Aflatoxins, or Another Reason to Shun Peanuts

We already tend to steer clear of peanuts for some obvious (to our readers) reasons: the fact that they’re legumes, rather than actual nuts; the potentially dangerous, “anti-nutrient” lectins found in them; and their prominent spot in the upper echelons of the “Most Common Food Allergens” list. But there’s another reason to steer clear of peanuts, something we’ve touched on briefly in the past but never expounded upon. Peanuts, along with a couple other crops we tend to avoid, like corn and cereals, are especially susceptible to a mold that produces a mycotoxin called aflatoxin.

Aflatoxin is a carcinogen that has been shown to cause liver cancer in rats (and, presumably, in humans). The amounts given to the rats in the study were highly concentrated, of course, with the express intent to study the effects of acute aflatoxicosis. You won’t be getting a couple grams of aflatoxin with every bag of peanuts or anything, so acute aflatoxicosis isn’t a big issue for people – at least in the US.

That’s not to suggest that correlations between aflatoxin ingestion and cancer rates in humans haven’t been found. In China, for example, a study of five groups of people from different villages found definite positive correlations between the amount of aflatoxin ingested and liver cancer mortality rates. Those villagers who ingested less aflatoxin were less likely to develop liver cancer; those who ingested more were more likely. Unsurprisingly, the three major sources of aflatoxins in this study were peanuts, peanut oil, and corn. Similar reports of aflatoxicosis have been made in India and Kenya.

India, China, Kenya – all developing countries with huge populations to feed. As the recent Chinese pet food contamination debacle attests, health and food standards in developing nations are often lacking. Aflatoxins develop because of these substandard conditions, whether it’s drought afflicted crops weakened and vulnerable to the mold that produces aflatoxin, or insufficient storage facilities letting in the moisture and humidity that creates the mold. Hot, humid climes and improper storage – the real culprits.

The FDA is aware of aflatoxin, and all susceptible foods are tested to ensure they pass muster. Of course, “muster” to the FDA could mean “not so much that acute aflatoxicosis becomes imminent.” What about chronic (a descriptor our nation’s health “experts” seem loathe to address) ingestion of aflatoxins? You know… long term effects? Eating toxic aflatoxin, even in relatively small amounts, over a long period of time (say, slathered on to your morning toast every morning) just doesn’t seem like the best idea.

Well, a link between aflatoxin exposure and stunted growth in West African children has been shown (bolstered by similar laboratory findings in animals), but no specific mechanism has been proposed to explain the relationship. Still, though, the very fact that much of the evidence seems to be pointing towards aflatoxin as a dangerous, development-stunting carcinogen, with a greater propensity to reside in peanuts and cereal grains, only bolsters my resolve to stay off impostor nuts and cereal grains (in or out of the closet alike). If there’s one thing everyone can agree on, it’s that increased liver cancer and stubby limbs are unequivocally devolutions.

I don’t know about you, but the evidence against eating corn and peanuts and cereal grains just seems to be stacking up incredibly high. So high, in fact, that were it not for the remarkably solid foundation of facts, scientific evidence, and personal experience, I would worry it might topple over.

Carol Esther Flickr Photo (CC)

Further Reading:

The Definitive Guide to Grains

Dear Mark: Nuts

10 Ways to “Go Nuts”

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72 thoughts on “Aflatoxins, or Another Reason to Shun Peanuts”

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    1. Aspergillus mold grows on almost ANY food staple, including peanuts, if IMPROPERLY stored. Eat GOOD peanuts and GOOD peanut butter. You do not eat moldy bread do you?
      Peanuts get a bum rap- like the one above- because kids eat so much peanut butter and kids’ livers are more susceptible to alfatoxin poisoning than adults.
      As an active 60-year old adult, and a PhD biologist, without a serious weight problem, I eat peanut butter almost every day.

