May 26, 2020

Popeye Was Right: Eat Your Greens

If you’re over a certain age, you are very familiar with the Popeye cartoons. The hapless sailor could achieve superhuman levels of strength (and save Olive Oyl) after eating spinach.

Mixed Salad GreensA new study published in The Journal of Physiology finds that leafy greens, which contain nitrate, do help you develop stronger muscles. The researchers found that nitrate, eaten in quantities easily accessible in a normal diet, improves muscle strength.

Nitrate occurs naturally in leafy greens and vegetables, such as spinach, beet greens, lettuce, and chard. It’s also found in beetroot juice. The amount given to mice in the study is equivalent to 200 to 300 grams of fresh spinach every day, or eating two to three beets. To put that amount into perspective, one cup of packed fresh baby spinach leaves weighs 30 grams. One 10-ounce package of frozen spinach weighs 300 grams.

After one week being fed nitrate in their drinking water, the muscles in the mice’s legs and feet were stronger. The mice on the nitrate diet had higher concentrations of two proteins, called CASQ1 and DHPR in their muscles. Those proteins help improve muscle contraction.

Beetroot juice may have another benefit: increasing tolerance to exercise. A 2010 article in the Journal of Applied Physiology found that the nitrate in that food reduces oxygen uptake (making your body more efficient at using oxygen), which makes exercise less tiring. The nitrates also reduce resting systolic blood pressure (the higher number).

Another study, published this year in the Journal of the Academy of Nutrition and Dietetics, found that nitrate consumption improves running performance.

The interesting fact about nitrates is that the compound has been linked to adverse health effects, except when consumed in vegetable form. When nitrate is consumed in water or cured meats, it may increase your risk for developing cancer.

But nitrate metabolism in the body is completely different from nitrosamine development in cured meats. Dietary nitrate converts to nitrite, then to nitric oxide in the body. Nitric oxide is crucial to cardiovascular health, since it widens blood vessels and regulates blood pressure.

When nitrates are converted to nitrites, which then react with protein in the presence of fat, they can form nitrosamines, which are carcinogenic. That’s why nitrosamines form in cured meats.  But in population and epidemiological studies, there is no link between increased nitrate intake and cancer development.

The vegetables with the highest nitrate levels include celery, watercress, chervil, beetroot, spinach, rocket (arugula), and lettuce. If you want to be a good athlete, eat your greens!

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