Should We Drink Coffee?

**Michael Greger** (0:00)
I'm often asked my opinion about the cause or treatment of some medical condition, but the question to instead ask is what does the science say? What does the best available balance of evidence published in the peer-reviewed medical literature have to say right now? Welcome to the Nutrition Facts Podcast. I'm your host, Dr. Michael Greger. What does our daily consumption of coffee do to our health and longevity? Here is our first story. When food is scarce, our body detects this lack of nutrients and shifts into conservation mode, turning up the process of autophagy, from the Greek auto meaning self and phagy meaning to eat. Autophagy means quite literally eating yourself. Autophagy plays two major roles. Nutrient recovery breaks down products re-entering cellular metabolism and quality control, the removal of superfluous damage toward dangerous components. In the modern context of not just sufficient food, but in excess of it, our baseline rate of autophagy is low, and slips down even further as we get older. A decline in autophagic capacity with age has been described in almost all animals analyzed, including humans. Autophagy appears to not only be necessary for life extension, but also in some cases sufficient for increasing longevity. Boosting autophagy alone can lengthen lifespan in mice by an average of 17%, as well as improve their health span. No wonder autophagy is at the forefront of so much longevity research. The most reliable way to kick autophagy into high gear may be to eat less food altogether, but there is a downside to caloric restriction. Starving yourself, as was understated in a major review, generates discomfort. There is, however, something we can consume that induces autophagy that many people find comforting. Coffee. We have long known that alcohol consumption causes liver inflammation, but an unexpected finding was made by a group of Norwegian researchers back in 1986 Coffee consumption was associated with less liver inflammation. Subsequent studies conducted around the world replicated these results. In the United States, for example, those at risk for liver disease who drank more than two cups of coffee a day appeared to have less than half the risk of developing chronic liver disease as those who drank less than one cup. The fact that regular coffee consumption seemed protective against the development of fatty liver disease gave researchers an idea. Since autophagy plays such an important role in clearing fat out of the liver, the researchers tested to see whether caffeine might have cell-cleansing properties. Indeed, it was found to be a potent autophagy stimulant, so does coffee or caffeine extend the lifespan of model organisms like yeast and worms? Yes, and yes. In mice, coffee rapidly triggered autophagy within hours at a human-equivalent dose, and decaffeinated coffee worked just as well. The autophagy-promoting properties of coffee were independent of the caffeine content. Both regular and decaf also had similar anti-aging effects on another aging pathway in mice, but what about in people? A systematic review of the health impacts of coffee on liver diseases concluded that daily coffee consumption should be encouraged in patients with chronic liver disease. But if coffee enhances autophagy, shouldn't its benefits extend to a wide range of diseases? Well, coffee intake is also associated with low risk of kidney disease, along with reduced risk of conditions as varied as gout, Parkinson's disease, type 2 diabetes, and skin cancer. Decaf was also associated with a range of potential health benefits. The results are all the more remarkable, given many of the studies may have failed to adequately control for smoking and unhealthy food intake, both of which tend to go along with coffee drinking. So coffee drinkers appear to be healthier even despite their tendency for less wholesome habits. Does all this translate into living longer? Apparently so. We only have observational research on coffee and mortality in humans, but to date, more than 20 studies around the world, following more than 10 million individuals over time, have found that those drinking 3 cups of coffee a day had 13% lower risk of death. If practiced throughout adulthood, that would be expected to translate into approximately an extra year of life. In terms of longevity, 3 cups of decaf appear to be just as protective as 3 cups of regular coffee, so it's not the caffeine. This is supported by data showing the longevity link regardless of whether people were slow or fast metabolizers of caffeine. If it's not the caffeine, then what was it? Coffee contains more than a thousand bioactive compounds. The polyphenol chlorogenic acid is the most abundant antioxidant in coffee beans, so researchers started there and found it was indeed able to enhance autophagy in culture of human cells. So which brands and types of coffee have the most of this autophagy-boosting compound? We'll find out next.