This isn’t just an issue of the need for human trials to confirm the results of animal trials before jumping to conclusions. It’s also about understanding what the mechanism is that could make coffee good or bad news for Alzheimers risk. There are two main theories: one is that it’s all to do with the formation of amyloid plaques that are found in the neurofibrilliary tangles in the brains of those with Alzheimer’s. The other is that high homocysteine levels predict and may cause the kind of brain damage seen in Alzheimers. These two hypotheses aren’t mutually exclusive.
For example, recent studies show that raised homocysteine can lead to neurofibrilliary tangles and may promote amyloid plaque. So, what about coffee? On the one hand this recent study shows that mice given a relatively high dose of caffeine produce less beta-amyloid protein, the implication being less formation of amyloid plaques. However, amyloid proteins in the mouse brain is certainly not the same thing as Alzheimers. On the other hand, it is well established the caffeine raises homocysteine. Coffee raises it more than caffeine alone so it is though that something else in coffee, as well as caffeine, has this potentially harmful effect. A double expresso raises homocysteine by 11% in 4 hours. The largest and longest survey, the Hordaland Homocysteine Study, finds a consistent increase in homocysteine with coffee intake. Do coffee drinkers have less memory loss or Alzheimer’s risk? Some studies says yes, others say no. Generally, there is no good evidence that coffee consumption reduces Alzheimer’s risk or lessens age-related memory loss. A more consistent benefit, however, is seen with tea and chocolate, as well as red wine.
This is thought to be due to their high flavonoid content. Although the newspaper headlines talk about Alzheimers reversal it’s way too premature to jump to this kind of conclusion from this two-month study. The proposed mechanism by the authors of this study are that caffeine somehow suppresses inflammatory changes in the brain that lead to an overabundance of amyloid protein, but caffeine has also been shown to increase certain markers of inflammation. All this makes me unwilling to add coffee to my list of foods and drinks that reduce Alzheimers risk. If you’d like to know more about how to protect your memory and prevent Alzheimer’s disease read The Alzheimers Prevention Plan.