Dr. Peter Borten, LAc, DAOM

Articles and Resources on All Facets of Health and Healing

Your Nose Should Know

(Originally published as a newsletter for The Dragontree Holistic Day Spa)

Most of the fats we eat are subject to a constant process of breakdown called oxidation. When fats become oxidized we call them “rancid.” A 2007 Israeli study stated that oxidation of fats is “one of the major degradative processes responsible for losses in food quality.” (1) It leads to the formation of free radicals and “advanced lipid oxidation endproducts” (ALEs) – chemicals that are toxic and damaging to our cells. Consumption of rancid fats appears to increase our risk of cancer and atherosclerosis (hardening of blood vessels). ALEs cause inflammation in the circulatory system, gut, liver, kidneys, and lungs.

I’ve found that many people don’t really know what rancid oil smells like. To me, rancid oils smell sort of musty or cardboardy. Sometimes they have a slightly sour “high note.” Here’s a good way to get a sense of it: The next time you buy some fresh cooking oil, make sure it was bottled fairly recently, since occasionally oil is already rancid when you open the bottle. Also make sure it has no added antioxidants, such as vitamin E, BHA, or BHT (since these help prevent rancidity and the experiment won’t work). Open it and take a whiff. There should be a clean, light smell – no mustiness. Put an ounce or two into a glass and leave it uncovered near a window. Unless your house is very cold, within two weeks (but probably sooner) it should be rancid. Smell it every couple days and you may detect the progression. The rancid smell is not necessarily glaringly unpleasant, which is probably why many folks aren’t aware of it. We have learned to accept a certain degree of rancidity as normal.

Another good place to learn the smell of rancid oil is at your local day spa or massage therapist’s office, where the sheets will inevitably have been saturated repeatedly with oil, perhaps over several years. Don’t worry, they’re clean and harmless, but the rancid smell is often persistent (especially at our spa, since we always use natural and scentless detergents).

The reason I had you leave the oil exposed to air and light is that these are the two main factors in rancidification. Heat, salt, water, bacteria, and molds in oils also contribute to rancidity. Besides cooking oils, other fat-containing foods are also susceptible to rancidity. These include seeds and nuts, as well as oily and starchy snacks such as crackers and potato chips. Rancid crackers are very common. Among nuts and seeds, all can go rancid, but I seem to smell oxidation most often in walnuts, sunflower seeds, pecans, pine nuts, and brazil nuts.

When nuts, seeds, and grains are intact in their shells or husks, they have some natural protection from oxidation. Once they’re shelled/hulled, their oils turn rancid more quickly. When they’re chopped or cracked, the oxidation process happens even faster. I have thrown away several jars of rancid almond butter that didn’t get eaten quickly enough. Early in my medical training, I studied the biology of cancer with a great professor at UMass Amherst named Dr. Albey Reiner. I’ll never forget how adamant he was about avoiding rancid oils. He once said, “If you ever put a bad nut in your mouth, I don’t care if the Queen herself gave it to you, spit it out.”

Some foods resist rancidity better than others. Flax seed goes rancid quite fast after being ground, so I always tell patients who like ground flax to buy it whole, grind just what they need each day, and throw out (or at least refrigerate) any extra. Saturated fats – those that stay solid at room temperature (such as coconut oil, butter, and lard) – are less susceptible to rancidity. Polyunsaturated fats – the ones that stay liquid even when cold (most vegetable oils) – are more susceptible to rancidity. Monounsaturated fats, such as olive oil, fall somewhere in between.

Although grains are less oily than nuts, they still have a tendency to oxidize after being ground. Thus, flour is a commonly overlooked source of rancid fat. Learn to smell rancid flour. I once put an old Saltine cracker in my mouth and immediately realized it was revoltingly rancid. Many people who don’t know what rancidity is might have thought it was merely stale. In this case, the cracker was offered to me by a relative in a social situation where it would have been difficult to tactfully get it out of my mouth, so I managed to swallow it. But my daughter had a handful of them and I was determined to not let her eat them, so I distracted her (she was three years old – it wasn’t hard) and switched the crackers out for an orange. Besides the rancidity factor, any food that is ground to a fine powder – such as flour and ground spices – has so much surface area that it will quickly degrade and lose its nutritional value. This is why powdered spices lose their flavor much faster than whole spices. So, if you consume flour, try to use fresh flour. You can even get a small grain mill and make your own if you don’t bake very often.

