Ask the Doctor: Q&A with Michael Greger, M.D. (#16)

This is another sampling of the more than 800 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 NutritionFacts.org. And remember, there’s a new video posted every weekday, so to make sure you don’t miss any:

Judy0520 asked on Ask the Doctor (Week 15)A booth at our farmers’ market is selling moringa. It is a nutrient based plant, exceptional supplementation. It is touted to be “nature’s perfect food.”. Opinions please.

I had to look that one up! I assume they’re talking about Moringa oleifera. There are a few in vitro studies (meaning in a test tube or petri dish outside of the body) showing that leaf extracts may have antiproliferative effects on human cancer cells (as has been shown with cabbage and onion family vegetables–see my #1 anticancer vegetable video). And of course there’ve been nonhuman animal studies but I was unable to find any clinical studies (meaning done with actual people).

Based on nutrition analyses it appears to be quite nutritious, though: in comparison with other foods, various parts of Moringa oleifera have more iron than spinach (5.3-28.2 mg  vs 2.7 mg in spinach), more vitamin C than oranges (120-220 mg vs 69.7 mg per orange), and more potassium than bananas (1324 mg  vs 422 mg per banana). The calcium content in the leaves of Moringa oleifera is also really high but I don’t know about the oxalate content. Bottom line: if it’s comparable in price to other healthy vegetables like broccoli I’d give it a try unless you’re pregnant or trying to get pregnant, as it has been noted to have antifertility and abortifacient properties.

Ericjay asked on Ask the Doctor (Week 13)Hi doc. Any research studies on dairy consumption and ear infections in children. My friend’s child had numerous ear infections and I recommended soy milk instead of cows milk plus to eliminate cheese, ice cream, etc. She asked a chief pediatric ENT at a big hospital who of course said there is no connection. Of course, if there were he wouldn’t make as much money so I’m sure he wouldn’t push that subject to anybody. This child incidentally was on numerous rounds of antibiotics and may have tubes inserted in her ears. I thought she should give it a try. Thanks Eric.

The association between cow milk exposure and recurrent ear infections in susceptible children has been documented for 50 years. Though there are rare cases of pathogens in milk causing ear infections directly (then meningitis), the link is thought to be due to milk allergies. In fact there’s a respiratory disease called Heiner Syndrome, a lung disease of infants primarily caused by milk consumption that can cause ear infections. Though milk allergy most often results in respiratory, gastrointestinal, and skin symptoms, as many as 1 in 500 may suffer speech delay due to chronic inner ear inflammation. For 40 years there’s been a recommendation to try “a 3 month trial on a strict cow’s milk elimination diet” for children with recurrent ear infections, but Dr. Benjamin Spock, probably the most respected pediatrician of all time, ended up recommending a life-long elimination of cow’s milk. See my video: Doctors’ Nutritional Ignorance.

hcdr asked on American vegans placing babies at riskI feel our family has a healthy and complete diet (in no small part thanks to you!) but do you have any specific recommendations or guidelines for those who would like to follow a vegan diet through pregnancy, infancy and childhood? Is the most important thing (apart from healthy, whole foods) kid-friendly B12 and DHA, and probably D?

There are two great new resources for those who want to raise their families on plant-based diets: one by Reed Mengels and one by Jack Norris and Ginny Messina. Ask for them at your local library.

vjimener asked on Better than green tea?I have read in a magazine that there are several types of vitamin K. According to the article, Vitamin K1 is found in vegetables. Vitamin K2 mk7 is found in meat, fish and eggs. The article also said that Vitamin K1 is stored in the liver for only one hour, time not enough to perform all its tasks. On the contrary, vitamin k2 mk7 would stay in the liver for the whole day. So my question is: should vegetarians take supplements of vitamin k2 mk7 (created from natto)?

Not sure what magazine you were reading, but the scientific consensus is that either one (menaquinone or phylloquinone, formerly K1 and K2) is fine for maintaining human vitamin K status. The recommended intake is about 100 mcg. A half cup of kale? >500. No need for natto; just eat your greens. In fact dark green leafies are so packed with vitamin K that if you’re on the drug coumadin (warfarin), a drug that works by poisoning vitamin K metabolism, you have to closely work with your physician to titrate the dose to your greens intake so as to not undermine the drug’s effectiveness! Learn more about the wonders of greens in my 25 videos.

ksduck asked on Dried apples versus cholesterolThis is a bit unrelated, but I eat a plant-based diet. I’m also a 20-something year old woman of child bearing age who runs, so making sure I’m getting enough iron from plant sources is important to me. I’ve heard that tannins in coffee, tea, and chocolate can hinder the adsorption of iron when consumed together. Is there evidence to support this? Thank you!

