A new study by the University of California, San Francisco (USCF) shows that drinking non-diet soda speeds up the aging process as much as smoking.

The study looked at more than 5,300 Americans between ages 20 and 65. Scientists took DNA samples of each participant to determine their biological age, and the participants were asked to record their diet. The average participant drank 12 ounces of soda per day. But 21% of the participants drank 20 or more ounces per day.

Researchers found that those who drank 20 or more ounces had an additional 4.6 years of biological aging. Biological age can be measured by a person’s telomere length. Telomeres, which we’ve written about in the past, are the tips at the end of chromosomes which regulate the aging of cells. The shorter the telomeres, the more rapidly cells age.

Telomere length naturally shortens as we get older. But this shortening process can be sped up by unhealthy activities such as smoking and, it now appears, drinking sugary soda.

According to Elissa Epel, senior author of the study and a professor of psychiatry at UCSF, “Regular consumption of sugar-sweetened sodas might influence disease development, not only by straining the body’s metabolic control of sugars, but also through accelerated cellular aging of tissues.”

The researchers were careful to point out that the correlation between short telomere length and drinking soda does not necessarily demonstrate causation. They are currently preparing a new study to better understand this link.