Michael Greger MD

Michael Greger MD

Posted September 18, 2011

Published in Health

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Ask the Doctor: Q&A with Michael Greger, M.D. (Week 2)

Read More: chocolate, cocoa, flax, omega 3, omega 3 supplement, omega 6, omega 9, vitamin B12, vitamin D, walnuts

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This is just a sampling of the 514 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 make sure you don’t miss any!

Yummy asked on Healthy Chocolate Milkshakes: In a previous video, it was stated that “regular” cocoa powder was healthier than the processed “dutched” cocoa powder, but this recipe states dutched. I prefer the unprocessed which I believe to be healthier.

You are absolutely right that alkali-processed “dutched” cocoa is not as healthy (See Update on Chocolate for the graph and Healthiest Chocolate Fix for some other chocolate comparisons). Dutched cocoa can have as few as half the phytonutrients, but that just means you have to use 50% more! Making things even more chocolatey has never been a problem for me, and I just like the taste so much better that my household uses Dutch, but if the taste of regular cocoa works for you, then go for it–you’re getting even more benefit per spoonful!

Jill asked on Optimum Nutrition Recommendations: If [someone] who is light skinned is out for more than 15-30 minutes in sunlight, can the Vitamin D be cumulative? And I have heard different ideas on the use of sun screen and vitamin D absorption, or is there a different post on sun screen and vitamin D?

Sunlight-induced Vitamin D is indeed cumulative but the same wavelengths that produce D in our skin can also cause us to burn. Sunblock can delay sunburns, but also interferes with the vitamin D production. So the recommendations [in the post] are for those not wearing sunblock.

Eric asked on Avoiding cholesterol is a no brainer: What would you suggest as an ideal omega 3,6,9?

I try to think in terms of whole food sources rather than nutrients (have you read The China Study? It has a whole chapter trying to make that point). I’d be happy to talk with you about ratios and percentages, but in terms of practical advice I’d encourage people to minimize their intake of the omega-6 rich oils (such as safflower, sunflower, and cottonseed, and all of the processed garbage manufacturers make with them), and try to eat healthy omega-3 rich whole foods such as walnuts and flax seeds every day. And especially for men as well as women who are expecting, breastfeeding, or even thinking about getting pregnant I would encourage consideration of taking an algae- or yeast-derived long-chain omega-3 supplement

Peter asked on Vegan B12 deficiency: putting it into perspective: I have just posted some of your recent B12 videos on facebook to try and help my friends who refuse to accept the need to have an intake of B12 on a vegan diet. Most are convinced their ‘friends’ have been told by the doctors they have ‘abnormally high levels’ of B12 and have to avoid Soya milk etc. Can you advise on this? I have read there is no upper recommended limit on B12 set, and surely consuming fortified soy products wont take you to dangerous levels? I have never heard of this before. Can you advise if there are any known risks of excess consumption?

You cannot take too much B12 orally–your body will just pee out the excess. High serum “B12″ levels (a lousy test) may be reflective of high levels of inactive B12 analogs (if, for example, they were eating sea vegetables). These B12 “look-alikes” are considered worse than useless and so they may in fact be at particular risk and I would urge them to start consuming B12-fortified foods or supplements with actual B12 in them.

-Michael Greger, M.D.