Dr. Katz
Dear Dr. Katz:
Should I add phytoplankton to my diet?
— Bill Robbs
Salt Lake City

Phytoplankton are the base of the marine food chain. These microscopic organisms are eaten by slightly less microscopic marine creatures called zooplankton. And then, larger sea creatures eat the zooplankton, and…you get the picture. The point is that digested phytoplankton are the source of the healthy omega-3 fatty acids found in other ocean life, such as seaweed and fish.

But I can find no credible research to suggest that humans swallowing phytoplankton derive any benefits. Much of the research on omega-3 fatty acids grew out of surveys of isolated populations—like the Inuit of Greenland—that ate a lot of marine creatures. Though the native diet of these people contained a shocking amount of fat and very little in the way of greens, even the very elderly had little or no heart disease. But the thing to remember is that these people ate fish—not phytoplankton.

You can easily—and more pleasurably—get the same nutrients by choosing foods further up the chain. A sushi salmon roll offers omega-3s in the seaweed wrapper and the fatty fish. In general, we are far less confident that swallowing isolated substances is as good as or better for you than eating wholesome foods. If you want to take a supplement, however, I'd recommend omega-3 (or fish oil) capsules (I take them)—there actually is positive research on these.

Until phytoplankton are subjected to the kind of rigorous study omega-3 supplements have undergone, I can say only that the hype is running well ahead of the science.