Harvard Health Letter

Ask the doctor: What is the upper limit for omega-3 fats?

Q. There's a lot of publicity about omega-3 fats being beneficial for heart, mind, joints, eyes, and so on. There are over-the-counter products of varying size. So, this is my question: is there a daily upper limit on fish oil consumption?

A. There isn't an official upper limit, but for most people, I'd be inclined to draw the line at a gram — 1,000 milligrams (mg) — of omega-3s from fish oil a day.

One of the main concerns about high omega-3 consumption has been that it could "thin the blood" and thus increase the risk of bleeding and, more specifically, bleeding strokes (the medical term is hemorrhagic stroke). That worry dates back to the classic studies of the Inuit people of Greenland and their traditional diet of seal and fish. Researchers observed that, along with the apparent benefits — low rates of heart disease, ischemic stroke, diabetes, and various inflammatory conditions — Inuit people had a tendency to bleed from the nose and urinary tract and had higher rates of hemorrhagic stroke.

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