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The True Shelf-Life of Cooking Oils

Cooking oil manufacturer “best-by” dates are put to the test by comparing the development of rancidity between almond oil, avocado oil, hazelnut oil, macadamia oil, grape seed oil, rice bran oil, toasted sesame oil, and walnut oil.

August 7, 2012 |
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Supplementary Info

The True Shelf-Life of Cooking Oils, 5.0 out of 5 based on 5 ratings

Sources Cited

Kochhar SP, Henry CJ. Oxidative stability and shelf-life evaluation of selected culinary oils. Int J Food Sci Nutr. 2009;60(Suppl 7):289-96.

Acknowledgements

Images thanks to @kevinv033.

Transcript

When you look at a bottle of oil in the grocery store there are “best-before” date, advising consumers how long they have to consume it before it starts going rancid and builds up oxidation products that can be particularly harmful to human health.

Here are the best-before dates for eight culinary oils: almond oil, avocado oil, hazelnut, macadamia, grape seed, rice bran, toasted sesame, and walnut oil. These are the best-before dates in number of months, counting from the day the oil is made. So if you make batch of walnut oil on January 1st 2012, the best-before date printed on the bottle from that batch would be 12 months later, January 1, 2013. Now this is making some pretty strict assumptions. This is based you are keeping the oil in the refridgerator in a airtight, dark containiner, so it’s not exposed to air, room temperature, or light, particularly after it’s opened.

This group of scientists were skeptical that the companies were printing accurate dates, and so they put all the oils to the test to find out that the true these expirations dates were. Would it match what the companies say? Would the companies put a longer duration trying to make the oil appear more stable than it really is? Or would they put a shorter duration on, to encourage people to buy their product more frequently?

For rice bran oil the company said 7 months. Actual estimated shelf-life found in their tests? 6.5 months. Not bad, pretty close. In some cases, though, the truth was stretched one way; in others it was stretched the other way. Look at almond oil. They said it would last over a year, and it really only stays good for 3 months, and remember that’s 3 months in the fridge, in the dark, and after production, not after when you buy it.

Macadamia oil and walnuts were the real outliers though. Mac oil lasted the longest —over a year, the company totally undersold it’s stability, but for walnut oil, they said a year and it only lasts about 2 and a half weeks, according to testing with the “Rancimat.”

To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring watch the above video. This is just an approximation of the audio contributed by Kerry Skinner.

To help out on the site please email volunteer@nutritionfacts.org

Dr. Michael Greger

Doctor's Note

What's the best way to consume walnut oil? In the walnut itself! (See for example, my video on toxins created by deep frying). But which type of walnuts are the best? Find out in tomorrow's video-of-the-day Black Versus English Walnuts. My latest video on the wonders of nuts was What Women Should Eat to Live Longer, though I have a few dozen other videos on the topic (not to mention a thousand other topics). If you haven't yet, you can subscribe to my videos for free by clicking here.

For some context, please check out my associated blog post, The True Shelf Life of Cooking Oils.

  • Michael Greger M.D.

    What’s the best way to consume walnut oil? In the walnut itself! (see for example, my video on toxins created by deep frying). But which type of walnuts are the best? Find out in tomorrow’s video-of-the-day Black Versus English Walnuts. My latest video on the wonders of nuts was What Women Should Eat to Live Longer, though I have a few dozen other videos on the topic (not to mention a thousand other topics). If you haven’t yet, you can subscribe to my videos for free by clicking here.

    • SJ M.D.

      Another argument to eat a whole foods plant based diet with as little added oils as possible. Oils are highly processed. You can easily get your fats from nuts, seeds, avocados etc.

    • AlanRoy

      What about coconut oil? How does it compare? The health conscious use coconut oil. Diabetics can use it without fear because it balances blood sugar.  It aids uptake of magnesium and calcium, improving dental and bone health.  It helps you loose weight.  It is a good kind of saturated fat that does not contribute to heart disease.  And in my experience, is stable for a year while sitting out on the counter.  Although I do not cook with oils, I understand that coconut oil degrade the least of all vegetable oils when heated. All other oils I only consume as part of the food it comes in.  Flax seed, hemp seed, walnuts, etc.

