THE QUESTION: Do shellfish turn toxic in late spring and summer?
THE FACTS: American Indians are said to have introduced this warning centuries ago to early settlers, and nowadays the saying is applied to the months without an R, namely May through August. But it may be outdated.
Shellfish can be problematic in the summer for several reasons. The first has to do with red tides, vast blooms of algae that collect along coastlines, usually in warm weather. They can spread toxins that are soaked up by oysters, clams and mussels.
Studies have linked toxic outbreaks to this phenomenon, but only when people ate locally harvested shellfish. Most shellfish sold in restaurants, supermarkets and urban areas are commercially harvested, and as a result are subject to regulations intended to eliminate such hazards.
Another problem in the summer is that it is usually when shellfish spawn. As any oyster aficionado knows, a fertile oyster turns unpleasantly thin, milky and soft — far from ideal. Many vendors avoid this problem by importing shellfish from cooler climates. Oysters can be genetically modified so they do not spawn. But while they taste the same as their regular counterparts, they tend to look different.
Finally, shellfish can spoil more easily on a hot day if not stored properly. This makes them unappetizing, but not necessarily toxic.
THE BOTTOM LINE: Commercial shellfish are no more likely to be toxic in summer than at any other time.