Each extra daily soda tracked with more heart disease, diet ones too
Across 34 studies, each extra daily serving tracked with 9% more heart disease for sugary soda and 8% for diet. These follow what people already chose to drink.
What the study found
An extra soda a day: 27% more type 2 diabetes risk, 13% if diet
Diet is not the flat line people assume it is. Across 34 long-running studies, each extra daily serving raised heart disease risk 9% for sugary soda and 8% for diet. A separate pooling of 39 studies put diet soda's obesity risk above sugary soda's, 21% against 12% per 250ml a day.
The caveat · Drink categories, not Coke itself
Both pools followed what people already chose to drink, so these are links rather than proof that either drink causes anything. Someone told to watch their weight or blood sugar tends to switch to diet, which would draw this same pattern with no effect from the drink at all. The pooled studies varied widely in their results for several of these outcomes. And these are drink categories, not Coca-Cola and Coca-Cola Zero specifically.
What we don't know
Both pools followed what people already chose to drink, so these are links rather than proof that either drink causes anything. Someone told to watch their weight or blood sugar tends to switch to diet, which would draw this same pattern with no effect from the drink at all. The pooled studies varied widely in their results for several of these outcomes. And these are drink categories, not Coca-Cola and Coca-Cola Zero specifically.