Fiber-Rich Foods

You don’t like vinegar? Instead of taking in acetic acid through your mouth, you can also introduce it into your bloodstream from the opposite direction. You know that vegetables and grains turn sour when they ferment, right? Think sauerkraut or sourdough. That’s because there are good bacteria like Lactobacillus that produce organic acids such as lactic acid. Acetic acid is one of the short-chain fatty acids that our friendly gut flora makes from the fiber and the resistant starch that we eat. These prebiotics are concentrated in legumes (beans, yellow peas, chickpeas, and lentils) and whole grains, but they exist throughout the plant kingdom. When we eat whole plant foods, the colonic flora ferments the fiber and produces the acetic acid itself. This acetic acid is then absorbed into our bloodstream. So we can activate AMPK “from above” by consuming vinegar, or “from below” by eating fiber.

How much fiber are we talking about here? Even if you take in only the tiny recommended minimum amount of about 30 grams daily, that can lead to the production of more than four tablespoons of vinegar in the colon. Some of it is inevitably excreted, so only about 40 percent of the acetic acid from the gut is absorbed, but if we consume enough healthy foods, this could have a considerable impact on our AMPK status. AMPK that is triggered by acetic acid from the colon is thought to be one of the reasons that a fiber-rich diet benefits metabolism.

Among other things, the study of human coprolites—fossilized excrement (paleo poop!)—has revealed that our early ancestors probably ate more than 100 grams of fiber a day. That is more than five times as much as the modern average American. Over the course of evolution, then, we became AMPK-activating machines, not only because we were often hungry and active, but because our digestive system, thanks to all the plants we ate, spit out spoonfuls of vinegar. And before you ask, no, you can’t just take a fiber supplement like psyllium (Metamucil), since it doesn’t ferment—that is, our gut bacteria can’t eat it. Although such fiber supplements can regulate bowel movements, they can’t be used as the main ingredient for activating AMPK.

Food for Thought

The discovery of AMPK is considered one of the most important breakthroughs in biomedicine of the past few decades. Since this enzyme is involved in the function of most regulators of the aging process, including autophagy, which I will discuss next, it’s hard to overstate the importance of AMPK in anti-aging measures.

The drug metformin activates AMPK, but it has unwanted side effects and may offer no benefit for healthy people. AMPK is an energy sensor, so it is activated when we eat less or move more. Some food components like saturated fats can suppress AMPK, while others like fiber can rev it up. We also find specific AMPK-activating components in barberries, black cumin, hibiscus tea, and vinegar.

To support this anti-aging option, you should, at every meal:

Autophagy

When food is scarce, our body goes into maintenance mode, slows down cell division, and begins autophagy. The word comes from Greek and is composed of auto for “self” and phagy for “eat.” Autophagy literally means to eat yourself.

The Trash Has to Go

As soon as our body recognizes that there isn’t much food, it begins a recycling operation, combing through cells in search of anything we don’t need—damaged proteins, malfunctioning mitochondria, and other broken stuff. It clears out the junk, upcycles it, turns it into fuel or new building materials, and in this way renews our cells. Autophagy therefore plays two major roles: nutrient recovery and quality control. The fact that the mechanism of autophagy has been preserved over more than a billion years of biological evolution underscores the importance of this universal recycling program. In 2016, the man who coaxed its secrets from it was honored with the Nobel Prize.

At any given time, our cells produce more than 10 000 different proteins and assemble them. Any one of them can be misfolded or damaged at any time and call for the cleaning crew on aisle three. But we evolved in a context of scarcity, where it was hard to get food. It wasn’t predictable when there would be something to eat again. So our body always assumes that hard times could be coming—maybe as soon as tomorrow—and assumes it can put off cleaning for that long. But nowadays, these lean times hardly ever occur. Most of us live in food abundance, so the body thinks: Why bother? We can just toss the faulty protein or the broken mitochondria in the corner and make new ones. And so cells are constantly hoarding more trash.

The accumulation of cellular debris is not only a waste; it is also harmful. Throwing out the old and replacing it with new not only replenishes supplies, it also clears out what’s gone rotten. Our ancestors often ate only once a day or had to go several days without food, so the autophagy switch was constantly being flipped. In our present-day world with three meals a day, our cells no longer need to look for their food under the couch cushions, and the mountains of trash grow.

In the modern context, in which we not only have relatively easy access to adequate nutrients but even to excessive amounts of food, our autophagy levels are low and slip even further as we get older. A decline in the ability to perform autophagy with age has been described in almost all animals studied. This can lead to further accumulation of cellular trash, which may then damage our aging cells even more. So it could be that insufficient autophagy is not only a consequence of aging, but also one of its causes.

Autophagy is pivotal in most life-span-extending interventions. Whether through diet, drugs, or genetic changes: if the metabolic pathways of autophagy are blocked, then so are many of the effects that promote longevity. And even more, autophagy appears not only to be necessary for lifespan extension, but in some cases also sufficient. Simply boosting autophagy can increase life span in mice by an average of 17 percent while also extending health span. No wonder autophagy is at the very forefront of such a large part of longevity research.

Fasting or Flying

The most commonly cited way to trigger autophagy is restricted food intake, which gives the phrase “cleansing through fasting” new meaning, but autophagy doesn’t really get going until after 24 to 48 hours of fasting, which is too long to do without supervision. But a moderate, long-term restriction of food intake might also work, as shown by muscle biopsies from volunteers in the Calorie Restriction Society. Details at see.hf/fast.