Doctor's Note

Which fruits and vegetables may be best? See Best Berries, and Biggest Nutrition Bang for Your Buck. Other videos on immune function include Kale and the Immune System, and Preventing Childhood Allergies. Also check out Preventing COPD With Diet, and Treating COPD With Diet, on preserving respiratory function.

And be sure to check out my blog posts for additional context: Mushrooms and Immunity, and Probiotics During Cold Season?

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  • Michael Greger M.D.

    Which fruits and vegetables may be best? See Best Berries and Biggest Nutrition Bang for Your Buck. Other videos on immune function include Kale and the Immune System and Preventing Childhood Allergies. Also check out Preventing COPD With Diet and Treating COPD With Diet on preserving respiratory function, as well as the gazillion (ok, more like a thousand) other topics I cover.

    • HemoDynamic, M.D.

      I just wanted to add a caveat.  I would caution persons who have autoimmune disorders such as Rheumatoid Arthritis, Lupus, IBS, Crohns Disease, Psoriasis, etc. to not try and boost their immune system unless they are completely plant based.
      Autoimmune diseases are when the bodies own immune system becomes confused and starts to attack itself (Molecular Mimicry) because it has been HYPER-stimulated by ingesting TOO MANY foreign substances (Usually foreign proteins) that look convincingly like our own tissues. 
      So boosting ones own immune system when it is already “boosted” tends to exacerbate the autoimmune disorder in patients not completely plant based. 

      This has been my experience in my autoimmune diseased patients; however, when they adopt a plant based lifestyle, they stop the assault on their bodies and immune systems and their immune systems eventually calm down ceasing their attack on themsleves.

      I have multiple patients with Lupus, RA, Crohns, Ulcerative Colitis, Psoriasis that have had complete resolution of their symptoms and some who don’t even test positive anymore for their autoantibodies, after they adopt a plant based diet.  It may take awhile but it works!!  Plants heal!

      So go ahead and Boost your Immune system once you have adopted a plant based lifestyle.

      I would encourage any feedback about anyone elses experiences in this department.

      Love thy plants!

      • Thea

         Dr HemoDynamic:  Wow, that is incredibly interesting.  It makes perfect sense, but you never know how valid an idea is until it is tested in the real world.  It is so interesting that you have seen this phenomenon in real people.  Thanks for sharing.

        • HemoDynamic, M.D.

          You might find this Vid from Dr. Greger interesting if you haven’t already seen it:

          • Thea

             Thanks.  I’ve seen them all, but I don’t have all that information at the front of my head.  That video you linked to is one of the great ones.

            What was extra interesting about your post was the point about boosting immune system may actually be bad for someone who isn’t all plant-based.  So fascinating.

          • HemoDynamic, M.D.

            I wish I had the time and money to commission a large study but for one I live in a very small community and it would be hard for me to recruit a lot of people.  But I will keep compiling a patient database like Dr. McDougall, Dr. Ornish, Dr. Barnard, (Dr. Greger?) does and hopefully one day be able to share those results.

            It is interesting for sure!

      • Ghazeltine

        Yup. Worked for me. I have a very rare autoimmune disease called acquired atricia. I completely changed my diet 4 years ago eliminating gluten, and dairy and eating a plant based, all organic diet. The inflammation in my ears is gone and my hearing is perfect.

        Food heals.

        • HemoDynamic, M.D.

          Excellent!!  Thanks for sharing.  I feel it’s important for people to share their plant based triumphs to motivate the many people who peruse this site but do not comment.

          Keep those positive comments coming!

        •  Great to hear!

      • Ghul

        after reading China Study i switched to plant based. i ve been vegan now for almost 5 years. Still got psoriasis though… was wondering if you got any tips to what might help it?

        • HemoDynamic, M.D.

          I wish I had the answer for you.  Sometimes there are just stubborn cases and genetic predispositions that defy even Plants.
          I would hope you have a local Doc that understands autoimmune abnormalities and understands and supports Plant based nutrition as a therapy but that could look deeper into the history of your disease. 

          Did your Psoriasis get better at all?

          Making sure you get plenty of direct sunlight can help but I’m sure you are already doing that.

          Not sure I was much help but thanks for posting.

          • Ghul

            thx for you reply HemoDynamic, M.D.!
            initially it got better so i think plants did indeed help but since last year it is slowing expanding and appearing at places where it hasnt been before nothing critical just gets me worried. i am waiting for a book form Dr. John O.A. Pagano and hoping to get some more insights from there.

