Michael Greger MD

Michael Greger MD

Posted January 28, 2012

Published in Health

  • digg
  • Delicious
  • Furl
  • reddit
  • blinklist
  • Technorati
  • stumbleupon

Ask the Doctor: Q&A with Michael Greger, M.D. (#17)

Read More: amla, antioxidants, apples, apricots, asthma, blood pressure, cancer, cavities, cholesterol, cinnamon, diabetes, food synergy, gum disease, hibiscus tea, indian gooseberries, iron, oxalates, pepper, plaque, polyphenols, prunes, raisins, salt, sodium, spice, sulphur dioxide, turmeric, vitamin C

Get VegSource Alerts Get VegSource Alerts

First Name


Email This Story to a Friend

This is another sampling of the more than 800 comments and questions I’ve responded to on (so far!). Please feel free to leave any follow-up questions here or on any of the hundreds of videos on the more than a thousand topics covered on And remember, there’s a new video posted every weekday, so to make sure you don’t miss any:

OmarLittle asked on Ask the Doctor (#16)Do you have any advice on which plant foods or beverages can help prevent cavities and gum disease?

Normally we just hear about things to avoid to protect our teeth and gums (like candy, acidic juices, smoking, etc.) but what about things we should be eating? Last year an Italian review actually looked at the “anti-cariogenic” (cavity-fighting) properties of polyphenol phytonutrients (read full-text here). Polyphenols are found in all flowering plants and have been ascribed anti-inflammatory, anti-oxidant and anti-cancer properties. There are thought to be more than 8,000 types. In the plant kingdom they serve a defensive role, including fighting off bacterial infections. Since cavities are primarily caused by bacteria eating away our tooth surfaces, researchers started looking into the potential of polyphenols to protect against cavities. And indeed they found that this class of phytonutrients could directly inhibit the growth of plaque bacteria and their ability to attach to teeth, produce acid, and produce the sticky “biofilm” we call plaque. My only caution is to hold off brushing your teeth for a half hour after eating acidic foods like berries, citrus, and vinegars to cut down on dental erosion.

patmcneill asked on Better than green tea?  According to the USDA Database, an 8 fl oz (237g) serving of hibiscus tea has 20.48 mg of Iron, while the RDA for a male is 8 mg with an upper limit of 45 mg. Furthermore, apparently the Vitamin C in the drink itself or added to increase the antioxidant content tends to increase the absorption of Iron by the body. Will a few glasses of hibiscus tea a day be a few too many from the perspective of potentially developing an Iron Overdose, and especially in males?

I love the USDA Nutrient Database! (accessible here). That’s where the data for videos like The Best NutThe Best Bean, and The Best Apple came from. I can see how you could get confused, though. I know it says “fluid ounce” but they’re just multiplying their 100 g portion by 2.37. So what they’re referring to is 237 grams of the dried bulk petals (the ash and fiber content can tip you off). So even if you chew and swallow the hibiscus flowers after you drink your tea (or do what I do: blend them in with a high speed blender), it would take about 400 cups to reach that 20 mg, so no need to worry!

rosaleah asked on Dried apples versus cholesterolI eat dried fruits (prunes, raisins, apricots and now apples) daily. Please tell me your thoughts about what may be the cumulative effects on an aging body of sulphur dioxide preservatives used in processing fruits for drying.

35 years ago studies started implicating sulphur dioxide preservatives in the exacerbation of asthma. This so-called “sulfite-sensitivity” seems to affect only about 1 in 2000 people, but if you have asthma I would recommend avoiding it whenever possible. For more on preservatives, please check out my videos Is Sodium Benzoate Harmful?Is Potassium Sorbate Bad For You?Is Citric Acid Harmful?, and Diet & Hyperactivity. And for more on asthma, Preventing Childhood AllergiesPreventing Allergies in Adulthood, and Inflammatory Remarks About Arachidonic Acid.

Evan Brand asked on Antioxidants in a pinchDoes the anti-oxi value decrease with age of spice (or berry)? If so, how much? Second, how much is “toxic”? I heard taking more than 1-2 tbsns of cinnamon a day could be toxic. Is one hurting oneself if one takes 2 tbs of all the above mentioned spices a day?

Please see my video Oxalates in Cinnamon in terms of dosing. I have a video coming up comparing the safety of the four common types of cinnamon:

  • Cinnamomum verum (“True cinnamon,” Sri Lanka cinnamon or Ceylon cinnamon)
  • Cinnamomum burmannii (Korintje or Indonesian cinnamon)
  • Cinnamomum loureiroi (Saigon cinnamon or Vietnamese cinnamon)
  • Cinnamomum aromaticum (cassia or Chinese cinnamon)

I’ll go through how you can tell which is which to choose the safest, but just wanted to give you the heads up to make sure you’re using Ceylon (not cassia cinnamon).

soupy commented on Amla: Indian gooseberries vs. cancer, diabetes, and cholesterol:  I stirred 1 teaspoon of powdered amla into my daily glass of V8 juice, along with a sprinkle of black pepper and 1/2 teaspoon turmeric – tasted OK.

That’s an even better idea than you might know! I’m working on a new video on food synergy, documenting evidence that when certain foods are eaten together the sum of nutritive value may be greater than the parts. And there is indeed an amazing reaction that takes place between the phytonutrients in black pepper and turmeric. Eating black pepper at the same time as turmeric boosts the bioavailability of curcumin–the chief purported cancer fighter in turmeric–by (you sitting down?) 2000%! My only suggestion would be to choose the low-salt V8, as there is new evidence on just how bad sodium may be for the heart. See also my video Salt OK if Blood Pressure is OK?

-Michael Greger, M.D.