Doctor's Note

UPDATE: Sound a bit too good to be true? It may be. A UPenn research team were unable to replicate the results. Read their paper here. Hat tip to Kasper for pointing it out. So at this point the data is mixed. I'll do another video once more studies are published and we have a better handle on whether it's useful or not.

Either way, it's better to prevent it in the first place:

What if you eat it instead? See, for example, Tree Nuts or Peanuts for Breast Cancer Prevention?

If you haven't yet, you can subscribe to my videos for free by clicking here.

To post comments or questions into our discussion board, first log into Disqus with your account or with one of the accepted social media logins. Click on Login to choose a login method. Click here for help.

  • Joevegan

    I didn’t smell that coming.

  • George

    The best thing is the patient gets to eat the test reagent after the test! Hospitals won’t like this test because they can’t charge a couple of thousand dollars for a cup of peanut butter. Thanks Dr. Greger.

    • mjs_28s

      Someone will come up with a $0.09 glass test tube with a fancy glass applicator built in with a 5 gram sample of peanut butter.

      You have to then break a special seal to free the applicator to then to the smell test. Of course the peanut butter will be colored so you cant be sure of what it is.

      Cost to the hospital: $3.00. Gross profit for the manufacturer: $2.17. Cost to the patient: $125 for the test, $750 for the materials. Gross profit for the hospital: $875 – $3 = $872

      DOH! Still too low :-)

      • aCountryVegan

        You forgot paying someone to analyze the test results at $1000 per reading.

        • Plantstrongdoc M.D.

          I am a neurologist – I will do it for 950$ !!

          • Matthew Smith

            You’re a neurologist? Thank you for sharing. Would you ever consider testing any of your brain patients for anemia? I know Iron is important for building a strong brain. We think Whole Foods Plant Based people have less deficiencies. I think that they might have less Alzheimer’s. What does Iron do in the brain? Would you recommend plant based sources of Iron? Is it possible to rebuild brain damage if you get the right materials? How do I earn a better life?

          • David D. Rosamond

            ha ha ha ”HELL YEAH” I’m a burnt out paper hanger I’ll do it for $750.00

          • Harvey

            I’m a Superannuitant I’ll do it for a cold pint of draught.

  • Kasper

    Dr Gregor this follow-up study seems to have found no such result

    • Joseph Gonzales R.D.

      It appears that is the case. However, I think he realizes this as he does mention “to date all the supporting evidence is really just circumstantial. It is clear, though, that changes in the sense of smell is among the first clinical signs of Alzheimer’s, occurring during the “preclinical phase” before there’s any noticeable cognitive decline.”

      I also find it interesting that the author of the study you posted has major conflicts of interest considering: “Competing interests: Richard L. Doty, is President and major shareholder of Sensonics International, a manufacturer and distributor of tests of taste and smell, including the UPSIT used in Study 2 of this paper.”

      Even if this test doesn’t work 100% it is pretty clear diagnosing Alzheimer’s is difficult and not 100% accurate either, even with the current expensive technology we have. I think it’s amazing such a test like this could even be considered for such a debilitating disease.

      • Thea

        Joseph: Eagle eyes! I appreciate your post to help put it into perspective. That doesn’t mean that the follow up study is wrong in some way. But knowing the conflict of interest sure does provide some context for the result. And sure does mean we probably need some more follow up studies on this. That’s my take anyway. Thanks.

        And I totally agree with you re: “I think it’s amazing…” Totally amazing and hopefully something that pans out.

        • Joseph Gonzales R.D.

          I think Dr. Greger and I were both shocked to see that paper. Thankfully we have such engaged folks (like Kasper) here on the site to help us understand this research a bit better. You for one have been a gem for many years and also help me and others when I don’t have the answers :-) So thanks! Gotta run… I smell my peanut butter (thank goodness) and toast and need to eat!

      • Charzie

        I thought it was also interesting that he (RL Doty) shows up in the brain scan study, and two others investigating smell issues related to AD, then again in the study denying the PB sniff test was valid! Hmmm….

    • Thank you so much–here’s the full-text PDF. I’ll collect all the subsequent data and do a sequel!

  • I did the test and could barely smell the peanut butter out of either nostril even straight out of the jar??

    • Christopher Addams

      Thought I’d try this with my wife. Even with a cold, she was fine with both nostrils. But I was like you Disqus. I couldn’t smell it in either nostril until it was right under my nose.

      Now, what in the world is that Peanut butter jar doing there?

      • Eva

        You both are probably very much deficient in zinc. One of symptoms of zinc deficiency is inability to smell and taste.
        I am a nutritionist, and administering zinc in cases like this always works (usually a dosage of 50mg for few months is enough.

