Doctor's Note

I demonstrated the not-all-fruits-and-veggies-are-the-same motif recently in my video How to Reach the Antioxidant RDA.

I explored the fat-enhanced absorption of carotenoid phytonutrients in Forgo Fat-Free Dressings?

Don’t eggs also have zeaxanthin? Find out how much in Egg Industry Blind Spot.

I wish there were more studies on under-represented minorities. I’ve covered a few, such as Preventing Breast Cancer By Any Greens Necessary, but am constantly on the lookout for more.

The only other video I’ve done on glaucoma is Prevent Glaucoma and See 27 Miles Farther, though I have a video coming up soon on treating the disease, Dietary Treatment of Glaucoma. Next, however, is macular degeneration: Dietary Prevention of Age-Related Macular Degeneration.

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  • Suzanne

    Thanks so much for continuing to look at Glaucoma. I look forward to your upcoming video on treatment. I live in Japan and have access to kale in all forms, but I especially find individual dry packets both convenient and palatable. I use a frother to whisk it into 6-8 oz fresh water at least once daily. Both wheatgrass and kale are very popular health drinks here. I am being treated for Glaucoma by nightly drops and hope to hear how my plant-based diet might help me further.

    Two other items: I notice that I do not see that much about wheatgrass on your website and wonder if it is worth continuing to drink wheatgrass juice or to stick with Kale. Also, I use a mushroom extract (“soluable agaricus granul -contains beta glucan” ) obtained locally in individual powder envelopes that I periodically mix into my miso soup. I have not noticed much on this topic and wondered if you would comment on the utility of agaricus blazie mushroom granules as it is sold ‘for healthy living’ and is promoted for those with cancer due to increased NK activity. It is sold in 3 gram packets (60 per box). Another company has it at 1.5 gram packets (90) per box and I’ve used both and cannot tell the difference. After 6 years, I’m wondering if this has been a good investment now that I see you discussing NK activity recently on your website.

    • Adrien

      Dr Greger had replied on the topic of wheat grass you can find it in the section Ask the Doctor:

      • Eric

        I used to drink much green juice and my tumors kept going full speed ahead. Not until I added 2 wheat grass drinks per day did it shut down the tumors. I felt them stop in 2 short days

    • Darryl

      I’m a big fan of β-glucans, but believe you should be aware that there have been reports of A. blazei extracts causing liver failure (1, 2). It might be high levels of agaritine, or cadmium accumulation from growth medium, but the second report suggests that one can ingest enough β-glucans to stimulate autoimmune attack against healthy cells.

      Modus omnibus in rebus

      • Suzanne

        Thank you for your knowledge and citations on A. blazei and cancer patients with liver failure. I surmised potential autoimmune problems and, as I say, am a periodic user. I have good health and do not use alcohol but happen to have periodic liver panels (use prescribed niacin). My liver function tests are always good. Your citation led me to the local Japanese name of this mushroom, which seems to be ‘himematsutake.’ I hope to find the whole food, which I prefer. As this mushroom was cultivated in Brazil, I did not expect to find it here, although we have a vast array of varieties of mushrooms. As an American with limited kanji proficiency, a thoughtful daily life here entails considerable research. I appreciate your help and how your contributions on this web site are always well done.

      • DanielFaster

        Darryl, another great post, thanks! Do you have references for more mushroom nutrient levels like this? I have a field of shaggy manes that grow in my yard in the summer, can’t find anything on them.

  • Leslie

    How about Barley Grass powder? I hear great things about this stuff but I don’t seem to be able to find any peer-reviewed research as to its merits alone, or compared to other “greens”. Thanks for this topic. Glaucoma is serious issue for lots, and many seem to be depending on things like barley grass supplements and wheat grass, and this might not be a good idea if the research does not support it when compared to the greens you have highlighted today.

    • Adrien

      Look at the link above in my answer to Suzanne.

  • Chris

    Over that past six months (since discovering this site) I have begun a regimen that is heavy in spinach and other whole foods. I have blue eyes and since my mother struggled with her eyes, (macular degeneration), I am greatly concerned. Should I be watch the amount of iron rich, green leafies I eat? I already try to stay away from other sources iron.

    • Coacervate

      Hi Chris, nice going. To me, the message seems eat the whole food and avoid the super-concentrated, isolated extract/supplements. Play the symphony, not the solo : )

  • Darryl

    The chemical mechanism via which carotenoids protect against UV damage is cool.