          • HemoDynamic, M.D.

            Pagano is a leader in the field and it is clear that what he has learned is that a plant based diet is highly effective at diminishing the disease, but some cases are clearly resistant.
            We clearly need to learn more about this disease, but in the mean time keep Plant-Strong!!
            I myself will try to learn more about this disease and relay any insight I learn.  Thanks for your post!

          •  If you consume any dairy, that may be the culprit! Try eliminating it and see, if you do.

        • Heidi

          I used to have psoriasis but it went away once I went vegan, and also switched to vegan natural based soaps and shampoos.
          When for the first year or two I was eating plant based but still using Pantene shampoo I still had psorasis on my scalp.

          • HemoDynamic, M.D.

            Thanks for posting!  I’m glad you found solace in plants.  ;-}

      • Veguyan

        Dr. Hemo: Is Hep. C considered an auto-immune situation? If so, would taking supplemental Vitamin D be a good idea?

        • HemoDynamic, M.D.

          Hep C is a viral infection and unfortunately one that tends to stay with people forever, and it is not classified as an autoimmune disorder.  The only known effective treatment is Interferon and Ribavirin but compliance is low with only about 25% completing the therapy secondary to severe adverse side effects.   And then only about 50% (variable) tent to have successful treatment.
          This is out of my area of expertise and a Gastroenterologist is well equiped to discuss the different treatment options. 
          However, adopting a Vegan lifestyle that is full of variety cannot hurt.  I have 5 chronic Hep C patients that have all improved their quality of life on a Vegan diet but I haven’t seen the viral loads decrease when they were measured.  Also, unfortunately, no supplements (eg Milk Thistle, N Acetyl Cysteine, Co Q10) have been shown to have much positive effect.

          Low vitamin D has been shown to increase the fibrosis associated with chronic Hep C.  So make sure you have adequate blood levels.  Below is a good article about Hep C treatment.

          I hope this helps.

          • Veguyan

            That is informative about the low Vit. D levels and increased fibrosis. I was only curious because it seemed to me that if the liver damage in those with Hep C was caused not so much by the virus as the immune system attacking the virus and hitting the liver, then increasing the immune function would be antithetical.

          • elsie blanche

            Hemo D, is there something to be said for abstaining from vitamin D by those with autoimmune diseases, as the vitamin D may “boost” the immune system, possibly triggering other autoimmune diseases? Also, as far as plants go, I have often heard that it is advisable for those with autoimmune diseases to avoid any herbs that stimulate and/or heighten the immune system, as it can adversely effect an already overactive immune system, I’ve heard the same logic is why one should abstain from chlorella and spirulina as well, if they have an autoimmune disease.

          • HemoDynamic, M.D.

            You are correct to stay away from Immune boosting foods if you continue to eat meat, dairy, eggs or any animal products. These foods cause inflammation stimulating your body to try and “heal the problem” but the problem is what you are placing in your mouth. So you end up with a confused immune system trying to figure out what is causing the inflammation, so it starts to attack parts of your body that it thinks are the inflammatory culprits which causes more pain and inflammation, and potentially a full blown autoimmune disorder.

            The animal products are the causes of 99% of the autoimmune disorders I have seen. So get them out ASAP. I have many patients who have had complete remission of their autoimmune diseases (Crohns, Ulcerative Colitis, Lupus, Rheumatoid Arthritis, Osteoarthritis, Thyroiditis, and others) by adopting a plant-strong lifestyle. Nearly all of the patients/people don’t have a problem with a boosted immunity unless they are eating meat and dairy. Then it is OVER-boosted so to speak. Your body will not attack itself unless it is given a stimulus to do so.

            Regarding Vitamin (Hormone) D, get 20 minutes of sun daily (best source by far). Not only is it vital in many body processes it has recently been discovered to dilate your arteries in your body reducing stroke and heart attacks. However, I haven’t personally seen anyone have problems with supplemented (orally taken) Vit D.

            Regarding plant foods and inflammation patients with autoimmune disorders sometimes do have flair ups with concentrated soy products like Faux Meats (Meatless ground) and soy sauce (Yes even Braggs brand). So eat the whole soybean or tofu, not concentrated soy protein isolates or derivatives there of.