        • Christopher Addams

          Thanks Eva.
          Funnily enough, I started some zinc supplement tablets last Friday to help with a cold. So that’s good timing!
          I will check the dosage.

        • PCK

          I lost much of my sense of smell after using zicam nasal inhaler with zinc for shortening duration & intensity of colds. It worked, however the loss of smell seems to be the residual side effect. Would oral zinc tablets restore the sense of smell?

          • Brux

            The one thing that bothers me about this site, or rather the discussion on it, are these diagnoses by unknown people that think they got cured of something by something and then proceed to jump on here and call and prescribe treatments for people sight unseen. Is there some kind of warning or disclaimer about this kind of thing. Some of these suggestions can end up being toxic for people, and who knows if they are helpful or not?

            To say that you used a zinc nasal inhaler that shortened your cold, but took away your sense of smell, and saying that worked, I think we have different definitions of what worked means.

          • Wilma Laura Wiggins

            Well Brux, I would say it was a fair warning and not an endorsement by PCK.

          • PCK

            Thank you for understanding my question.

  • smith

    so would einstein of the world be able to use their left nostril to detect cancer ?

  • Serge Boyer

    This reminds me on a story of the russians in outer space. The americans & NASA developped a pen to write in weightlessness. It cost them millions of $$$ so when the american & russian became joint in the space program, NASA asked the russians what they did to develop. The answer was: a leadpencil. Proving sometimes it’s not always the most complicated things that are evident.

    • Matthew Smith

      The problem with this story is that pencils were already ruled out because of pencil shavings, breaking pencil lead. and the need to sharpen pencils. A pencil would not pass flame testing in America and we don’t know how it did in Russia. America did help invent the mechanical pencil and the ball point pen. Taking this story to its conclusion, Astronauts would be asked to write with a crayon, which might melt.

  • Brux

    Is this natural or Skippy type peanut butter? There is a big difference in the smell – to me anyway.
    Does it matter?
    Why peanut butter, could anything else be used or is peanut butter slow to diffuse?
    Chunky or creamy? ;-)

    • Julie

      As mentioned in the video, the study used “14g of peanut butter, plain ground peanuts.” Since we’re primarily looking for a large discrepancy between right and left nostrils, the type of peanut butter used may not matter all that much.

  • Noe

    grandma on the test!
    My 83 years old grand mother ,after follow the the advices of traditional medicine(meat, milk for the bones, antibiotics, not move to much..) for a life have quite a lot of health problems..(high blood pressure, osteoporosis, artrosis, arritmia, brockiostacias, diverticulitis, and few more, back pain..)
    since few month she lost short memory and for first time she ask thing for 3 times in 15 minutes..(same question)..
    she is now on an anti inflammatory diet (wfpd), most has i can because she have diverticulitis and many times she get diarrhea when eats a lots of fiber (so i give everything with rice if i can).

    the question is is any study shows an improvement in memory and attention in short time in arterioscleritic patiens?
    i have notice an improvement in her vitality with the diet ,and in general.. but i wonder if is posible to slow down the decline in a advance stage person has her.

    so if any food that show to improve memory capacity ?

    Thank you!

  • Plantstrongdoc M.D.

    There are predictors of neurological disease. Eg rem sleep behavior disorder and parkinson’s disease. It may even antedate the occurrence of motor symptoms by decades. So if you experience this – please start eating healthy (in my opinion as close to WFPB diet as possible) !!!

  • marlene g

    Dr Greger – First, I want to thank you so much for your tireless work. I’ve become a big fan and whenever a health question arises, I find myself asking “what would Dr. Greger have to say about this?” Who needs WebMD when there is NutritionFacts.Org :-)

    Having said that, I would be interested to see if you have any studies or information related to preventing brain aneurysms? Just this week, two teenagers here in the U.S. (both athletes) collapsed while playing their sport and died not long after in what appears to be from a brain aneurysm. I found this news heart wrenching and would appreciate any information you may be able to share with your readers regarding prevention. Thank you in advance and again for all you do!

    • Joseph Gonzales R.D.

      Thanks for the nice note, Marlene G! This is what we have on aneurysms, but not sure the videos relate to brain aneurysms. Dr. Greger has plenty on brain health. From a quick search I found a study suggesting proper nutrition after an episode plays a role, but it did not focus on prevention. A few others popped-up (where I think #8 and #10 may be interesting), but this seems like an area with little research. If I find more I’ll post, but hopefully others can help us clarify.