    UV light can excite the electrons of ordinary oxygen molecules into a higher energy and highly reactive state, called singlet molecular oxygen. Our cells have few means of inactivating singlet oxygen before it does damage, but carotenoids like zeaxanthin can. See the long polyene chain of alterating single and double bonds in zeaxanthin:

    When singlet oxygen bumps into a carotenoid, it transfers its excited electronic energy to the polyene chain, where its passed back and forth along the narrowly spaced electron orbital energies of those double bonds, propelling the carotenoid a bit each time, until the excitement energy is dissippated as harmless heat. This process, called physical quenching, doesn’t consume the carotenoid as chemical quenching would. Its ready to physically quench another singlet oxygen immediately.

    Physical quenching by carotenoids is estimated to be 2000 times greater than their chemical quenching, but most antioxidant assays, including ORAC, don’t measure physical quenching of singlet oxygen. Hence ORAC markedly underestimates the in vivo antioxidant potential of high carotenoid foods, like kale, tomatoes, spinach, mustard greens, Swiss chard, collards and (then) carrots. Lycopene from tomatoes is the most potent physical quencher, and eating tomato paste prevents sunburn, but lutein & xeazanthin (high in kale, spinach, Swiss chard, mustard greens, radicchio & collards) are the only carotenoids found in the retina of the eye.

    • guest

      That truly is fascinating. I thought I knew a decent bit about nutritional chemistry, and even I had never heard of the level to which this effect (physical, non deconstructing, quenching) can achieve! There is so much wonderful science out that that if only every new paper could be put into action in terms of preparing some kind of monthly check list of the things we should eat and their amounts and preparation methods, that would be incredible. Alas, places like this are about the closest we will ever get to such a collection. This site is a god bless, but consolidating everything into a universal daily, weekly, monthly diet regimen that would be easy for even the layman to understand would be wonderful. Of course, everyone being different, ‘universal’ might be too word. Maybe just guidelines.
      Also, I wanted you to know that I appreciate the time you take in helping us poor souls out with the nuances of this field. I look forward to your tips each video almost as much as the video itself. I know often the science isn’t exact so its hard to steer people with 100% certainty toward the best option, but even taking that into account, you are saving lives by walking us through it.

    • DanielFaster

      Awesome post Darryl, thanks!

  • Mike Quinoa

    I alternate my breakfasts between steel-cut oats (with walnuts, blackberries and unsweetened soy milk) and quinoa (with blueberries, almonds, ground flax seed and unsweetened soy milk). Then, time permitting, I make a green smoothie consisting of kale and / or collard greens. I got someone at work drinking the kale concoction, and she loves the clean feeling it gives you.

    This is a little bit off-topic, but here is a very well put together website on some amazing vegan athletes. Be sure to vote for the Vegan Athlete of 2013 while you’re there:

  • guest

    I was hoping the good Doctor might be willing to write a column or produce a video on orthorexia nervosa, which appears to be a common phenomenon among users of nutritional websites. Many vegans have the best intentions but more than a few are just feeding orthorectic eating habits.

    • Veganrunner

      Was a medical term coined for the population that eats crap or only for the people who care enough about their health to be proactive?

      • Darryl

        May I suggest: pararexia nervosa

        As with orthorexia, it won’t find its way into the DSM, but its fun to diagnose strangers from our armchairs.

        • Veganrunner

          That will work. Some of that stuff definitely isn’t food.

  • Deepak L

    Dr, is it ok to have the kale and greens as green juices or does one need to have them cooked , to prevent glaucoma ?

    • Darryl

      It doesn’t seem to matter. In this study, the bioavailability of lutein from whole leaf, minced, and liquified spinach was about the same. There is evidence that adding oil (from avocados or avocado oil in this study) increases lutein bioavailability from salad 4.3-to-6.7 fold. I suspect the situation would be similar with juices.

  • Ronald Chavin

    Dr. Greger forgot to tell us why he used zeaxanthin in the description of this video. There are more than 100 beneficial phytochemicals in each of the plants that he mentions in this video.

    Green cruciferous vegetables (kale greens, collard greens, turnip greens, mustard greens, broccoli, watercress, Brussel’s sprouts, and cabbage) contain the carotenoids, lutein, neoxanthin, violaxanthin, beta-carotene, and only a moderate amount of zeaxanthin. Crucifers also contain various glucosinolates and myrosinase, which will convert into various isothiocyanates when chewed.

    Whole raw oranges, which did well in this study against glaucoma, are moderately rich in the carotenoids, beta-cryptoxanthin and beta-carotene, but they contain very little zeaxanthin. The only citrus fruits that are high in zeaxanthin are red grapefruits (but not white grapefruits).

