I heard that sardines are lower on mercury because they are lower in the food chain. But let's say I eat 250g of Atlantic Portuguese sardines per day, every day. Am I getting more than the daily allowable limit for mercury?
Mercury bioaccumulates through trophic levels. Sardines are low on the food chain - so their consumption is safe. Here is a link to a website that has a calculator to see how much mercury you are getting from your fish:
Assuming that you are 150lbs (just a random number) and the 250g = 8.82 oz, you are getting 8% of your daily allowable intake of mercury.
And just to explain what a daily allowable intake is - it is the maximum amount of mercury that a human can ingest without any observable effect reported. Please note that most of the toxicological studies done have been on rats though, so err on the side of caution!
Please remember to add up each type of fish that you are eating though!
It's impossible to say what you're getting in mercury unless you test every single batch of fish you eat. But here's what you've got in your favor:
If you're not eating tons and tons of tuna or salmon or swordfish, if you're not going around handling free mercury from a broken thermometer or something, and if you otherwise try to avoid mercury as much as possible, you should be OK.
Here is more information about the fish family sardines belong to. They eat plankton, pretty much.
i don't think bpa free is necessarily much better than a can with bpa. who knows what else is in the can, which is highly heated with the sardines inside. sigh, i wish i could have canned sardines as an easy fix but there are just too many things about it that are unhealthy it seems. we can't get them fresh around here.
As has already been pointed out, sardines are relatively low on the marine food chain and don't accumulate as much mercury as predatory fish.
If you're concerned though, take a little selenium now and then. Selenium has been shown to be protective against mercury. (Yummiest way to very easily get some? Brazil nuts!)
I don't have a link to the studies handy at the moment, but I read a few in a graduate level course on vitamins and minerals. It's the real deal.
How selenium keeps you safe from mercury toxicity in most fish.