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How Citrus Might Help Keep Your Hands Warm

May 1, 2014 by Michael Greger M.D. in News with 11 Comments

How Citrus Might Help Keep Your Hands Warm

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 quercitin, are widespread in plant-based foods. We can tell something is widespread in the plant kingdom when one can even find it in iceberg lettuce!

Others, however, are only found in specific plant families. For example, hesperidin 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 cut our risk of stroke the most.

The citrus phytonutrient hesperidin increases blood flow. Using a machine called a Doppler fluximeter (sounds like something from Back to the Future) one can measure blood flow through the skin using a laser beam. When researchers give people the amount of hesperidin found in two cups of orange juice, blood flow goes up. It works even better when they gave them the orange juice itself, so there’s other beneficial stuff besides just the hesperidin in citrus.

For example, if we measure the changes in genetic expression, orange juice consumption induces changes in the expression of 3000 of our genes, whereas hesperidin alone only modulated the expression of about 2000. Still, the fact that nearly 2000 stretches of our DNA expressed differently because we consumed just one of the thousands of phytonutrients in plants is pretty mind-blowing.

These changes in blood flow are not just in theory. Researchers took volunteers with cold sensitivity (cold hands and 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 nine degrees Fahrenheit. The fingers of those consuming low or high doses of citrus didn’t get nearly as cold because their blood flow remained steady. In my video, Keeping Your Hands Warm with Citrus, we can see the laser test of the subject’s blood flow. When we’re exposed to cold temperatures our body starts to clamp off peripheral blood flow to keep our core warm, but if we eat a bunch of oranges before we go skiing our risk of frostbite may go down since we’re keeping up our blood flow to our fingers and toes.

They even took these poor women and plunged their hands into some chilly water, and their finger temperature rebounded faster towards normal in the citrus group, demonstrating that citrus phytonutrients not only keep our extremities warmer but may also warm us back up faster.

But don’t forget, don’t brush your teeth immediately after consuming citrus. We have to make sure to rinse our mouth with water and wait 30 minutes before brushing to protect our tooth enamel (see Plant-Based Diets: Dental Health).

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 orange juice, as seen in my video Reducing Muscle Fatigue with Citrus.

-Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my videos for free by clicking here and watch my full 2012 – 2014 presentations Uprooting the Leading Causes of Death, More than an Apple a Day, and From Table to Able.

Image credit: macjryan / Flickr

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Dr. Michael Greger

About Michael Greger M.D.

Michael Greger, M.D., is a physician, author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial. Currently Dr. Greger proudly serves as the Director of Public Health and Animal Agriculture at the Humane Society of the United States.

View all videos by Michael Greger M.D.

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  • DGH

    I remember the study by Dean Ornish where putting patients on a plant-based diet (men with early laboratory indications of prostate cancer) actually modulated hundreds of genes (and prolonged telomeres). This reminds me of that. Impressive! Please keep up the good work!

  • guest

    Do the reported antibiotic properties of lemon kill any of the good bacteria inside of us? What is the longterm effect of lemon-juice ingestion and our beneficial microbiome? I ask this because I use two whole lemons everyday, and am wondering what beneficial bacteria that has maybe suppressed in my mouth, and all the way down and through my entire GI tract and body. I hear so much that lemons are a good antibiotic, but does the consistent use of citrus somehow compromise the POTENTIAL AND VIABILITY of our microbiome?
    This possibility is one of the reason that some people avoid honey, because of the thinking that it will eventually kill and or weaken the good bacteria as well. Any research studies you’ve come across show that lemon, limes, and other very sour citrus fruits won’t do this?

  • jennym

    Love citrus and citrus juices…but now that I’m over 60 I find them very irritating to the urinary tract. Dr. has told me not to drink oj, etc. How can I reduce the irritation to allow me to benefit from citrus?

    • guest

      In what way are they irritating? Do you pee more or less when including citrus?

  • brec

    “…two cups of orange juice, blood flow goes up. It works even better when they gave them the orange juice itself.”

    orange juice itself -> orange itself ?

    EDIT: As solo points out below, the preceding words that I elided supply crucial context.

    • guest

      confused as well.

    • solo

      No, it said “…the amount of hesperidin found in two cups of orange juice…”

  • Mark Emde

    When I eat citrus (antioxidant) foods my body temperature goes down, and if I eat a lot I will feel cold and my hands may turn white.

  • Corrie Campbell

    I think there may be an error in this sentence, it doesn’t make sense. “When researchers give people the amount of hesperidin found in two cups of orange juice, blood flow goes up. It works even better when they gave them the orange juice itself…” Was is supposed to be when given “the orange itself”???

    • Kate McConaughy

      He has it right

  • Kate McConaughy

    Citrus is in season during winter and melons, which are cooling, in summer. Eating in season seems like a good way to go.

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