      Thanks again,

    • Aneurysms develop from weakened areas in the arteries. A recent study by Fukuda and Aoki in Acta Neurochir Suppl hypothesized that they resulted from chronic inflammation triggered by hemodynamic stress and macrophages. WFBD’s tend to be less inflammatory (see videos on Omega 6 to avoid being a vegan with high inflammatory tendencies). The higher the blood pressures the more stress on these areas. Brain aneurysm’s tend to most commonly rupture in middle age but as you mentioned rupture can occur earlier. We have new treatments which don’t require surgery which is a tremendous advance. Unfortunately they are often without symptoms until they rupture. For me the key to minimize the chance of having an aneurysm and decreasing the likely hood of rupture if you have one is to keep your arterial tree in good health by eating a whole food plant based diets. Studies such as were done in the Sudan with the Mabaan tribe showed that “normal” blood pressures tended run between 115 and 105 systolic between ages 25 to 75. Matched controls in the US started with blood pressures of 125 and went to 145+ systolic between the same ages. From my perspective elevated blood pressures are the bodies normal response to inflamed, constricted and blocked arterial tree. It’s as if the heart is increasing pressure to overcome the resistance. Clinically patients who adopt a WFPB diet can expect some good improvement initially but will continue to show improvement in their blood pressures over several years. Of course patients on medication should work with their physicians to avoid problems.

      • Plantstrongdoc M.D.

        Genetics play a role in the development of aneurysms in the brain. Smoking is also – a preventable – risk factor.
        Endovascular coiling of aneurysms are an option in many cases, so the patient dont need open surgery. Despite this progress it is a catastrophic event. Many patients die before they even reach the hospital, and many die in the hospital. Spasms of the vascular tree is a known complication, so there are a very high risk of infarcts in the brain. Pneumonia is nearly mandatory in the postoperative fase. Most survivors suffer some degree of brain damage. Some patients experience a warning leak (small bleeding from the aneurysm) before the rupture. So if you experience a sudden unexpected, severe, uncommon headache you have to see a neurologist immediately.

        • Well said… unfortunately the first result of some problems like aneurysms or more commonly heart attacks is sudden death and even for those who survive their is accompanying disability. Sure makes a case for primary prevention through proper lifestyle especially nutrition… based on “facts” not “opinions”.

  • Serge Boyer

    Thank you Mathew for the info.

  • Chicovegano

    What if you can barely smell the peanut butter with your nose stuck in the jar?
    At retirement age and neither myself or spouse can smell many of the common fragrances that used to be detected from the next room.

    • Wade Patton

      See the replies to Noe below. Also look at “cognitive decline” videos. You don’t indicate how you eat or if you smoke. Both things play a huge role in brain function and ageing. Best of luck.

      • Chicovegano

        I had thought the name Chico vegan o could have been a clue. We do not smoke, try to eat green, no meat, no cheese or milk products. Could have lost sense of smell to some degree due to dust from mowing grass, weeds and poison ivy (live in the country) or wood dust (wood working). Followed doc Gregor for years, attended his talk in St. Louis years ago. Just seems like the access to the nerves in the nose is blocked off, or dry or something. I plan on trying the test with relatives.

        • Wade Patton

          Yeah, I missed that obvious clue. A quick glance is all I took and your “name” looked a bit like a big city in Illinois. But it is best to make no assumptions, I’ll bet there are yet some oil eating vegans. I also live rural and have done a lot of mowing of lawns and fields (less now), exposure to automotive and shop chemicals, walk through poison ivy every day (mowing it with slingblade these days). My woodworking is mostly with hand-tools, but do recognize that many wood dusts can have a wide degree of toxicity (no issues with that yet). All that and aside from tinnitus (for dozens of years) my senses are yet rather sharp and I hear better than most despite the ringing. But then I’m only 48. Just found Dr. Greger recently, but have been a student of nutrition for quite a while (on and off before, now “on for the duration”). Maybe get tested for neurotoxins? Namaste

          • Chicovegano

            Seems we are in the same boat on many issues. I had missed the note earlier re: zinc. I plan on giving that a go to see if any improvements can be had. Side note, I also am into hand tools for working wood. Quite pleased when I finished the old English tool chest to safely store many of those same tools. The Dutch tool chest is for when I work at the bench.

    • Eva

      Inability to smell and taste is a sign of very advanced zinc deficiency. Usually 50mg of zinc for quite few months helps.

      • Chicovegano

        Thank you, I just realized it was posted earlier and plan to give zinc a try.

  • Julien Brown

    If this is an effective test, is there a way to get it covered by Medicare in Canada? It’s not so easy to perform this test in a home since the smell lingers.

  • jen

    Unrelated question here. Wasn’t sure where to post it. I’m a HUGE smoothie fan, our family has them daily, full of spinach, flax, berries, bananas, dates, almond milk, cocoa. Recently I’ve heard some physicians I respect, Dr. Esselstyn and T. Campbell make comments about sharp rises in blood sugar, increased insulin, possible liver issues from all the fructose. My gut says my blender is just doing a better job than my teeth and making some of the nutrients more available to me and I should still be receiving the benefit of the the fiber. Their comments suggest the fiber is separated from the sugars and I’m getting a big sugar spike, and will feel hungrier later for taking so many calories in a liquid. I remember a study of soup and actually the pureed soups left participants feeling fuller for longer, though they weren’t full of natural sugars. What do you know about this? Are there studies looking at green smoothies and blood sugar spikes?

