Skin carotenoid levels are associated with blood amyloid-beta 42/40 ratios in healthy individuals under 60 years of age

Dementia prevalence is increasing worldwide, with Alzheimer’s disease (AD) being the most common type. Amyloid-beta (Aβ) aggregation is an early pathological event in AD. Although carotenoids have been shown in vitro to inhibit Aβ aggregation through antioxidant and anti-inflammatory effects, human evidence remains limited.

Recently, blood-based biomarkers such as Aβ42/40 ratios, phosphorylated tau (p-tau181, p-tau217), and neurofilament light chain (NfL) have enabled assessment of AD-related pathology. We analyzed 770 participants from the 2024 Iwaki Health Promotion Project in Japan. The associations between circulating carotenoid levels (skin and blood) and blood AD-related biomarkers were examined using adjusted linear and nonlinear regression models in a cross-sectional design.

Among participants under 60 years, those in the highest quartile of skin carotenoid levels had significantly higher Aβ42/40 ratios than those in the lowest quartile (β = 0.0024, 95% CI: 0.0003–0.0046). The magnitude of the association was comparable to the cross-sectional difference in Aβ42/40 ratio observed across approximately 4–8 years of age. Among the blood carotenoids measured, lutein and α-carotene were positively associated with Aβ42/40 ratios.

In summary, higher circulating carotenoid levels were associated with more favorable Aβ profiles in individuals under 60 years. We sincerely acknowledge the staff involved in the Iwaki Health Promotion Project. This study was supported by the JST COI (grant numbers JPMJCE1302, JPMJCA2201, and JPMJPF2210), KAGOME CO., LTD. (Aichi, Japan), and Sysmex Corporation (Kobe, Japan).

Department of Medical Data Intelligence, Research Center for Health-Medical Data Science, Graduate School of Medicine, Hirosaki University, Hirosaki, Japan Diet & Well-being Research Institute, KAGOME CO., LTD., Nasushiobara, Japan Toshitaka Yamauchi, Naoko Waki & Shigenori Suzuki Central Research Laboratories, Sysmex Corporation, Kobe, Japan Shun Murakami, Kengo Ishiki, Kazuto Yamashita, Masahiro Miura & Toshiyuki Sato Strategic Technology Planning, Technology Strategy, Sysmex Corporation, Kobe, Japan Department of Vegetable Life Science, Graduate School of Medicine, Hirosaki University, Hirosaki, Japan Tatsuya Mikami, Koichi Murashita, Shigeyuki Nakaji, Yoshinori Tamada & Ken Itoh Department of Preemptive Medicine, Innovation Center for Health Promotion, Hirosaki University Graduate School of Medicine, Hirosaki, Japan Research Institute of Health Innovation, Hirosaki University, Hirosaki, Japan Department of Stress Response Science, Biomedical Research Center, Hirosaki University Graduate School of Medicine, Hirosaki, Japan T.Y., N.W., and S.S. are employees of KAGOME CO., LTD. S.M., K.Is., K.Y., M.M., J.S., and T.S. are employees of Sysmex Corporation. All other authors declare no competing interests.

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Below is the link to the electronic supplementary material. Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material.