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New research suggests that coffee may have a protective effect against inflammation and cardiovascular disease as we age, possibly even helping to increase life expectancy.

Carried out by Stanford University School of Medicine, the team looked at blood samples, survey data and medical and family histories taken from more than 100 participants taking part in the Stanford-Ellison cohort, a long-term program started 10 years ago by two of the study's authors to look at the immunology of aging.

The participants fell into two groups -- one group of healthy participants ages 20-30 and another group 60 and above.

The researchers compared blood taken from both groups to see which genes tended to be more highly activated in older people, focusing in on two groups of genes whose activity is associated with an inflammatory protein called IL-1-beta.

They then focused in on two groups of older people -- those with high activation of one or both inflammatory gene clusters and those with low activation levels.

Those with high activation were found to be much more likely to have stiff arteries -- a risk factor for cardiovascular complications -- than those in the "low" activation group.

Those in the low group were also eight times more likely than those in the high group to report having at least one close family member who had lived to age 90 or older, while those in the high group who were older than 85 in 2008 were also significantly more likely to have died by 2016 than those in the low group.

When compared to the low group those in the high activity group were also more likely to have high blood pressure, increased activity of free radicals -- which can harm cells -- and increased levels of the inflammatory protein IL-1-beta.

Interested by a possible link between the older participants' health, the activation levels and their self-reported rates of caffeine consumption, the researchers once again tested the blood from the groups, finding that blood from the group with low activity had higher levels of caffeine and a number of its metabolites, including theophylline, also found in tea, and theobromine, also found in chocolate, when compared with blood from the group with high cluster activity.

To research further the team then incubated immune cells in mice with caffeine, finding that the caffeine substantially prevented on inflammatory effect on the cells.

"That something many people drink -- and actually like to drink -- might have a direct benefit came as a surprise to us," said one of the study's co-authors Mark Davis, who also noted however that the study did not prove a causal link. "We didn't give some of the mice coffee and the others decaf. What we've shown is a correlation between caffeine consumption and longevity.'