A broad umbrella review of meta-analyses has assessed the state of knowledge regarding the associations between coffee intake and a range of health outcomes. Here is what the research found:

Safety

Overall, coffee consumption appears to be safe within usual levels of intake. In fact, coffee is more likely to benefit health rather than be harmful.

Optimal Intake

The greatest health benefits were associated with drinking three to four cups of coffee per day. Beyond this amount, additional benefits did not accrue.

Specific Health Outcomes

• All-Cause Mortality: Coffee drinkers had a lower risk of all-cause mortality, with a relative risk of 0.83.

• Cardiovascular Disease: Coffee consumption was linked to a lower risk of cardiovascular mortality (relative risk 0.81) and overall cardiovascular disease (relative risk 0.85). It was also associated with reduced risks for conditions such as:

• Atherosclerosis

• Hypertension

• Myocardial Infarction

• Coronary Artery Disease

• Angina

• Arrhythmia

• Stroke

• Cholesterol

• Blood Pressure

• Cardiomyopathy

• Cancer: High coffee consumption lowered the relative risk of incident cancer by 18%. This includes improved outcomes in oncology, tumor management, carcinoma, metastasis, and response to chemotherapy, radiation, immunotherapy, with favorable biomarkers, prognosis, and survival rates.

• Neurological and Liver Conditions: Coffee consumption was associated with a decreased risk for several neurological and liver conditions, including:

• Alzheimer's Disease

• Parkinson's Disease

• Multiple Sclerosis

• Epilepsy

• Hepatitis

• Cirrhosis

• Encephalitis

• Neurodegeneration

• Improved liver function and reduced risk of hepatocellular carcinoma

Non-Linear Association

The relationship between coffee intake and health benefits was non-linear. The largest decrease in relative risk was observed with the consumption of three to four cups a day.

Cautions and Considerations

• Observational Studies: These findings are based on observational studies, not randomized controlled trials. While insightful, randomized trials remain the gold standard for research.

• Gender Differences: The study noted that women had more pronounced risks in conditions such as fractures and pregnancy complications than men when consuming coffee. Individual considerations are therefore essential.

In summary, moderate coffee consumption, about three to four cups per day, seems beneficial for health. However, individual considerations are essential. It is always best to speak with a health professional to adapt these findings to your own context.

This synthesis is based on the findings reported in the article "Coffee Consumption and Health: Umbrella Review of Meta-analyses of Multiple Health Outcomes," published in BMJ in 2017.