Michael Greger MD

Michael Greger MD

Posted April 5, 2012

Published in Health

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Ask the Doctor: Q&A with Michael Greger, M.D. (#21)

Read More: amalgam, beta-carotene, bitter melon, blood sugar, cancer, carcinogen, carotenoids, cholesterol, coconut water, diabetics, electrolyte, fenugreek, flax, hijiki, kelp, mercury, miso, omega-3, plant-based diet, sea vegetable, seaweed, sugar, tuna, vegan, yerba mate

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This is another sampling of the nearly 1,000 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:

veggiechick asked on Preventing Allergies in AdulthoodWhat would you recommend for nasal allergies? Hubby and I are both on a plant based diet and our allergies are better since going vegan, but it’s spring & it’s bad this year already lol.

Oh, I’m so sorry you’re suffering! There was a new study published last week on diet and allergic rhinoconjunctivitis (runny nose/itchy eyes) that confirmed that meat is associated with increased risk (in this case 71% higher), but that’s no help to a couple vegans! There are four plant foods, however, associated with cutting one’s risk in approximately half:
1. Seaweed. An ounce of sea vegetables appears to lower risk 49%–just make sure to avoid kelp and hijiki.
2. Dark green leafy vegetables. Greens of the land may protect as much as greens from the sea. A study found that those with the highest level of total carotenoids in their blood stream (alpha-carotene, beta-carotene, lutein/zeaxanthin, canthaxanthin and cryptoxanthin) had a significantly lower prevalence of seasonal allergies. See my video Egg Industry Blind Spot for a list of some of the best sources and Raw Food Nutrient Absorption and Forgo Fat Free Dressings? for the best ways to boost bioavailability.
3. Flax seeds. Similar to the carotenoid finding, those with higher levels of both long and short chain omega-3 fatty acids in their blood stream were found to have less allergic rhinitis in a cross-sectional study.
4. Miso. A teaspoon of miso a day was associated with about 41% lower prevalence. So try my favorite dressing on those greens: Blend until smooth in high-speed blender 3 T white miso. 1/4 cup brown rice wine vinegar, 1/4 cup water, 2 carrots, a small beet, an inch of fresh ginger root, and 1 T freshly toasted sesame seeds. Just watch your clothing as it comes out BRIGHT purple!

scorpiomoon asked on The Dangers of Broccoli?I have seen several health experts talk about the benefits of coconut water that comes straight from a young Thai coconut. However, I have read conflicting information about the coconut water one can get in packages (such as Vita CoCo).

Obviously packaged coconut water is pasteurized and not as good as fresh, so from that perspective it isn’t as beneficial. The thing I am wondering about is the sugar content. It’s my understanding that sugar is not added to coconut water, yet there is a high amount of sugar per serving. Is the sugar in coconut water bad for you? Is packaged coconut water something we should stay away from?

These days, coconut water is hugely popular. Is it just another form of unhealthy empty calories marketed as something healthy?

Vita Coco just settled a $10 million class action lawsuit for claiming its coconut water was “super-hydrating” “nutrient-packed” “mega-electrolyte” “super-water,” yet independent testing showed that the actual electrolyte levels were a small fraction of what the label advertised. Earlier this year a study in the Journal of the International Society of Sports Nutrition compared coconut water to a manufactured sports drink and found no difference between the two in terms of hydration or exercise performance, and in fact those drinking the coconut water reported feeling more bloated and experienced greater stomach upset–and the study was funded by the Vita Coco!

vetstud asked on Amalgam Fillings vs. Canned TunaHow did you come up with your calculation about how many mercury-containing dental fillings are equivalent to eating a can of tuna once a week?

Three national brands of canned tuna were recently tested for mercury. They averaged 600 ppb of mercury, exceeding the U.S. Environmental Protection Agency’s safety level for human consumption (500 ppb). The drained solids in a can of tuna weigh about 170 grams, so that comes out to be about 100 mcg of mercury per can of tuna. A conservative estimate of the amount of mercury we’re exposed to on a daily basis per amalgam-filled tooth is 0.5 mcg, so eating a single can of tunafish a week is like having 29 teeth filled with mercury-based fillings day in and day out.

Poxacuatl asked on Is Yerba Maté Tea Bad For You?Whoa! Really?! It seems there must be a lot of problems for the South Americans who consume loads of this daily? I haven’t read anything negative — any other info on how this is affecting people who have been drinking it for years?

The latest review suggests that the drying method (using firewood) may be to blame for the high levels of carcinogenic polycyclic aromatic hydrocarbons found in maté drinks, so a different production method may obviate this problem. That would be great since new evidence suggests that yerba maté may protect bone strength and improve blood sugar and cholesterol control in diabetics. I’ll let you know if I find more research in this evolving area.

Data asked on A Harmless Artificial SweetenerWhat is your take on the following substances? Gurmar…jamun… bitter melon…[and] fenugreek?   Lastly, Dr. Greger what do you think of Citruline and L Argenine in their role as helping out in repairing the endothelium cells ( Citruline ) and the later helping in promoting Nitrous Oxide formation if one used the drug versions instead of Citruline absorbed thru Watermelon rind where a large portion of citulline is usually discarded?

I’ve often wondered about bitter melon myself (Momordica charantia, also known as karela, or bitter gourd). I’m glad you brought it up to give me an excuse to look into it. I’ve seen it at the Indian spice stores I frequent (looks kind of like a ridged warty cucumber), but never tried it. I hear it lives up to its name, though. In fact the more ripe it gets, the more inedibly bitter it evidently becomes! But with enough heavy spicing I guess anything can be made palatable (the best way to mask the taste appears to be tomato-based sauces).

study published just a few days ago found that an extract of the fruit appeared to slow the growth of a rare cancer in a petri dish (adrenocortical carcinoma, an aggressive 1 in a million cancer of the adrenal gland), something that extracts of blueberries, zucchini, and acorn squash couldn’t do. Similar findings were reported in 2011 with prostate cancer cells and in 2010 with breast cancer cells. Traditionally, bitter melon has been used to lower blood sugars in diabetics, though most of the studies to support this use have been small and methodologically weak. There was a randomized controlled study published in 2007 that found no significant improvement in long-term blood sugar control in diabetics, but there have also been case reports of children having hypoglycemic seizures (and one even sinking into a coma) after drinking bitter melon tea, so presumably there is some blood-sugar-lowering effect there somewhere. If you are going to try it, I would recommend eating the fruit itself, not some extract. For example, there is a published report of a man who started throwing up blood after chugging two cups of bitter melon juice, which apparently ate through the wall of his stomach.

I'll have to look into gurmar and jamun; as for citrulline and watermelon, I cover that in my video Watermelon as Treatment for Erectile Dysfunction, which is chapter 33 of my Latest in Clinical Nutrition DVD, volume 8, and should air here at by the end of the month. I’ve also got upcoming videos on fenugreek, so I leave you in suspense (*spoiler alert*: fenugreek seeds appear to have both muscle-building and anti-cancer properties, but do have an unusual side effect: they may make your armpits smell like maple syrup!).

-Michael Greger, M.D.