      1. Dear ray. Sadly,my super healthy skinny father was diagnosed and subsequently died due to liver cancer. He didn’t drink nor did he have hepatitis, but he always had a can or jar of peanuts to munch on.. I am convinced his demise was due to prolonged exposure to aflatoxin infiltrated peanuts. Everyone beware. We had a namebrand in our house. Our family has great genetics with no incidence of cancer. Be careful! Sandy

        1. Cancer isn’t always caused by something we ingest, smoke, drink, breath, etc. Sometimes it just happens. I’m confident peanuts didn’t cause your dad’s cancer.

  1. Hi,
    Does this apply to peanut butter as well? As a vegetarian, I am slowly losing my sources for good protein (after reading your soy post and now this!)

  2. Almond butter is delish tho! And it doesn’t have the same issues as does peanut butter. Yay for real nuts!

  3. I second Jane’s opinion, Almond butter is healthier and it tastes better. On peanuts, it seems the amount of aflatoxins a person inhales/eats effects their cancer risk, but if we eat fresh, clean peanuts, is it safe to assume the aflatoxin levels are minimal? After all, the cancer rates in China were based on people who were working at a peanut mill, inhaling the aflatoxins.

  4. Mark – I’m a big fan, but I think there are some problems here.

    Let’s not forget that walnuts, almonds, and other nuts also can and do have aflatoxins. While we can’t do anything to reverse this problem with premade nut butters (peanut, almond, or whatever), aflatoxins can be neutralized with the Price-Pottenger recommended method of soaking the nuts for around 8 hours in salt and then roasting them at very low heat (such as in a food dehydrator) until completely dry. We should be soaking our nuts anyway to keep the enzymes in tact.

    1. Yes but that does not get rid of the lectins. It also means buying and soaking raw nuts. Not many people will do this.

  5. I have always know that aflatoxins = bad… but more because I have been told. I never really bothered to research it or understand why they are bad. Thanks for the info Mark!

    The SoG

  6. Well, now you gave given the best reason ro srear clear of peanuts but also of CORN! I don’t mind, but that will not make my folks proud. The only carb they really eat are corn tortillas. Coincidentally I was telling my mum about Gary Taubes’ Good Calories Bad Calories, and I told her to give up the tortillas for 30 days. Good timing, I hope.

  7. We stick w/ Valencia peanut butter (organic). Trader Joes carries this for a good price. It isn’t ideal, but I’ve always heard Valencia peanuts were naturally resistant to aflatoxin, at least to a degree.

  8. You will have to pry my peanut butter out of my cold dead hands! After giving up sugar and gluten, it is my one omega-6 filled “junk” food. 😀

    Almond butter is way too expensive for my student budget, but it’s nice to know there’s a healthier alternative.

    1. Or grow your own peanuts like we do. It is the easiest crop to grow and can be grown in pots or barrels or in the ground. In fact, they will grow in spite of you. My wife and I live on a very small lot, but grow most of our own fruits and vegetables (vertically). We harvest about 10 pounds of peanuts twice a year (we live in Southern California). That is plenty for just the two of us old empty-nesters. Shell them right away after harvest, set aside the 20 or so you want to replant, then dry thoroughly, roast and eat or store the rest. Dried, roasted peanuts have a long shelf life. We go from harvest to harvest to harvest…
      A lot of food for very little work.

  9. All this talk about bad peanuts and sweeeeet almonds… makes me want an almond! But seriously, great idea to extrapolate on why peanuts aren’t the best kind of nut for anyone.

    All the Best,

    Andrew R

  10. Yes, supposedly Valencia peanuts are grown in more arid conditions making them less resistant to mold? Do you know anything about that Mark?

  11. @bethinNC and Ellen:

    I like peanut butter too much to give it up and buy a brand made from Valencia peanuts for the reason explained by Ellen. Peanut butter is an occasional treat, not a daily staple, so I’m not terribly concerned about an overload of aflatoxins.

