In Part 1, we looked at the fundamental underlying structures of fats & oils, and naming conventions. Now, we’ll explore how this is relevant in a more practical sense.
First, let’s look at stability. Oils, like any raw rood, have limited shelf lives. This is important to remember to ensure proper storage conditions in the kitchen to prevent spoilage. Relatively, saturated fats are the most stable during storage, and conversely, the more double bonds, the less stable (more precisely, double bonds are more reactive in fatty acids than the single bonds are). Heat, light and oxygen from the air can speed up the degradation of fatty acids.
With food, this is is relevant when storing cooking oils. The fridge is a good place for storing flax and camelina oil, or even olive oil if you let it sit for a few minutes to warm up before you want to use it (this will let the solidified part liquify again). Before it gets to the grocery store, oil has too be squeezed out of the seeds or fruits it comes from, so processors need to be aware of this through the whole process. Have you seen how oil is extracted? Here’s an animation of a mini screw-press, showing oil being squeezed out and the non-oil part (“meal”) being separated (no, not sponsored):
Imagine on a large-scale, these can heat up quite a bit and there is air (thus, oxygen) all around, so processors have to calibrate equipment to prevent that spoilage.
For non-food use, this can also cause headaches as far as feedstock storage life will go, and also introduce the need for upstream treatments prior to converting it to biofuel. Watch for another post specifically about biofuels.
The next characteristic summarized is variation of chain length:
We typically see labels referencing fatty acid length on some coconut oil labels, for example, “medium-chain triglycerides” or MCT. Again, such a label is incomplete data – are these MCTs saturated? Monounsaturated? Polyunsaturated? What length are they within the “medium” category? How do they compare to MCTs of other plant oils, with the same or different characteristics? What does the diet look like into which MCTs might be added and/or increased? There have been quite significant marketing efforts, which may or may not be sponsored, around eating more MCTs and/or substituting longer-chain fatty acids to enhance weight loss. It appears such claims are based on 2 concepts: that MCTs are biochemically “processed” differently in the body than are long-chains, and thus where they end up differ; and, that per equal amounts of MCTs or long-chain fatty acids, more energy is used to process the MCTs. I think it’s important to consider the context (ie. diet) in which these are being examined, and consider that other factors such as intensity & frequency of exercise, and/or caloric intake to energy expenditure, should also be considered. Another question that I have in this context is: rather than choosing the “lesser of two evils” – substituting one saturated fat with another saturated fat simply because one burns a bit more energy to digest – why not just reduce or remove altogether the part of the diet that has detrimental effects??
It seems there is merit in using coconut oil in topical applications, but can have adverse effects on cholesterol levels when ingested. A bit further down in this post, there’s a chart to compare total saturated fatty acid content to other fatty acids, in several plant oils – worth taking an objective look at. There are tons of studies and reviews out there, and it’s always worth looking at who’s publishing the data/reviews (just like it’s important to note any sponsored or affiliate promotions with critics’ or supporters’ posts) but I think the jury is still out on the health benefits or risks of regularly ingesting large amounts of coconut oil. Any political or economic agendas that exist, as they do with most food commodities, are beyond the scope of this post.
Ok so remember, saturated fats cannot have double bonds; unsaturated fats must have at least one double bond:
Think back to the frozen vs. liquid water analogy in Part 1: something is solid when the molecules are physically packed close together and not “vibrating” much with energy, and to melt it (in other words, to force the molecules apart) requires more energy to be added; this is the case for most things regardless of what molecules it’s made of. Changing state basically results from the amount of energy (heat) added or taken away; the temperature at which the transition between solid or liquid state depends on chemical structure (what molecules it’s made of).
Generally, the more simple and linear the molecule, the “easier” (ie., the less energy needing to be removed) it is to cause that transition from liquid to solid. Put another way, temperature doesn’t need to be forced as low to cause “freezing” in something with high content of linear structures, as compared to something with many bent or non-linear structures. Think of a stack of paper for a printer: you might have a hundred pages that, when stacked flat fresh out of the package only take up a few centimetres of height, and a breeze from walking past the stack quickly won’t really cause them to blow around. But, imagine if you folded each paper in half, then unfolded them, and stacked them up again: the hight of the stack is going to be taller because physically, they don’t line up as closely anymore. Quickly walking past them could cause some disturbance, and you’d have to apply quite a bit of pressure on the stack of papers to get them to stack in as short of a pile as they would without creases. The more creases in each individual paper, the less densely they stack together.