      • HemoDynamic, M.D.

        AlanRoy,
        In response to “Diabetics can use it without fear because it balances blood sugar.”  Doesn’t follow what I see in my daily practice nor what is well published in the literature. 

         I have had many diabetics turn to Vegan diets and their Diabetes becomes worse.  Then I find out they added coconut oil and Avocados as well) because it’s “good” and their blood glucose goes through the roof!  Remove it and BG goes down. 

        Almost all fats (except Omega 3) appear to cause insulin resistance which has been well documented in the research, so I like to say that there is no such thing as a Good or Bad fat, ONLY essential.  And the only essential fats we need are Omega 3 and 6.  We can synthesize all the other fats.  And how much do we need? About only one half a walnut a day supplies us with all the Omega 3+6 fat we need.

        Regarding Coconut oil here is a recent article showing its detrimental effects on insulin resistance, weight gain and atherosclerosis from Pub Med: http://www.ncbi.nlm.nih.gov/pubmed/20832799.

        If I had more time I would get more of the research regarding Diabetes but here is a nice resource from PCRM: http://www.pcrm.org/pdfs/health/diabetes/DiabetesLitSearchRecentandClassicArticlesontheEffect.pdf

        Please also remember, The Fat You Eat is the Fat You Wear!  So if you want to look like a coconut (nice and round –and hairy?) go ahead and eat one.
        :-}

        • SJ M.D.

          I think it was Michael Klaper M.D. who said: When the pathologist examines the arteriosclerotic plaque (that killed the patient) the answer always come back: Saturated fat and cholesterol, NEVER residues from broccoli and tofu…..

        • BPCveg

          HemoDynamic,

          Have you found any smoking gun proof (in human studies, of course) to support elimination of all non-essential fats (including those of nuts and seeds)?

          Based on my read through Brenda Davis’ book ‘Becoming Raw’, I was of the impression that there are two vegan schools of thought on the fat issue – one school supports very low fat veganism and the other school supports consumption of a diet rich in monunsaturated and polyunsaturated sources (up to 30%) of calories, which is analogous to the Mediterranean pattern of eating. Based on the videos presented on this website, doesn’t it seem like Dr. Greger is supporting the latter school of thought? 

          My impression was that the fat issue was unsettled, which is why I was surprised by your suggestion that we should eat half a walnut per day.

          • Thea

             BPCveg: I don’t know about Dr. Greger supporting up to 30% of fat calories.  From my interpretation of the videos and blogs, Dr. Greger seems to strongly support seed and nut consumption, but in relatively small amounts. 

            For example, in the Uprooting Leading Causes of Death vidoe, Dr. Greger talks about longevity benefits from 2 handfuls of nuts a week.  A week.  A day, that would be like, what, less than quarter cup a day?  And I seem to remember another video or blog talking about the benefits of even a half walnut a day. 

            Dr. Greger’s latest nutrition recommendations are to include a variety of seeds and nuts in one’s diet, but he doesn’t say how much.

            It seems to me that the “no fats” and the “30% fats” proponents are two ends of the spectrum.  What about a healthy middle?

            Just some thoughts.  I’m not necessarily arguing against anything you said.  I’m just participating in the discussion. 

            I know that there are more videos about nuts in Volume 10.  Perhaps we will learn more about nuts then.

          • BPCveg

            Hi Thea,

            I think Dr. Greger hasn’t clearly stated what percentage of calories from fat to consume.

            In his video titled ‘Halving Heart Attack Risk’ on September 4th, 2010, Dr. Greger specifically states that a single handful of nuts per day can cut heart attack risk in half. But, he doesn’t go on to say, don’t eat more than that! In fact, he says ‘don’t ever not eat nuts’.

