A morning brew might not just be a welcome way to relax now but it could impact how you age in future. Scientists have carried out a major study investigating the tea, coffee and cola drinking habits of almost 50,000 women. It discovered coffee can have an effect on mental and physical health as women get older.

The researchers found coffee could help women stay sharp, strong and mentally well as they get older. But to achieve the positive results the coffee must contain caffeine as those drinking decafinated coffee did not have the same benefits.

Those who prefer a cup of tea also missed out on the health benefits. But worse still, those who preferred cola had a “significantly lower chance of healthy ageing”.

Dr. Sara Mahdavi, of Harvard T.H. Chan School of Public Health, said: “While past studies have linked coffee to individual health outcomes, our study is the first to assess coffee’s impact across multiple domains of ageing over three decades.

“The findings suggest that caffeinated coffee—not tea or decaf—may uniquely support aging trajectories that preserve both mental and physical function.” The findings were presented by Dr Mahdavi at Nutrition 2025, the flagship annual meeting of the American Society for Nutrition.

She said: “Our study has several key strengths. In addition to the large sample size and 30 years of follow-up, we assessed several different aspects of longevity and healthy ageing as well as very comprehensive information on nutritional and lifestyle habits that were collected every four years after the initiation of the study.”

Researchers looked at 47,513 women from the Nurses’ Health Study with dietary and health data collected since 1984. They assessed caffeine intake using validated food frequency questionnaires that included consumption of top contributors of caffeine such as coffee, tea, cola and decaffeinated coffee.

They then defined healthy ageing as living to age 70 or older, being free from 11 major chronic diseases, maintaining physical function, having good mental health, exhibiting no cognitive impairment and showing no memory complaints. After 30 years of follow-up, the team estimated how the likelihood of healthy ageing changed for every 80 mg of caffeine that study participants consumed per day.

They also looked at specific drinks like coffee, tea, decaffeinated coffee and cola. These preliminary analyses accounted for other factors that might influence healthy ageing such as body weight, smoking, alcohol use, physical activity, education level and protein in the diet.

Data showed that by 2016, 3,706 of the women met all the requirements for being considered healthy agers. In mid-life, ages 45-60, these women typically consumed an average of 315 mg of caffeine per day — roughly the amount in three small cups of coffee or one and a half large cups by today’s standards. More than 80% of that caffeine came from regular coffee consumption.

For women in the healthy agers group, each additional cup of coffee per day was linked to a 2% to 5% higher chance of doing well later in life, up to five small cups per day, or about 2.5 cups according to today’s measures. The scientists did not find any significant association between drinking decaffeinated coffee or tea with an increased likelihood of healthy ageing.

However every extra small glass of soda was associated with a 20% to 26% lower likelihood of healthy ageing, reinforcing that not all caffeine souces have benefits.

Dr Mahdavi said: “These results, while preliminary, suggest that small, consistent habits can shape long-term health. Moderate coffee intake may offer some protective benefits when combined with other healthy behaviours such as regular exercise, a healthy diet and avoiding smoking.

“While this study adds to prior evidence suggesting coffee intake may be linked with healthy ageing, the benefits from coffee are relatively modest compared to the impact of overall healthy lifestyle habits and warrant further investigation.”

The researchers said that generally up to two cups of coffee a day should be safe and potentially beneficial for most people. Beyond that, drinking more may offer additional benefits for some but may not be healthy for others.

In a separate study, Dr. Mahdavi and colleagues showed that genetic variation can influence the relationship between caffeine intake and health outcomes. This means more caffeine isn’t always better, particularly for people with lower caffeine tolerance or specific genetic susceptibility (Mahdavi et al, 2023).