Vegetable Nitrates to Combat Muscle and Artery Aging

Nitrate supplementation can significantly increase exercise tolerance and exercise performance, not only because it enables your body to extract more energy from oxygen but because it also helps dilate your arteries to deliver more oxygenated blood to your muscles, and even directly improves muscle function (contractility) through an unknown mechanism. Nitrate-rich diets have been associated with improved muscle strength and physical function, leading researchers to conclude “vegetables may be an effective way to limit any age-associated declines in muscle function,” but cause-and-effect can’t be inferred due to the snapshot-in-time nature of the data.

The Harvard Nurses’ Health Study followed tens of thousands of older women for decades and found that those eating seven or more servings of fruits and vegetables a day seemed significantly less likely to become frail as they aged (compared to those eating less than three daily servings). And, of the dozens of fruits and vegetables they reviewed, the one that appeared most protective was leafy greens. That still doesn’t prove cause-and-effect, though.

There have been acute interventional studies. Older men and women (average age 71) given a beet juice supplement equivalent to about a cup (240 ml) of cooked greens experienced a significant boost in power and velocity in their quads. Based on the steady annual rate of muscular decline, the extent of the nitrate enhancement was said to be “functionally equivalent to acutely reversing the effects of several decades of aging.” A similar age group and dose also significantly improved upper body strength recovery, in terms of forearm handgrip. Could this by why fruit and vegetable consumption has been correlated with better physical function in general?

Men and women between the ages of 65 and 85 were randomized to continue to eat up to two servings of fruits and veggies a day or to increase to at least five daily servings for 16 weeks. There was a large increase in grip strength in the extra servings group, but it didn’t reach statistical significance, and there was no significant difference in physical function overall. Perhaps this is because study participants self-selected their own produce, preferring low-nitrate choices likes bananas and tomatoes.

What about the most important muscle? In an editorial entitled “Cardiac aging and the fountain of youth,” a Mayo Clinic research chair commented on the results of an “impressive array of experiments suggesting that this dream of reversing cardiac aging might not be as mythical as we had once believed.” Spiking the water of old mice with nitrates was able to reverse age-related heart and artery stiffness. What about in people?

A meta-analysis of a dozen randomized, controlled human trials found that between two-thirds of a cup (160 ml) to two cups (480 ml) of cooked greens worth of nitrates significantly improves artery function as measured in the arms or legs. Does this actually translate into clinical benefit?

Hundreds of millions suffer from peripheral artery disease, where atherosclerotic clogs impair blood flow to their legs. This can cause a cramping pain in the calves called claudication when they try to walk too far. This is why my grandmother was confined to a wheelchair (before her near miraculous recovery from heart disease gave her 31 more years of vim and vigor on her own two feet). Compared to a nitrate-free placebo, a single slug of beet juice (containing the nitrate content of about a cup and a half (360 ml) of cooked greens) enabled peripheral artery disease patients to walk 18 percent longer without pain.

Given their ability to facilitate the natural relaxation of our arteries, nitrate-rich vegetables are also considered an “easy, accessible, safe, and evidence-based strategy to reduce blood pressure.” For example, eating a high-nitrate soup (spinach) every day for a week lowers blood pressures more than a week of low-nitrate soup (asparagus), and the effect can be seen almost immediately. For example, randomize people to eat a green leafy salad with arugula and spinach, and within hours blood pressure drops lower than when eating a greens-free salad of cucumber, green beans, and cherry tomatoes.

The healthiest way to get your nitrate fix may be to eat a big salad every day. Vegetables are considered safer than taking nitrate- and nitric-oxide-boosting supplements. The benefits of nitrates may explain why eating your greens is associated with reduced rates of heart disease and a longer life span, not to mention the “veggie Viagra” effect. There appears to be a link between vegetable consumption and improved sexual function, as well as improved blood flow to the most important organ of the body, the brain. What about V8 juice, which boasts both beet and spinach juices? It must not have much, because you’d have to drink nineteen quarts (18 L) of V8 a day to reach your daily nitrate intake target.