Abstract
The association of habitual coffee consumption with a lower risk of diseases, like type 2 diabetes mellitus, chronic liver disease, certain cancer types, or with reduced all-cause mortality, has been confirmed in prospective cohort studies in many regions of the world. The molecular mechanism is still unresolved. The radical-scavenging and anti-inflammatory activity of coffee constituents is too weak to account for such effects. We argue here that coffee as a plant food has similar beneficial properties to many vegetables and fruits. Recent studies have identified a health promoting mechanism common to coffee, vegetables and fruits, i.e., the activation of an adaptive cellular response characterized by the upregulation of proteins involved in cell protection, notably antioxidant, detoxifying and repair enzymes. Key to this response is the activation of the Nrf2 (Nuclear factor erythroid 2-related factor-2) system by phenolic phytochemicals, which induces the expression of cell defense genes. Coffee plays a dominant role in that regard because it is the major dietary source of phenolic acids and polyphenols in the developed world. A possible supportive action may be the modulation of the gut microbiota by non-digested prebiotic constituents of coffee, but the available data are still scarce. We conclude that coffee employs similar pathways of promoting health as assumed for other vegetables and fruits. Coffee beans may be viewed as healthy vegetable food and a main supplier of dietary phenolic phytochemicals.
Highlights
In recent years, numerous meta-analyses have come up with positive health outcomes associated with habitual coffee consumption in the general population, and this has changed the perception of coffee from that of a luxury stimulant drink to that of a health promoting beverage, if consumed within usual levels of intake
Phytochemicals other than caffeine appear to account for most beneficial properties of coffee
As in vegetables or fruits, polyphenols and phenolic acids represent a major portion of phytochemicals in coffee beans
Summary
Numerous meta-analyses have come up with positive health outcomes associated with habitual coffee consumption in the general population, and this has changed the perception of coffee from that of a luxury stimulant drink to that of a health promoting beverage, if consumed within usual levels of intake. There were no consistent associations of the genotype for faster caffeine metabolism (and more caffeine/coffee consumption) with positive health outcomes [11]. An epidemiological study of nearly 500,000 participants of the United Kingdom Biobank finds associations between the number of cups of coffee consumed per day and decreased all-cause mortality, regardless of genetic caffeine metabolism score, i.e., the circadian level of caffeine in circulation [15]. Caffeine does not appear to account for the lower risk of type 2 diabetes with habitual coffee consumption, since this is seen in association with drinking decaffeinated coffee. Health effects appear to be associated with other prominent constituents of the coffee brew These include chlorogenic acids, trigonelline, N-methylpyridinium, the diterpenes kahweol and cafestol, polysaccharides, peptides and melanoidins. Non-digestible components of coffee may modulate the composition and function of the microbiota, as is known for other plant foods
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