While coffee boasts numerous health benefits, concerns mainly stem from its caffeine content. A recent study by Ohio State University found that consuming excessive coffee might lead to health issues such as increased heart rate, acid reflux, and insomnia. Yet, moderate consumption, typically up to four eight-ounce cups daily, can be safe for most adults. The key is to recognize individual limits, as the effects and metabolism of caffeine vary among individuals.
  

Key Points: 

1. Regular coffee consumption has been linked to extended life spans and a reduced risk of various diseases, including Type 2 diabetes and some cancers.
2. Overconsumption of caffeine can lead to symptoms like jitteriness, nausea, and sleeping disturbances.
3. For most adults, up to 400 milligrams of caffeine, equivalent to about four eight-ounce cups of brewed coffee, is considered safe daily.
4. Individual metabolism of caffeine varies; genetics can influence how quickly one processes caffeine, with some clearing it from their system in as little as two hours while others may take up to ten hours.
5. Pregnant women are advised to consume no more than 200 milligrams of caffeine daily due to increased risks associated with higher intake.

Source: https://www.nytimes.com/2023/09/26/well/eat/coffee-benefits-caffeine-risks.html