            In his video titled ‘Plant-Based Atkins Diet’ on February 2nd, 2012, Dr. Greger argued that a low-carbohydrate diet (which according to the study was 43% fat) reduced mortality substantially. In fact, the study also showed reduced LDL in this low carbohydrate diet.

            These are some of the main reasons I think that he is supporting the higher fat end of the spectrum.

            By the way, there are no links in this comment because when I added links it kept getting flagged for moderation and then didn’t publish.

          • Thea

             BPCveg: Thanks for taking the time to clarify your thoughts for me.

            It’s so interesting to me how different minds thing.  I look at that same info, at least for your first example, that you look at and come to a different conclusion.  :-O

            It is telling to me that Dr. Greger hasn’t chimed in on this question, and that his latest “Optimum Nutrition Recommendations” from Volume 10 do not specifically address this question.

            For me, the answer is: do at least the minimum amount of recommended nut/seed intake and then take more only if your calorie requirements allow.  But that’s just my take on it all.

          • BPCveg

            Thea: I agree with you that there is definately some ambiguity on this topic, given what has been said on this website thus far. In the meantime, your suggested answer sounds very reasonable.

            Thanks for the exchange of opinions. Hopefully we will get our answer soon.

          • Michael Greger M.D.

            I believe posts with links only get flagged if you’re not registed. This

            is to prevent spammers that aren’t registered from junking up the blog. So please register and link like crazy!

          • BPCveg

            By the way, Brenda Davis, an experienced dietician who specializes in whole-foods vegan diets recommends 15-30% of calories from fat.

            The main arguments that she gives against the low-fat vegan diet are:

            ”
            Very low-fat diets may provide excessive bulk and insufficient calories,
            particularly for infants, children, and people with very high energy
            requirements, like athletes or labourers.
            Very low fat diets often contain inadequate amounts of essential fatty
            acids, especially the omega-3 fatty acids (discussed below).
            Insufficient fat can compromise absorption of fat-soluble vitamins (A, D, E,
            and K), minerals (including iron, zinc, manganese, and calcium), and healthful
            phytochemicals (like the lycopene in tomato products). 
            People on very low fat diets often become “fat phobic.” They assume all high
            fat foods are bad and that all low fat foods are good. This often leads them to
            choose foods that are actually “nutritional washouts” (packaged fat-free
            cookies, cakes, and chips, for example) while obsessively avoiding higher-fat
            plant foods that are very nutritious, like avocados, olives, nuts, seeds, and
            tofu.
            Very low fat diets can cause a drop in HDL-cholesterol (“good
            cholesterol”) and a rise in triglycerides (another potentially damaging blood
            fat, like LDL-cholesterol), actually increasing your risk for
            cardiovascular disease. However, this is not normally a problem unless you
            replace the fat with refined carbohydrates, like sugar and white flour
            products.”
             
            You can find the source document by searching on google “brenda davis winnipeg making sense of fat” –> leads to a ivu page.

          • Thea

             BPCveg:  I’m a big fan of Brenda Davis!  I heard her talk at at a conference a couple of years ago and she had a huge positive influence on my thinking that I could “do vegan” healthily and it wouldn’t be hard.  I read one of her books and thought it was most helpful.

            Thanks for sharing that info! 

            One thing that strikes me from that text is that, in my humble opinion, 15-30 is a wide range.  For me, 30% seems high and 15% seems “low-good”.  But that’s my intuition, not based on anything I can point to.

            I’ve never seen the point in a super-low fat diet when the fat comes from whole foods.  My concern is when people see 30% and assume that means that the fat can come from oils and they are eating healthy.  It seems to me that the discussion on fat always needs to be put into context for people – that healthy fats are those that come from whole plant foods (with some exceptions like coconut).  If everyone were on the same page on that one point, then the discussion of what percentage of our diet ideally comes from fat might become much less important or resolve itself differently.