    The fact that 100% fruit juices did poorly compared to whole raw fruits indicates fiber, not carotenoids or polyphenols, delivered the glaucoma-preventing benefits.

    The fact that canned and dried peaches did poorly compared to whole raw peaches indicates that the good bacteria that thrive on raw plants may have delivered the glaucoma-preventing benefits and not the fiber, which feeds the good bacteria, or the carotenoids and polyphenols. In any event, peaches aren’t that high in zeaxanthin.

    The fact that iron supplements caused severe eye damage is not surprising because, like copper, manganese, and aluminum, iron is a pro-oxidant which, if consumed in excess, will damage every cell in our bodies and increase our risk of developing numerous killer diseases.

    The fact that calcium supplements caused severe eye damage is a bit of a surprise. I’ve heard that calcium supplements can cause calcified arteries, cardiovascular problems, and various cancers but I was not aware that swallowing calcium supplements can increase our risk of developing glaucoma.

    • Ronald Chavin

      Correction: Red grapefruits are high in the carotenoid, lycopene, but contain zero zeaxanthin. Therefore, all citrus fruits are low in both lutein and zeaxanthin.

      Whole raw carrots performed moderately well against glaucoma in this study. Carrots are extremely rich in beta-carotene but not that high in lutein or zeaxanthin.

      • Violet

        Actually, the video says that cooked carrots are better for the eyes. Min 2:21 “Perhaps the African American subjects tended to eat the carrots raw limiting the absorption of certain nutrients…”

    • William Dwyer

      Too much calcium can be a risk factor for glaucoma just like too much iron, because calcium, like iron, is an oxidant. The studies show that 800 mg or more of SUPPLEMENTAL calcium increase one’s risk just as 18 mg or more of SUPPLEMENTAL iron do.

  • Mike Quinoa

    I alternate my breakfasts between steel-cut oats (with walnuts, blackberries and unsweetened soy milk) and quinoa (with blueberries, almonds, ground flax seed and unsweetened soy milk). Then, time permitting, I make a green smoothie consisting of kale and / or collard greens. I got someone at work drinking the kale concoction, and she loves the clean feeling it gives you.

    This is a little bit off-topic, but here is a very well put together website on some amazing vegan athletes. Be sure to vote for the Vegan Athlete of 2013 while you’re there:

  • FooBlahGrl

    I’m confused… the initial premise was that black women suffer *more* from glaucoma than white women. Then it proceeds with how black women eat tons more greens and have dark-pigment eyes, while white women eat no such greens and have pale eyes. So…. huh?

    • Thea

      FooBlahGrl: It’s a valid question. I haven’t looked at the studies, so I can’t answer with any authority. But here’s my guess: As a population, black people probably eat more kale and collards, but there would still be a lot of variability within the population. So, you could take that population and compare those who eat more to those who eat less. Where as, it is presumably hard to find a “eat more” group of significant size of the white women. What do you think?

    • Violet

      I was confused too about that and rewatched the video. The scientists wanted to see if kale and collards were protective but they couldn’t find enough white people eating them so they studied a group of African Americans. Amongst that group there were people who ate them and people who didn’t and the ones who ate them had far less incidence of glaucoma.

  • Scott Geiger

    Doctor Greger, there’s an article floating around on Facebook called “The Dark Side Of Kale (And How To Eat Around It)” that I found troubling. as a huge fan of Kale (I put lots of Kale in my breakfast smoothie each day), I am having trouble believing that this is a credible article.

    Can you please address this article?

    The article that I am referring to is here:

  • Jason Newstedt

    Hi Doctor,
    I suffer from a bad thyroid that eventually stabilized with levothyroxine treatment (129mcg/daily). I’ve heard so much about the health benefits of greens such as kale that I’ve included it in my juicing diet I’ve started recently.
    However, I’ve been hearing that cruciferous vegetable contain goitrogens which can cause more harm with those suffering from thyroid disorders. Could you consider a video or article regarding this issue and any possible alternatives for those who want to add greens to their diet with this problem?

  • Lee Vize

    I need referrals to sharp eye doctors. I will watch all videos that approach the puzzling topic of glaucoma that presents to people like me with IOP =10; the lowest number in the normal range. My VFL is 20% now. My cholesterol is quite high, overweight by 20 pounds; on a vegan diet for the last 4 months. I need real help, and advances to glaucoma research are paltry. Several catagories eye drops were of no benefit. The surgery suggested by my doctor is medieval, trabeculectomy, and only addresses IOP. My IOP can’t be any lower without destroying my vision now, versus waiting for blindness later. Thank you for reading about my problem.
    God bless you and your family. I wish you well.