While rancid oils in food have gotten some press, I haven’t heard anything about the issue of rancid oils in skin products. These, too, are worth avoiding – especially if you use large amounts of them (such as body oil).  Our skin is highly absorbent, especially of oils. If you’ve ever put some oil on your skin and noticed that after a little while your skin isn’t oily anymore, it’s because your skin drank most of it up. I have purchased sticks of natural lip balm that were already rancid when I first opened them – and these are meant to be applied to the thin, super-absorbent skin of the lips! Free-radicals are a major contributor to the aging process. Why speed up this process by administering them directly to your skin in the form of rancid oils? Start sniffing your lotions and cosmetics and toss them if they’re rancid. Unfortunately, if they’re strongly scented, this may mask the smell of their rancidity.

What to do: Throw away rancid oils. Buy oils, nuts, grains, and flour in small enough quantities that you’ll use them up within a few months at most. Keep them in dark, cool places. You can break open a few vitamin E capsules and add the contents to your oils; because it’s a antioxidant, it will delay rancidity (but won’t prevent it altogether). Wrap oily foods well and store them in airtight containers. It’s a good idea to treat skin products similarly, though they usually contain stronger preservatives that protect against rancidity. Consider taking a few thousand milligrams of vitamin C daily – it’s one of the best and safest antioxidants. Antioxidants, as the name implies, protect against oxidation and sometimes reverse oxidative cell damage.  (Some other powerful antioxidant nutrients include beta carotene, manganese, lycopene, lutein, selenium, and coenzyme Q10). Finally, eat lots fresh fruits, vegetables, and spices (rosemary, sage, garlic, etc.) since they are the most abundant food sources of antioxidants, and of course, they’re just plain good for you.

(1) Kanner J. (2007, Sept.). Dietary advanced lipid oxidation endproducts are risk factors to human health. Molecular Nutrition & Food Research. 51(9), 1094-101.

32 Comments

  1. Gaye Ringness

    April 2, 2014 at 9:41 PM

    Hello Dr. Borten,
    Thanks for your article. I found it most helpful in the midst of the sea of blogs sharing experiences and opinions. I’m in search, however, of an answer to this question: What can I eat or take to alleviate the nausea I’ve been feeling after having eaten a bag of un-shelled peanuts that were very possibly rancid? I so enjoy nuts of all types that I didn’t take notice of its rancidity. I threw up that night, though not the peanuts unfortunately, and have been off most food since…. it’s day 4.
    Thanks again and I look forward to any assistance you can offer.

    • Peter Borten

      April 3, 2014 at 3:45 AM

      Hello Gaye,
      Sorry to hear about your ingestion of rancid peanuts. I like to see a patient’s tongue and feel their pulses before writing an herbal formula, but there are a few generic formulas and other remedies that would probably work just fine.
      One is a patent formula called Pill Curing, also known by the common Chinese misspelling Pill Culing. You can Google it and find many sources online, or if you live near a Chinese market, you can find it there. It comes in vials, each containing dozens of tiny pills. You can take one or two entire vials at a time, three times a day.
      Another option is activated charcoal capsules. Activated charcoal is an adsorbent that binds up poisons and carries them out of the body. A drink (slurry) of activated charcoal powder in water is used for many kinds of poisoning. However, it’s questionable as to whether this would really help at this point, since the peanuts are presumably long out of your body.
      Next there’s good old ginger. Grate fresh ginger (about a 1 inch piece) and pour boiling water over it. Steep for 10-15 minutes, then strain and drink. You can do this a few times a day.
      Some other good anti-emetics you could probably get your hands on are cardamom, mint, and chamomile. You can make strong teas of one or more, and drink liberally.
      After consumption of rancid oil, it’s a good idea to take some antioxidants (though I wouldn’t expect this to help your nausea), such as vitamins A, C, and E, alpha lipoic acid, etc., or antioxidant foods like green tea, fresh, colorful fruits and vegetables, garlic, rosemary, oregano, etc.
      To be honest, I can’t think of a reason why rancid nuts would do this to someone, beyond perhaps the initial event and maybe the next several hours. It makes me wonder if the peanuts were contaminated in some other way, or if you have an unrelated GI virus, or if you contracted food poisoning from another source. Food poisoning usually doesn’t last this long, and is typically more violent and affects, ahem, both ends of the GI tract.
      Best,
      Peter