  12. I’m going to throw in a comment here related to this site’s great information. Life is not risk free, and you cannot spend all your time trying to eliminate every infinitesmal risk. I’d like to see more risk assessment data here accompanying the posts. For example, every time you step into a car, which many people do every day, this behavior poses a risk that in all probability greatly exceeds that of consuming peanut butter. I just saw a very fit 84-year old, he still travels the world and does zip lines; and he told me he finishes each day with a dollop of peanut butter.

    I’m also suggesting a great Grok-style form of winter exercise; uphill snow-shoeing. I did it yesterday on a Vermont mountain. I moved very slowly up for a couple of hours, I spent much time standing still in the silence taking in the spectacular nature scene, interspersed with sporadic “sprints” on steep sections, the only time my heart rate exceeded about 110. And at the top…I ate a PB & J!

  13. I’ve given up so much in my quest to be healthy. I’m with Loren B., you’ll have to pry the peanut butter out of our “cold dead hands”! However I am going to look into making my own almond butter.

  14. I also love peanut butter. Living in SA I have not seen Almond Butter on sale yet. Can anybody give me the recipe please?
    Thanks so much. Hard work to get healthy, but ultimately worth it.

  15. The corn issue is frustrating for me. I love eating Mexican food and have given up the flour tortillas. Now I hear the corn are not good either. Without either one, it makes dinner difficult if we are having beef or fish fajitas. It is so fun to pile the meat, avocado, lettuce, cheese and fresh salsa on a tortilla and munch away!


  16. @Mike:

    Koreans and Japanese wrap grilled meat and toppings in lettuce leaves and other raw greens. I find it easier and less messy to eat burrito or fajita fixings in a bowl.

  17. Sonagi – thanks for the lettuce tip. I had started doing that as a substitute for pita bread when eating middle eastern beef shawarma. When eating fajitas, I just need to think of the lettuce as something that wraps the food instead of going on top!

    I was lucky enough to have the lettuce wrap grilled meat while in Korea once and though I looked ridiculous trying to roll the lettuce with my chopsticks, I enjoyed the food very much.

  18. Almond cream good for you? I guess you still trust in the FDA. It is full of cyanide I wonder why they are not banning marzipan. Peanuts are too healthy for you that is why the FDA wants to ban it because it is controlled buy the pharmaceutical companies. Is it not strange that its always this salmonella scare? They just want to increase “food safety”. In other words irradiate food so there would be no health benefits left in them at all. Oh my gush, 120 people had to go to the toilet 2 times more than before. What about the other 300 000 000? A joke. Of course my letter will probably never make it because they want their foolish opinion heard and they want you to not drink bottled water because fluoride is good for you, and they care so much. That is why most people are aspartame, GM food, MSG, hydrolyzed oils, palm oil…. are in your food. Isn`t that interesting??

  19. I tried the lettuce wraps for my Mexican food per Sonagi’s suggestion. It was OK, but, lettuce really cannot hold much food. I am looking for another type of edible substrate for my mexican food nights in place of the tostada or flour tortilla. I am starting to think about some kind of fried plantain or squash or ???? Anyone got some new ideas on this one?

  20. I don’t get this one-

    Grok & Erg are out foraging, Erg finds a heaving peanut (vine, tree, bush, dispenser…?) and starts to eat, when Grok says,”whoa, Erg, no eat yummy energy dense peanut, it a legume, not actually a nut.”

    Our ancestors would not have known/cared about the classification, and raw peanuts are non-toxic, right? How is the peanut not primal food?

  21. I’m currently reading The China Study and wanted to know what one of my favorite meat eaters thought about it so I searched your site and got this article as one result.

    The research in The China Study shows that there is a direct correlation of aflatoxin exposure expressed as liver cancer to dietary animal protein. The higher the animal protein intake (20% of diet) the more likelihood of liver cancer. The lower animal protein (5%) intake did not promote liver cancer. Plant protein of any percentage did not lead aflatoxin exposure to liver cancer and could in fact reverse tumor growth if it replaced animal protein.

    Wondering what you think about The China Study’s findings in regards to aflatoxin.