          • BPCveg

            Then we agree that:

            Oils are bad;
            Whole fats are good;
            Brenda is awesome!

            :)

          • GSH

            BPCveg I think dr. hemo was referring to the study regarding the 1/2 walnut per day. “Who could eat just 1/2!”

            If I didn’t eat nuts and seeds I would have the hardest time maintaining my weight.

          • BPCveg

            Good point GSH.

            By the way, as a vegan, I have found that adding more liquid calories to my diet (from soups and smoothies) also helps me from losing weight.

          • GSH

            Here we are struggling to maintain our weight and 1/3 the population is getting fatter by the day!

            Eat plants!

          • HemoDynamic, M.D.

            This is a complex question to answer but the short of it is, it depends on what you are trying to achieve.

            Remember, the fat you eat is the fat you wear so if you are trying to lose weight then minimizing fat intake with have the greatest impact on weight loss, since the body loves to store a ready-made package of fat.  It doesn’t have to convert it to anything it just stores it (this is somewhat simplistic but is basically what happens).

            So this is where the one half a walnut a day comes in.  One half a walnut weighs in at about 1.5 to 3 grams depending on size. There is 90 mg Omega 3 per 1 gram of walnut, so we are looking at 135 to 270 mg Omega 3 per half a walnut.  http://nutritiondata.self.com/facts/nut-and-seed-products/3138/2

            The general consensus for Omega 3 daily intake is about 250-500mg (Because of its alpha-linolenic acid (ALA) content) http://www.goedomega3.com/health-care.html
            So a half a walnut a day, plus general daily food servings for a Plant Based eater, will more than give us our recommended daily allowance of Omega 3 and Omega 6, for the essential ALA and LA (Linoleic acid) content respectively.

            Interestingly, if you want more bang for your buck than have a Tsp of Flax:  One Tsp is 3 grams which is about 680mg of Omega 3 and 170 mg Omega 6, which is a much better ratio of Omega 3 to Omega 6 (4:1).  Walnuts are a 1:4 Omega 3 to Omega 6 ratio, so not a favored nut/seed in my opinion–but I like to say One half a walnut because it gets my point across as to how little we actually need in our diet. 
            Also remember the more Omega 6 (LA) in your diet the more the conversion to ALA is inhibited, and the more LA the more inflammation (Arachidonic acid).
            Is more better? Maybe to a point but Moderation is a problem with someone suffering from Unstable angina, super-morbid obesity, or diabetes .  So again it depends on what one is trying to achieve.

        • Kathi

           Thank you so much for the info on coconut oil. I generally only use it on my skin. I love coconut so I do tend to probably eat more than the average person (maybe I should cut back some). My dogs do get about a teaspoon of coconut oil in their food daily. Their coats all look great and they are very healthy. But dogs, like humans, can get heart problems. Hmm

          • Thea

             Kathi:  I have a dog who I used to feed some almond oil.  A few years ago, I switched to giving him ground flax seed mixed with water.  He LOVES it.  He slurps it down.  This way he is getting a whole food, but one that is high in healthier fats. 

            I don’t have a study to back up the concept of giving dogs flax seed.  But I did get the idea from a vet who works with vegan dogs.  And you are absolutely right that dogs can (and do) get heart disease.

            I just wanted to share.  Good luck with your dogs.

          • Kathi

             Thanks Thea. I used to give my dogs ground flax and have sort of fallen off of that. Need to get back on it. Funny though, my holistic vet said that the dogs didn’t absorb flax oil the way we do. Maybe it comes from not giving them the whole seed. Off to grind up some flax and pumpkin seeds for them, and me.

          • Coacervate

            Is it ethical to feed a meat eater plants?

  • http://www.facebook.com/profile.php?id=640861216 Gary Yuen

    Really the healthiest thing is ground nuts and seeds added to food. It makes modern recipes perhaps difficult but ah well. Not sure about ghee but I’d guess if it was made from animals that had a plant-based diet as they do in nature, it could be ok as many say.