  2. Thank you for making this website so easy to find info. good stuff. Saving this one for later.

  3. Hi Peter, I am taking these B vitamin capsules from Emerald Laboratory. It’s a raw whole foods formula, called coenzymated B healthy. They sound like the perfect choice but taste rancid to me. I am wondering if I am confusing the rancid taste with the taste given by the mix of all those plants that are in the blend. Also, what can get rincid in this plant mix. Can it be the raw whole food sprout powders ( alfaalfa, quinoa, Mung Bean, millet, Broccoli)? What is your opinion: should I trash them? Thanks!

    • Peter Borten

      May 14, 2015 at 8:59 AM

      Hi there. I do like food-based supplements, though I have wondered if the organic compounds, especially once finely powdered, are susceptible to degradation. Rancidity pertains to fats specifically, and these plants are very low in fat. However, the part that’s highest in this case is the seed, and that’s what these sprouts are made from. In the sprouting process, the seed coat breaks open, making the contents more susceptible to oxidation through exposure to air, light, and moisture (all of which are present for sprouting). Then I’m assuming they’re dried, ground, and encapsulated. It’s not the first thing I’d think of as being susceptible to rancidity, but it does seem possible. I have smelled rancid millet and quinoa, but not mung beans, broccoli seeds, or alfalfa seeds. The sprouts have some sulfur in them which could be contributing to what you’re smelling, though to me that smell is different from rancid fat. So, I guess I haven’t given you a straight answer, which wouldn’t be possible without my smelling them (and even then I could only guess, if it’s a complex smell), but I can only say “it’s plausible.” You might call the company. At the very least, they’ll probably send you a replacement (hopefully from a newer batch). More companies are switching from expiration dates to manufacture dates … maybe they can tell you the manufacture date if you give them the lot number. I’d doubt a product like that could last much more than a year. Be well, Peter

      • Thank you, Peter, for your reply. I appreciate very much the information you provided and it also showed me that my way of thinking was on the right path ( as in: there are not so many fatty things inside, to get rancid). Also, even if I don’ t feel like there is the sulphur smell, I remembered that a similar smell I could feel inside any jar of Psillyum I’ve put my nose in. I always called that ” rancid”. Does this particular smell of the Psillyum sounds familiar to you? Maybe I was not lucky and not all Psillyum smells like that (i.e. is rancid(?)). If you know what I mean, would you call that rancid? On another hand, I checked expiration date on the vitamin bottle and it is Jul 2017, so they seem to be quite “fresh” (I suppose validity time is 3 years). I think it is a good idea to contact the Company and ask about the strange smell, so I will do it! Thanks so much for sharing the knowledge with me and all the others!

  4. sir,which criterion we should use to check if a brown walnut is infected from inside.(in terms of smell,taste & insect if it is there).

    • Peter Borten

      November 20, 2015 at 8:05 PM

      Hi Ajay, Sorry – I don’t know! I would say you’d have to open it to see. Maybe someone in the walnut industry could tell you.
      Peter

  5. Hi quick question. I have an abrasion and I saw coconut oil was a good remedy so I applied one I had found experation says 2020 so I used it. Later finding a mother jar and seeing it looks and smells just a tad different. I think the one I applied to my wound might have been ranced. Is there any harm that can come of this??? I washed it off about 5 minutes after applying because I researched into it

  6. Here’s a funny story. A while ago I became concerned about what rancid oil smells like, so I sought an answer in a chefs’ forum. I posted a question along the lines of “Have you ever found nuts that tasted like linseed oil window putty? Any opinions/advice?” The reply came back “Yes you’re a d…ck!”. Then the forum’s moderator stepped in and said there was no need to be so rude – even if weird people asked daft questions about food tasting of strange things. This sparked off a heated debate about whether off-topic posts should be banned. I said I was surprised because I had assumed that most chefs were gastronomic experts, concerned with the finer study of flavour, aroma and nutrition. My mistake. Looking through the other threads on the forum, I saw they usually discuss how to create meals from leftovers.