    • Wade Patton

      I’m no study, but I did eat green fruit smoothies for breakfast for quite a while (and lost weight for the first time) when doing 80/10/10-ish eating. I just saw some (sample) videos of a doctor who explained that the effectiveness of the fiber in such smoothies is reduced by that mechanical shredding. The fact that I had to eat so much and so often to stay satiated on such an eating plan is one of the reasons I abandoned it. Now I’m WFPB eating and have lost the same weight, eat less volume of food and really see the benefits of flaxseed/fiber. To be clear, I only started with flaxseed recently. Flaxseed alone may have change my experience with the green smoothies, but I’m too fond of oatmeal and grits now (with fruit and flaxseed added) to fret over it. FWIW.

  • Dommy

    Since no one has yet mentioned it, remember that smoking reduces olfactory sensitivity.

  • ZK Farrell

    Is it just me who finds the voice over unbearably annoying?

    • Brux

      Probably not but you are in a small minority. Most people I assume find “the voice” just fine and care more about the information and ideas here. What did you hope to gain by mentioning it …. subtitles? ;-)

      • Eva

        Love the voice!!! Perfectly modulated. Can’t imagine anyone else providing this info in a better way.

    • Legume

      That’s Dr. Gregers own voice. He does his own VO.

    • Wade Patton

      Nearly every video has a transcript and sometimes an article in “topics” that goes along with it. No voices there. I wasn’t thrilled with the Doc’s voice at first and indeed I found it worse in the first few years when he was whispering. I got over it. It helps to see some of his annual, hour-long presentations as well as interviews and also his testimony at the Guidelines Committee to put a face and expressions with the voice. I’ve seen hundreds of his videos and videos of him since finding this source only a few months ago. The info is pretty good. Cheers.

      • aribadabar

        Actually the “whispering” voice of previous years was softer and more pleasant. This almost sarcastic tone is indeed annoying.

        • Wade Patton

          Sticky wicket eh? Some like it hot, some like it cold…

  • Coolcat

    I read on you tube that Virgin coconut oil can reverse Alzheimers disease. The disease can not get the proper amount of glucose to cross the brain blood barrier, and results in dementia. This man gave 8 tablespoons of VCO to his aged father, and his congestive abilities started to improve. The VCO can pass from the brain blood barrier and be used as alternate fuel to nourish the brain. Alzheimers is Diabetes type 3.

    • 2tsaybow

      Hi Coolcat,
      Dr. Greger has an article on this subject. It is called: Is Coconut Oil Bad For You?

      It’s a few years old but relevant to the question that you asked.

  • sf_jeff

    Please tell me this wasn’t funded by the peanut butter lobby.

  • Rebecca

    A zinc deficiency causes one to lack both taste and smell, so that must be considered. However, I don’t think there would be a discrepancy between nostrils with a lack of zinc.

  • Chris Gould

    But what’s the point of knowing what the problem is, if you can’t fix it?

  • Matt K

    What if I can’t smell the peanut butter in a jar until its 3 inches away from either one of my nostrils?

  • Peanutbutter

    Maybe I have missed some point but could any other product or reactive be used instead of peanutbutter, for example, Coffee or any other well known product will enough smell properties?

  • Jennifer Mendenhall

    Terrible voice over. Why did you feel the need to dumb it down?

  • Dan Winkler

    There was an attempt to replicate these results and it failed which seems like it might cast doubt on their validity:

  • Wilma Laura Wiggins

    I wonder what it means if u can only smell it in your left nostril and not at all in your right?

  • Psych MD

    As stated below, an attempt to replicate this study failed. However, a more promising and objective diagnostic procedure involves our old friend curcumin. One of the hallmarks of Alzheimer’s disease is the presence of beta amyloid plaques. Interestingly these appear in the retina decades before the disease manifests itself. Feed someone curcumin and the plaques take up the substance, giving off a fluorescent glow, detectable in a noninvasive retinal exam. Unfortunately I lost the link to the study that showed the images. To summarize they compared normal and demented subjects. The curcumin-enhanced plaques were seen only in the Alzheimer’s patients. Those with other forms of dementia, such as microvascular, showed no evidence of retinal abnormalities.

  • Danielle Renee

    What are your thoughts on the new silica craze and the theory behind removing aluminum from the brain>

  • Philip Vardara

    Yes. And the UofF was a very small sample that was NOT replicated by a second study at the UofPenn. Sorry. More internet mythology until settled with a larger power double blind study. .