In Western culture, the main focus as we age is to keep ourselves “looking young,” which is usually pursued by buying special skin and hair-care products. In Japan, avoiding “kareishu”, or “old people smell,” is a significant focus in aging, and special soaps and washing products are promoted to meet this need.
What is “Old People Smell”?
“Old people smell” is the characteristic ‘greasy, grassy odor’ most noticeable in nursing homes and long term care homes, beyond that of urine, feces, and spilled food. In fact, many independent-living older adults also have “old people smell” — although they have become desensitized to it themselves as it had increased gradually since middle age. Many times, their children and grandchildren are very aware of it.
While body odour can be caused by foods containing a lot of onion, garlic, ginger and certain spices, or may be a side-effect of some medications, “old people smell” originates from 2-noneal, a volatile chemical compound caused by the oxidative degradation of palmitoleic acid and vaccenic acid, two omega-7 unsaturated fatty acids that increase on the skin from age 40 years, onwards [1].
Compared to adults under 40 years of age, 2-noneal increases by up to 6 times beginning at 40 years of age [1], although the reason for this increase is not yet known.
Research has also shown that the more omega-7 unsaturated fatty acids or lipid peroxides that are on the skin’s surface, the more 2-nonenal there is in body odour [1].
As with all unsaturated fats, omega-7 unsaturated fats are more prone to getting oxidized — literally going rancid, just as unsaturated kitchen fats, such as seed oils.
Keeping omega-7 fats from going rancid, as well as cleaning the skin, bedding, and clothing from these unstable unsaturated fats, will significantly reduce, if not eliminate, “old people smell”. Since 2-noneal is fat-soluble, it is not removed from skin or clothing using ordinary water-soluble soaps and detergents. As a result, targeted products are required.
Targeting “Old People Smell” — lifestyle and dietary changes
Lifestyle Changes
Lifestyle changes that have been recommended to reduce kareishu (“old people smell”) include wearing clothes made of natural fibers, such as cotton, linen, or silk, so that the fatty acid compounds on skin can more easily transfer to clothing, and then be washed.
Regular washing of bedding and clothing in an enzyme-activated detergent can break up the fatty acids that cause the smell. Washing with body soap that contains polyphenols extracted from Japanese persimmon tannins* has been shown to remove 2-noneal from the skin [2].
*It is important to note that widely available soaps containing persimmon juice, or persimmon leaf, are not the same as those containing the concentrated tannins from Japanese persimmon extract used in the study.
Dietary Changes
Since it is known that the more palmitoleic acid and vaccenic acid (omega-7 unsaturated fatty acids) on the skin’s surface, the more 2-nonenal there will be in body odour, two dietary approaches are to reduce the intake of foods high in these fatty acids, and to increase the intake of dietary antioxidants that can neutralize 2-nonenal.
Reducing Intake of Palmitoleic acid and Vaccenic acid
Reducing the intake of foods high in palmitoleic acid and vaccenic acid is one dietary approach to decreasing 2-nonenal body odour.
Palmitoleic acid is found primarily in macadamia nuts and macadamia nut oil, avocado and avocado oil, olive oil, sea buckthorn oil, and anchovies..
Vaccenic acid is a naturally occurring trans fat found in the fat of ruminant animals, including the fat of cows and sheep, and dairy or butter from the milk of these animals [3].
While decreasing the amount of foods high in palmitoleic acid and vaccenic acid may decrease the amount of 2-noneal, it is important to note that since omega-7 fats are non-essential, they don’t need to be available in the diet. The body can make them by converting carbohydrates, other types of fat, and proteins we eat, in a process known as de novo lipogenesis [3].
While seed oils such as soybean and canola are not high in omega-7s, they are easily oxidized, especially when heated, and quite inflammatory. As a result, they are best not used at home, and avoided at restaurants by not ordering food fried in them. Another way to avoid these fats is not to eat highly processed foods, which are made with them.
At the same time, storing real, whole food that is high in palmitoleic acid and vaccenic acid, such as macadamia nuts and oil, avocado and avocado oil, anchovies, and olive oil in the fridge, will significantly slow the process of them going rancid. Many of these oils are sold in dark glass bottles, which slow oxidation, but keeping them in the refrigerator, especially during the summer, is prudent.
Increasing Intake of Dietary Antioxidants
Eating real foods naturally high in vitamin C, vitamin E, selenium, and polyphenols, which are all natural antioxidants, can neutralize free radicals and lipid peroxidation products, preventing oxidative damage and rancidity.
Catechins are a type of antioxidant flavonoid polyphenol found in plants, including green tea and berries. A study from 2006 found that green tea, which contains the catechins epigallocatechin gallate, epigallocatechin, epicatechin gallate, and gallic acid, showed a strong deodorizing effect against 2-noneal [4].
A double-blind placebo-controlled parallel-group study conducted in Japan in 2015 with 80 men and women subjects aged 50–79 years found that daily ingestion of 50 mg/day, 500 mg/day, and 1000 mg/day of mushroom extract made from champignons (white button mushrooms) had increasing benefit in the reduction of both pillow and pyjama odor that was caused by 2-noneal. The study concluded that white button mushroom extract can be a safe and effective target for a dietary supplement to reduce the incidence of kareishu (“old person smell”) [5]. Increasing dietary consumption of different types of mushrooms known to be high in polyphenols is a delicious way to increase intake of these odor-fighting polyphenols. Mushrooms that are very good sources include shitake and oyster mushrooms, and to a lesser degree, porcini and portobello mushrooms.
A recent study from 2025 determined that the polyphenol N–trans-feruloylputrescine in eggplant can significantly reduce the body’s production of 2-nonenal [6]. While some people avoid eggplant because it is part of the nightshade family, eating a wide variety of eggplant may be another way to limit the production of 2-nonenal.
A 2019 study found that the presence of 2-nonenal on the skin of middle-aged and older adults was reduced by 28% when they consumed a powder made from New Zealand blackcurrants for 7 days [7]. This effect was thought to be the result of the high anthocyanin content of blackcurrants. Other berries, such as elderberry, blackberries, blueberries, and raspberries, also have very high amounts of anthocyanins, as do acai berries and pomegranate [8].
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.
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Joy
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References
- 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):520-4. doi: 10.1046/j.0022-202x.2001.01287.x. PMID: 11286617.
- Tatsuguchi, I., Matsuoka, T. et al, Preventive effect against the aged men’s body odor by the soap containing polyphenol, Journal of Japan Association on Odor Environment, 2012, Volume 43, Issue 5, Pages 362-366.
- Venn-Watson, E., Fatty 15, Omega 7: What To Know About This Fatty Acid, https://fatty15.com/blogs/news/what-is-omega-7
- 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. PMID: 16582024.
- 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. PMID: 28053896; PMCID: PMC5198824.
- 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. PMID: 40430302; PMCID: PMC12114487.
- Willems, M, Todaka M, et al, Effect of New Zealand Blackcurrant Powder on Skin Emission of Volatile Organic Compounds in Middle-Aged and Older Adults, 2019, Current Developments in Nutrition,, Volume 3, Supplement 1,
2019, https://doi.org/10.1093/cdn/nzz031.P06-092-19 - Lakshmikanthan M, Muthu S et al, A comprehensive review on anthocyanin-rich foods: Insights into extraction, medicinal potential, and sustainable applications, Journal of Agriculture and Food Research, Volume 17, 2024.
101245, https://doi.org/10.1016/j.jafr.2024.101245.
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