Keeping Your Hands Warm with Citrus

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Phytonutrients in citrus, such as hesperidin, may increase blood flow sufficient to warm the hands and feet of those with cold sensitivity.

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Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

In 1936, Albert Szent-Györgyi, who won the Nobel Prize for discovering vitamin C, described a “vitamin P,” which we now know encompasses a class of thousands of phytonutrients called flavonoids. Some, like quercetin, are “widespread in plant-based foods.” You can tell something is widespread in the plant kingdom when you can even find it in iceberg lettuce.

Others, however, are only found in specific plant families. For example, hesperitin is “found primarily in citrus fruits.” This may be one of the reasons that, out of all the different types of fruit that have been looked at, citrus may help cut our risk of stroke the most.

The citrus phytonutrient hesperitin increases blood flow. Using a machine called a Doppler fluximeter, you can measure blood flow through the skin using a laser beam. A laser Doppler fluximeter; sounds like something from Back to the Future. And, if you give people the amount of hesperitin found in two cups of orange juice, blood flow goes up, though if you instead just give them the orange juice itself, that works even better. So, there’s other beneficial stuff besides just the hesperitin in citrus.

For example, if you measure the changes in genetic expression, orange juice consumption induces changes in the expression in 3,000 of our genes—whereas hesperitin alone only modulated the expression of about 2,000. Still, nearly 2,000 stretches of our DNA expressed differently because we consumed just one of the thousands of phytonutrients in plants—pretty mind-blowing.

And these changes in blood flow are not just kind of “in theory.” Researchers have taken volunteers with cold sensitivity—cold hands, cold feet—put them in an air-conditioned room, and measured the temperature of their fingertips after drinking a placebo drink—like orange Kool-Aid—versus drinks with two doses of actual citrus phytonutrients. In the Kool-Aid group, their fingers got colder and colder, dropping nearly 9 degrees Fahrenheit. But, the fingers of those consuming low or high doses of citrus didn’t as much. That’s because their blood flow remained steady. Here’s that laser test again.

When we’re exposed to cold temperatures, our body starts to clamp off peripheral blood flow to keep our core warm. But, if you eat a bunch of oranges before you go skiing, your risk of frostbite may go down, since you’re keeping up your blood flow to your fingers and toes.

They even took these poor women, and plunged their hands into some chilly water. And, as you can see, their finger temperature rebounded faster towards normal in the citrus group. Of course, having warm hands is nice, but maintaining blood flow to your fingers is not as important as maintaining blood flow to your brain.

Please consider volunteering to help out on the site.

Images thanks to PetitPlat – Stephanie Kilgast via flickr. Thanks to Ellen Reid and Shane Barrett for their Keynote help.

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

In 1936, Albert Szent-Györgyi, who won the Nobel Prize for discovering vitamin C, described a “vitamin P,” which we now know encompasses a class of thousands of phytonutrients called flavonoids. Some, like quercetin, are “widespread in plant-based foods.” You can tell something is widespread in the plant kingdom when you can even find it in iceberg lettuce.

Others, however, are only found in specific plant families. For example, hesperitin is “found primarily in citrus fruits.” This may be one of the reasons that, out of all the different types of fruit that have been looked at, citrus may help cut our risk of stroke the most.

The citrus phytonutrient hesperitin increases blood flow. Using a machine called a Doppler fluximeter, you can measure blood flow through the skin using a laser beam. A laser Doppler fluximeter; sounds like something from Back to the Future. And, if you give people the amount of hesperitin found in two cups of orange juice, blood flow goes up, though if you instead just give them the orange juice itself, that works even better. So, there’s other beneficial stuff besides just the hesperitin in citrus.

For example, if you measure the changes in genetic expression, orange juice consumption induces changes in the expression in 3,000 of our genes—whereas hesperitin alone only modulated the expression of about 2,000. Still, nearly 2,000 stretches of our DNA expressed differently because we consumed just one of the thousands of phytonutrients in plants—pretty mind-blowing.

And these changes in blood flow are not just kind of “in theory.” Researchers have taken volunteers with cold sensitivity—cold hands, cold feet—put them in an air-conditioned room, and measured the temperature of their fingertips after drinking a placebo drink—like orange Kool-Aid—versus drinks with two doses of actual citrus phytonutrients. In the Kool-Aid group, their fingers got colder and colder, dropping nearly 9 degrees Fahrenheit. But, the fingers of those consuming low or high doses of citrus didn’t as much. That’s because their blood flow remained steady. Here’s that laser test again.

When we’re exposed to cold temperatures, our body starts to clamp off peripheral blood flow to keep our core warm. But, if you eat a bunch of oranges before you go skiing, your risk of frostbite may go down, since you’re keeping up your blood flow to your fingers and toes.

They even took these poor women, and plunged their hands into some chilly water. And, as you can see, their finger temperature rebounded faster towards normal in the citrus group. Of course, having warm hands is nice, but maintaining blood flow to your fingers is not as important as maintaining blood flow to your brain.

Please consider volunteering to help out on the site.

Images thanks to PetitPlat – Stephanie Kilgast via flickr. Thanks to Ellen Reid and Shane Barrett for their Keynote help.

Doctor's Note

Because different families of fruits and vegetables can have entirely different phytonutrient profiles, variety is important. See, for example:

Eating oranges is always better than drinking juice. I discuss the difference further in Reducing Muscle Fatigue with Citrus.

Please make sure to rinse your mouth with water after consuming sour fruits to protect your tooth enamel (see Plant-Based Diets: Dental Health).

For additional context, check out my associated blog posts: How Citrus Might Help Keep your Hands Warm and Citrus to Reduce Muscle Fatigue.

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