  • Teepeeb

    Dr. Greger – Great as usual. But how about the very common oils like Olive, Canola & sesame seed? Thank you – Tom

    • http://twitter.com/CheshireKaz CheshireKaz

      That’s my concern – most of us tend to rely on them.

      • Valnaples

        And coconut oil is really being talked up too; so many “health” pages and websites say people should eat it every day…YIKES!! I use the extra virgin coconut oil on my skin as a wonderful moisturizer but I don’t eat it (yet).

    • http://www.facebook.com/profile.php?id=640861216 Gary Yuen

      I use oils only for skin massage. If one is to eat, isn’t it always healther to use a whole food? whole olives or sesame?

  • Thea

    When I use oil at all, I usually use almond oil.  So, this study is very sad for me.  I do keep it in the fridge.  I don’t use much oil at all.  Because I don’t use much oil, it lasts a *very* long time in my fridge – certainly longer than 3 months.  I figure it might even be 3 months in the light on the store shelf before the bottle makes it into my fridge… argh!

    Like the others, I am also interested in olive oil and some others just for comparison.  But this is really interesting data right here.  It says a lot.  Time to get some (probably outrageously expensive?) macadamia nut oil?  I wonder if I could even find it.

    The most oil I use is spray oil – just enough to keep something from sticking.  I wonder 1) should those cans be kept in the fridge?  2) is there any testing on the rancidity of those oils? – which do not see light. 3) how bad for one’s health would it really be to keep say the baking tofu from sticking to a pan using the spray oils even if they are (hopefully little) rancid?

    Just some questions that would be nice to answer at some point.

    • CLC

      Along the same lines as Thea, I am wondering what oil should be used to season a cast iron pan or a steel pan? Some people recommend flax oil, claiming that the seasoning oil needs to oxidize to complete the seasoning process. Is that correct? If flax oil is used, and if it is oxidized on the pan, is there a risk that some of that oxidized oil would come off the pan and be encorporated into the food cooked in the pan? Please advise on the healthiest oil for seasoning cast iron pans and steel pans, especially where such pans will be used for high heat cooking. Thanks!

  • AlexanderBerenyi

    Great find.

    • http://poxacuatl.wordpress.com/ Strix

       Was it lost? ;^)

      I don’t do oils.I like the fruit, the whole fruit, and nuttin’ but the fruit!

      • SJ M.D.

        So help you nut……

        • http://poxacuatl.wordpress.com/ Strix

           :^)

  • LKSkinner

    This latest information about oils helps adds to my thinking that refined products, whether oils or sugars, are harmful for us to consume. 
    The fragility of some of these oils is even greater than what I thought. It seems that once you remove the oil from its “package” all the other attributes of the food that would help preserve the oil part are lost. 
    Also, when we remove the oil for use we lose all the other attributes that make the food fitting for us to consume. 
    So the takeaway here is keep the oil in its “package” for the healthiest eating and to get the full benefit of the food. 

  • JD MD

    This posting brings up a potentially very important issue regarding health-promoting benefits of a plant based diet: How important is rancidity in considering the health promoting benefits of foodstuffs? This is the only video that comes up when searching the term ‘rancidity’. There is strong evidence that rancid foods and the free radicals present within are much more harmful to consume than nothing at all. Given that foodstuffs that have fatty acids can become rancid, some have argued that many of the foodstuffs we buy including whole grain containing foods, oils, nuts, seeds, seed butters, etc are rancid by the time they make it to our homes from the supermarket. I would love to see a more thorough analysis of the scientific literature regarding the harmful effects of buying and consuming these types of foodstuffs from the primary sources available to most of us, supermarkets and health food stores.

    • Mike

      Good question about nut butters!

