2-Nonenal and Avoiding That “Old People Smell”

This article was written on September 1, 2025, and updated on July 11, 2026.

What is “Old People Smell”?

“Old people smell” is the characteristic ‘greasy, grassy odor’ most noticeable in nursing homes and long-term care facilities, beyond the smells of urine, feces, and spilled food. Many independent-living older adults also have it, though they may have become desensitized to it. Children and grandchildren are often more aware of it.

In Western culture, the main focus as we age is to keep ourselves “looking young,” usually pursued by buying special skin and hair-care products. In Japan, avoiding “kareishu”, or “old people smell,” is a significant focus in aging. There are special soaps and washing products promoted to meet this need, as well as research into foods that can neutralize it.

While the most common solution to the problem of “old people smell” resulting from 2-nonenal is the use of specially designed and marketed Japanese persimmon extract soap, minimizing the production of 2-nonenal can be addressed by knowing what types of fats are easily oxidized, and which antioxidant foods can reduce their production.

What Actually Causes Old People Smell?

While body odor, in general, can be influenced by eating foods such as onions, garlic, ginger, and certain spices, and certain medications, “old people smell” comes mainly from 2-nonenal, a volatile compound formed by the oxidative breakdown of palmitoleic acid and vaccenic acid, which are two omega-7 unsaturated fatty acids that increase on the skin from about age 40 onwards [1].

Compared to adults under 40, 2-nonenal can increase by up to 6-fold, though the exact reason is unclear [1]. More omega-7 fatty acids or lipid peroxides on the skin correlate with higher 2-nonenal levels [1]. Like other unsaturated fats, omega-7s are prone to oxidation.

Targeting “Old People Smell” — Lifestyle and Dietary Changes

Lifestyle Changes

Recommended lifestyle measures include wearing natural fibers such as cotton, linen, or silk to allow fatty acid compounds to transfer to the clothing, which can then be easily washed. Washing bedding and clothes in enzyme-activated detergents can break down odor-causing fatty acids. Soaps containing polyphenols, such as concentrated Japanese persimmon extracts, have been demonstrated to reduce 2-nonenal on the skin [2]. Note: Regular persimmon juice or leaves are not equivalent to concentrated tannin extracts used in studies.

Dietary Changes

Since higher levels of palmitoleic acid and vaccenic acid on the skin increase 2-nonenal, dietary strategies include reducing intake of these fats and increasing dietary intake of antioxidants.

Reducing Intake of Palmitoleic Acid and Vaccenic Acid

Limiting the oxidation of omega-7 fats, as well as keeping skin, bedding, and clothing clean, can significantly reduce “old people smell.” Because 2-nonenal is fat-soluble, ordinary water-based soaps may not be effective in removing it. Polyphenol-containing soaps have been shown to reduce 2-nonenal on the skin [2].

Foods rich in palmitoleic acid include macadamia nuts, macadamia oil, avocado, avocado oil, olive oil, and sea buckthorn oil [3]. Vaccenic acid is found in ruminant fats, including beef, lamb, and dairy products [3]. Reducing these foods may decrease 2-nonenal formation. Omega-7 fats are non-essential, as the body can synthesize them via de novo lipogenesis [3].

Can Antioxidants Help Reduce “Old People Smell”?

Yes, some antioxidants and polyphenols may help reduce lipid oxidation that leads to 2-nonenal formation. Below are some examples.

Green tea catechins have antioxidant activity that may help reduce oxidative odor precursors [4].

Champignon (white button mushroom) extract was shown in a 4-week trial to reduce body odor in adults, although the study is limited in sample size [5]. Eggplant phenolamides have demonstrated 2-nonenal scavenging activity in vitro and in animal models, suggesting potential reduction in odor [6].

Blackcurrant powder rich in anthocyanins has been documented to reduce 2-nonenal skin emission in middle-aged adults [7]. Other anthocyanin-rich foods, such as elderberries, blackberries, blueberries, raspberries, acai, and pomegranate, may have similar effects [8].

Clinical Conclusion

When I was a newly graduated Dietitian, I worked in a long-term care facility and eventually oversaw multiple sites as a Regional Manager.  At the time, I mistakenly assumed that “the smell” common to these facilities was unavoidable and was due to urine-soiled clothing or bedding, and spilled food. Knowing what I know now, I believe that many families of people living in long-term care facilities would be glad to bring their family members green tea and berries, instead of candies, and to be able to buy something as simple as a persimmon tannin extract soap, to help make the quality of life of their family member that much better.

