Michael Greger MD

Michael Greger MD

Posted December 10, 2011

Published in Health

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Ask the Doctor: Q&A with Michael Greger, M.D. (Week 12)

Read More: acai, arsenic, erythritol, frozen fruit, rice, soy lecithin, Tuberculosis, vitamin D

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This is another sampling of the more than 700 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:

filippodibari asked on Evolutionary argument for optimal vitamin D levelYour attention to Vitamin D is very relevant these months, also to the huge discussion about the use of Vitamin D supplementation in Tuberculosis in developing countries.

Vitamin D is thought to be why the TB sanatoriums of old proved effective. They used so-called “heliotherapy,” which just meant exposing people to sunlight, 62 years before vitamin D was even discovered. Once vitamin D was identified and purified, it was used therapeutically both before and after antibiotics were introduced.

There is evidence that vitamin D supplementation may help prevent other respiratory diseases as well. For example, one study found that those randomized to 2000 IU of vitamin D a day (the amount I recommend) appeared to reduce their incidence of colds and the flu by 90%.

The official vitamin D recommendation recently tripled to 600 IU (see Vitamin D Recommendations Changed), though the Endocrine Society just released guidelines suggesting 1,500-2,000 IU a day is better. To offer some insight into the behind-the-scenes wrangling on this issue, I’m in the process of rolling out a 9-day series of videos on the topic that will finish up this coming week. I’m always conflicted about the level of depth I should go into on individual topics. I’d love everyone’s feedback on whether they prefer the one-off 2-minute highlight-type videos, or these longer series where I delve deeper into the backstory.

Don Brix asked on Pink juice with green foamI was unable to understand the name of the sweetener you suggested in the recipe for homemade cranberry juice in the video of 12/03. I’d be grateful if you could send along the spelling of the product.

“Erythritol,” a nearly noncaloric sugar alcohol found naturally in certain fruits. I have a video about it here: A Harmless Artificial Sweetener. My family goes through about a pound a month. A study published last month adds a cautionary note, though: consuming erythritol with a large load of fructose (as can be found in certain confectionery and soft drinks) could inhibit fructose absorption in the small intestine and result in bloating and discomfort from fructose fermentation in the colon. I don’t imagine people would typically be mixing their diet and regular soda together, but if they did, it could be a bad combo.

evanbrand asked on Pink juice with green foamAre there published studies providing evidence about the efficacy of frozen fruit (vs fresh)? What are viable sources of acai in the US? Sambozan adds soy lecitihin to their acai product.

I found two good studies comparing fresh to frozen fruit. One on strawberries and one on raspberries. They both found the same thing: “no statistically significant differences between the…[antioxidant levels] for fresh and frozen strawberries” and “It is concluded, therefore, that freshly picked, fresh commercial, and frozen raspberries all contain similar levels of phytochemicals and antioxidants per serving.” And in fact, frozen last longer than fresh, are available year-round, and tend to be cheaper and more convenient. If you look in my freezer, normally it’s half frozen greens and half frozen berries (though this time of the year it’s also stuffed with 20 pounds of fresh dates!).

In terms of your acai question, I’m not sure what your concern about soy lecithin is. Even people with soy allergies are often able to tolerate lecithin (soy proteins are more than 100 times less allergenic than other allergens such as eggs and dairy). I love the frozen packs of unsweetened acai pulp (featured in my videos Superfood Bargains and Antioxidant Content of 300 Foods), though if you’re extremely allergic to soy you may just have to stick to less exotic berries.

Rick asked on Arsenic in RiceI eat rice 2 or 3 times a week. When i go out to eat, I eat brown rice. When I make it at home, it is generally a wild rice blend. Does wild rice contain the same levels of arsenic?

Wild rice appears to have levels of arsenic comparable to regular rice, whether sourced from China, sold in the U.S., or specifically from Wisconsin. Chicken appears to be a more important source of arsenic in the American diet, though. See my video Arsenic in Chicken and blog Dr. Oz, Apple Juice, and Arsenic: Chicken May Have 10 Times More. Recently, Consumer Reports vindicated Dr. Oz’s concerns about the unregulated levels of this toxic element in juice.

-Michael Greger, M.D.