Upping coffee consumption can result in an "immediate" reduction in diabetes risk, say scientists.
Increasing intake by more than one cup a day was associated with an 11% lower risk of Type 2 diabetes over the next four years, experts found.
Reducing consumption by at least one cup had the opposite effect, raising diabetes risk by 17%.
People drinking three cups or more were 37% less likely to develop Type 2 diabetes than those consuming one cup or less.
The research, involving almost 124,000 men and women, adds to previous evidence linking coffee drinking and protection from diabetes.
Unlike previous research, it only found a positive association with caffeinated coffee - possibly because so few participants drank decaf.
The authors, led by Professor of Nutrition Frank Hu, from the Harvard School of Public Health in the US, wrote in the journal Diabetologia: "The findings of the current study.. demonstrate that change in coffee consumption is associated with both immediate and long-term diabetes risk.
"Changes in coffee consumption habits appear to affect diabetes risk in a relatively short amount of time."
A study of pooled data published in the journal Diabetes Care in February, also led by Prof Hu, showed that consuming six cups of coffee a day lowered Type 2 diabetes risk by a third compared with drinking no coffee. In that study, it made no difference whether or not the coffee contained caffeine.
For the new research, scientists analysed the results of three large US diet and lifestyle investigations involving health professionals: the Nurses' Health Study, the Nurses' Health Study II, and the Health Professionals Follow-Up Study.
Participants' diets were assessed every four years by questionnaire, and those developing Type 2 diabetes identified. In total, 7,269 cases of diabetes were recorded.
There was no evidence that tea consumption had a similar effect on diabetes risk. Again, this may have been due to the low number of people who drank tea or altered their tea consumption, said the scientists.
Co-author Dr Shilpa Bhupathiraju, also from the Harvard School of Public Health, said: "Our findings confirm those of previous studies that showed that higher coffee consumption was associated with lower Type 2 diabetes risk.
"Most importantly, they provide new evidence that changes in coffee consumption habit can affect Type 2 diabetes risk in a relatively short period of time."
Dr Richard Elliott, research communications officer at Diabetes UK, urged people to treat the findings with caution.
He said: "While this study found evidence of a connection between how much coffee you drink and your risk of Type 2 diabetes, this does not mean that increasing your coffee intake will reduce your diabetes risk. Even if people who drank more coffee did tend to have a lower risk of Type 2, it does not necessarily follow that coffee consumption was directly responsible.
"Other factors that this study has not identified could also be involved and it is even possible that being at high risk of Type 2 diabetes encourages people to reduce their coffee intake. What we do know is that the best way to reduce your risk of Type 2 diabetes is to maintain a healthy weight by eating a healthy, balanced diet and by being regularly physically active."
More than two million people in the UK have diagnosed Type 2 diabetes. The disease occurs when the body produces too little insulin or fails to respond to the hormone properly, raising blood sugar.