Polyunsaturated fatty acids have become a hot topic of debate in the skincare world. Also known as PUFA, these controversial fatty acids can be found in high percentages in popular nut and seed oils like Rosehip, Borage, Almond, and more. Are PUFA really controversial though? Are they unstable and dangerous as some have said? Are your precious facial oils aging your skin aka. doing exactly the opposite of what they claim? Or...is it mostly misinformation? Today, we’re breaking down the science behind polyunsaturated fatty acids in skincare, so you can decide for yourself.
Let’s start at the beginning.
Did you know that the sebum your skin produces naturally contains PUFA? Human sebum contains between 15-30% free fatty acids, along with cholesterol, wax esters, squalene, etc.
"The most abundant polyunsaturated fatty acid (PUFA) in human skin is the 18-carbon fatty acid, linoleic acid...The 20-carbon fatty acid, arachidonic acid, is the second most prominent PUFA in the skin."
PUFA are a necessary component of human sebum and have to be present in order for the other components - including wax esters and squalene - to synthesize.
“Decreased concentration of linoleic acid has been observed in skin surface lipids of acne patients. In particular, its level has been found significantly reduced in wax esters making it reasonable to assume that linoleic acid is directly involved in the sebaceous lipid synthesis.”
In fact, certain skin ‘types’ have been shown to lack PUFA, particularly linoleic acid, which contributes to imbalances and symptoms (ie. acne) that we’ll get into later.
If PUFA are a natural part of our skin, why are some saying I should avoid them?
Great question. The argument around polyunsaturated fatty acids in skincare centers around one main point - oxidation. PUFA haters claim that PUFA oxidize very quickly, therefore causing oxidative stress, inflammation, free radical damage, and ultimately, skin aging. So...are they right? Ehh. Kind of.
According to science, the "oxidation and degradation" of PUFA in human sebum actually initiates an important chain of events that gives sebum it's powerful anti-microbial properties. So, is the oxidation of PUFA always a bad thing? Not necessarily.
"Ge et al. identified stearoyl-CoA Δ-6 desaturase as the major fatty acid desaturase in human sebaceous glands, which induces rapid oxidation and degradation of linoleic acid and its derivatives in sebaceous gland cells. Due to the rapid degradation of linoleic acid in the sebaceous cells, stearoyl-CoA Δ-6 desaturase is able to convert palmitic acid into sapienic acid...Sapienic acid exerts strong antibacterial and antifungal activities."
In the context of plant oils and skincare, PUFA are indeed less stable than saturated fatty acids. This means that PUFA-rich oils do oxidize more quickly and oxidized oils (outside of your skin's natural processes) = no bueno for your skin. Exposure to air, light, heat and free radicals cause this to happen more quickly. You can generally tell if an oil is oxidized by the way it looks or smells - it may change color over time or have a rancid, unappealing scent.
However, just because an oil can oxidize quickly doesn’t mean it will. Steps and measures can be taken to prevent or delay oxidation. These include - adding a powerful antioxidant like vitamin E to the oil, storing the oil in glass that limits UV exposure (ie. miron glass), storing the oil in a cool environment (ie. refrigerator), using an airless mechanism or pump (as opposed to a dropper), and ensuring that the oil is fresh and has been produced in a way that preserves its nutrients (ie. by Co2 extraction or without heat.)
So, while yes, there is a risk of oxidation and you should always buy PUFA-containing skincare from brands you trust (ie. don’t trust super cheap oils!), the point is that there are fresh, unrefined, non-oxidized PUFA that actually have incredible, science-backed benefits for your skin.
So, what exactly are the skin benefits of PUFA?
Let’s look at what the science says...and there’s a lot of science on the function and mechanism of PUFA in skincare.
Polyunsaturated fatty acids have been shown in study after study to help modulate and decrease inflammation in the skin. In fact, certain PUFA are known to be ‘anti-proliferative’ aka. to inhibit the growth or spread of inflammation caused by the free radicals (UV rays, pollution, etc.) our skin encounters on a daily basis.
