Sensitivity of Pressure-Mediated Reflection Spectroscopy to Detect Changes in Skin Carotenoids in Adults Without...

The sensitivity of commercially available devices to detect changes in skin carotenoids is not known.

We aimed to determine the sensitivity of pressure-mediated reflection spectroscopy (RS) to detect changes in skin carotenoids in response to increasing carotenoid intake.

Nonobese adults were randomly assigned to a control (water; n = 20; females = 15 (75%); mean age: 31 ± 3 (SE) y; mean BMI: 26 ± 1 kg/m²) or one of 3 carotenoid intake levels: 1) LOW - 13.1 mg; n = 22; females = 18(82%); age: 33 ± 3 y; BMI: 25 ± 1 kg/m²; 2) MED - 23.9 mg; n = 22; females = 17 (77%); age: 30 ± 2 y; BMI: 26 ± 1 kg/m²); or 3) HIGH - 31.0 mg; n = 19; females = 9 (47%); age: 33 ± 3 y; BMI: 24 ± 1 kg/m². A commercial vegetable juice was provided daily to ensure that the additional carotenoid intake was achieved. Skin carotenoids (RS intensity [RSI]) were measured weekly. Plasma carotenoid concentrations were assessed at wk 0, 4, and 8. Mixed models were used to test the effect of treatment, time, and their interaction. Correlation matrices from mixed models were used to determine the correlation between plasma and skin carotenoids.

A correlation was observed between skin and plasma carotenoids (r = 0.65; P < 0.001). Skin carotenoids were greater than baseline starting at week 1 in the HIGH (290 ± 20 vs. 321 ± 24 RSI; P ≤ 0.01), week 2 in the MED (274 ± 18 vs. 290 ± 23 RSI; P ≤ 0.03), and week 3 in the LOW (261 ± 18 vs. 288 ± 15 RSI; P ≤ 0.03). Compared with control, differences in skin carotenoids were observed starting at week 2 in the HIGH ([268 ± 16 vs. 338 ± 26 RSI; P ≤ 0.01] except for week 3 [287 ± 20 vs. 335 ± 26 RSI; P = 0.08]) and week 6 in the MED (303 ± 26 vs. 363 ± 27 RSI; P ≤ 0.03). No differences were observed between the control and LOW.

These findings demonstrate that RS can detect changes in skin carotenoids in adults without obesity when daily carotenoid intake is increased by 13.1 mg for a minimum of 3 wk. However, a minimum difference in intake of 23.9 mg of carotenoids is needed to detect group differences. This trial was registered at ClinicalTrials.gov as NCT03202043.