In the case of fatty acids, it’s a similar idea, and you can probably find examples at home: have you ever put olive or flax or olive oil in the fridge, and even though it’s not spoiled, there seems to be solid chunks at the bottom of the bottle or flakes floating around? Well, (assuming you weren’t eating toast over top of the open bottle for some reason) the solid parts are the saturated fatty acid component of the oil – the proportion that doesn’t require much energy be removed to “freeze” – have settled together until more energy is added (ie. removing the bottle from the fridge at ~4°C, to room temperature at ~23°C). Keep in mind that plant oils are mixtures of several different fatty acids; I think waiting a few minutes for the floaties to melt is a small price to pay to prolong the life of the healthy unsaturated fatty acids by refrigerating them. More details about the number of double bonds are summarized here:
These characteristics also influence how & where they’re used in the body, once eaten. Hopefully by now it’s obvious that a “one size fits all” approach doesn’t work too well when it comes to choosing what fats & oils to use in the diet. There are a lot of research publications and reviews out there that go deep on this topic. Fatty acid imbalances can have impacts on things from energy metabolic disease, to cancer, to neurological disorders, to immunological disorders.
So, now we’ve illustrated what all these labels are referring to, how important they are, and how to store & use them, you’re wondering, “ok, so which is the best oil?” I can’t answer that. What I can suggest is: what are you trying to achieve with any particular oil, and how are you using it? Take a look at this handy chart from the Canola Council (also not sponsored). Note that “essential” means your body can’t construct the molecule from other foods you ingest, so you have to find it intact from food sources):
This is a great resource when it comes to identifying the qualities of common plant oils (& lard) that are used in the kitchen. Consuming these sources raw (assuming seeds are broken), buying the bottled oil, and/or buying the encapsulated supplements are all good options – just make sure you check the expiry date before buying and store them properly. A lot of nuts also have these oils – check the Canada Nutrient File for detailed nutrition information. I actually store my omega fatty acid supplements in the fridge even though the label doesn’t state that. This is because mine also have a couple other omega-3s added: Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA) (and the cool temperature won’t harm anything, so why not?). EPA and DHA both originate from marine sources, but where I live it’s more economical to consume them in supplement form than regularly buying fish, unfortunately. (side note: these are considered “conditionally essential” since the body can actually synthesize them in trace amounts in specific conditions 1, 2, 3). EPA and DHA are 20-carbon and 22-carbon length fatty acids (see Part 1 if this doesn’t make sense), extremely healthy, but also very prone to degrade if not stored properly. All omega-3s and omega-6s are super healthy, but to simply say, “I add omega-3s to my diet” isn’t the full story (see Part 1). Because even though it’s important to get omega-3s from the diet, each will have different functions. EPA and DHA are particularly significant in cognitive function, for example.
Sometimes people ask if it’s better to eat oilseeds directly or to use the bottled oil. The short answer is that there should’t be a difference, with a few caveats: For the seed, it’s important that the seed is broken open so your body has access to the oils once eaten, rather than have them pass through the system intact. Also with seeds, you’ll get a lower quantity of oil per unit bought compared to pure oil, but you also get fibre and other nutrients that a seed could provide, so it depends what else you’re eating with it. Buying the oil will be more cost-effective in terms of oil per dollar spent, but you’ll be eating less of the other good stuff. A bottle might have a shorter shelf life compared to the whole seeds, once the bottles opened.
Here’s another factor to consider: it has been hypothesized that until very recently in history, omega-6s and omega-3s were consumed in relatively equal proportions, 1:1 or 1:2; in North America, this has severely shifted to 10:1 to 25:1. Why is that significant? Well, remember that molecules from food, such as fatty acids are sometimes used as the starting point to create more complex molecules with different functions in the body. It turns out that omega-3s and omega-6s compete for the same biosynthetic pathway in the body; depending on the input (the fatty acid), the output can be pro- or anti-inflammatory:
So by diets changing over time to shift the input from 1:1 in the past, to ~25:1 today (in other words, wayyyy more omega-6s than omega-3s), we’re constantly overloading our bodies with the inputs for the pro-inflammatory effects. Chronic inflammation is associated with a plethora of illnesses.
Understanding these aspects, you can make a general rule of thumb for grocery shopping, proper storage or food prep. The types of fatty acids in the oil are not only relevant to whether it’s solid or liquid, but also to its shelf life and also dietary implications. Due to the chemical nature of double bonds, they are relatively more prone to be degraded compared to single bonds; when double bonds are degraded, it can cause “free radicals” – basically rogue electrons – to start bouncing around wreaking havoc on other molecules, which of course is a bad thing when those molecules are part of your body. Both heat and light will speed up that degradation, and thus to slow or prevent that degradation, high PUFA-content oils should be kept in lower temperatures in the dark (ie. in the fridge). This is also why some oils come in dark-tinted glass, or non-transparent bottles, and why you usually find flax oil in the fridge in the grocery store. (I think camelina oil should also be stored this way but I’ve only seen it on the shelf at room temperature). Indirect heat (such as baking in an oven) is less severe than direct heat (for example, pouring oil into a pan and heating it) and the latter will have the most severe effect on degrading high-PUFA oils, but note this doesn’t happen instantly, so don’t think you need to immediately stop frying with oil..!
