Some people swear that their morning coffee boosts their mood and makes them more productive at work. Others say that drinking caffeine can trigger anxiety, heart palpitations and ulcers.

In other words, what works for one person may not work for another.

There aren't enough proven health benefits or risks for experts to say that people should or shouldn't drink caffeine. But most medical experts agree that up to 400 mg of caffeine a day is OK for adults. That's about 3 to 4 cups of coffee.

Here's what research has shown about caffeine's effect on your health:

• Caffeine may have some unexpected health benefits. Most people know that caffeine can improve focus and relieve headaches. But moderate caffeine intake also can help reduce the risk of diabetes, stroke and liver cirrhosis.
• Caffeine helps prevent Parkinson's disease for some, but not others. Research shows that drinking coffee or tea can reduce your risk of Parkinson's — unless you're taking hormone therapy after menopause, in which case caffeine increases your risk of Parkinson's.
• Drinking coffee can affect your Alzheimer's disease risk. People who drink 1 to 4 cups of coffee a day tend to have a lower risk of developing Alzheimer's. However, drinking 4 or more cups is linked to a higher risk of getting the disease.
• Too much caffeine may carry some health risks. Drinking too much caffeine (over 400 mg a day) may increase risk of osteoporosis, bone fractures and anxiety. Long-term users may be more likely to have chronic migraines.
• Caffeine typically doesn't cause heart problems. A latte may make your heart pound when you drink it, but caffeine doesn't cause heart disease. It also doesn't increase your risk of heart rhythm problems.
• Caffeine usually only raises blood pressure temporarily. Blood pressure spikes caused by coffee tend to be stronger in people who don't drink it regularly. If you have high blood pressure, ask your healthcare team if you should cut back on caffeine.
• Some medicines interact with caffeine. Certain medicines that treat asthma, seizures, psychiatric disorders and other conditions could have harmful effects if taken with caffeine.
• Coffee may trigger heartburn or bladder irritation. If you think coffee is causing these symptoms, talk to your healthcare team.

Note that coffee or tea additives, like sugar or flavored syrups, come with their own health risks. For example, nondairy creamers often contain trans fatty acids, which can increase your cholesterol levels.