    Be well, Carla aka

    1. Yes! The China Study. PROVES that Aflotoxin exposure WILL trigger some type of cancer/mutation in a lifetime if one has an acidic diet.

  22. I will await further data on this. Peanut butter is one of the most satisfying snacks from a taste perspective, and I continue to enjoy it most days. To me, Almond butter is a sad, sad substitute with respect to flavor even though it is apparently healthier.

  23. Wow! I didn’t know! Thank you!
    Costco has a huge and cheap Almond Butter. Also we just tried several other nut butters from Whole Foods (not as cheap at all but good). Sunflower Butter and Cashew Butter.

  24. I have had bad reactions to nuts for several years, and now I believe that Aflatoxins were the culprit. Once, after ingesting a handful of walnuts (two or three tasted “bad”), the pain in my liver area was so bad that my doctor told me that I would be breaking out in the rash for Shingles by the following week. When I didn’t, he was stunned.

    Five years ago, 15 minutes after ingesting a peanut butter sandwich, I was nauseous, achy, and the liver once again ached. This went on for three days. I was scheduled for surgery the following week, and the doctor thought I had gall bladder disease. He suggested scheduling the general surgeon at the same time so they could remove the gallbladder. After speaking with the surgeon, he was not convinced it was the gallbladder. It’s still there.

    At the time, I thought I was allergic to peanut butter, but never had any rashes or other symptoms besides the nausea, vomiting, pain in the liver, and general malaise.

    Several weeks ago, after adding peanut butter to my kefir smoothies at lunchtime, and buying a couple cans of “cocktail nut mixes”, the pain is back. It is not as bad as it has been
    in the past, but I now know that there is a direct correlation between peanut butter and nuts, and the symptoms.

    That is what brought me to this site. I already gave up corn, as it is a GMO, and will now give up nuts for a while, to see if that will help. I listen carefully to what my body tells me, and I am beginning to think that I am very sensitive to aflatoxins- even in small amounts such as rancid nuts, oils and other sources. I wold be interested to know if anyone else has had this problem.

  25. Just wanted to give an FYI that corn tortillas are not a worry. The process of ‘nixtamalization’ gets rid of most of the aflatoxins, should they be present (they aren’t always). The traditional method of soaking the corn works best, but the commercial way isn’t that much worse. Unfortunately, we mostly eat corn incorrectly. The Mexican method of treating the corn is best as it gets rid of most to all of the toxins and it creates a protein out of a starch. So eat corn tortillas. Preferably in Oaxaca, where they are made on a wood-fired clay comal!

  26. I have talked to folks at framers markets. I buy raw sprouted peanuts from an organic sprout vendor. They assured me that organic peanuts should be free of aflatoxins because they are organic and not stored like other peanuts and reamain fresher it would be very uncommon to contain any aflotoxins.

  27. Ah it doesn’t measure up to slam peanuts. Peanuts are low in carbs like nuts are low. So all this flack against peanuts is ridiculous. Toxic? Come on! Everyone enjoys peanut butter. I’m sure Grok would have eaten it if he dug em up. BTW Almond butter? It really sucks. Horrible taste.

  28. For years I had a huge craving for peanut butter. But, the “health care professionals” always insisted it was okay, nothing’s wrong with you. Even when I was over 200 pounds, and was exercising like a fiend and never losing an ounce, and also getting sick all the time. I stopped eating peanut butter, and you know what? I HATE PEANUT BUTTER NOW. I HATE THE SMELL OF IT. The smell makes me SICK TO MY STOMACH. I will never be convinced again that peanut butter is good eats, when obviously it is not.

  29. Ah see peanut butter is one of those things that I can’t give up. I’m paleo, well except for the peanuts, that is. I buy organic peanuts, soak them, dehydrate and roast without the skins. I mostly make my own peanut butter, though sometimes I buy too, not always.

