Taking extra vitamins may help some women with diabetes avoid heart disease, but may worsen clogged arteries in others, Israeli and U.S. researchers reported on Friday.
They said a simple blood test, to detect genetic variations in a blood protein called haptoglobin, may predict which patients would benefit from supplements and who should avoid them.
Diabetes greatly increases the risk of heart disease, so the test may offer useful alternatives to the millions of patients worldwide with type-2 diabetes, the team from the Technion-Israel Institute of Technology in Haifa, George Washington University in Washington and elsewhere said.
Post-menopausal women with diabetes who carry two copies of the variation known as haptoglobin-2 increase their risk of atherosclerosis, or narrowed arteries, if they take doses of the antioxidant vitamins C and E, Dr. Andrew Levy found.
But vitamins seem to slow clogging in diabetic women who have two copies of haptoglobin-1, Levy’s team reports in the April issue of the journal Diabetes Care.
“This study says that you can find subgroups of people who actually might benefit and subgroups which will actually be harmed by antioxidant vitamins, so it is important to know which haptoglobin type you are,” Levy said in a statement.
Genetic variation could predict heart risk
Levy’s team has done considerable research on haptoglobin, a blood protein that interacts with hemoglobin -- the iron-rich component that makes blood red.
Researchers have found that different versions of haptoglobin can predict a diabetic’s risk of heart attack or having an artery clog again after being cleared.
His team looked at vitamins E and C because studies show they can either help or hinder heart disease. Some research has suggested the vitamins can worsen heart disease by interfering with blood cholesterol levels and cholesterol-lowering drugs.
The researchers studied 299 post-menopausal women with at least partial blockage in one coronary artery who either took vitamin E and vitamin C twice a day or placebo pills.
After three years, heart disease was slowed only in women who had two haptoglobin-1 genes and took vitamins. The effect was especially clear in women with diabetes.
But the arteries seemed to narrow faster than usual in diabetic women with two haptoglobin-2 genes who took vitamins, although those without diabetes were not badly affected.
Levy believes haptoglobin affects oxidative stress, or damage to cells in everyday life or from exposure to chemicals or radiation.
Taking vitamins called antioxidants should theoretically slow or reverse this damage but studies have shown mixed results in both heart disease and cancer.