Today were going to cover as much info as possible. I want to be as clear as I can and to come from a place of neutrality that way the information is presented in a way that is not one sided. Then of course at the end I will give my wonderfully blunt and professionally unprofessional opinion.
I have heard from so many that seed oils are terrible for your overall health, that they cause inflammation, they also contribute to the obesity issue that is consuming Americans. I've also heard and believed for a long time that seed oils in skincare is a major no-no. They're also called PUFAS, Polyunsaturated fats and Omega 6s. Many influencers and businesses in the natural skincare niche say this. With all this information what are we supposed to believe? Is this simply a situation where we swear off seed oils all together? Including never using them on our skin? Seed oils in skin care are they bad or what? We need to look at this topic from a purely scientific perspective and look at the most recent information and evidence that shows if they're beneficial or not, the down sides, and what parameters are they to be used in?
BRIEF HISTORY OF SEED OILS
Seed oils have been around since the early 1900s most notably in the machinery industry where it was used for lubrication for metal, car parts and big heavy machines. Seed oils at the time were a byproduct of cottonseed and corn, after not knowing what to do with it people started feeding it to their livestock and took note of how fat it quickly made them. Thus, the seed oil industry was born and it wasn't too long until it was being sold in grocery stores to the masses. At that point all major health diseases that we see now started to skyrocket. Some of the most popular seed oils for cooking are canola, peanut, soybean, and vegetable oil which is a blend of canola, corn and soy. It was pushed heavily by Proctor & Gamble when they discovered crisco(Shocking History of Seed Oils - Mitchell Landon).
WHY ARE THEY BAD FOR HEALTH?
Let's briefly go over this since it's not the focus of today's subject. The main issue with seed oils is that they are naturally high in linoleic acid also known as Omega 6s. Instead of having one carbon bond they have multiple which tends to make them unstable and oxidize easily when exposed to oxygen, heat and light. The way most industrial seed oils are processed is typically by heating them and dissolving them in hexane. Then they are deodorized and the smell is removed. This process completely breaks down the oil then it’s heavily deodorized to remove the smell. Partially hydrogenated vegetable oils are not good to consume at all because they can have trans-fat which has a direct link to heart disease (Trans Fats | American Heart Association). Crisco is a well-known and popular partially hydrogenated oil. These oils are made by heating them with hydrogen and a catalyst usually nickel which convert some of the polyunsaturated fats to saturated fats and some to trans fats (Hydrogenation - an overview | ScienceDirect Topics). This makes it more shelf stable (which is hard to believe) but worse for your health. Naturally occurring trans fats aren't bad, but unfortunately these highly processed oils contain non naturally occurring trans fats, and they are in every single processed food out there now. They're unnecessarily added to everything so its hard to avoid. They're are also being marketed as healthy.
The big obvious issue with seed oils is that they have a double bond between carbon atoms which make them prone to oxidation more so than saturated fats which have no double bonds. The way they are processed is another big issue and studies do show a negative correlation with excess industrial seed oil consumption and health.
SEED OILS IN SKINCARE?
Now lets talk about seed oils in skincare. Grapeseed, Rosehip, Black seed, Pomegranate Seed, Backuchiol, Apricot Kernal, Cranberry Seed, Carrot seed, all of these are popular seed oils used in skincare. All of these oils have one thing in common-high linoleic content upwards of 50%-85%. Now these are typically not cooking oils, the seed oils in skincare are normally cold pressed and extracted-at least they should be. These differ from the manufacturing process that industrial cooking oils go through. They are handled much more gently so that's important to remember.
To understand these oils and the benefit they bring to the skin we need to evaluate one very important aspect of these oils. Are they stable? Do they have oxidative stability when exposed to oxygen, light, heat? Im going to be delving into different studies and tests performed on certain oils mainly rose hip seed oil which will give us a better perspective.
STABILITY OF COLD PRESSED SEED OILS
Let's take a look at the oxidative stability of Rose hip Oil since there is a good amount of testing on this oil, and its a good baseline for other oils. This oil is usually made by cold pressing the rose hip seeds. The linoleic content can vary from species of roses and extraction methods. I will be linking where I obtained the testing information throughout this blog. Feel free to read them.
Rosehip also contain Phenolic acids as noted on several of the studies above Phenolic compounds, Carotenoids, Lipophilic antioxidants, and natural tocopherols are also present in rosehip seed oil.
