Researchers at the University of Nevada-Reno have discovered that used coffee grounds can be transformed into biodiesel, meaning one day cars could run on fuel that smells like cappuccino. But while coffee may fuel vehicles in the future, doctors warn that your first morning cup might not be the healthiest way to fuel yourself.

Health experts suggest delaying coffee until mid- to late-morning, ideally between 9:30 a.m. and 11:30 a.m. That’s because drinking it immediately after waking can backfire. On an empty stomach, caffeine spikes stress hormones, and when paired with sugar, it can lead to sharp blood glucose crashes that make you feel more tired.

Coffee also interferes with the absorption of essential minerals such as iron, magnesium, calcium, and B vitamins. These nutrients are crucial for healthy bones, strong nerves, and overall energy balance. Regularly starting your day with coffee before food can gradually deplete these reserves.

Another downside is its effect on digestion. Coffee stimulates the colon, which may cause diarrhea or stomach upset. For those who add milk or cream, symptoms can worsen if they are lactose intolerant.

Caffeine has a strong impact on the nervous system. Since stress hormone levels are already high in the morning, an early coffee may intensify feelings of anxiety or jitteriness.

It can also disrupt sleep cycles if consumed too early in the day, increase cravings for sugary snacks, and contribute to gradual weight gain. These effects are magnified when coffee becomes a daily ritual on an empty stomach.

Dehydration is another risk. Coffee acts as a diuretic, which can dry out skin, leaving it more prone to wrinkles and other premature aging signs.

Finally, coffee may raise blood sugar levels, further contributing to skin issues and energy fluctuations. Experts advise pairing coffee with a balanced breakfast or waiting until later in the morning for a healthier boost.