I know, most often on this blog we don’t put much value on epidemiological studies linking disease over decades to food consumption captured by a one-time limited food frequency questionnaire at the beginning of the study period. Knowing the limited reliability of such a food consumption method, intricate relationships between different food groups and changes in food consumption patterns with increasing age it is surprising that it is even called science. But this time it might be different (or is that wishful thinking from our side?).
A new study praises the benefits of coffee
This new epidemiological study of coffee consumption and health is quite elaborate. Firstly, it involved 208,501 participants with 31,956 deaths in three large cohort studies allowing detailed statistical calculations. Secondly, it repeated the food frequency questionnaire each four years to capture food pattern changes. And thirdly, it actually validated the food frequency questionnaire against a multiple week dietary record showing a correlation of 0.74 and reproducibility of 0.80. So a good starting point strengthened by the fact that previous studies have shown that coffee intake is one of the food items showing the highest validity and reproducibility when using food frequency questionnaires and a beverage less prone to misreporting.
Detailed information on caffeinated and non-caffeinated coffee consumption was available as well as other dietary and lifestyle factors. The initial analyses showed a positive correlation between coffee consumption and smoking and because of the deleterious effects of smoking on health, smokers were excluded from the further analyses.
In summary, the good news showed that regular consumption of coffee was inversely associated with risk of total mortality and in particular mortality due to cardiovascular disease and neurological diseases like Parkinson’s. No significant association between coffee consumption and total cancer mortality was found, so unless the International Agency for Cancer Research (IARC) has 799 studies showing the opposite, coffee should be in the clear (I am referring to the dubious nomination by IARC of whole categories of meat or meat products as cancer suspects based on 800 studies we have not yet been able to verify).
Optimal coffee consumption
Three to five cups a day seemed to have the optimal protective health effects with the mortality rate 12% less compared to non-coffee drinkers. Similar associations of caffeinated and decaffeinated coffee consumption with risk of total and cause-specific mortality were found. Thus the caffeine is not the protective compound. There are several other compounds in coffee that could be responsible for the positive effects. The authors list chlorogenic acid, quinides, lignans, trigonelline and magnesium as likely contenders as they reduce insulin resistance and systemic inflammation that in turn might prevent diabetes as well as cardiovascular disease.
There could be another reason linked to the dubious findings of IARC and meat consumption. Apart from the obvious culprits associated with meat consumption, like polycyclic aromatic hydrocarbons formed during wood smoking and barbecuing, nitrite added to processed meats and heterocyclic amines formed during high temperature frying, the only compound inherent to meat itself (providing some justification for nominating a whole food category as carcinogenic) is haeme iron. As it happens haeme iron is an excellent source of bioavailable iron, but new research points to excess iron being responsible for a range of human illnesses as well as promoting bacterial growth (in a further blog we will delve into the details of the influence of iron on human health).
Why not try a cup of coffee after dinner?
Now a cup of coffee after dinner inhibits the efficient uptake of iron by the human body. This might be a double whammy in that you can enjoy your red and processed meat without much worry and get an extra kick by the coffee. We told you about the importance of the whole diet with intricate relationships between different food groups.
Maybe IARC should be a bit more careful in the future in looking at individual foods, otherwise it will not be much left to eat. Arsenic in rice cause cancer, too much milk has been associated with prostate and breast cancer, a range of refined and processed foods contribute to weight gain with obesity a factor in cancer development. The list goes on and on. But stick to coffee and you might be fine (although your sleep pattern might be disturbed by a late cup).