Michael Greger MD

Michael Greger MD

Posted October 1, 2011

Published in Health

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Ask the Doctor: Q&A with Michael Greger, M.D. (Week 3)

Read More: apple juice, arsenic, breast cancer, cabbage, cancer, chicken, chili peppers, cruciferous, mammography, manure, mushrooms, penis size, phthalates, poultry, thermography

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First, please allow me to apologize to all those who have submitted questions that remain unanswered. In the first month, more than 1,300 comments/questions were posted to and I've been so busy posting a new video every day that I haven't been able to get to even half of them! Hopefully my upcoming Call for Dietitians will bring some much needed relief and we'll be able to clear through the backlog. Here is a sample of some I was able to get to this week:

Kristen asked on Dr. Oz, apple juice, and arsenic: chicken may have 10 times more : Does "organic" chicken fare any better?

Great question, Kristen! In a survey of arsenic levels in U.S. chicken, while nearly three-quarters of the breasts, thighs and livers from conventional producers carried detectable levels of arsenic, of certified organic or other "premium" chicken parts or whole chickens, just one-third had detectable arsenic. This suggests consumers who continue to eat chicken can lower their arsenic intake by choosing organic. Unfortunately, arsenic-laced chicken manure can still be used to grow organic produce. For more videos on chicken, see and for more on organic versus conventional in general, see

Damian commented on Cancer prevention and treatment may be the same thing : Thermography is the new early detection method. Check it out.

Unfortunately thermography alone may have a sensitivity of only about 83% in detecting breast cancer (according to the latest review). A combination of mammography and thermography may bring it as high as 95%, though, so while there may be a role for the technology, thermography alone is condemned as a substitute for mammography by the American Cancer Society and the Susan G. Komen for the Cure.

Mammograms and all other early detection methods are, by definition of course, too late in that they don't prevent cancer. And sadly, in many cases, may even be too late to significantly alter the course of the disease. Please see, for example, the latest open access review on the subject, The Benefits and Harms of Screening for Cancer with a Focus on Breast Screening." As you'll note even in just the abstract, regular breast self‐exams do not appear to reduce breast cancer mortality, the effects of physician breast examination are unknown, and it's not even clear that screening for breast cancer with mammography, thermography, ultrasound or magnetic resonance imaging does more good than harm on a population level because of the need to balance the cases in which there is benefit with the number of unnecessary biopsies and surgeries. I still encourage women to follow the guidelines of the USPSTF, but ideally the focus would be on primary prevention, meaning preventing the emergence of the tumor in the first place. Please see my blog post Breast Cancer and Diet for a review of my latest videos on the subject.

Raychel83 commented on Vegetables versus breast cancer : I really thought this was going to be cabbage before I saw the video. I have read that new research says cabbage can be good against certain cancers but I don't remember if breast cancer is one. Both of my grandmothers had breast cancer so I am VERY interested in breast health. Thank you for this information. I love mushrooms and my daughter and I will up our consumption. Is there a recommended weekly amount and any particular kind better than others?

I would have guessed broccoli myself! You're absolutely right about the cancer-fighting effects of the cruciferous (cabbage-family) vegetables. See my video The Healthiest Vegetables, and if you're interested in cabbage in particular, Superfood Bargains. Given your strong family history (sorry to hear about your grandmothers) please feel free to check out my 30 other videos on breast health. And in terms of which mushrooms are best, check out

maybush1 asked on Are Chili Peppers Good For You? : In some instances I've read about deleterious results (gastric and skin cancers) from capsaicin and hot peppers. See, for example this research:;

Dr. Greger, can you help in clearing up this confusion and debate?

The ScienceDaily piece you mentioned appears to deal just with rodents, so you may not want to share salsa with your pet mouse, but as a physician I have a bias towards human data. Veterinarians like to joke that us doctors are really just inadequate vets as we know only one species--I guess there's some truth to that! :) The Mexico study you mention did certainly give the medical community pause (when it was performed 20 years ago) but later studies (including data suggesting a cancer-fighting effect) led the most recent reviewers of the subject to conclude chili peppers are safe. A listing of 50 more Harmful, Harmless, or Helpful? videos here.

Bix asked on Eating chicken may lead to a smaller penis: Hi there Dr. Greger. I was wondering, in the Colacino study it says, "Vegetable consumption was also significantly associated with MEP levels, which was one of the strongest effects measured." I don't mean to detract from your message about poultry, which I think is an important one. I do wonder though about the presence of phthalate metabolites in vegetables, and how much of an impact they have. The study said they were lower molecular weight metabolites and are more water soluble. But I don't understand the implication of that. Can you shed some light? Thank you.

Thank you so much for actually taking the time to read the primary sources. Always linking to the primary sources is one of the many things I'm proud to say sets apart from other nutrition sites on the web.

As you noted, it you look at the breakdown (here's the direct link to the table) you can see that like other industrial pollutants (dioxins, PCBs, etc) there can be widespread contamination of the food supply. For example, this year there were studies published measuring phthalate concentrations in both wastewater and dust. The best consumers can do is try to minimize their exposure (see for example my Industrial Pollutants in Vegans and Flame Retardant Chemical Contamination videos). And so although there are fewer such toxins in the bloodstream, fatty tissues, and breast milk of, for example, vegetarians and vegans, it doesn't mean they're not exposed at all. There can be trace pesticide residues even on organic produce, for example; nevertheless, one can reduce one's risk by choosing organic. Similarly, if one wanted to stay away from the most concentrated sources of the riskiest phthalates one would be wise to stay away from the most contaminated foods, such as chicken.

The most concerning phthalates in terms of anti-androgen (countering male hormone) effects appear to be the DEHP metabolites (such as MECPP, MEHHP, MEHP, MEOHP) associated with poultry consumption. For example, maternal levels of DEHP metabolites were found to be most significantly associated with undermining free testosterone levels in the umbilical cord blood of their infants. The Swan, et al. study noted by the Science Daily article mentioned by Dan, "Prenatal Phthalate Exposure and Reduced Masculine Play in Boys," can be found here. Again, the DEHP metabolites I talked about in the chicken and eggs/penis size video were most significantly associated with a reduction of male-typical play in boys (for example, choosing to play with Barbie rather than with toy trucks).

And just as a sidenote, the study didn't measure levels in various foods; it went one step further and measured levels in the urine of people eating those foods. (Just because something is in a food doesn't mean it's absorbed, so that's one of the reasons this was such a great study-the fact that it found its way to the kidneys means it was necessarily absorbed into the human bloodstream.) And the most statistically significant association between food intake and the most concerning phthalate levels in the urine was with poultry (but as I noted in the video it's possible this could result from the chicken plastic wrap packaging or something, but that wouldn't explain the extraordinarily high level associated with eggs). The "p"-value <0.0001 means that the association between poultry consumption and mono-2-ethylhexyl phthalate was found to be so strong that there's less than a 1 in 10,000 chance that it could have happened just by coincidence.