Quoting from “Green tea does not inhibit iron absorption” published 2009 in the International Journal of Cardiology, “The only reference that I could find in the literature about a negative effect of tea drinking on iron absorption came from Tunisia. But the experiment was carried out on rats. Therefore, unless you are a rat and a rat in Tunisia, you should not worry about development of iron deficiency anemia from tea drinking.”

In 2008, though, a study in India found that drinking tea with meals could cut iron absorption in half. This is a function of publication delays. The cardiology journal piece was published in 2009 but was written in 2007, before the India study surfaced. The good news, though, is that the study found that vitamin C triples iron absorption, so as long as you’re drinking tea with lemon, or eating vitamin C rich foods at your meals (like citrus, broccoli, tropical fruits, bell peppers, etc.) then this shouldn’t be an issue. If, however, you don’t like lemon (and lemon in coffee? Yuck!) and aren’t eating these kinds of foods, then menstruating women may want to lay off tea and coffee (and cocoa and peppermint tea) during meals and up to an hour before to maximize iron absorption. In men (and nonmenstruating women), the reduction of iron absorption may not necessarily be a bad thing. In fact, the effect of coffee on iron absorption has been used to explain why coffee consumption has been found to be protective against diseases tied with iron overload such as diabetes and gout.

-Michael Greger, M.D.

  • OmarLittle

    Do you have any advice on which plant foods or beverages can help prevent cavities and gum disease?

    Thank you a lot for your time,
    – Carlo (following your blog from Italy each and every day!)

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    • Michael Greger M.D.

      Fantastico Carlo! Normally we just hear about things to avoid to protect our teeth and gums (like candy, acidic juices, smoking, etc.) but what about things we should be eating? Last year an Italian review actually looked at the “anti-cariogenic” (cavity-fighting) properties of polyphenol phytonutrients (read full-text here). Polyphenols are found in all flowering plants and have been ascribed anti-inflammatory, anti-oxidant and anti-cancer properties. There are thought to be more than 8,000 types. In the plant kingdom they serve a defensive role, including fighting off bacterial infections. Since cavities are primarily caused by bacteria eating away our tooth surfaces, researchers started looking into the potential of polyphenols to protect against cavities. And indeed they found that this class of phytonutrients could directly inhibit the growth of plaque bacteria and their ability to attach to teeth, produce acid, and produce the sticky “biofilm” we call plaque. My only caution is to hold off brushing your teeth for a half hour after eating acidic foods like berries, citrus, and vinegars to cut down on dental erosion.

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      • jim.artmeier

        How do I square this with JHT’s post below that states “Tannins and other anti-nutritional factors. Polyphenols, commonly known as tannins, occur widely in many different plants, especially those from tropical regions. Their consumption by animals has adverse effects on productivity and health. They are present in various agro-industrial by-products such as Acacia nilotica pods, Madhuca indica seed cake, Mangifera indica seed kernel, Panicum miliaceum polish, Garcinia indica cake and Theobroma cacao pods” My understanding is that all polyphenols are not alike. For instance the catechin and flavonol content of green tea and cocoa are responsible for significant health benefits. “Reduction in atherosclerotic plaques was seen in animal models.[6] Reduction in carcinogenesis was seen in vitro.[7]

        Many studies on health benefits have been linked to the catechin content. According to Norman Hollenberg, professor of medicine at Harvard Medical School, epicatechin can reduce the risk of four of the major health problems: stroke, heart failure, cancer and diabetes. He studied the Kuna people in Panama, who drink up to 40 cups of cocoa a week, and found that the prevalence of the “big four” is less than 10%. He believes that epicatechin should be considered essential to the diet and thus classed as a vitamin.[8][9][10]

        According to one researcher[11] epigallocatechin-3-gallate is an antioxidant that helps protect the skin from UV radiation-induced damage and tumor formation.
        [edit] DNA protection

        Catechins, when combined with habitual exercise, have been shown to delay some forms of aging. Mice fed catechins showed decreased levels of aging, lowering of oxidative stress in mitochondria, and an increase in mRNA transcription of mitochondrial-related proteins.[12]” To look up these references, please refer to http://en.wikipedia.org/wiki/Flavan-3-ol

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  • rosaleah

    I have a question rather than a reply. What may be the cumulative effect on an aging body from daily eating dried fruits processed with sulfur dioxide?

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  • David Schmidt

    Doctor, have you ever done any reviews on butter substitutes like Earth Balance, Country Crock etc.?
    PS I know we shouldn’t eat any of them, but wondering which is least bad for us.

