The carrots (Beta Rich) were purchased from an online marketplace. Prior to use, all carrots were washed with tap water and cut into stick shapes with a thickness of 1.5–2 cm. Carrot juice was prepared by juicing the washed carrots using a low-speed blender juicer (H410; Hurom Co., Ltd., Seoul, Korea). For clinical trials, the carrots and carrot juice were freshly prepared on the day of the test, while for the in vitro experiments, the carrots and carrot juice were freeze-dried using a freeze dryer and stored at −20°C until analysis. All organic solvents and other chemicals were of analytical grade or complied with the standards required for the cell culture experiments or high-performance liquid chromatography (HPLC) grade.

β-carotene was extracted from the carrots and their corresponding carrot juices using a modified version of the method described by Kim et al. [10]. All samples were freeze-dried and ground into powder. For each sample, 0.5 g of the powdered sample was mixed with 20 mL of ethanol (EtOH) and shaken in a water bath at 75°C for 10 min. Subsequently, 5 mL of 80% potassium hydroxide (KOH) was added, and the mixture was shaken again at 75°C for a further 10 min before being placed on ice for 5 min to cool. After cooling, 5 mL of hexane and an equal volume of distilled water were added, and the mixture was vortexed vigorously for 5 min. The mixture was then centrifuged at 1,977 g for 3 min at 5°C. The upper hexane layer was collected and transferred to a rotary evaporator. The remaining EtOH–water phase was discarded, and the pellet was resuspended in 10 mL of ethanol, vortexed, and shaken again at 75°C for 10 min. After 5 min of cooling on ice, 2.5 mL of hexane and an equal volume of distilled water were added, and the mixture was vortexed vigorously before centrifugation. The upper hexane layer was collected and combined with the previous extract. This process was repeated once more for a total of 3 extractions. The combined hexane layers were concentrated using a rotary evaporator under reduced pressure at 40°C until thoroughly dried. The dried extract was dissolved in 2 mL of ethanol (85:15, v/v), vortexed for 2 min, and filtered through a 0.45 µm syringe filter for β-carotene analysis.

This study was a randomized, controlled, crossover trial with 2 groups: a raw carrot group and a raw carrot juice group. Sixteen healthy adults, male and female, aged 20 to 30 yrs, were recruited. None of the participants were smokers. The participants were instructed to completely abstain from consuming processed or raw carrots, as well as any foods or supplements containing β-carotene, for one week before the experiment as a washout period. The participants’ physical characteristics were assessed by measuring their height, weight, body mass index (BMI), waist circumference (WC), hip circumference (HC), blood pressure, and blood glucose levels. The nutrient intake was assessed using the 24-h recall method, and the CAN program 6.0 (The Korean Nutrition Society, Seoul, Korea) was used to evaluate the nutrient intake data. The 16 participants were assigned randomly to the carrot (carrots 320 g + canola oil 50 mL; β-carotene 25 mg) or carrot juice (530 g + canola oil 50 mL; β-carotene 25 mg) groups. During the experimental period, the participants were provided with standardized meals, as shown in Table 1, which did not contain β-carotene. Blood samples were collected from each participant before consumption (0 h) and at 0.5, 1, 1.5, 2, 3, 4, 6, 8, 12, and 24 h after consumption. The collected blood samples were used to analyze the bioavailability of beta-carotene and assess the antioxidant capacity and the ability to reduce DNA damage. This study was approved by the Institutional Review Board (IRB) of Kyungnam University (approval number: KUIRB 1040460-A-2024-005), and informed consent was obtained from the participants who volunteered for the study.

The oxygen radical absorbance capacity (ORAC) The antioxidant activity of plasma, in terms of the change in fluorescence decay caused by the generation and elimination of oxidative radicals, was measured using an ORAC assay [12]. Peroxyl radicals were generated using 5 mM 2,2'-azobis(2-methylpropionamidine) dihydrochloride. The fluorescent standard solution was prepared with 40 nM fluorescein using the method reported by Ou et al. [13]. Fluorescence measurements were taken using a FLUOstar microplate reader (BMG Labtech, Ortenberg, Germany) with an excitation and emission wavelength of 485 and 535 nm, respectively. The results are expressed as the micromolar Trolox equivalents (μM TE) per gram of the sample by comparing the area under the curve protected using 1 μM Trolox, a water-soluble derivative of vitamin E (6-hydroxy-2,5,7,8-tetramethylchroman-2-carbonyl acid).

