Michael Greger MD

Michael Greger MD

Posted January 7, 2012

Published in Health

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Ask the Doctor: Q&A with Michael Greger, M.D. (Week 15)

Read More: ALA, annato, artificial coloring, dyes, e. coli, flax, green tea, hibiscus, hormones, hydrogen peroxide, kidneys, lisinopril, pasteurized, prostate cancer, raw milk, saffron, skim milk, stroke, Tuberculosis, turmeric, whole milk, World Health Organization

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question2.jpgThis is another sampling of the more than 750 comments and questions I’ve responded to on the site (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:

organicsauce asked on Glycotoxins: I have a question regarding the use of hydrogen peroxide internally. I’m not finding much information on the subject and I have a family member who’s looking into it based on some (limited) online research. Thoughts and feedback would be appreciated.

Yikes! Hydrogen peroxide should never be taken internally. It can cause irritation of the gastrointestinal tract with nausea, vomiting, and foaming at the mouth (the foam may obstruct the respiratory tract or result in pulmonary aspiration). Within minutes of ingestion, confusion, coma, convulsions, cyanosis and cardiorespiratory arrest may ensue if the concentration is high enough. Oxygen gas embolism in the brain may cause a stroke even after just a few sips. Most problems occur at concentrations >10%, but even dilute solutions can be toxic. If your family member wants to oxygenate their blood they should try exercising!

bsmithson asked on Latest in Nutritional vol. 7 DVD now available (proceeds to charity): I’d like to know if annato is helpful, harmful, or neutral...In general, do you know of natural food dyes? I think you mentioned that in place of using the dye from the cochineal beetle that cherries could be used. I have used spinach and mint for green, and beets for red and raspberries for pink. I think annato is used for the yellow-orange color. I did ruin one dish going for red coloring where the beet flavoring was too strong. I’ll try shaving the vegetables after cooking and then dehydrating and grinding to reduce the flavor.

Annatto is a food dye derived from the seeds of the achiote tree. Although there have been case reports of severe allergic reactions and irritable bowel syndrome-type symptoms reported, there haven’t been any comprehensive studies done to date on humans. In fact data is so sparse that the World Health Organization just pulled their tentative Acceptable Daily Intake specifications. If I see anything new I’ll let you know. In the meanwhile, I find the WHO expert reports to be trustworthy when it comes to food additives, accessible at:

Bottom line, I’d try to stay away from artificial food colors (see my videos Artificial Coloring in Fish, Are Artificial Colors Harmful?, and Are Artificial Colors Bad for You?. And if you’re looking for a colorful health-promoting spice I’d suggest turmeric (see video here) or saffron (see Saffron for the treatment of Alzheimer’s and Saffron versus Aricept).

cbetter commented on Better than green tea? An FYI. My mother used to take Lasinopril (sp?) for high blood pressure. It gave her a terrible dry cough and she quit taking it. Then I read hibiscus tea was good for high blood pressure and bought her tea where hibiscus was the 2nd ingredient. Then one day I found one where it was all hibiscus tea and bought that. It made her dry cough come back (so the active ingredient in lasinopril must come from hibiscus). Anyway, if you develop an unknown cough, it could be from the hibiscus tea.

The mechanism of action for the blood pressure lowering effect of hibiscus tea does appear to be the same (at least in part) as that very drug. Both hibiscus and lisinopril act to inhibit an enzyme called ACE. When our kidneys detect a drop in blood pressure they release an enzyme called renin into our bloodstream which converts a protein secreted by our liver into something called angiotensin I which in our lungs is converted into angiotensin II by our angiotensin converting enzyme (ACE). That angiotensin II then acts to constrict our arteries and boost our blood pressure–isn’t our body neat? Anyway, lisinopril (and the anthocyanin phytonutrients that so brilliantly color hibiscus flowers) inhibits ACE, preventing the formation of angiotensin II and subsequent rise in blood pressure. But that’s not all ACE does; it also degrades bradykinins, which can increase cough reflex sensitivity. So that’s the reason ACE inhibiting drugs may cause coughing in up to a third of users and it makes sense that hibiscus could cause a similar reaction. So there’s definitely science to back up your intuition cbetter–thanks so much for sharing (and letting me geek out on physiology :). If you do develop a chronic cough on hibiscus, please stop drinking it.

WKing asked on Hormones in Skim vs. Whole MilkWhat about Raw Milk? I know the general arguments against milk as ‘Toxin’ cites above, personally I am a vegan, but what is the actual research on Raw milk vs pasteurized milk. I work in the area of local food and farmers markets and I am exposed to vegetarians and omnivores that are big boosters for raw milk. With so much propaganda and misinformation being flung from both the sides of the raw vs. pasteurized milk its hard to make sense of it all. What does the research say? I find it hard to believe that raw milk is the super food a lot of people claim it is.

There was a systematic review published in November that looked at some of the claims of raw milk advocates. The researchers basically concluded that the impact of pasteurization on the nutritive value of milk appears to be minimal. The greater issue is that of infectious disease (the reason it’s illegal in most states). Advocates argue that consuming raw milk is a matter of personal choice, but not when they go on to infect others. For example, in a raw milk outbreak of E.coli O157:H7 that hospitalized a number of children in Connecticut, in one household one kid who consumed raw milk infected a sibling who didn’t, who then infected a third. For those who are interested there are a number of recent commentaries on the dangers (here and here for example). Before pasteurization and the virtual elimination of bovine tuberculosis, hundreds of thousands of Americans died as a result of TB-infected milk. Let’s not go back to that era.

Pasteurized or not, organic or not, there continue to be public health concerns about the hormones present in all milk (particularly skim). See, for example, my videos Dairy Hormonal Interference and Acne & Cancer Connection.

DSikes asked on Just the Flax, Ma’am: There are a lot discussions and articles online about the supposed connection between flax seeds (ALA) and prostate cancer – suggesting that more flax consumed = increase chance of prostate cancer. I haven’t found this issue addressed on your website (sorry if I missed it). Can you comment? Thanks!

The latest meta-analysis of prospective studies found that, if anything, alpha-linolenic acid (ALA, the omega-3 fat in flax) was protective against prostate cancer. Men consuming more than 1.5 g/day appeared to have significantly lower risk (the amount found in about a tablespoon of ground flax seeds).

One of the reasons there’s been so much conflicting data is that ALA is found in great foods (dark green leafies) and less than great foods (meat), and so ALA intake is not necessarily a marker of healthy eating. What you want is a randomized controlled study of men with prostate cancer. Give half of them flax and see what happens. And that was done! (full text here)

Researchers at the University of Texas Anderson Cancer Center took a bunch of men with prostate cancer about a month before they were to go into surgery. Half were put on a few tablespoons of ground flax a day and after surgery their cancerous prostates were examined. The proliferation rates of the cancer in the flax-eaters were only half that of the controls, confirming the test-tube studies done on prostate cancer cells suggesting that flax can indeed slow prostate tumor growth.

-Michael Greger, M.D.