Daily Consumption of a Fruit and Vegetable Smoothie Alters Facial Skin Color

Abstract

Consumption of dietary carotenoids or carotenoid supplements can alter the color (yellowness) of human skin through increased carotenoid deposition in the skin. As fruit and vegetables are the main dietary sources of carotenoids, skin yellowness may be a function of regular fruit and vegetable consumption. However, most previous studies have used tablets or capsules to supplement carotenoid intake, and less is known of the impact of increased fruit and vegetable consumption on skin color. Here, we examined skin color changes in an Asian population (Malaysian Chinese ethnicity) over a six week dietary intervention with a carotenoid-rich fruit smoothie. Eighty one university students (34 males, 47 females; mean age 20.48) were assigned randomly to consuming either a fruit smoothie (intervention group) or mineral water (control group) daily for six weeks. Participants' skin yellowness (CIELab b*), redness (a*) and luminance (L*) were measured at baseline, twice during the intervention period and at a two-week follow-up, using a handheld reflectance spectrophotometer. Results showed a large increment in skin yellowness (p<0.001) and slight increment in skin redness (p<0.001) after 4 weeks of intervention for participants in the intervention group. Skin yellowness and skin redness remained elevated at the two week follow up measurement. In conclusion, intervention with a carotenoid-rich fruit smoothie is associated with increased skin redness and yellowness in an Asian population. Changes in the reflectance spectrum of the skin suggest that this color change was caused by carotenoid deposition in the skin.

Fig 1. Study design and participant attrition.

Considering total carotenoid and calorie intake in baseline diet, participants were assigned into intervention or control group by block randomization. Participants received either a smoothie or water every weekday for 6 weeks, and skin color was measured at baseline and in weeks 5, 7 and 9. 80.5% of the participants in the smoothie group and 85% of the participants in the control group completed the intervention.

Fig 2. Skin color measurement of face regions.

Locations of skin color measurements. Measurements were made from the left cheek, right cheek and forehead using a Konica Minolta CM2600d spectrophotometer. Measurements were made in the CIELab color space, in duplicate. Mean values across both measurements and all 3 locations were calculated for luminance (L*), redness (a*) and yellowness (b*) color axes. The individual in the image has given written informed consent (as outlined in the PLoS consent form) to publish her image.

Fig 3. Change in skin yellowness.

Skin yellowness was determined before (week 0), during (week 5), and at the end (week 7) of the intervention period, and at two week follow-up (week 9), using a handheld reflectance spectrophotometer. Solid line indicates the intervention group, dashed line indicates the control group, error bars represent the standard error of the mean.

Fig 4. Change in skin redness.

Skin redness was determined before (week 0), during (week 5), and at the end (week 7) of the intervention period, and at two week follow-up (week 9), using a handheld reflectance spectrophotometer. Solid line indicates the intervention group, dashed line indicates the control group, error bars represent the standard error of the mean.

Fig 5. Change in skin luminance.

Skin luminance was determined before (week 0), during (week 5), and at the end (week 7) of the intervention period, and at two week follow-up (week 9), using a handheld reflectance spectrophotometer. Solid line indicates the intervention group, dashed line indicates the control group, error bars represent the standard error of the mean.

Fig 6. Changes in the reflectance spectrum of the skin.

To confirm that color changes in the skin were likely to be correlated with carotenoid deposition in the skin, the change in the spectral reflectance of the skin between the baseline and week 5 measurements was calculated at 10 nm intervals from 400–540 nm. An increase of skin reflectance between 450 nm and 510 nm was seen in the intervention group (solid line), while no increased skin reflectance was measured in the control group (long dashed line). Absorption spectra for β-carotene (dotted line) and lycopene (short-dashed line) in 80% ethanol, 20% ether are included for comparison.