Homocysteine is made from the dietary protein, but high levels of the chemical can be lethal, researchers say.
Studies on the chemical were published in Tuesday's issue of the journal Annals of Internal Medicine.
Over five years, men with high levels had twice the death rate as those who didn't, researchers discovered. Women in their 40s had twice the rate of strokes.
At Rush Presbyterian Medical Center, anyone with heart disease, and anyone with even a family history of heart disease, is tested for homocysteine levels.
"It's an important risk factor," says Dr. Robert Rosenson. "It increases the risk anywhere from two- to threefold if you have a high level."
Homocysteine increases risk of a heart attack because the chemical injures heart vessel. That leads to a block, and ultimately, a heart attack or stroke.
The good news is that high levels of homocysteine can be treated with a common vitamin. Taking folic acid - a B vitamin - can lower homocysteine levels. If everyone received the daily folic acid in a single multivitamin, it would prevent 50,000 deaths from heart disease every year, Dr. Breen says.
Another recent study showed that people who took a daily multivitamin with 400 micrograms of folic acid cut their risk of a heart attack in half. The same amount of the vitamin can come from just a single serving of some fortified cereals, or green leafy vegetables.
However, if you consider taking a multivitamin, don't take one with iron. Taking too much iron can also raise your risk of heart disease.
People who have suffered a heart attack or who have a family history of heart disease should consult their doctor about testing homocysteine levels.
Reported By Dr. Michael Breen