    I’ve had almond butter, even made my own. I’ve made pretty much any other nut into nut butter(soaked and dehydrated first). I don’t really care for almonds or almond butter and frankly, even after soaking and dehydrating, it still bothers me. Other nuts seem to be okay with me aside from almonds. So I’m not sure, anyway, I don’t eat peanut butter everyday.

  30. For all those people worried about aflatoxins in corn tortillas: Don’t expect there to be many, mainly due to the process of nixtamalization used in the preparation of said tortillas. The ancient process for the most part kills most of the aflotoxins. So keep on eating corn tortillias and masa by products, as far as freaking over some type of ingredient because its toxic, I would be more worried about things like msg, corn syrup, hydrogented vegetable oils, and weird preservatives causing far more dammage than eating peanuts.
    Rats are slightly different than people remember. Its also like the example sasafrole, native peoples have been eating sassafras for centuries, the fda does a study on rats, and sassafrole and decides its deadly toxic. Turns out rats can’t digest components of sassafrole like humans can but noone is the wiser on that one. Also most almonds grown in the states are irradiated so all those touting almond butter. Honestly the raw nutrient value isn’t there any longer once its under gone irradiation. So I’m not really sure thats a great alternative but hey who really knows anymore?!!!!!!!
    pecan butter sounds yummy to me but thats just me haha

  31. I LOVE, LOVE, LOVE Peanut Butter. I buy the organic kind from Earth Fare. I really hate to hear it might be bad for you:( Almond Butter really doesn’t agree with my ummmm hmmm, digestion. Anyone else have that problem???

  32. I just ate some organic cashews, most of which were delicious, except the last one I ate, which was a bad one. I spit most of it out, but couldn’t get the taste out of my mouth for a minute or two. I could tell immediately there was something toxic in it, and think it was probably aflatoxin or else the toxic portion of the cashew shell that I was tasting. It seemed a lot stronger than the random bad peanut you get.

  33. I definitely had some stomach problems after eating almonds and other nuts daily. I only eat raw nuts and I try to get them organic. Whoever it was that was saying they had problems from eating nuts… I eliminated nuts from my diet for a while and now I can eat them again. Another weird thing. Apparently I’m allergic to peanuts according to a blood test taken, but I have absolutely no symptoms whenever I eat it. I wonder if my body has grown tolerant of it since I’ve eaten it throughout my life. Anyway, I’m enjoying being able to eat nuts again, but I’m going to be careful not to over do it! I’ve known about the mold thing in peanuts for a while. And after reading the comments, I’m curious about the Trader Joe’s Organic Valencia peanuts. If that’s true, then I’ll be buying that kind from now on because I do like to have a little from time to time. Especially in my green smoothies!

  34. I have been eating organic valencia peanut butter for a long time with no ill effects….from time to time, i do cleanses, including liver cleanses, just to stay overall detoxed…

  35. Why, when one buys in-the-shell peanuts by the bag, is there no certification on the bag that the contents were inspected? Even p-butter should show whether it is inspected, yes?.
    Also, what can a whole-peanut consumer watch for when opening peanuts? Some shells are a dark color inside — does that matter? If a kernel tastes weird, should it be carefully and completely expelled? Does or does not roasting, or re-roasting increase safety? Questions, questions…

  36. Hey, after a bit of research, I found a very informative article regarding U.S. standards regarding aflotoxins:

    It cites an FDA maximum limit of 20 parts per billion for this toxin in human food. I’ve seen from the UN FAO that those European countries that have legal limits have set them at 5 to 10 to 15 parts per billion for coffees:

    Last, I saw a pie chart from the UN FAO showing the breakdown of foods that are responsible for aflotoxin exposure:

    I did not see a category for oil nuts (like peanuts) except “Other”.

  37. I thought I would chime in since my mom worked for the USDA in the lab that examined almonds. I am pregnant and was mentioning my plans to add almond flour and almond butter to recipes when she warned me not to use store-bought varieties because of the aflatoxin.

