Green Slows Things Down

Reduced calorie intake slows metabolism and could thereby extend the lifespan of animals. Like a candle that burns longer with a smaller flame. If we eat a big salad every day, we achieve a similar effect on metabolism with the nitrates from green leafy vegetables.

The nitrates that naturally occur in green leafy and root vegetables improve the performance of our mitochondria, the tiny power plants in cells that pull more energy out of every breath and thereby boost athletic performance. That’s why, for example, divers can hold their breath 30 seconds longer than usual after just one small glass of beet juice. What else vegetable doping can do for athletic performance, you can see in see.nf/nitrates. No medication, supplement, steroid, or anything else can do what vegetable nitrates can do.

But beets just barely make the top ten of nitrate-rich, normal foods. Eight of the top ten are green vegetables, and with a nitrate content four times higher than beet greens, arugula tops the list with an astonishing 480 milligrams of nitrate per 100 grams.

Top ten nitrate sources in normal foods

Overall, we get up to 80 percent of our nitrates from green leafy vegetables. So could we slow our metabolism with lots of leafy greens because our bodies then work more efficiently and pull more energy out of every calorie? In fact, researchers found that participants’ resting metabolism dropped by an average of 4 percent after they consumed the amount of nitrates equivalent to just a few servings of leafy greens or beet greens. That’s almost 100 fewer calories burned a day. The scientists concluded that our bodies adapted long ago to conserve energy during times of hunger by means of vegetables. Either way, a slowed metabolism likely has a positive effect on our longevity, and it could explain why people who eat more vegetables often live longer than others.

Vegetable nitrates against muscle aging

Taking nitrates can improve endurance and performance, because nitrates not only enable the body to get more energy out of oxygen, they also dilate the arteries so they can deliver more oxygen-rich blood to the muscles, and they even improve muscle function directly (contractility) via a mechanism that is still unknown. A nitrate-rich diet has been associated with improved muscle strength and function, and scientists concluded that “vegetables could be a powerful way to limit any age-related decline in muscle function.” Since these are cross-sectional data, however, no causality can be inferred.

Take a look at see.nf/nitrateaging to learn more, but intervention studies are being conducted, for example one in which men and women with an average age of 71 were given the equivalent of a cup of cooked greens in the form of beet juice. The subjects experienced a significant improvement in knee flexion strength (squats) and speed. Based on the annual loss of muscle strength, it was calculated that the improvement from the nitrates “functionally corresponds to reversing the signs of aging by multiple decades.” In a group of similarly aged participants who received a similar amount of nitrates, upper-body strength (forearm grip strength) improved significantly.

Vegetable nitrates against arterial aging

In the editorial “Heart Aging and the Fountain of Youth,” the chair of a Mayo Clinic research group reported on the results of “some impressive experiments suggesting that the dream of reversing heart aging might be less mythical than we thought.” In one experiment, researchers added nitrates to old mice’s drinking water, thereby reversing age-related stiffening of the heart and arteries. But would that also work in humans?

The meta-analysis of a dozen randomized controlled human trials found that an amount of nitrates equivalent to two-thirds of a cup to two cups of cooked green leafy vegetables significantly improved arterial function as measured in arms and legs, and as I describe in detail in see.nf/nitrateaging, that led to clinical benefits: For example, patients with peripheral artery disease were able to walk 18 percent longer without pain.

A big salad a day is the healthiest way to get your nitrate shot. Subjects randomized to eat a large leafy salad with arugula and spinach had lower blood pressure within hours compared with others who ate a salad of cucumber, green beans, and cherry tomatoes, but without leafy greens. You could also take nitrates and nitric oxide via supplements, but their safety and effectiveness are known to be questionable. How about 100-percent vegetable juice that contains beets and spinach? The V8 brand apparently doesn’t contain much of either, since you’d have to drink 18 liters a day to meet the daily nitrate target (details in see.nf/nitratetarget).

Food for the oral microbiome

Taken together, all studies show that nitrate-rich vegetables lower blood pressure significantly on average, but a few studies found no benefit. To understand these differing results—and also why eating vegetables becomes more important with age—you first have to know how nitrates are activated as the first step in the mouth, thanks to the good bacteria on the tongue. I explain the whole fascinating process in see.nf/scrape, but the bottom line is: Eat nitrate-rich vegetables regularly to support the growth of the oral bacteria that metabolize nitrates, don’t use antiseptic mouthwash, and brush your tongue daily (unless you have heart valve problems, a pacemaker, or for some other reason have an endocarditis risk.)

How to prevent nitrates from turning into nitrosamines

The nitrate strategy works only in the context of a healthy diet. If you add saturated fats (as meat and dairy products) to the vegetable-heavy Mediterranean diet, it raises blood pressure; it doesn’t lower it. What’s more: The nitrate strategy is safe only in the context of a healthy diet.

The activation step on the tongue turns nitrates into nitrites. Wait a minute—nitrites? Isn’t that the stuff used to cure meat? Why are nitrates and nitrites from vegetables okay, but in meat they’re carcinogenic? Because the nitrites themselves aren’t carcinogenic; they’re converted into carcinogenic substances. Nitrites don’t become harmful until they turn into nitrosamines and nitrosamides. For that to happen, you need amines and amides, both of which are abundant in animal products.

So when meat is treated with nitrites, carcinogens form. (So-called “uncured” bacon sometimes lists “fermented celery juice” or something similar on the ingredients list; that’s sleight of hand meant only to avoid the word “nitrites,” even though they’re in there.) The danger posed by processed meat is so great that the second-largest prospective study ever conducted on cancer and diet found that if less than 20 grams of processed meat were eaten per day—less than the size of a matchbox—there would be 3 percent fewer deaths overall in Europe. According to the largest prospective study of diet and health in U.S. history—the NIH-AARP study with more than half a million Americans—the share of avoidable deaths could be even higher. For example, if in the United States the women who eat the most processed meat reduced their consumption to less than half a strip of bacon a day, the scientists said, 20 percent of their deaths from heart disease could be prevented. No wonder, then, that the American Institute for Cancer Research recommends “avoiding processed meats such as ham, bacon, salami, hot dogs, and sausage.”