"The skin encounters daily onslaught by exogenous stimuli. Noxious stimuli sometimes result in injuries and/or infections, leading to wound, inflammatory dermatoses, skin aging, or skin carcinogenesis. Inflammation takes place in response to these damages to the normal skin barrier...the intensity of inflammation and the time to resolution are critical in avoiding or at least limiting damage to normal skin tissue. Thus, modulation of inflammation is important in maintaining skin homeostasis...Linoleic acid...in the epidermis is metabolized via the 15-lipoxygenase pathway mainly into 13-hydroxyoctadecadienoic acid, which possesses anti-proliferative properties."
"[PUFA] are also transformed mainly into monohydroxy fatty acids...These monohydroxy acids exhibit anti-inflammatory properties in vitro."
In addition, polyunsaturated fatty acids have been shown to have very promising benefits for those who suffer from inflammatory skin conditions like dermatitis, psoriasis, and acne. In fact, they encourage the production of lipids that are known to reduce inflammation.
"Supplementation with the n-3 polyunsaturated fatty acids (EPA) and (DHA) have shown promise as therapeutic agents in a number of inflammatory skin conditions, altering the lipid profile of the skin and production of bioactive lipids such as eicosanoids, docosanoids and encocannibinoids."
"As well as contributing to the structural integrity of the skin, PUFA such as LA, AA, EPA, and DHA are metabolized to octadecanoids, eicosanoids, docosanoids, endocannibinoids and related bioactive lipid species, known to mediate inflammatory and immune reactions in many tissues, including skin."
This is not to say that you can't have too much of a good thing - because you can. Too much of anything, including PUFA, will generally cause sensitization and/or inflammation. You don't have to worry about this if you have a balanced skincare routine like this one.
The topical use of polyunsaturated fatty acids also comes with pretty amazing, anti-aging benefits. Certain PUFA contribute to the formation of ceramides (aka. an improved skin barrier), promote collagen (aka. more elastic, plump skin), and have photoprotective properties that reduce UV-related skin-aging. Studies even argue that skin that lacks PUFA will have a compromised barrier and therefore, be more susceptible to premature skin-aging.
“...This highlights the importance of systemic long-chain PUFA supplementation for skin health...Indeed, the essential fatty acid, linoleic acid, is of particular significance to skin health, as it contributes to the formation of ceramides essential for the structure of the epidermal barrier, and the absence of LA-containing ceramides in the stratum corneum results in barrier permeability problems.”
"Eicosapentaenoic acid (EPA, 20:5n‐3) is a long‐chain n‐3 PUFA reported to protect the skin against deleterious UVR effects, reducing UVR‐induced inflammation and indicators of photoageing and photocarcinogenesis.”
"In addition to the prevention of extracellular matrix degradation, topical EPA is reported to promote expression of pro‐collagen I and the elastic fibre components, tropoelastin and fibrillin‐1 in intrinsically aged human skin through elevated TGF‐β signalling."
The chemical process initiated by three common PUFA. Each path (A, B, C) is shown to inhibit or block the synthesis of inflammatory leukotrienes while activating anti-inflammatory metabolites.
And what about acne, you might ask? Acne-prone individuals have been shown to 1. over-produce sebum and 2. lack PUFA, particularly linoleic acid, in their natural sebum. This is relevant because PUFA have been shown to inhibit inflammatory chemicals called leukotrienes (See above graphic) as effectively as some acne treatments. Leukotrienes up-regulate, or increase, sebum production. More leukotrienes = more sebum = more breakouts. PUFA are able to inhibit leukotrienes from forming.
Secondly, less or no linoleic acid in your natural sebum means less anti-inflammatory and anti-microbial activity. This means that acne-prone skin faces the unique problem of having sebum that is less protective against inflammatory and acne-causing aggressors and having too much of it - issues that can be at least partly addressed and regulated by topically applied PUFA.
