What's Wine Got to Do with Old Person Smell?
2-Nonenal and What We Can Do About It
Wine changes its aroma as it ages because its chemistry changes. Compounds interact and transform, new aromatic compounds develop, and oxidation plays a key role.
Our skin is no different.
As we age, the fatty acid composition of our skin changes, along with the antioxidant defences that protect those fatty acids from oxidation.
One consequence of those changes is the formation of a compound called 2-nonenal, associated with the rather unflattering expression old person smell.
What makes 2-nonenal interesting is the chemistry responsible for producing it, and what that chemistry tells us about supporting healthy skin function as we age.
What Changes in Our Skin as We Age?
In 2001, Japanese researchers investigating age-associated body odour identified 2-nonenal, a compound with a distinctive greasy, grassy odour.
They found it in participants aged 40 and above, but not in younger participants.
The researchers discovered that older participants had higher proportions of omega-7 fatty acids on their skin, including palmitoleic acid and vaccenic acid, along with higher levels of lipid peroxides, compounds formed when fats undergo oxidation.
When they oxidised omega-7 fatty acids experimentally, 2-nonenal was produced.
A subsequent study in 2010 found that palmitoleic acid, an omega-7 fatty acid capable of producing 2-nonenal, was 67% higher in the epidermis of older participants compared with younger participants.
As our skin ages, the proportion of omega-7 fatty acids increases, providing more of the precursors from which 2-nonenal can form.
Our skin has built-in antioxidants that help protect its fatty acids from oxidation. As the proportions of fatty acids in our skin change with age, our antioxidant defences are also declining.
This matters because 2-nonenal forms when susceptible omega-7 fatty acids undergo oxidation.
Two age-associated changes therefore contribute to the formation of 2-nonenal: an increase in omega-7 fatty acids, particularly palmitoleic acid, and a concurrent decline in antioxidant protection.
2-nonenal has a distinctive odour, but it is not necessarily unpleasant. Nor is its presence an indication of poor personal hygiene. Washing can remove odour compounds from the skin's surface, but it does not prevent their continued formation.
Understanding the chemistry behind 2-nonenal formation gives us another approach to mitigating its production: carefully considering the fatty acids we apply to our skin and how we support and protect its fatty acids from oxidation.
What We Know and What We Can Do
As skin ages, the fatty acids present and the antioxidant protection available change. Those changes influence lipid oxidation and the formation of compounds such as 2-nonenal. By being selective about the fatty acids and antioxidants we apply, we can influence aspects of our skin's biochemistry.
The research gives us three practical considerations.
1. Be Very Selective About the Fats and Oils You Apply
Know their fatty acid profile!
The proportions of individual fatty acids vary considerably between botanical oils and fats. When applied topically, these fatty acids have distinct biological activities in the skin. In skincare language they are the "actives". Not all fatty acids are beneficial to healthy skin function.
Sea buckthorn pulp oil and macadamia oil, for example, contain substantial proportions of palmitoleic acid, an omega-7 fatty acid associated with 2-nonenal formation.
Grapeseed oil, by comparison, is predominantly linoleic acid, an omega-6 essential fatty acid.
If omega-7 fatty acids are precursors to 2-nonenal, avoiding unnecessary topical addition of omega-7-rich oils is a reasonable precaution.
This does not mean that applying these oils has been demonstrated to cause old person smell. It means recognising that botanical oils or fats are not interchangeable and that their fatty acid composition matters.
2. Support Antioxidant Protection
The oxidation reaction of omega-7 fatty acids produces 2-nonenal.
Our skin has its own antioxidant defences, but these decline as we age.
Cold-pressed grape seed oil retains a complex profile of naturally occurring antioxidant compounds, including tocopherols and tocotrienols (the vitamin E family), while grape seed extract supplies additional polyphenols with antioxidant properties.
These antioxidants can help limit the oxidative reactions that damage fatty acids.
Research has also demonstrated, grape-derived polyphenols can react directly with some of the aldehydes produced during lipid oxidation.
This suggests two complementary mechanisms: limiting the formation of oxidation products and interacting with certain compounds after they form.
Whether grape seed polyphenols can directly neutralise 2-nonenal on human skin remains to be established, but the chemistry suggests that this is plausible.
3. Supply Biologically Essential Fatty Acids
Linoleic acid is an essential fatty acid. Our bodies cannot produce it, yet our skin requires it to build and maintain a healthy skin barrier.
Research has demonstrated that applying linoleic acid-rich lipids can influence the fatty acid composition of the epidermis and support the formation of ceramides, lipids essential to barrier structure and function.
What we apply to our skin can therefore influence its fatty acid composition.
Although research has not established that topical linoleic acid prevents age-related increases in omega-7 fatty acids, consistently supplying this essential fatty acid supports healthy skin function throughout life.
Bringing the Chemistry Together
Vitis V Face TonIQ Essential Face Oil brings together two components relevant to this chemistry.
Cold-pressed Australian grape seed oil supplies linoleic acid, an essential fatty acid required for healthy epidermal barrier function.
Unfermented grape seed extract supplies polyphenols with antioxidant properties, alongside the naturally occurring antioxidant constituents of the oil.
Together, they provide essential fatty acids to support healthy skin structure and antioxidant compounds to help protect lipids from oxidation.
These are complementary approaches to supporting the skin's lipid environment as we age.
They are based on what we know about fatty acid chemistry, antioxidant protection and healthy skin function.
Ageing Is Chemistry
A wine doesn't have the same aroma at ten years of age as it did when it was first bottled.
Its chemistry has changed.
Our skin's biochemistry changes too.
Ageing is part of living, but that doesn't mean we have no influence over the chemical reactions that accompany it.
The fatty acids we apply, the antioxidant protection we provide and the biological requirements of healthy skin are all factors within our influence.
Smelling like an old person is not a foregone conclusion as we age.
Understanding how our skin's chemistry changes with age allows us to make informed choices that support healthy skin function and mitigate the formation of 2-nonenal.
Ageing is inevitable. How we support healthy skin function as we age is something we can influence.
Vitis V - Essential for Life
References
2-Nonenal newly found in human body odor tends to increase with aging
Photography - Nathan Blackaby on Unsplash