    • Peter Borten

      November 30, 2015 at 5:25 PM

      Oh geez. Thanks for sharing. Unfortunately, I’m not sure your story is what I’d call “funny.” It’s a shame, really, that people exploit the anonymity of internet forums to unleash their most immature, hurtful emotional toxins. Clearly, there are a lot of people out there who have some deep pain and don’t know a healthier way to manage it … or can’t be bothered to take a moment and ask themselves, “Is this the kind of energy I want to put out in the world?” or “Is this who I want to be?” I’ve definitely had a handful of such comments on my site, where someone decided what I had written was bullsh*t and thought it was purposeful to tell me so in a cutting, accusatory way.
      Oh well. Luckily there are millions of people out there who are inspiring, beautiful souls, doing really impressive work, creating amazing art, loving with all their hearts, etc., and I firmly believe that cultivating these higher states of consciousness is therapeutic for everyone. These saintly people are elevating even the internet trolls!
      Anyway, thanks again, Jason.

    • To the rancid subject: All the walnuts I have bought in the last year or so were rancid (Harris Teeter, Food Lion, Aldi, Wal- Mart). The only ones that tasted fresh were from Trader Joe’s. They don’t sell online. Pecans and almonds are most always fresh tasting.

      • Peter Borten

        August 9, 2016 at 8:23 PM

        Thanks, Helga. Yes, walnuts seem to be quite prone to rancidity, though I agree – I have gotten some recently from Trader Joe’s that were great.

  7. How can I get nuts esp. Brazil nuts that are not rancid and should I store them in the fridge? Brazil nuts have selenium in them and a good source of it. But when they came they already smells rancid I just thought I’m too sensitive maybe they put an oil on the outside and that goes rancid could that be? Any advice on this would be helpful.

    • Peter Borten

      August 9, 2016 at 8:35 PM

      Ah yes, Brazil nuts are probably the most-often-rancid nut I’ve encountered. I don’t have a good answer as to where to buy ones that aren’t rancid, but you might want to look for a store that goes through their stock quickly. Then, yes, store them in the fridge in an airtight container.
      – Peter

  8. Hi

    I bought a bottle of Argan oil to use on my skin on a trip last year to Morocco. I forgot about it and recently opened it to use and noticed it had a funny smell when I inspected the bottle I noticed it had white spores on the bottom of the bottle. I think it’s safe to say it’s gone bad. I wonder if there is a fix or if I can still use? I know you stated we shouldn’t use bad oil but I was hoping Argan oil is different.
    Thank you 🙂

    • Peter Borten

      August 9, 2016 at 8:28 PM

      I would guess that it’s not good anymore, though I don’t know enough about argan oil to say whether it’s possible that what you’re calling “spores” are actually some other natural phenomenon that occurs with that oil.
      – Peter

  9. Great information! Made a box of lemon bars tonight and they tasted terrible. After looking around on the web, discovered that something in the box must have been rancid. Also had some raunchy saltines in my house a while ago. It was a mystery as to why they smelled and tasted terrible. I never knew they could actually go bad. This will definitely change the way I purchase some of these items. Thanks for the info!

  10. So i just went to andy frozen custard and a concrete with oreos pecans and hot fudge while i was eating it i did noice there was an off taste to the pecans but me being 19 i did not think too nuch off it until 30 mins im on the tiolet with one diarrhea 🙁 now should i be worried about cancer this is the first time to my knowledge. Eating i guess bad nuts so ik wondering is the cancer aspect more on if u eat a lot of them or one time and BAM! kind of freaking out cuz nobody wants the i gave ny self cancer feeling ever.

    • Peter Borten

      April 12, 2016 at 5:16 AM

      Don’t worry about it! You’re young. Your body is still excellent at finding and killing pre-cancerous cells. You’re doing it all the time.
      If you’re really feeling paranoid, take 1000-2000 mg of vitamin C 3 times a day for a few days.
      As you get older … 40s, 50s, 60s, 70s, your body will get less effective at managing oxidative damage, but at age 19, you’re fine!

