Although fish is an excellent source of high quality protein and beneficial fatty acids, many fish contain worryingly high levels of a toxic form of mercury (methylmercury) which can accumulate in your body, and may put your fertility and baby at risk. Exactly how much risk is up for debate. How much mercury are you comfortable with when you are trying to conceive is the question? Excessive mercury could be a cause of infertility or sub-fertility and has been shown to lower IVF success rates which mercury levels are elevated within ovarian follicles.
Tuna is thought to be particularly risky. Independent tests done on 42 different samples of canned and pouched tuna carried out by Consumer Reports found that every single sample contained mercury and some types of tuna contained more mercury than others. Albacore tuna had about six times the mercury level of light tuna.
As a result of these tests consumer reports advised that women who are pregnant should consider avoiding canned tuna or tuna in pouches altogether and should also avoid other high mercury fish such as swordfish, shark and tilefish. Eel, commonly used in sushi is also a high mercury fish.
If you like to eat fish you may want to familiarize yourself with the types of fish that contain the lowest amounts of mercury such as wild Alaskan salmon, shrimp, clams and tilapia. Click on the link to the NRDC below - the Natural Resources Defense Council - to check out their guide to mercury contamination in fish. Here, you can find an extensive list of low, moderate and high mercury fish to help you make safer choices. The NRDC low mercury fish category includes;
Mackerel (N. Atlantic, Chub)
One caveat, when you buy a filleted fish it may not be the fish that you thought you were purchasing! Numerous studies have shown that even restaurants often substitute cheaper fish for the fish named on the menu. When you buy fish, especially filleted fish it is often mislabeled making it hard to know exactly which type of fish you are ordering or buying. The only way to know for sure is to buy from a reputable fish market or fish counter and buy a whole fish that is recognizable as the fish that you desire. You can of course have it filleted once you are sure that you have the right fish and are not being duped with a cheap imposter!
Farmed fish - especially farmed salmon - may come with other risks too; some studies have shown that farmed salmon is especially high in PCBs (polychlorinated bisphenols) which have been associated with reduced fertility and lower IVF success rates. You my want to consider avoiding farmed salmon if you are trying to conceive and want to keep your PCB intake low.
This article is intended for informational purposes only and is NOT intended to diagnose, offer treatment, or replace medical or nutritional advice for which you should consult a suitably qualified physician and/or dietitian.
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Consumer Reports on Health Vol. 23 No. 2 Feb 2011