per million and no more than 14 ounces per week of fish with levels averaging 0.5 part per million.

Typical methylmercury levels in fish are outlined in

Table 15

.

Fish

Methylmercury

(ppm)

Swordfish

1.00

Shark

0.96

King Mackerel

0.73

Red Snapper

0.60

Orange Roughly

0.58

Bass, Saltwater

0.49

Marlin

0.47

Tuna (fresh or frozen)

0.32

Lobster Northern (American)

0.31

Halibut

0.23

Crab Dungeness

0.18

Tuna (canned)

0.17

Table 15. Typical methylmercury levels

in fish, in parts per million.

Supplements Methylmercury

. Supplements available in the US probably contain

less than 1.5 parts per billion.

Polychlorinated biphenyls (PCBs)

. Fish oil supplements in the US

probably do not have appreciable PCBs or dioxin.

Summary

Alpha-linolenic acid (an omega-3 fatty acid) and linoleic acid

(an omega-6 fatty acid) are both essential fatty acids.

The marine-derived omega-3 fatty acids, eicosapentaenoic acid

and docosahexaenoic acid, can be synthesized from alpha-linolenic acid or obtained in the diet.

US diets tend to be higher in omega-6 fatty acids than omega-3

fatty acids.

Increased dietary marine-derived omega-3 fatty acid intakes are

associated with decreased risks of cardiovascular diseases.

The American Heart Association recommends that all adults eat

fish, particularly fatty fish, at least twice weekly.

Nutrition for Sports, Essentials of 86