An article by Beautyeditor (now rebranded as The Skincare Edit) recently came to my attention, thanks to some readers who pointed me in its direction. In it, she blames polyunsaturated oils for aging, tells you to avoid them in your skincare AND diet, and tells you to use saturated fatty acids (in particular squalane) instead.
The facts about unsaturated oils
Let’s start with what Beautyeditor/The Skincare Edit got right. Unsaturated fatty acids are indeed less stable than saturated fatty acids, which means they’ll have a shorter shelf life.
Fats and oils are collectively known as triglycerides. Unsaturated triglycerides oxidise more easily than saturated triglycerides because they contain more double bonds, which are more reactive than single bonds. You’ll know an oil’s been oxidised when it goes rancid and smells a bit gross. The oils will react when exposed to air, light, heat and free radicals (though adding antioxidants like vitamin E to the oil will slow this down).
Triglyceride molecules consist of 3 fatty acids (blue) linked to a glycerin molecule (purple):
It’s the fatty acids that can vary and contain double bonds. Fatty acids are divided into saturated (no double bonds), monounsaturated (1 double bond) and polyunsaturated (2 or more) fatty acids.
Here are some common fatty acids in each category:
- Saturated: lauric, myristic, palmitic, stearic
- Monounsaturated: oleic (omega-9), palmitoleic
- Polyunsaturated: linolenic, eicosapentaenoic, and docosahexaenoic (omega-3), linoleic (omega-6)
The fatty acids can vary, so you can get a triglyceride that contains, say, 2 saturated fatty acids and 1 polyunsaturated fatty acid. Most natural fats and oils aren’t entirely saturated or monounsaturated or polyunsaturated, but very few have an even balance of all three.
- Mostly saturated fats and oils include coconut oil, butter, palm oil, beef fat
- Mostly monounsaturated fats and oils include avocado oil and olive oil
- Mostly polyunsaturated fats and oils include fish oil and most of the common skincare oils: safflower, sunflower, rosehip, almond, hemp, and grapeseed oils
Why might unsaturated oils be bad?
So far so good, but does this instability have an effect on your skin? Here’s where her argument gets dicey.
It turns out that Beautyeditor/The Skincare Edit is a follower of Ray Peat, who believes that polyunsaturated fatty acids (PUFAs) are a big cause of aging. He advocates avoiding them in the diet because he thinks they cause oxidative stress, which builds up to cause aging. This goes against the advice of pretty much all recognised medical bodies. PUFAs include the essential omega-3 and omega-6 fatty acids, which are called “essential” because we can only obtain them from our diets. They’re required for all sorts of things in our bodies including healthy heart and brain function, and more importantly making cell membranes which all cells need, hence why there are recommended intake guidelines.
Other things Ray Peat recommends: avoiding exercise, increasing white sugar consumption, increasing dairy consumption, eating more ice cream (I’m serious).
The case for unsaturated oils
OK, so Ray Peat is clearly a quack (see here for why cranks who opposite “mainstream experts” are usually full of BS). But his argument for rancid PUFAs causing negative health effects is theoretically plausible.
However, studies where unsaturated fatty acids and oils been used on skin have usually found beneficial effects. The oils in those studies would have been susceptible to oxidation, much like an oil you’d use in your skincare routine.
Not all of these studies are high quality, but they give you an idea of the overwhelming consensus: that polyunsaturated oils are probably more good than bad, and the scaremongering is unnecessary. It’s also worth noting that I couldn’t find any studies that found that unsaturated oils increased the signs of aging. This isn’t surprising, since we have plenty of unsaturated fatty acids and lipids in our skin naturally. Unsaturated fatty acids are required for making skin, in particular for making ceramides.
Applying them to skin can be beneficial:
- Linoleic acid treats hyperpigmentation and reduces blocked pores, and a linoleic acid/ceramide cream can be used to treat and prevent psoriasis
- Grapeseed oil protects against irritation
- Sunflower oil increases skin integrity and hydration
Some skin conditions are associated with PUFA deficiencies:
- Insufficient linoleic acid is linked to acne and scaly skin
- Lack of linoleic acid-containing ceramide-1 in skin is associated with eczema
- Removing PUFA from mouse diets cause eczema-like symptoms
There’s no evidence behind the claim that polyunsaturated oils are detrimental and cause aging. There’s also no evidence behind a lot of the other dodgy claims in her unsaturated oil posts. A selection:
- Squalane is an antioxidant: Bad news, squalENE works as an antioxidant because it has double bonds. SqualANE can’t work in the same way.
- The sun isn’t the main cause of skin aging, it’s diet: There are no reliable sources for this, it seems to just be Ray Peat’s gut feeling. This study on 300 women found that “UV exposure seems to be responsible for 80% of visible facial aging signs [in Caucasian women]”, and is a bit more reliable since it’s actually a study and aligns with what every other study on the topic has found.
- Age spots aren’t from the sun but from PUFAs: Except linoleic acid treats hyperpigmentation.
- 20-60% of stuff applied on your skin get absorbed into your bloodstream: This is complete poppycock, luckily. You’d gain a lot of weight from moisturiser…and you’d have eaten all your clothes.
- It takes four years to detox PUFAs from your tissues: You probably don’t want to do that, unless you really hate having cells.
Use oils to your heart’s content!
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