Researchers do not yet know everything they would like to know about how nutrition affects your heart, the US Mayo Clinic says, but as research continues into the role of soyfoods, the ``results appear promising.'' In the latest edition of the ``Mayo Clinic Heart Book,'' physicians and staff at Mayo confirm that in cultures where soy is the main source of protein, such as the dietary intake of many Asian populations, ``rates of cardiovascular disease and some kinds of cancers are low.'' Increasing evidence shows that isoflavones, which are found in soy, can play a role in promoting health: ``Research shows that eating about an ounce (25 grams) of soy protein a day can reduce three important numbers in your lipid profile by about l0 percent,'' the book's authors said. The three ``important numbers'' are total cholesterol, LDL or ``bad'' cholesterol, and triglycerides. ``Eating soy also may help improve your 'good' HDL cholesterol,'' the Mayo Clinic Heart Book recommends.