The Fatty Acid profile of cold pressed Rosehip is comprised of:
Linolenic- 16%-26%
Linoleic- 36%-55%
Oleic- 14%-22%
^This study was in 2015 which breaks down the stability of Rose hip oil and its antioxidant properties that affect its oxidative stability. This study goes over the different tocopherols, and peroxide value of several different oils after 3 months of shelf life. In short its a test which measures the level of oxidation in an oil. Peroxides are the precursor to oxidation.
^This image is from this study (Characteristics and Antioxidant Potential of Cold-Pressed Oils-Possible Strategies to Improve Oil Stability - PubMed (nih.gov)()
This study is showing the peroxide values of each of these oils after three months. A peroxide value of over 30 is considered rancid. Its important to note the extraction methods of these oils, and the conditions they were stored in as those are variables to their peroxide values, and acid values. This study also notes that a cold pressed oils stability depends highly on its phytosterols content in the omega 3 portion of the oil, its also synergistically dependent on the ratio of tocopherols to linoleic acid. This study was in 2020.
It seems that from this study we can conclude that the higher the linoleic/linolenic content in a seed oil the faster it oxidizes. Linolenic oxidizes the fastest out of all the fatty acids followed by linoleic and oleic. Rosehip and several other oils have the potential to offset this by a small amount with the naturally occurring Tocopherols (Vitamin E) present in a portion of the saturated fats of the oils. phytosterols along with the tocopherols help slow down the rate of the oxidation in the oil. According to the Pubmed study that ran oxidation tests which measures the peroxide values, acid values, P-anisidine values, and conjugated triene values, rosehip oil has a slight increase of peroxides by the three-month mark. Peroxide values are the precursor to oxidation. The peroxide values at the three months mark we're still under 30 MeQ O2/KG which means it has not yet oxidized. The other oils tested were Walnut nut oil, pumpkin seed oil, camelina seed oil, flaxseed oil, and milk thistle oil. The other oils had much faster oxidation rates, showing high levels of peroxides by the three-month marks with the exception of milk thistle oil which showed similar peroxide values as rosehip. The faster oxidation rate would likely be due to the higher linoleic/linolenic values and not having enough tocopherols and phytosterols in the antioxidant portions of the oils.
Conclusion: it seems rosehip oil has some oxidative stability when compared to other seed oils and this is due to the antioxidant properties and the naturally occuring tocopherols and phytosterols. These two synergitically working compounds work together to add some shelf life and stability. Other factors will influence this though such as how the oil is stored, and how much exposure to heat, oxygen and light it undergoes.
COMPARISON
Lets look at another seed oil and their fatty acid profiles.
Grapeseed: Linoleic-66%-75%, oleic-14%, Stearic- 2-4%, palmitic-7% (Fatty acid composition, oxidative stability, antioxidant and antiproliferative properties of selected cold-pressed grape seed oils and flours - ScienceDirect)
Oxidative stability of grapseed oil-(NON-CONVENTIONAL (NON-STANDART) METHODS FOR STUDYING PROTEIN CRYSTALLIZATION (CRYSTAL NUCLEATION) (bas.bg))
Unfortunately grapeseed oil has poor oxidative stability. Even with added antioxidants the stability was never quite achieved, and this is due to the very high linoleic content. It is one of the highest sources of linoleic out of all the seed oils.
OTHER USEFUL LINKS
Fatty Acid Composition and Oxidative Stability of Cold‐pressed Edible Seed Oils - Parker - 2003 - Journal of Food Science - Wiley Online Library This is an older study on the oxidative stability of several different oils based on the linoleic content.
Cold pressed carrot (Daucus carota subsp. sativus) seed oil - ScienceDirect This study looks at the importance of cold pressed oils versus other extraction methods. The cold pressed method retains all the antioxidents.