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    • Toxins

      David, looking through the ingredients of these butters, I struggle to find anything healthy. I am reading a lot of oils (empty calories, fat without nutrition) , some soy protein isolates (which are harmful) and “natural flavors”. This is essentially a junk food product, it provides quite a bit of saturated fat and provides no nutritional benefit. I would avoid it like I would avoid butter.
      http://www.earthbalancenatural.com/eb_pdfs/products/original-nutrition-info.pdf

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      • David Schmidt

        Thank you so much for replying Doctor!

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        • Toxins

          Hello David, I am actually not a doctor, I just help Dr. Greger answer people’s questions!

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  • jaycee

    I am a vegetarian since last 11 yrs and vegan since last one year.I have a question.Actually it was from a meat eater friend who argues in favor of meat eating. the question is about “The Inuit Paradox” – High Protein & Fat,no Fruits/Vegetables and yet Lower Heart Disease and Cancer.Will you ask an inuit eskimo to eat vegetarian food?

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    • Toxins

      Jaycee, I believe that it has already been discovered that the genetics of the Inuit allow them to consume a high protein diet without developing atherosclerosis or other westernized diseases. They do have quite a high rate of osteoporosis and you should also note that they live 10 years less than the average Canadian (about 65). So although they survive on this high meat diet, it doesn’t mean we have the same genes as them, and if we did, we would still not survive as long as an average American with westernized diseases. Its a lose lose in my eyes. We should not idolize primitive people’s diet, they have no understanding of nutrition and eat purely for survival. just because that is how our “ancestors” MIGHT have been brought up doesn’t mean we can’t improve on it.

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  • LouiseF

    Any research on Raynaud’s Disease and a plant-based diet?
    I have been vegan for 10 months and have had no symptoms of Raynauds since then. Before, I was a vegetarian and had it.
    Is this just a coincidence?
    Thank you!
    Louise

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  • Toxins

    Dr. Greger, I have heard some talk about the dangers of fluoride. When I research this all I stumble upon are propagandists websites without scientific backing. Is there any truth to these claims that fluoride in our water supply and toothpaste is damaging our health?

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    • Michael Greger M.D.

      The proposed EPA changes to water fluoridation have sparked a resurgence of many of the old anti-fluoridation arguments, which as far as I can tell were successfully debunked over 50 years ago. According to the CDC, fluoridation of drinking water joins vaccination (another unjustly vilified practice) as one of the greatest public health achievements in the last last century.

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      • Toxins

        Thanks!

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  • rcaiken

    Could you please direct me to the literature that helps to explain why plants developed to serve the nutrient needs of the human being so well? As our appreciation of the value of the constituent contents of plants for human health ever increases, I wonder why it is so. It would seem plants would have been less foraged – and therefore less depleted – if they all were not even edible to animals much less so exquisitely valuable. Did we adapt and evolve to the chemistry of plants? Was there at some early point in evolution some synergism between plants and animals?

    Certainly I appreciate any reference or comment!

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  • jht

    Re Moringa Oxalates, is 4.1% significant? Are any of the other mentioned anti-nutritional factors a concern?

    The source for this number is: http://www.moringatree.co.za/reviews1.html

    Here is the relevant text:
    Tannins and other anti-nutritional factors. Polyphenols, commonly known as tannins, occur widely in many different plants, especially those from tropical regions. Their consumption by animals has adverse effects on productivity and health. They are present in various agro-industrial by-products such as Acacia nilotica pods, Madhuca indica seed cake, Mangifera indica seed kernel, Panicum miliaceum polish, Garcinia indica cake and Theobroma cacao pods (Makkar et al., 1990; Makkar and Becker, 1998). The unextracted leaves had negligible amounts of tannins (1.4 %) and condensed tannins were not detectable. The content of total phenols was 3.4 % (Table 14). A total phenol content of 2.7 % has been reported by Gupta et al. (1989) for the unextracted leaves. At this concentration, these simple phenols do not produce any adverse effects when eaten by animals. In the extracted leaves, no tannins were detected and the content of phenols was very low (1.6 %). The tannins are soluble in aqueous organic solvents such as ethanol, methanol, acetone etc. (Makkar and Singh, 1992) and therefore, tannins would also be present in the isolated hormonal preparation obtained through the process in which the leaves are treated with 80 % ethanol. The absence of an increase in gas production on addition of polyethylene glycol (a tannin bioassay based on incubation of a feed in a buffered medium containing rumen microbes; Makkar et al., 1995) also indicated absence of tannins in the extracted and unextracted leaves.