            Also thanks to Dr. Greger I was educated on some plant foods having inflammatory properties like white potatoes where as Purple Potatoes are anti-inflammatory (use NF.orgs search engine to find that study).

          • elsie blanche

            Thanks so much for the reply.

          • elsie blanche

            Hemo D, do you have any experience with chlorella, and have you observed any positive and or negative results? Do you have any concerns with chlorella in regards to it affecting the immune system in adverse ways, or is it just positive? I hear and read conflicting opinions.

        • Not directly related to your topic, but I was indoors a lot and my legs felt tired when I exercised. I really thought it was because I wasn’t getting enough sun (as I suspected from watching Dr. Greger videos and the like). So I took a blood test, found out I had low D levels as I suspected. I then took high doses of D2 (vegan) that the doctor prescribed. My levels went almost back to normal, but my energy also went up.

          Now I supplement D2 on my own and I now my legs are much more energetic and I don’t even feel lactic acid until I push my body too hard, when I power up the hills on a run, usually way ahead of the training pack, or swing a kettlebell.

          Just my own anecdote I know, but conclusion: Along with a plant-based diet, vitamin D supplement really boosted my athletic performance.

      • HemoDynamic, M.D.

        In replying to myself, and importantly so, I just got emailed John McDougall, M.D.’s newsletter. 

        This is such an important editorial that compares and contrasts Plant vs Animal based diets like the Paleo, Atkins etc. 

        It is fully referenced with links and is a MUST READ for anyone who is consuming food ;-}

        Thanks to Dr. McDougall and Dr. Greger, and the many others fantastic researchers and physicians, for their tireless effort in getting the word out to the world: 

         EAT PLANTS!

        • Veguyan

          I’ve been vegan for 40 years and I appreciate the support from Dr. Greger and Dr. McDougall and yourself, but I still don’t know what to say to people who speak from their experience and say that they’ve been vegan for nine or sixteen years or whatever and “it almost killed me” until they went back to eating animals. Do you have a response to this phenomena?

          • HemoDynamic, M.D.

            Do you have to respond to them?  It’s probably they didn’t have enough variety or that it is just an excuse for them to eat meat.  Either way, unless you have to respond, then don’t respond.

            You can say well it works for me and leave it at that.  People can only change themselves, I (you) can’t change anybody.

            And as I have repeated before the Old Buddhist proverb, “When the student is ready the teacher will appear.”

          • Brigitte

            Hi HD, M.D.!
            To answer or not to answer, that is the question!
            The book from Carol J Adams, “Living among Meat Eaters” is very useful for understanding defensiveness, and helping relationships.

          • HemoDynamic, M.D.

            Funny, I haven’t seen any articles in the local paper or any scientific research showing that Veganism killed people, but I have seen multiple articles showing how eating animals and their product did.

            There are deficiencies such as B12 and Vitamin D that are real but have to be tested for.

            Anyway, I hope these answers help.

          • They’re the minority. Think of all the people who eat meat and it was killing them until they turned plant-based.

            I don’t know what those former vegans were eating, but if we could get them in a controlled setting and fed them plant-based whole foods for a good period of time, we can really see if the diet is failing them or they’re failing the diet.

            Anecdotes: I know two former vegans and they’re both overweight. No one really explains to me what’s in the meat that “saved” their lives. They just blame the plant eating for making them unhealthy.

          • Brigitte

            Maybe it’s because of a non-balanced diet? Were they eating junk vegan food? or not well supplemented in vitamin B12, and vitamin D?
            Are they healthy now?

      • Anupama Swamy

        Do you have any specific recommendation for lupus?

  • Paulc

    What is it about fruits and vegetables that enhances the immune system. I suppose that the first thing that comes to mind as a suspected cause is  phytochemicals or antioxidants. However, I’ve also read that fiber boosts the immunity. It would be interesting to know what the actual active agents in plant foods are.

  • I wish more elderly thought like this:”It’s never too late to eat healthier”; instead of, “It’s too late now,” or “I’m old, I’ve ‘earned’ the right to do (eat) what I want!”
    It seems so many are hard-pressed to change. Telling them anything is tantamount to relegating them to children, and they just resent it.

