That’s the New York Times’ headline this morning. Should pregnant women be advised to eat more tuna? There are, apparently, trace amounts of mercury in tuna, or there were, or something. Ages ago it was advised that people eat less tuna due to this heavy metal which is not easily eliminated from the body, and because it is implicated in nerve damage if the concentration gets high enough.
This article is an absolute blast to deconstruct, because of all of the fun statistics in play.
“Tuna is responsible for nearly seven times more mercury exposure than the four high-mercury fish that the Federal Food and Drug Administration advises pregnant women not to eat”
That little math problem falls immediately after this variable is set a paragraph earlier;
“They (the Dietary Guidelines Advisory Committee) noted that even when women ate double the recommended weekly amount of tuna, the benefits far outweighed the risks. “All evidence was in favor of net benefits for infant development and (cardiovascular disease) risk reduction”
The four high-mercury fish are tilefish, shark, swordfish and king mackerel. Here is my exposure in the listed order: Never heard of it, never ate it, never tried it, saw cans at the store, but might just be peasant mackerel, not king. Tuna is responsible for all of my exposure to mercury from high-mercury fish. That equals an infinite number of times my exposure from the other four, since it would be a divide-by-zero kind of equation. I am actually surprised that tuna is only responsible for seven times more exposure. See, the way it’s worded, calling out “exposure”, means that they are combining the mercury dose with the number of times you consume that dose per person, per year. That would be your exposure. In any case, your exposure from all sources is going to be a very low number. When the Committee noted that even if you double your tuna-mercury dose the benefits far outweigh the risk, it is because the dose is so low in tuna.
Later in the article there are REAL numbers, not percentages:
The benefits of fish consumption on a developing fetus are clear. In a Harvard study of 135 mothers and infants, researchers tracked fish consumption during pregnancy and tested the mother’s hair to measure her mercury exposure. They found that for each weekly serving of fish the mother ate while pregnant, her baby’s score on visual recognition memory tests increased an average of four points. At the same time, a baby’s score dropped by 7.5 points for every one part per million increase in mercury found in the mother’s hair sample. The babies who scored highest on the memory tests were those whose mothers had consumed two or more servings of fish each week during their pregnancy, but were tested to have very low mercury levels.
Apparently the omega 3 essential oil that is contained in fish are passed up the food chain to the mother, who passes it on to the fetus, who uses this essential oil to develop a superior brain. Mercury exposure would detract from that, but apparently the net effect is up, because the mercury dose is so low, and the exposure period of nine months, tops, is so short that the low dose ends up being a low exposure. The net recommendation is that its better for you child that you eat tuna during your pregnancy. It’s also probably better for you, as the mercury scare is one of those things where the dire warning is actually a bit shrill compared to the actual risk involved.
The omega 3 oil in predator fish is there because they eat foods that graze on algae and other grass-like foods in the water. I would like to point out, expectant mothers, that there is another way to get omega 3 oils that does not involve any mercury exposure. Eat grass fed and pastured meat animals from a local farm. These meats are also a known good source of omega 3 oils. You can take little capsules or eat flax seeds, but if you drink milk from a natural cow, eat eggs from a natural chicken, eat bacon from a natural pig or eat steaks from a natural steer you are going to get a natural amount of omega 3 oil in exactly the proportions that nature and evolution have programmed your body to receive.
This fall Consumer Reports issued a lengthy paper on fish and mercury exposure, noting the special concerns about canned tuna due to its popularity. Six ounces of canned tuna contains 60 micrograms of mercury compared to just 4 micrograms of mercury in a six-ounce serving of salmon, according to Consumer Reports. (A six-ounce serving of swordfish contains 170 micrograms, the magazine said. )
So, there are 60 micrograms of mercury in a six ounce can of tuna. If you eat two cans of tuna per week for the next twenty years, and each one contained exactly that much mercury, then you would have exposed yourself to just over 1/10th of a gram of mercury. That much mercury would barely be visible. To put it in perspective, there are about three grams of mercury in a thermometer, or about twenty times more mercury than you would get by eating two cans per week for twenty years. See! Fun with numbers!
I am not going to say that eating tuna is safe, but I am going to say, without reservation that eating tuna in the can is safer than eating low-fat yogurt. Eating tuna is safer than eating processed foods. Getting all excited about sixty micrograms of mercury is pretty bold when you won’t raise an eyebrow to added sugars and their dangers. Diabetes is a real danger to our children if you feed them and drink them with the crap that is advertised every morning on their little kid programs, and it doesn’t take a lifetime to happen, its pretty much right away. Want to improve the lives of little kids, don’t recommend shunning tuna, recommend shunning processed foods, industrial meats, artificial ingredients, added sugar.