Diet soft drink consumption was significantly associated with white race; diabetes and elevated blood sugar; low HDL cholesterol; elevated waist circumference and body mass index; and metabolic syndrome. Regular soft drink consumption was associated with black race; high total daily calories; and low HDL cholesterol.
The primary end point was a combination of incident vascular events, including stroke, heart attack, or vascular death. Over the mean follow-up period of 9 years, 559 new vascular events occurred, including 212 strokes and 149 heart attacks.
Because the study showed association – not causation – it’s impossible to determine the exact link between diet soda and vascular disease, Dr. Gardener said.
"We don’t have any information about previous dietary behavior, so we can’t presume cause and effect," she said. "The mechanism is really unknown; further studies are needed to elucidate this. Previous studies have shown a relationship between regular soda consumption and the metabolic syndrome of elevated blood pressure, waist circumference, high triglycerides, and low HDL – which are all important vascular risk factors. We can control for those at baseline, but that doesn’t exclude them as a possibility in the causal pathway."
Because she considers the findings preliminary, Dr. Gardener said it’s too early to make any recommendations about soda consumption. "The next steps are for longitudinal cohort studies, preferably conducted in a younger population with more diet soda consumption and with collection of dietary data at multiple time points," she said. "Only if the results are confirmed can we suggest that diet soda may not be an optimum substitute for sugar-sweetened beverages, which have been shown to have health consequences."
The Northern Manhattan Study is supported by a grant from the National Institute of Neurological Disorders and Stroke. Dr. Gardener had no financial disclosures.