Buckwheat contains two flavonoids with significant health-promoting actions: rutin and quercetin. It is also a very good source of magnesium (it has 86 g of magnesium in a 1-cup serving) and has a good supply of manganese, fiber, phosphorus, pantothenic acid, and protein. Finally, the protein in buckwheat is a very-high-quality protein, containing all eight essential amino acids. In this way, buckwheat is quite complementary to other grains and will provide an even more complete protein when combined with them.
The salutatory effects of buckwheat are in part due to its rich supply of flavonoids, particularly rutin and quercitin. These flavonoids extend the action of vitamin C and act as antioxidants. They also maintain blood flow, keep platelets from clotting excessively, and protect low density lipoproteins from free-radical oxidation into potentially harmful cholesterol oxides. Diets that contain buckwheat have also been linked to a lowered risk of developing high cholesterol and high blood pressure. As a result, they can lower heart disease. One Chinese study clearly showed that buckwheat intake was associated with lower total serum cholesterol, lower levels of LDL (the cholesterol linked to cardiovascular disease), and a high ratio of HDL (the health-promoting cholesterol) to total cholesterol. Even though buckwheat lacks bran and germ, it still rates as a very good fiber source.