Final Thoughts

As the saying goes, “beauty is more than skin deep“, and just as young skin and hair aren’t achieved by applying cosmetics and hair dyes, “smelling young” isn’t achieved only by using special soaps.

While cosmetics, special soaps, and detergents can certainly help, the essence of looking young and smelling young is primarily achieved by eating real, whole food rich in natural antioxidants and nourishing oneself from the inside out.

Unfortunately, to limit costs, public long-term care centers rarely provide their residents with the types of antioxidant-rich foods known to minimize the characteristic ‘greasy, grassy odor’ found in these residences. They don’t have to smell like that.

When we become parents, we learn how to feed our infants and children — but who teaches us how to feed ourselves as we age, or our aging parents? Eating well at any age doesn’t just happen by chance.

Enabling seniors to remain independent into their advanced years begins with dietary and lifestyle changes in middle age (or sooner), including eating sufficient amounts of the right types of protein to maintain muscle and bone mass, and eating real, whole food rich in antioxidants.

More Info?

I help adults to be the best they can be at any age. You can learn about me and the Comprehensive Dietary Package that I offer.

To your good health!

Joy

You can follow me on:

Twitter: https://twitter.com/jyerdile
Facebook: https://www.facebook.com/BetterByDesignNutrition/

References

1. Haze S, Gozu Y, Nakamura S, Kohno Y, Sawano K, Ohta H, Yamazaki K. 2-Nonenal newly found in human body odor tends to increase with aging. J Invest Dermatol. 2001 Apr;116(4):520‑524. doi:10.1046/j.0022-202X.2001.01287.x [https://pubmed.ncbi.nlm.nih.gov/11286617/]
2. Tatsuguchi I, Matsuoka T, Izumi R, Ijichi S, Shibata H. Preventive effect against the aged men’s body odor by the soap containing polyphenol. Jpn Assoc Odor Environ. 2012;43(5):362–366 [https://www.jstage.jst.go.jp/article/jao/43/5/43_362/_article/-char/en]
3. Venn-Watson E. Fatty 15, Omega 7: What To Know About This Fatty Acid. [https://fatty15.com/blogs/news/what-is-omega-7]
4. Cabrera C, Artacho R, Giménez R. Beneficial effects of green tea — a review. J Am Coll Nutr. 2006 Apr;25(2):79‑99. doi:10.1080/07315724.2006.10719518 [https://pubmed.ncbi.nlm.nih.gov/16582024/]
5. Nishihira J, Nishimura M, Tanaka A, Yamaguchi A, Taira T. Effects of 4‑week continuous ingestion of champignon extract on halitosis and body and fecal odor. J Tradit Complement Med. 2015 Dec 11;7(1):110‑116. doi:10.1016/j.jtcme.2015.11.002 [https://pmc.ncbi.nlm.nih.gov/articles/PMC5198824/]
6. Kim HM, Kim JH, Jeon JS, Kim CY. Eggplant Phenolamides: 2‑Nonenal Scavenging and Skin Protection Against Aging Odor. Molecules. 2025 May 12;30(10):2129. doi:10.3390/molecules30102129 [https://pmc.ncbi.nlm.nih.gov/articles/PMC12114487/]
7. Willems M, Todaka M, Banic M, Cook M, Sekine Y. Effect of New Zealand Blackcurrant Powder on Skin Emission of Volatile Organic Compounds in Middle‑Aged and Older Adults. Curr Dev Nutr. 2019;3(Suppl 1):nzz031.P06‑092-19. doi:10.1093/cdn/nzz031.P06‑092-19 [https://pmc.ncbi.nlm.nih.gov/articles/PMC6576077/]
8. Lakshmikanthan M, Muthu S, et al. A comprehensive review on anthocyanin-rich foods: Insights into extraction, medicinal potential, and sustainable applications. J Agric Food Res. 2024;17:101245. doi:10.1016/j.jafr.2024.101245 [https://www.sciencedirect.com/science/article/pii/S2666154324002825]

Privacy Policy | Terms of Use