    Cheers to those who do change, though :^)

    • Troy

      My 97 y.o. grandma is adamant to do away with herself – falling out of bed, tripping down stairs – I will tell her to ditch the apples and oranges instead :)

      •  Ditch the apples and oranges????! Nooooo! How ’bout MORE apples and oranges? Oh, and LOTS of leafy greens! ;^)

  • Thea

    I’m SO PROUD of my parents, 65 and 70, who have made an effort to start eating more healthy.  They are mostly (not all, sigh) eating whole-plant foods vegan for the first time ever. 

    It has made a huge difference in the life of my 70 year old father.  He was told that he could cut back on heart medication after only 3 months worth of more-healthy eating.  And then he was told that instead of needing to check in with the doctor every 3 months like he had been doing, he could now come back in 6 months.  I can’t wait to see what good things continue to happen if he keeps with it.

    One of the reasons they have decided to make this change is the information from Dr. Greger’s videos.  Go Dr. Greger!!!!

    • Stone Benjamin

      That is tremendous to hear, good for you, and them!

  • I have the worst sleep out of everyone I know, so I better be a good boy and eat my greens.

  • Ilana

    Hi Dr Greger, could you post what you know regarding vaccines in general? TThe amount of toxins like formaldehyde and aluminum? The risks/benefits and why it’s worth it to still get vaccinated? And are they all really necessary? Thanks!

  • Nat

    I would really love some advice. I have decided not to vaccinate my daughter. she is a very healthy 11 month old. We live in Israel. I am planning to travel to India and Guatemala. Am i supposed to reconsider my decision and vaccinate her? I am so confused.

  • Melani

    The above comment is on the inadequate intake of fruit and vegetables. In my experience: I ate huge amount of vegetables and fruit, while also consumed plenty of animal protein. Still my immune system was weak and got infected by TBC. I am 55. When I switched to a vegan diet, I experience less flu and other


  • Roy

    One question: If you are eating a plant based diet, do you still have to be worried about taking vaccination?

    • JacquieRN

      Are you referring to the pneumonia and influenza vaccines Dr. Greger referred here?

      • Roy

        Well sure, more explanation on that would be helpful. But I meant in general overall.

        • JacquieRN

          HI Roy, Pneumonia and influenza can be deadly for many people so please take the appropriate vaccinations. The study cited here shows that diet affected the body’s response to make more antibodies and thus provide a better level of protection. Some vaccines as you know are recommended at different ages and for different populations.

          For instance, the Pneumococcal Polysaccharide Vaccine (PPSV) mentioned in the study is for pneumococcal disease which is caused by Streptococcus pneumoniae bacteria. It is a leading cause of vaccine- preventable illness and death in the United States.
          Anyone can get pneumococcal disease, but some people are at greater risk than others:

          – People 65 years and older
          – The very young

          – People with certain health problems
          – People with a weakened immune system
          – Smokers
          Pneumococcal disease can lead to serious infections of the:
          – Lungs (pneumonia),
          – Blood (bacteremia), and
          – Covering of the brain (meningitis).

          Pneumococcal pneumonia kills about 1 out of 20 people who get it. Bacteremia kills about 1 person in 5, and meningitis about 3 people in 10.

          If anyone wants to review vaccine information it can be found here:

  • Anupama

    I have adopted a plant based life style. It is working slowly for my lupus. What more can I do to get more results?

  • val

    Definition of elderly please? thanks! What exact age are we talking about here?

  • sonicmonty2

    Any literature on the effectiveness of the flu vaccine? I am not an advocate and have read that its effectiveness has not been proven in ALL populations. I would like to be able to give a reference to my patients. Thank you.

  • Dr. Greger you mention in this video: that certain infectious diseases such as the common cold, flu, and small pox did not exist or were rare before the domesticating of animals. Question, if our society moved to a vegan diet and ethic- eliminating animal agriculture and the breeding of animals- would it then be possible that such infectious and common diseases like the common cold and flu be eradicated or rare? I understand that food borne illnesses would be eradicated if animal agriculture no longer existed, but curious about certain infectious diseases like the ones you mentioned in the you tube video link that I provided where you spoke about this. Thank you for any insight as I am always learning- even being a vegan for 26 years now.

    • Joseph Gonzales R.D.

      Hey Carrie good to see you post here! Ok this is definitely Dr. Greger’s area. Have you read Bird Flu? It is available for free, here. He says that the flu would probably start going away as what happened with influenzavirus B. Hope that helps a bit. Thanks again for posting.

  • vetrel

    So do you recommend that the elderly take the pneumonia vaccine?