Oxidative Stability and Shelf Life of Vegetable Oils - ScienceDirect
THE ROLE OF LINOLEIC ACID
Did you know your skins sebum has linoleic acid in it? Linoleic acids play an important role in the body's functions including keeping the skin healthy among many other functions. We do absolutely need them. Having them in the balanced right amounts is key. There are studies showing a correlation of acne prone skin being deficient in linoleic acids on their skin. Acne Vulgaris and Intake of Selected Dietary Nutrients—A Summary of Information - PMC (nih.gov) This is an excellent recent study on certain dietary markers that affect Acne Vulgaris. This study also shows if you scroll to the bottom that the patients who consumed foods with higher linoleic content such as fish, seeds, nuts, and seed oils, that there was a decrease in their acne vulgaris at the end of the trial. This study also shows the effects of a high glycemic index diet on the skin and that patients who ate a high glycemic index (High sugar/carbs) diet had worse acne symptoms. The thought is that adding naturally occurring linoleic to your diet will help decrease the sebum production on the skin. The evidence from other studies also show adding linoleic to acne prone skin helps decrease acne vulgaris.
THE BENEFITS OF ROSEHIP SEED OIL
Lets look at some of the reported benefits of seed oils.
Rosehip Seed Oil — Botanical Formulations- This link shares some great information about the skin benefits of rose hip oil and some clinical studies with people using it on their skin and some of the benefits they had from it. It also discusses how to avoid rancinity with rosehip oil.
Rose hip oil is a complex oil that has vitamins A, E, Phenolic Compounds, phytochemicals, phytonutrients, it also has precursors to Vitamin A. A natural form of Vitamin A if you will. People have reported a reduction in acne, wrinkles, sun spots, hyperpigmentation and the list goes on and on. So its obviously helped a lot of people with their skin.
MY CONCLUSION
Since we only really took an extra close look at rosehip oil and grapeseed my conclusions will be based on those, but this information is useful when assessing any high linoleic oil. So, are seed oils ok in skincare? The questions i would want to know the answer to before I put a seed oil on my skin are-1. is it cold pressed? 2. When was it made and how was it stored? 3. Does it have an added antioxidant such as rosemary extract/vitamin E? What are the linoleic/Linolenic numbers? Those are pretty important factors when deciding to use a seed oil. Now rosehip is one of those oils that demonstrates slightly more oxidative stability than many of the other seed oils. I'm not saying all seed oils are bad but some are definitely better than others. If it smells funny, and the price was really cheap then I wouldn't use it.
My suggestion would be to do the research on whatever oil you're wanting to try out. Look at its fatty acid profile and oxidative stability. You don't have to use the oil with the highest linoleic content to improve your skin, even oils with 20% linoleic would be effective. I think right in the middle around 40%-50% Linoleic would be effective. I suggest calling the company you are wanting to purchase from and find out where they got their seed oil and when it was made and how they store them. If they're a reputable company, then that helps too. Another suggestion, dont use them and go out in the sun. Remember they are sensitive to heat, light and oxygen. I personally would be using them at night. Or if using in the morning wait until its fully absorbed before venturing outside and use a sunscreen. To preserve the oil longer keep in a cool dark place and minimize the oils exposure to oxygen.
Most seed oils say to use them within 6 months to a year. I personally say use them within three months of purchasing then throw them out. If they have vitamin E, rosemary extract, or an added antioxidant then possibly six months at the maximum this will depend on the type of seed oil you're using. The high linoleic content unfortunately does cause them to degrade much faster. Not all seed oils are created equal. A good rule of thumb is the higher the linoleic/linolenic values the faster it will oxidize, and you don't want to be putting oxidized oil on your skin. I cannot deny that seed oils do contain some powerful antioxidants and skin loving phenolic compounds and I think they can be used responsibly and benefit your skin. The more we research before we purchase the better.
Now if you're wondering if I will be using seed oils in my products, I already do. Jojoba oil is made from jojoba seeds, and we use expeller pressed canola in our soaps at 5%, but will i be using high linoleic seed oils in my leave on products? Probably not, this is not because they dont have value, but considering I do long infusions with heat and extractions with alcohol, the instability of seed oils does not work for that. Not to mention I would have to sell them very quickly to avoid them oxidizing before they reached the customer. Also, I live in Arizona where it's really hot. I need oils and fats that aren't heat sensitive which are saturated fats. I could definitely spend more countless hours researching the topic of seed oils in skincare and perhaps I will write several more blogs in the future on it, but for now, this will have to do. I feel the small amount of info we went over today should help you when researching and deciding to use seed oils in skincare.
A lot of this depends on your skin type. I think there can definitely be a middle ground with using them in skincare. Considering I was anti seed oil in skincare for the last several years its a humbling experience to do the research and see that I was not properly informed on the use of them. Please ask any questions and make comments if you like!
Signing off,
Jen with Grassland Beauty