Five cups and you're fine. Six cups and you've entered the danger zone.

A huge study of nearly 350,000 people found a link between overconsumption of coffee and rates of high blood pressure that can lead to heart disease.

The study-published in the American Journal of Clinical Nutrition-found that, while moderate coffee consumption (1-2 cups per day) is actually associated with a reduced risk of heart disease, populations that consumed more than six cups per day were more likely to experience levels of high blood pressure, and a 22 percent increase in risk of cardiovascular disease. The study found that overconsumption can, as well, cause other unpleasant symptoms such as irregular heartbeat, irritability, and severe headaches.

To determine the amount of daily coffee that is not detrimental to our health, University of South Australia researchers examined data from 347,077 participants in the UK Biobank. (Participants were habitual coffee drinkers.) Researchers "used logistic regression to test for the association between coffee intake and CVD [cardiovascular disease] risk," they say.

Interestingly, the study found that while drinking more than six cups of coffee per day was associated with a 22 percent higher risk of heart disease, drinking no coffee at all was associated with an 11 percent increased risk, and drinking only decaf was associated with a seven percent higher risk of eventual heart disease problems. This led researchers to conclude that "heavy coffee consumption was associated with a modest increase in CVD risk."

Six cups of a coffee is quite a lot, and hopefully you don't drink that much on a daily basis. But this study does give a hard stopping point for the next time you feel you need to power through with yet another double shot of espresso-or any other highly caffeinated beverage. If you do need an energy boost, here are four natural energy boosting drinks and foods you can try instead.

Coffee Cups
Photo: Getty Images