Consumer Reports' fish-safety experts make the following recommendations for consumption of canned tuna.
Pregnant women: The magazine's experts say it's prudent for pregnant women to avoid canned tuna entirely.
Young children (up to about 45 pounds): About one-half to one 6-ounce can (roughly 4.5 ounces drained) of chunk-light tuna per week, or up to one-third of a can of solid-light or white, depending on the child's weight.
Women of child-bearing age who aren't pregnant: Mercury can linger in the body after you stop eating fish, so these women are advised to eat no more than about three chunk-light cans per week, or one can of solid-light or white tuna.
Older children: For children 45 pounds to 130 pounds, no more than one to three cans of chunk-light tuna per week, depending on their weight, or one-third to one can of solid-light or white tuna per week.
Men and older women: The same weekly intake that's considered safe for women of child-bearing age who are not pregnant -- roughly three cans of chunk-light tuna or one can of solid-light or white. They can likely eat more than that without harm, but the exact amounts are not known.