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.
Table 1.
Composition of carotenoid rich smoothies.
Participants in the intervention group consumed a carotenoid rich fresh fruit smoothie (500 mL) every weekday for 6 weeks. Fruit and vegetables were peeled and juiced with the exception of chiku, banana and red dragon fruit, where fruit pieces were blended with the mixed juices and the lipid source. Energy content (kcal) was calculated from values published in Tee et al [12], the Canadian Nutrient File [13] and Carotino’s manufacturer [16].
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.
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.
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.
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.
Table 2.
Physiological characteristics of participants at baseline.
At baseline, participants’ height and weight were measured, and their body composition, total body water (TBW) and basal metabolic rate (BMR) estimated using a Tanita SC-330 body composition analyzer. Skin color was measured in the CIELab color space using a Konica Minolta CM2600d spectrophotometer.
Table 3.
HPLC analysis of carotenoid content of smoothies: Representative smoothie samples were collected every study day and stored at -20° C until analysis.
Quantity of carotenoids was determined by HPLC-UV. Each smoothie sample was extracted and analyzed in triplicate. Six different smoothie recipes (A–F) were created to deliver variations in taste, and depending on availability of raw ingredients, smoothie A–F were prepared on 9, 8, 2, 7, 7 and 4 study days respectively. Values in the table are average carotenoid content in each of the 6 smoothie variations used in the study (± SD).