"Eicosapentaenoic acid (EPA) from fish oil, and gamma-linolenic acid (GLA) from borage oil, have been reported to inhibit the conversion of arachidonic acid into [leukotrienes] to the same degree as the [leukotriene]-inhibiting acne drug candidate, Zileuton."
“A diminished amount of linoleic acid has been proposed as a factor predisposing to comedones formation. Moreover, low level of linoleic acid also produces impairment of the epidermal barrier function, which might account for increased permeability of comedonal wall to inflammatory substances.”
"There was a significant effect of topically applied linoleic acid on the size of follicular casts and microcomedones, an almost 25% reduction in their overall size being achieved over a 1‐month treatment period."
There’s so much more we could say here about polyunsaturated fatty acids and acne, like the fact that populations with the lowest amount of PUFA in their diet have the highest rates of chronic acne. Or the fact that individuals who consume less PUFA-rich foods like fish and seafood are at a significantly higher risk for acne.
Suffice to say that the science is prettttty dang clear. Polyunsaturated fats have an undeniable place in skincare, especially for individuals whose skin is already deficient in those fatty acids and is suffering as a result.
OTHER THINGS TO CONSIDER…
Before we go, there are a few more things to consider. In the context of skincare, ingredients and formulas are designed to work synergistically. Unless you’re dealing with a single-ingredient product, there are going to be other ingredients in the formula that have been carefully chosen for their specific properties, benefits and chemical compositions. Ingredients don’t function in a vacuum, so it’s important to consider the entire product and formula in order to decide if it’s right for you. If you trust the brands you’re buying from, how they're formulated, and the ingredients they source, this should be easy to figure out!
"When applied topically, constituents of plant oils (triglycerides, phospholipids, fatty acids, phenolic compounds and antioxidants) may act synergistically by several mechanisms: (i) promoting skin barrier homeostasis; (ii) antioxidative activities; (iii) anti-inflammatory properties; (iv) direct and indirect (upregulation of antimicrobial peptides) anti-microbial properties; (v) promoting wound healing; and (vi) anti-carcinogenic properties."
On that note…every oil is different. Literally no two plant oils are exactly the same! If you trust in Mother Nature like we trust in her, then not vilifying any plant oil that contains PUFA is a no-brainer. Chemical composition varies from plant to plant, from oil to oil, and there are pros and cons to using any natural ingredient. In fact, because every individual's skin and biological makeup is different, all natural ingredients come with both benefits and potential ‘risks.' If you do your research and trust the brands you buy from, this shouldn’t be an issue.
"Topical applications of plant oils may have different effects on the skin according to their composition and the pathophysiological context of the skin. The composition varies by different extraction methods."
Lastly, how a plant oil and product is produced matters. Oils that haven't been heat-treated or refined are going to be the most nutrient-dense and slower to oxidize because they contain more of the natural antioxidants of the plant. You can tell fresh, unrefined oils by their vibrant colors and scents - they possess an earthy quality that lower quality, refined oils just don't have.
If you’re unsure or concerned about PUFA in a product, find out how it’s produced. Is the oil cold-pressed? Unrefined? Has the ingredient or product been treated with heat at all? How is it stored (ie. in a temperature-controlled environment)? As a consumer, you have a right to ask these questions, so don’t be afraid to.
"Although there are different ways to obtain plant oils, cold-pressed plant oils have better nutritive properties than those that have undergone the refining process. This is because cold-pressing procedure does not involve heat or chemical treatments, which may alter their composition and therapeutic effects.”
Phew. We made it! We hope we’ve cleared some of your questions around polyunsaturated fatty acids in skincare. We at Wabi-Sabi Botanicals love us some PUFA, especially for oily and acne-prone skin, and make sure to take the necessary steps (ie. sourcing the freshest, highest-quality ingredients out there!) so that your skin truly benefits from them. As our friend, Laurel, so eloquently says, “I see all plants as medicine. If a plant is being vilified, then it’s being misused or misunderstood.”