The total radical-trapping antioxidant potential (TRAP) of plasma was measured using the inhibition assay method described by Rice-Evans and Miller [14]. This method measures the degree of absorbance inhibition of the 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation, which is formed by an interaction of ferryl myoglobin radical species, generated by activating ABTS (150 mM) and metmyoglobin (25 mM) with H₂O₂ (75 mM). Absorbance inhibition is proportional to the antioxidant capacity present in the sample (0.84% plasma). The samples were incubated at 30°C for 8 min, and the change in absorbance was measured at 740 nm using an ultraviolet-visible (UV-VIS) spectrophotometry (UV/VIS) spectrophotometer. The total antioxidant capacity of the plasma sample was calculated using a Trolox calibration curve and is expressed as the Trolox equivalent antioxidant capacity (mM).

All data were entered into an MS Excel database system and analyzed using SPSS (version 23.0) for Windows (IBM Corp., Armonk, NY, USA). The percentages and mean values ± SE deviation or SE of the mean were calculated for each variable. The differences over time within the raw carrot or raw carrot juice groups were evaluated using analysis of variance with Duncan’s multiple range test, with significance determined at P < 0.05. In addition, the differences between the raw carrot and raw carrot juice groups were assessed using a Student’s t-test, with statistical significance set at P < 0.05.

Table 2 lists the β-carotene concentrations in raw carrots and carrot juice. The β-carotene concentration in carrots was significantly higher than in carrot juice (7.88 ± 0.24 vs. 4.78 ± 0.24 mg/100 g). Based on this analysis, the participants consumed 320 g of carrots and 530 g of carrot juice to ensure the intake of 25 mg of β-carotene in both groups.

Table 3 lists the demographic and baseline characteristics of the study participants. Both groups, those consuming carrots and those consuming carrot juice, consisted of 16 participants each, with six males and 10 females in both groups. The average age of the participants was 22.75 ± 0.48 and 22.38 ± 0.42 yrs in the carrot and carrot juice groups, respectively. The height, body weight, BMI, systolic blood pressure (SBP), diastolic blood pressure (DBP), WC, and HC were similar in both groups. Based on the dietary and nutritional information assessed prior to the clinical trial, the participants’ average daily caloric intake was 2,535.8 ± 177.9 kcal, with carbohydrate, protein, and fat consumption within the normal range. Furthermore, the intake of β-carotene was 0 mg per day (data not shown).

Figs. 1 and 2 show the plasma fat-soluble vitamin measurement results. Fig. 1 provides a visual representation of the mean ± SE for both groups, indicating the overall trends in the plasma β-carotene concentrations. Significant differences in β-carotene absorption between the raw carrot and carrot juice groups were observed from 0.5 to 6 h post-consumption, with the plasma β-carotene levels peaking at 1.5 h in both groups. The raw carrot group reached 3.74 ± 0.39 μg/mL, while the carrot juice group peaked at 8.72 ± 2.72 μg/mL, as shown in Fig. 1. The peak plasma concentration in the juice group was 2.33 times higher than in the raw carrot group. By 8 h post-consumption, the plasma β-carotene levels returned to near the baseline in both groups.

Furthermore, the area under the curve (AUC) for β-carotene absorption was 2.09 times greater in the juice group than in the raw carrot group, suggesting enhanced bioavailability from carrot juice (raw carrots: 15.58 ± 2.36 μg/mL, carrot juice: 32.56 ± 4.39 μg/mL, data not shown). The plasma α-carotene levels increased in both groups after consumption, but significant differences were observed within each group. Similarly, no significant changes in the plasma concentrations were observed for retinol, γ-tocopherol, α-tocopherol, lycopene, or coenzyme Q10 following the consumption of raw carrots or carrot juice (Fig. 2). Hence, carrot juice significantly improves the bioavailability of β-carotene compared to raw carrots, likely due to the breakdown of the cell walls and the improved release of β-carotene during the juicing process.

Table 4 lists the changes in plasma antioxidant activity, measured using the ORAC and TRAP assays, following the intake of carrots and carrot juice. The ORAC values peaked at eight and 12 h in both groups (1.03 ± 0.09 or 1.15 ± 0.09 μM TE for carrots and 1.27 ± 0.14 or 1.14 ± 0.04 μM TE for carrot juice). On the other hand, the TRAP values did not show a similar trend, with fluctuations observed in both groups.