    Another group of anti-nutritional factors reported to occur in the unextracted Moringa leaves are the saccharides raffinose and stachyose which produce flatulence in monogastrics. According to Gupta et al., (1989) these compounds comprise 5.6 % of the dry matter in the unextracted leaves but occur in higher concentrations in legumes. They can however be removed to a large extent by soaking and cooking in water (Bianchi et al., 1983). These flatulence factors are determined after extraction in 80 % aqueous ethanol (Williams, 1984; Gupta et al., 1989), and would therefore be absent in extracted Moringa leaves. Other antinutritional factors present in unextracted Moringa leaves are nitrate (0.5 mmol/100 g), oxalate (4.1 %), saponin (1.2 %) and phytate (3.1 %). Trypsin inhibitor activity was not detected (Gupta et al., 1989). Phytates are present to the extent of 1 to 5 % in legumes and are known to decrease the bioavailability of minerals in monogastrics (Reddy et al., 1982). The leaves of Moringa are quite rich in minerals and the presence of oxalates and phytates at concentrations of 4.1 % and 3.1 % respectively is likely to decrease the minerals’ bioavailability. Saponins from some plants have an adverse effect on the growth of animals but those present in Moringa leaves appear to be innocuous (did not show haemolytic activity), and humans consume them without apparent harm. Cyanogenic glucoside and glucosinolates were not detected in leaves (Makkar and Becker, 1997). Most of the antinutritional factors mentioned above are soluble in aqueous ethanol and would most probably be absent in the extracted leaves.

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  • aguccione@sbcglobal.net

    Hi rcaiken:
    Here is the literature I subscribe to that supports why a plant-base diet works so well with the human body; it is called the Hebrew Literature:

    “God said: Behold, I have given to you all herbage yielding seed that is on the surface of the entire earth, and every tree that has seed-yielding fruit; it shall be yours for food.” Genesis 1:29

    Not only humans, but in Genesis 1:30 it records that even animals were given a vegan diet as well!

    So the Creator of the human body designed it to thrive on plants.
    Regards, ag

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    • Toxins

      Although interesting, I do not think we should be using religion as a source of evidence.

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  • rcaiken

    Hi Ag; your theory is the first one suggested – appreciated! In my mind knowing why plants just happen to provide not only sustenance but health, wellness and longevity through a great variety of protective molecular mechanisms is rather fundamental to advancing the movement away from eating animals and toward plants. The scientific literature is ever more convincing – though fragmented – but it would be helpful to have an integrative understanding.

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  • http://www.facebook.com/joiriwin Joanne Irwin

    Class participant heard that celery should be avoided for colon cancer patients. Only thing I’ve read about celery is to consume only ‘organic’ as conventional grown veggie is extremely high in pesticides. Do you know any other reason it should be avoided?
    Thanks.

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    • Michael Greger M.D.

      Celery avoidance makes no sense to me. In fact celery may have a “strong protective effect against colorectal cancer.” And in terms of for people already fighting the disease, a study was just published a few weeks ago elucidating the mechanism by which one of the key phytonutrients in celery (luteolin) arrests the growth of human colon cancer cells in vitro. For a comparison of the anti-cancer activity of a variety of vegetables, see my videos Veggies vs. Cancer and the follow-up, #1 Anticancer Vegetable.

      For some reason the subject of nutrition appears especially wrought with myths, exaggerations, and baseless opinions. That’s in fact one of the reasons NutritionFacts.org was started. When it comes to what we put in our bodies, critical thinking is, well, critical. Any time anyone hears anything like that I would encourage you to ask what their source was for their information. If there really is science backing up their assertions I’d be happy to review it and offer my thoughts.

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  • Elvin

    Dr Greger:

    Am I misreading this sentence: ‘My only caution is to hold off brushing your teeth for a half hour after eating acidic foods like berries, citrus, and vinegars to cut down on dental erosion.’? It seems to say to wait a half hour before brushing your teeth after consuming … vinegar! If so, I have never heard anything more counter-intuitive. This would seem to say that the polyphenols in (say, even) rice vinegar outway the harm of acidic substances in contact with the teeth for 30 minutes. Well?

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    • Michael Greger M.D.

      Rinsing your mouth out with water after consuming acidic foods is a good idea, but brushing when your enamel is in a softened state can exacerbate erosion. If you google terms like acidic brushing enamel erosion, etc. you’ll see that it is the position of the mainstream dental establishment.

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  • Susan Dykhuis

    what foods other than animal cadavers provide vitamin B12 ?

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  • Susan Dykhuis

    Many people tell me that vegan diets cannot provide B12 or Calcium.  Is that true?  Please tell me what foods other than “meat” “poultry” “fish” provide sufficient sources of B12 and Calcium.  Thanks in advance.

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