    Her explanation was that these products are made from the broken pieces of nuts that remain after all the higher grade nuts have been sorted out. They have the highest allowance for “serious damage” meaning nuts unfit for human consumption (3% for Grades U.S. No. 1 Whole and Broken and US No. 1 Pieces). Additionally, some portion of samples from each manufacturer is allowed to be above the USDA maximum. When her colleague assessed various almond products for aflatoxin those made purely from the lowest grade nuts had the highest concentrations. Organic can actually be worse because the pesticides prevent much of the mold responsible for aflatoxin.

    Her recommendation was to buy whole almonds (or whole peanuts, she didn’t comment on Valencia) and grind them into your own butter or flour. The US #1 whole almonds have allowances of 1 1/2% or lower, and you can remove shriveled or damaged nuts as you find them.

    She did comment that peanut butter is even worse, so the same recommendations would apply. Overall, she said it’s fine to have processed nut products once in a while since everything has risks, but if you eat them often or are pregnant or feeding little ones, make your own from higher grade nuts.

  38. Who cares if peanuts are a “real nut” or not? What matters is its nutritional profile. In many ways this is more similar to nuts than to legumes and what’s so bad about legumes anyway?

  39. High dosed vitamin C neutralizes aflatoxins just like it neutralizes innumerable other poisons. Everyone should be taking at least 10grams/day.

  40. Read this whole post and all the comments while eating a bag of salted peanuts- shells included. I have no regrets.

  41. I live in Thailand. I’ve been eating about 2 lbs per week of pistachios – air cooked, in a recloseable bag, for the last couple months. I don’t have ANY faith in the Thai food standards, and I’ll be stopping all peanut consumption over here. One of the problems of living in a 4th rate country.

  42. You say that Aflatoxin affects the livers of rats and you prove that with a very extensive scientific study by Janet L. Clifford and K.R Rees, but you presume that they also affect humans. The link of the study that you are referring to is not available. What study were you referring to? Exactly how much would a human have to eat in order for it to affect their liver? And how long were the subjects eating aflatoxin? their whole lives? a short period of time? Are their other factors in this (developing) country that could potentially affect the liver?

  43. I have had mouldy tasting organic cashew butter – the kind that comes in individual pouches. Had to spit it out. Waited a few months, bought another one, same reaction. Now I will not touch the stuff. Never had that reaction over peanut butter,
    and don’t have/haven’t had trouble with cashews in general. but. wow, that particular taste is baaaaad.

  44. I just wanted to mention something here, in case anyone is still reading this thread (which I’m sure they are). I recently went to my local farmer’s market in Los Angeles. There was a guy there selling peanut butter and peanuts from (i think?) near Fresno. I asked him what his thoughts were about molds and safety of peanuts. He said that the problem occurs when peanuts are left to sit in a moist field in humid or rainy climates. He said that his peanuts were completely dry all the time because of the weather in that region. I thought that was an interesting point, and since I’m not planning to give up peanuts entirely, looking into where specific peanuts come from, and what the weather is like there, may be a helpful strategy.

  45. Oh, and I should add… He believed that if you buy from very small farmers, the peanuts were much less likely to be contaminated, because it is very difficult to properly take care of all your peanuts when you have too many. I mentioned the study that found the larger peanut butter companies had less mold in them, but he reminded me that small brands did not equal small farms. The off-brands were more likely to buy peanuts from random sources, which may have changed hands a couple of times and were probably not that fresh. I guess his point was that if you buy from small, local farmers (especially in a dry climate), that is where your contamination rate is likely lowest. Who knows if this is true or not, but it sounds good to me.

  46. “were it not for the remarkably solid foundation of facts, scientific evidence…”

    Such as?

  47. So are there any ways of getting rid of the aflatoxins in peanuts, or at least reducing the aflatoxins?

    I don’t think anything could survive five minutes in my pressure cooker on high. That’s the only idea I have for reducing the aflatoxins. I like peanut butter and I generally blend my own to cut grocery costs.

  48. What about organic Valencia peanuts? Also, if this is true why does Primal Kitchen make peanut butter protein bars?