  11. I just opened a box of bilberry tea that smells like rancid oil. Can bilberries go rancid?

    • Peter Borten

      May 17, 2016 at 9:20 PM

      That’s an odd one. I think it’s highly unlikely that the bilberries themselves would go rancid. Moldy, perhaps, but there’s not enough oxidizable oil, I would think, to produce a rancid smell. And you’d think the innate antioxidants in the bilberry would prevent that. Perhaps something went wrong in the manufacture process (like molding) or they were sprayed, treated, packaged, or contaminated with something that’s responsible for what you’re smelling.

  12. gregory barton

    June 2, 2016 at 6:57 AM

    Hi, thanks for a great post. I have a question. I live in Australia, and its almost impossible to get fresh walnuts out of season. The ones I buy shelled are almost always stale. But is a stale walnut a rancid one? I always assumed if it is not bitter, then its not rancid. But Im getting worried. Can you advise?

    Kind Regards

    Greg

    • Peter Borten

      August 9, 2016 at 8:26 PM

      Hi Greg,
      It’s hard for me to say without smelling them myself, but I think I know what you mean, and I’d guess that what you’re calling a “stale” walnut is probably not rancid, or is minimally rancid. Of course, rancidity isn’t like an on/off switch – the oxidation of fats in food products is a gradual process. So every time we eat seeds, nuts, and oils, we probably consume a certain percentage of oxidized fat. I think you’re probably ok eating your stale walnuts as long as they don’t smell frankly rancid, though you might want to take some vitamin C with them, or another antioxidant, or consume them with an antioxidant-rich food.
      Be well,
      Peter

  13. Thank you for the very informative article. I bought a bag of chopped walnuts yesterday so. That I could make several liaves of banana bread for the weekend. When I opened the bag, I knew immeduately that something was wrong. The chemical smell was quite strong. Since the exp date on the package is june 2017, I called the manufacturer/producer to inform them, giving them the lot number. I intend to take the bag back to the store. I don’t care about a ‘refund’, I just hope that someone with a less informed ‘nose’ will not get sick! Again, thank you for making ‘rancid’ so clear.

  14. Hi,

    Please help! I used rancid coconut oil in my hair 3 times over the past week or so. I didn’t realize it shouldn’t smell like that. I massaged it into my scalp and on my body, and now I’m worried that it may be causing the recent hair loss I’m experiencing, or could be very hurtful to my body.

    Do you think rancid coconut oil could be causing hair loss? What can I do to try to counter the effects and detoxify my skin and scalp??

    • Peter Borten

      August 9, 2016 at 8:22 PM

      Hi Jasmine, I would be pretty surprised if the rancid coconut oil affected your scalp in a significantly negative way from just three applications. I wouldn’t expect anything negative in terms of whole-body effects from just three times, either. You could try enlivening your scalp with a mixture of about 25% apple cider vinegar in 75% water, and then add a few drops of essential oils of tea tree, peppermint, and rosemary. Work that into your scalp, let it sit for a few minutes, then rinse. Also, it wouldn’t hurt to eat more anti-oxidant rich foods.
      Be well,
      Peter

  15. It is such a helpful article. I want to know that I am trying flaxseed oil remedy for greying hair, but the problem is to get fresh flaxseed oil here. Can you suggest a suitable alternative for flaxseed oil that is equally nutritious, easily available and does not get rapidly rancid . I bought flaxseed oil but it tastes strongly nutty and like bitter almonds, looks crystal yellow, and smells nutty but now I am confused to use it or not because I am not confirmed it is rancid or not. Would you kindly tell whether these are signs of a rancid oil or not because I heard there is always slight bitterness in flaxseed oil .

    • Peter Borten

      December 1, 2016 at 10:18 PM

      Once flaxseed oil is opened, it needs to be kept refrigerated. It DOES go rancid quite quickly if not refrigerated. BUT, it sounds like you may just be tasting the usual flaxseed oil taste, which is slightly bitter and a bit unpleasant to me. There ARE some flavored flaxseed oil blends out there now which you may prefer. The other option is to get fresh bulk flaxseeds and use a coffee grinder to grind up a few tablespoons each day and eat it in a smoothie or in cereal or over a salad. Just grind up only as much as you’ll eat immediately.
      Be well,
      Peter

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