  • AlexanderBerenyi

    I understand that keeping the oil in the whole food itself is one of the best ways to prevent rancidity, but do you notice a trend here — the higher the ω−6, the quicker the oxidation, & the reverse being true for mono and sat fats? Hence the results for mac oil vs walnut…

  • Thea

    Coacervate: I consulted 6 vets from across the country.  All said that dogs are omnivores and that a vegan kibble would be fine.  Since switching my dog from a meat kibble to a vegan kibble, his health has improved by several measures.  So, yes, it is not just ethical, but a very good idea.

  • Toxins

    We should all remember that oil is not a healthy food and that we should ALWAYS consume the whole food itself

    Dr. Vogel conducted a study that compared different fats and oils (olive
    oil, canola oil, and salmon) and how they impaired our endothelial
    cells. Our endothelial cells are within our blood vessels lining their
    walls. They keep clots from forming and keep our blood running smoothly.
    It also helps our blood vessels dilate and contract when needed. The
    participants of the study ate a meal containing 3.5 tablespoons of olive
    oil and the examiners measured their arterial damage after 3 hours.
    “Contrary to part of our hypothesis, our study found that omega-9 (oleic
    acid)-rich olive oil impairs endothelial function postprandially.” They
    also make note that “In terms of their postprandial effect on
    endothelial function, the beneficial components of the Mediterranean and
    Lyon Diet Heart Study diets appear to be antioxidant-rich foods,
    including vegetables [and] fruits”
    http://content.onlinejacc.org/cgi/content/full/36/5/1455

    It
    was even noted that “In a clinical study, olive oil was shown to
    activate coagulation factor VII to the same extent as does butter. Thus,
    olive oil does not have a clearly beneficial effect on vascular
    function.”
    http://www.ncbi.nlm.nih.gov/pubmed/9409274

    Another
    study looked at different oils (olive, soybean and palm oils). They had
    their patients eat a potato soup. The soup either had 3 tablespoons of
    each oil OR they fried the potatoes in the oil. They too examined the
    extent of damage on the volunteers’ arteries. this is what they found
    “All the vegetable oils, fresh and deep-fried, produced an increase in
    the triglyceride plasma levels in healthy subjects.”
    http://www.ncbi.nlm.nih.gov/pubmed/17174226

    This
    2 year study looked at coronary artery lesions of the heart after
    consuming different types of fat. Polyunsaturated fat (omega 3 type of
    fat) Monounsaturated fat (75% of which makes up olive oil) and Saturated
    fat (the kind found in mostly animal products). They looked at
    angiograms a year apart after intervening with increasing one type of
    fat in each group. All 3 fats were associated with a significant
    increase in new atherosclerosis lesions. Most importantly, the growth of
    these lesions did not stop when polyunsaturated fats and
    monounsaturated fats were substituted for saturated fats. Only by
    decreasing all fat intake including the polyunsaturated and
    monounsaturated fats did the lesions stop growing.
    http://jama.ama-assn.org/content/263/12/1646.abstract?sid=47d1d016-3c15-43f4-a013-0d10144ef8e3

    • Thea

       Toxins:  Thank you, thank you, thank you!

      I’ve been trying to tell some friends that all “free oils” are bad for them.  They are big proponents of olive oil.  They didn’t like the Jeff Novik video I sent.  (personality conflict)  Dr. Greger’s one video that I could find on olive oil found it to be neutral.  (Though that was way back in volume 1.) 

      I think when I pass on your information, it will carry a lot of weight – because you are listing multiple scientific studies and because there is no personality to contend with.

      Thanks!!

  • amcken3

    It’d be nice to know about oils like olive oil and coconut, more popular oils. 

  • CLC

    I am wondering what oil should be used to season a cast iron pan or a steel pan? Some people recommend flax oil, claiming that the seasoning oil needs to oxidize to complete the seasoning process. Is that correct? If flax oil is used, and if it is oxidized on the pan, is there a risk that some of that oxidized oil would come off the pan and be encorporated into the food cooked in the pan? Please advise on the healthiest oil for seasoning cast iron pans and steel pans, especially where such pans will be used for high heat cooking. Thanks

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