Knowing different “smoke points” of the oils you’re cooking with – basically, the temperature at which the oil degrades and starts burning – will help optimize your diet too (adapted from Canola Eat Well):
(typo edit: sunflower high oleic should read sunflower high oleic cold press):
The green dotted line represents medium/high frying pan temperature (~180°C) that the oil would be in contact with. NOTE that this is just a rule of thumb, not precise, since pan material, stove type, duration of cooking, stove settings, etc. could all impact this cutoff point. Both saturated fat (the red, in the previous chart comparing profiles of different plant oils) and monounsaturated fat (the bright yellow) are quite tolerant to higher heats, and that’s reflected in this smoke point chart.
There’s one more aspect that is important to note as you’ll likely see it in the grocery store. Below is an illustration of several processes to reach the end product, the bottled oil – each line represents a different processing path that could be taken (the oil would be processed in only ONE of these flows, NOT all of them together! I just put them all on one illustration – follow the colour-coded paths). Here’s an overview of extraction starting with a screw expeller common to most plant/seed oil extraction processes. The new labelling information that I hadn’t previously mentioned is the “virgin” and “extra-virgin” labels are, however, these are normally only seen on olive oils:
Here’s something kind of neat: region and climate can slightly influence the colour, flavour, and nutrients in an oil, to give it a distinct “terroir” – the “taste of place” (in some parts of Italy, olive oil terroir tours are typical, similar to what you’d expect in wine country!). Some canola producers initiated a similar marketing campaign, I think this is really cool, an approach that maybe more of the agriculture industry in Canada could capitalize on!
To be clear, (with the exception of trans-fat), none are inherently “good” or “bad;” this depends on what you’re using the oil for – what your end goal is. There are also vitamins and antioxidants in oils; basically, the darker the colour, the more of the “other stuff” you get with it. Here’s an interesting note though; this podcast goes into detail about olive oil, and suggests that most Americans associate rancid oil as the definitive olive oil flavour! But, I’ve opened new bottles of flax oil, stored in the fridge, and it was still rancid. I eat it often so I’m familiar with the non-rancid flavour, but I wonder how many people buy it once in a while, store it in a cupboard for a year, and associate the rancid flavour with flax oil (similar to the olive oil podcast), because it’s all they know? (FYI you can return it if it’s not past the expiration date and rancid). Yeah, if you store oil above the stove, that’s one of the worst places. You could refrigerate most of it, and then add some to a small container to keep beside the stove instead. How do you even know if it’s rancid? Usually the rank smell it gives off is a good indication. It’s a similar distinct odour of rancid peanuts, for example. The higher the saturated fatty acid content, the less prone the oil is to spoiling and going rancid.
This is an interesting battle that the food & agriculture industries are up against. High value commodities can fetch a premium price, but with that comes a lot of attention. This means that premium food commodities are targets of fraudulent activity, meaning that these foods commonly targets of adulteration – basically, minimizing content of what it’s labelled as, and using a cheaper (and less healthy) alternative. Honey and olive oil are common targets of this adulteration. How do you know that the olive oil you’re buying is indeed olive oil?? How can countries protect against this when foods are produced prior to import??
I think the blockchain approach has a lot of merit here. Imagine a Google Sheets file that everyone in the world can view and add to, and once the data is entered, it cannot be erased or edited; each block of data would be connected in a linear fashion so it can always be traced back to its origins. The Google Sheet, although only one master copy exists, is backed up across multiple servers around the world, resulting in a decentralized database that cannot be falsified or disputed. Similar to crypto currency. Maybe I’ll do a dedicated post on this topic…
Anyways, in summary, here’s a generalized chart to consider for your kitchen escapades:
And a quick guide simplifying the previous illustrations, to show relationships between different fatty acids:
There is a phrase that says, “the dose is the poison.” In other words, anything can be good or bad for you depending on the quantity ingested. Absolute praise or demonization of something should raise flags about underlying agendas. To reiterate, no plant oils are good or bad; it depends on what your goals are. Budgets, health conditions & goals, food texture, kitchen equipment availability, geography, and desired flavour & aroma can and should all be considered when making dietary choices around fats & oils. Arm yourself with information, call BS when you see it, and make informed decisions.