Foods That Could Inhibit Autophagy

As I discussed in the last chapter, we know that the enzyme AMPK activates autophagy. Accordingly, anything that suppresses the activation of AMPK, such as the intake of saturated fats, could also deactivate autophagy. Conversely, the enzyme mTOR (see the chapter on mTOR) deactivates autophagy, so anything that activates mTOR, like animal protein, could also suppress the autophagy process. When study participants fasted completely for 36 hours and then were given a drink with whey protein, their level of autophagy was suppressed much more substantially than if they had been given even more calories from pure carbohydrates. However, some carbohydrate-rich foods, especially French fries and potato chips, can suppress autophagy through another mechanism: acrylamide formation.

See see.nf/acrylamide for details, but essentially, acrylamide is a chemical substance that forms when carbohydrates are exposed to particularly high temperatures, and it prevents autophagy—at least in the Petri dish. That would explain why high acrylamide exposure is associated with increased mortality. That the life span of people who frequently eat fast food and salty snacks is reduced is nothing new. But in the video you will see an experiment comparing the effect of potato chips with that of boiled potatoes mixed with the same amount of salt and fat. Accordingly, there seems to be a link to the chemical, although acrylamide is not the only potentially harmful byproduct of frying. As one of the first textbooks of geriatric medicine presciently concluded back in 1849, “frying is an abomination.”

Foods That Could Enhance Autophagy

Any food that activates AMPK should also set autophagy in motion, so any of the AMPK-boosting foods from the last chapter should do the trick. However, autophagy can also be activated directly, independently of AMPK. The most reliable way to massively kick autophagy into gear is to eat less, but caloric restriction has a downside: hunger, as one large review understatedly put it, “leads to discomfort.” We can, however, consume something that many people find comforting: coffee.

Coffee

We have long known that alcohol consumption and liver inflammation go together, but in 1986 a group of Norwegian researchers made an unexpected discovery: coffee drinking is associated with less liver inflammation. Subsequent studies were able to reproduce these results worldwide. In the United States, for example, researchers studied people at high risk for liver disease—those with overweight, for instance, or individuals who drank excessive amounts of alcohol—and found that those who consumed more than two cups of coffee per day had not even half the risk of developing chronic liver problems compared to those who drank less than one cup. The fact that regular coffee consumption seems to protect against fatty liver gave researchers an idea.

Since autophagy plays such an important role in freeing the liver of fat, they tested whether caffeine cleans cells out. And indeed, they found that it strongly promotes autophagy. So, do coffee or caffeine extend the life span of model organisms like yeasts and worms? Yes and yes. Mice, too. In mice, coffee in amounts analogous to human consumption triggered autophagy within hours. What’s more, autophagy was promoted independently of caffeine content—decaffeinated coffee worked, too. Both regular and decaffeinated coffee also had a similar anti-aging effect on another pathway of aging (mTOR)—in mice. But what about in humans?

Good Drop by Drop

A systematic review on the health effects of coffee concluded that patients with chronic liver disease “should be encouraged to consume coffee daily.” If coffee enhances autophagy, shouldn’t it also have a positive effect on other diseases? Yes. Coffee drinking is also associated with a lower risk of kidney disease, as well as various conditions such as gout, type 2 diabetes, skin cancer, and Parkinson’s. Decaffeinated coffee is healthy as well. These results are all the more remarkable because many of the studies did not adequately account for smoking and unhealthy eating, both of which often go along with coffee drinking. Coffee drinkers therefore seem to be healthier, even when they consume a lot of unhealthy things. Do they therefore live longer? It certainly looks that way.

Intervention studies in rats showing that coffee extends life span have existed since the 1940s. For humans, we have only observational studies on coffee and mortality. To date there are more than 20 of them with more than ten million participants, and therefore we know that the risk of overall mortality was 13 percent lower among those who drank three cups of coffee daily. If you keep up the habit for your entire adult life, that translates into about one additional year of life.

It’s not due to caffeine, because three cups of decaffeinated coffee have the same protective effect. This is also supported by data showing that the link to longevity is the same in people who, due to genetics, metabolize coffee more slowly or more quickly. So if it’s not the caffeine, then what is it? Coffee contains more than 1000 bioactive substances. Chlorogenic acid, a polyphenol, is the most abundant antioxidant in coffee beans, so researchers started there and found that it can indeed enhance autophagy in human cell cultures.

The Healthiest Coffee

More than 100 kinds of coffee were tested, and the amount of chlorogenic acid they contained varied by more than 30-fold. Interestingly, Starbucks coffee stood out the most, since its chlorogenic acid content was extremely low—on average ten times lower than the others. That could be because Starbucks roasts its beans so dark. Caffeine is relatively heat-stable, but heavy roasting destroys up to 90 percent of the chlorogenic acid in the beans. Light and medium roasts, however, did not appear to differ—at least not in boosting the overall antioxidant status in the blood of the people who drank the coffee.

Don’t be fooled by “low-acid” coffee or “stomach-friendly” coffee. It does not help with sour belching, heartburn, or the stomach problems that plague some coffee drinkers. The coffee being low in acid refers to the low content of chlorogenic acid—exactly what we don’t want. The makers of stomach-friendly coffee slowly roast the beans so that the substance that activates autophagy is destroyed. That is just like an orange juice producer going to every effort to destroy the vitamin C and then promoting its OJ as “low-acid.” Technically that’s true, because vitamin C is ascorbic acid, but the juice maker would be boasting of having destroyed part of the nutritional value. And that’s exactly what the companies that make low-acid coffee are doing.

Coffee with or without milk?

Milk or animal-derived coffee creamer can negate the benefits of coffee. The milk protein casein binds to chlorogenic acid and thereby blocks its absorption in the digestive tract. Studies of human urine suggest that milk in coffee reduces the bioavailability of chlorogenic acid from 68 percent (in black coffee) to under 40 percent (in a caffè latte). Milk protein also undermines the benefits of tea, berries, and chocolate.