Q. I've heard that natto has health benefits. Can you explain?

A. A number of studies have found that natto, a traditional Japanese food made from fermented soybeans, not only benefits your bones but can also help prevent blood clots.

Natto is unusually high in vitamin K2, a nutrient that can prevent bone loss and reduce fracture risk. A 2001 article in the journal Current Opinion in Clinical Nutrition and Metabolic Care points out that vitamin K2 is important for bone physiology because it preserves bone micro-architecture and prevents loss of bone mass. The Journal of Bone and Mineral Research reported in 2000 that vitamin K2 may increase bone strength in women who have osteoporosis and has also been found to prevent the recurrence of new fractures. Natto may be one reason that women in Japan have a lower incidence of osteoporosis than Western women.

Natto also contains the enzyme nattokinase, reported to reduce and prevent blood clots. Although blood clotting is vital for survival — it's what keeps you from bleeding to death if you have a cut or ruptured blood vessel, for instance — some people suffer from excessive thrombosis, or blood clotting, even if they haven't been injured.

Dr. Hiroyuki Sumi, of Japan's Miyazaki Medical College, discovered that nattokinase could be effective not only in treating but also in preventing blood clots. A number of animal studies done in Japan found that nattokinase can break down clots by reducing excessive levels of an enzyme (plasminogen activator inhibitor type I) responsible for their formation.

To make natto a part of your bone-building and blood-clot prevention plan, explore Japanese cuisine. In Japan, natto is often eaten with chopped green onions, soy sauce and mustard on rice. (The restaurant Kai at 1427 Makaloa Street has a delicious version.) For people at risk of deep-vein thrombosis from air travel, eating natto before flying may be a good idea.

For many people, natto is an acquired taste — it has a pungent smell and a slimy texture — so give yourself time to get used to eating it. You can also take vitamin K2 as a supplement for your bones; researchers used a dose of 45 milligrams daily.

Nattokinase is also available in capsule form; the recommended daily dose is 100 to 200 milligrams. (Caution: supplementing with nattokinase should be discussed with your physician. Avoid natto and nattokinase if you are on blood-thinning medications such as Coumadin, Plavix or warfarin.)

Laurie Steelsmith is a naturopathic physician and licensed acupuncturist in Honolulu, and the author of "Natural Choices for Women's Health" (Random House). Reach her and look at her past columns at www.drlauriesteelsmith.com. This column is for information only. Consult your health provider for advice.