提供一篇英文短文，并要求生成翻译为中文的摘要，长度为2-3句话。


英文短文：It is well known that coffee contains caffeine, a stimulant that can enhance brain function and increase alertness. Research has also suggested that moderate coffee consumption can have other health effects, such as reducing the risk of Alzheimer's and Parkinson's diseases. However, excessive coffee consumption can lead to negative side effects, such as irritability and insomnia.
英文短文摘要：Coffee can enhance brain function and reduce the risk of Alzheimer's and Parkinson's diseases through moderate consumption, yet excessive consumption may lead to negative side effects such as irritability and insomnia.

中文翻译摘要：适量咖啡因摄入可以提高脑功能并降低阿尔茨海默症和帕金森病的风险，但过度饮用可能会导致反应不佳和失眠等负面影响。