Drinking a daily soft drink increases risk factors associated with heart disease, whether you drink diet soda or regular, researchers said.

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Boston University researchers found that at the start of a study of more than 9,000 people, those who drink soda daily were 48 percent more likely to have metabolic syndrome than those who did not.

Metabolic syndrome is a diagnosis for people who show several risk factors that can indicate a potential for developing heart disease or diabetes. The measures include waist size, blood pressure, triglyceride levels and cholesterol levels.

"We were struck by the fact that it didn't matter whether it was a diet or regular soda that participants consumed, the association with increased risk was present," said Dr. Ramachandran Vasan, head of the study.

Prior studies linked soft drink consumption to multiple risk factors for heart disease. However, this study showed that association not only included drinking regular but also artificially sweetened diet sodas, the researchers said in a news release.

The researchers found a similar effect when looking at 6,000 people without metabolic syndrome over a four-year period. The risk of developing it was 44 percent higher in those who drank a daily soft drink.

Vasan noted that high-fructose corn syrup in regular soft drinks is often blamed for obesity, but you would not expect to see the same result with diet drinks, which use other sweeteners.

He said another possible explanation is that people who drink a lot don't reduce the size of the next meal, as is often the case with people who eat more.