Five cups of coffee a day may keep the doctor away

Coffee drinkers rejoice! The Dietary Guidelines Advisory Committee (DGAC) recently released their 2015 report on dietary recommendations. In the report they suggested that consuming 3-5 cups of coffee per day (~ 400 mg of caffeine) is not associated with health risks amoung healthy individuals. The report can be found at this link (http://www.health.gov/dietaryguidelines/2015-scientific-report/PDFs/Scientific-Report-of-the-2015-Dietary-Guidelines-Advisory-Committee.pdf). It should be mentioned this does not apply to people consuming dairy and sugar with their coffee (more fat and calories), but rather drinking coffee black. I have always been a proponent of black coffee, not only is it a healthier option but it allows you to experience the variation in growing regions and roasting methods.

The report moves on to present studies that have shown a coffee reduces the risk of some health related disorders. Type 2 diabetes and cardiovascular health are amoung the two most talked about. The Dutch Famine of 1944, while very tragic, provided some insight into dietary regulations seen today. A study by van Dam RM et al. (2002) found that in a cohort of 17,111 Dutch individuals 306 new cases of type 2 diabetes was found. This study went on to show that those who drank 7 cups of coffee per day were half as likely to develop type 2 diabetes1. A recent Meta-analysis, with a cohort of 457,922 individuals, found similar results and concluded that drinking 3-4 cups of coffee per day recued risk of type 2 diabetes by 25%2.

Coffee has also been shown to influence the diagnosis of Parkinson’s disease (PD). Two recent meta-analysis, 46 studies all together, reported that the risk of developing PD decreased by up to 31% in coffee drinkers than non-coffee drinkers3,4. Their reports found ~4 cups of coffee were adequate to produce these reduction figures. While only shown in animal models a mechanism for this reduction has been postulated.

The Basal Ganglia is a region within the brain that is thought to be the area most involved in PD. It is here that neurons degenerate, leading to the presentation of classic PD symptoms. Within the Basal Ganglia there is a subset of neurons referred to as dopaminergic neurons, because they tend to release primarily the neurotransmitter dopamine. On these neurons there are two important receptors: Adenosine 2A receptors (A2AR) and dopamine 2 receptors (D2R). The A2A receptors help regulate the amount of D2 receptors on the surface of the neuron at one time. If there are too many D2 receptors then the A2A receptors will “internalize” the excess D2 receptors. If there are too little D2 receptors then the cell body will produce more, which are imbedded back into the cell membrane. A recent Nature article by Volkow et al. (2015) found that caffeine blocks the action of the A2A receptors while enhancing the production of more D2 receptors. This in turn provides more binding sites for dopamine. PD is a loss of dopamine production and binding within the Basal Ganglia. It seems coffee counteracts these effects, allowing an increase in dopamine binding by increasing the amount of D2 receptors present.

While the mechanisms of coffee are not fully understood, cohort studies have provided useful information on the general effect coffee has on health. Several studies continue to examine the effects coffee has on health, I am positive we will find more health effects in the future. So go have another cup of coffee, don’t feel guilty about having an extra cup.

References:

  1. Van Dam R.M. et al. (2002) Coffee consumption and risk of type 2 diabetes mellitus.Lancet, 360:1477-1478.
  2. Huxley R. et al. (2009) Coffee, Decaffeinated Coffee, and Tea Consumption in Relation to Incident Type 2 Diabetes Mellitus.Archives of Internal Medicine, 169:2053-2063.
  3. Hernan M.A. et al. (2002) A meta-analysis of coffee drinking, cigarette smoking, and the risk of Parkinson’s disease. Ann Neurol, 52:276-84.
  4. Costa J. et al. (2010) Caffeine exposure and the risk of Parkinson’s disease: a systematic review and meta-analysis of observational studies. J Alzheimers Dis, 20 Suppl 1:S221-38.