Drinking four cups of coffee a day may increase the risk of mortality for people under 55 according to a new US study but the British Heart Foundation (BHF) is skeptical about the results.
Published in Mayo Clinic Proceedings, the associational study by Junxiu Liu et al – which nonetheless adjusts for confounding factors – reports a 50%+ increase in mortality rates for men and women in this group and a 21% higher risk for men of all ages who drank this much coffee.
“On the basis of these findings, it seems appropriate to suggest that younger people avoid heavy coffee consumption (i.e. averaging 4+ cups per day),” the scientists write.
But Liu et al. warn that further studies are needed to assess the long-term effects of coffee drinking and consumption changes over time on CVD and all-cause mortality.
Coffee science mixed
Studies of coffee drinking in respect of mortality were limited and results controversial, noting positive or inverse associations between the drink and deaths of men and women, Liu et al write.
Some research indicates that coffee has potentially beneficial effects on inflammation and cognitive function but caffeine also stimulate's epinephrine release, the researchers warn.
It also inhibits insulin activity, increases blood pressure and release homocysteine release – high levels of the latter increase the risk of heart attacks, strokes, blood clots and possibly Alzheimer's.
The researchers looked at deaths from cardiovascular disease in the Aerobics Center Longitudinal Study (ACLS) cohort of nearly 45,000 highly educated men and women.
From 1979 to 1998 their lifestyle habits – including coffee drinking – were recorded, with 33,900 men and 9,827 women included in the final investigative analysis.
Over the next 17 years 2,512 deaths occured (men 87.5%, women 12.5%) with 32% due to CVD, but those who drank more coffee were more likely to smoke and were less fit.
Study changes nothing - BHF
Citing consumer confusion as to the effects of coffee on heart health, BHF heart health dietician, Tracy Parker, notes that the mortality link was only associational and pointed to the possible confounding factors.
“The research showed no link between death from cardiovascular disease and coffee drinking and it doesn't change the current recommendations, which maintain that four or five cups of coffee a day won't damage your heart,” Parker said.
Noting limitations with their own study, Liu et al. admit that the ACLS data does not measure long-term coffee consumption changes, preparation methods, marital status or total energy consumption.
83% of US adults drink coffee and 63% do so every day – up 5% on 2012 – according to 2013 National Coffee Association data.
Title: 'Association of Coffee Consumption With All-Cause and Cardiovascular Disease Mortality'
Authors: Liu, J., Xui, S., Lavie, C.J., Hebert, J.R., Earnest, C.P., Zhang, J., Blair, S.N.
Source: Mayo Clinic, Published Online August 9 2013, http://dx.doi.org/10.1016/j.mayocp.2013.06.020