Am J Clin Nuir 1994:59:1369-75. Printed in USA. © 1994 American Society for Clinical Nutrition 1369

Plasma response of children to short1erm chronic/3-carotene supplementation�3

Jesus Bulux, Julieta Quan de Serrano, Anna Giuliano, Rosalba Perez, C’armen Yolanda Lopez,

Carlos Rivera, Noel W Solomons, and Louise M Canfield

ABSTRACT Plasma concentrations of fl-carotene and reti-

nol after supplementation of children with fl-carotene in supple-

ments and in foods were compared in Guatemalan children. The

children received 6 mg/d /3-carotene [1000 retinol equivalents

(RE)] as purified supplements or as carrots for 20 d and the ef-

fects on plasma /3-carotene and retinol concentrations were as-

sessed. Plasma concentrations of f3-carotene were increased by

0.59 ± 0.65 and 0.60 ± 0.67 �umol/L after supplementation with

�3-carotene capsules for 10 and 20 d, respectively. Addition of

cooked carrots to the diet resulted in no significant change in

plasma /3-carotene. Fasting plasma retinol concentrations were

I .23 ± 0.35 j�tmol/L and were not significantly changed in re-

sponse to supplementation with either of the carotene treatments

or with retinyl palmitate ( 1000 REid) for 20 d. Possible expla-

nations for the differences in effects of plasma concentrations

between the two methods of supplementation are discussed.

Am J Clin Nutr 1994;59:1369-75

KEY WORDS /3-Carotene bioavailability, vitamin A, vita-

mm A deficiency, absorption, carotene supplementation

Introduction

Mild to moderate degrees of vitamin A deficiency predispose

children to increased morbidity and mortality (1 -3). Carotenoids

in foods furnish the majority of vitamin A for the world’s pop-

ulation. Thus, efficient intervention programs to improve vitamin

A status in children of the Third World are needed. Although

effective as a short-term solution, programs that rely on admin-

istration of vitamin A as retinyl palmitate are costly and logisti-

cally difficult in developing countries (4). Due to their lower cost

and abundance in most food systems, dietary provitamin A ca-

rotenoids would be the preferred long-term solution to the prob-

1cm. We have previously shown that single doses of 15 or 30 mg

/3-carotene produce measurable and sustainable increases in

plasma carotene concentrations when administered to children

(5). In addition, we have presented preliminary evidence that

plasma retinyl ester concentrations can be increased in vitamin

A-low-to-deficient children (6) by single doses of purified /3-

carotene. These data suggest that /3-carotene can provide a retinol

source for vitamin A-deficient children; however, neither the

amounts required in the diet nor the factors affecting /3-carotene

availability from foods have been determined. As a first step to-

ward these determinations, we compared in children the response

of plasma /3-carotene and retinol to supplementation for 20 d with

/3-carotene capsules or with carrots. Both purified supplements

and carrots provided 6 mg /3-carotene/d, to approximate the range

of the recommended dietary allowance (RDA) of retinol for chil-

dren (7). As a frame of reference, plasma retinol response to

retinyl palmitate supplementation was measured.

Subjects and methods

Subjects

Seventy-five school-age children (7- 12 y) of both sexes with

weight-for-height adequacies between 86% and 137% with re-

spect to the National Center for Health Statistics (NCHS) stan-

dard (8) were selected from 168 first- to fourth-grade children at

the Escuela Belen in Antigua, Guatemala, a colonial city, 45 km

from the present capital of the Republic. Parents were invited to

a meeting in which they were informed about vitamin A defi-

ciency in Guatemala, the purpose of our study, and the candidate-

selection criteria. To meet the selection criterion for the study,

we required that the child be: I) enrolled in the first to fourth

grades of the school, aged 7- 12 y; 2) willing to be in the study;

3) in general good health and with adequate anthropometric nu-

tritional status; 4) without a history of chronic gastrointestinal

disease; and 5) not taking any regular gastrointestinal medica-

tions. Parents of children who were chosen as candidates to par-

ticipate in the supplementation study signed an informed consent

form that was previously approved by the Human Subjects Corn-

mittees at both CeSSIAM and the University of Arizona.

On the days of study, the children arrived at school by 0730,

having consumed breakfast at home. Subjects were identified

with code numbers and a blood sample (4 mL) was drawn from

each child’s forearm by venipuncture. The blood was transferred

to a heparin-coated glass tube and centrifuged at 600 x g at room

temperature for 5 mm. Plasma was separated, placed in a light-

� From the Department of Biochemistry, University of Arizona, Tuc-

son, AZ and, the Center for Studies of Sensory Impairment, Aging andMetabolism (CeSSIAM), Research Branch for the National Committeefor the Blind and Deaf of Guatemala, Guatemala City. Guatemala.

2 Supported by grants from the Thrasher Fund (2801 -0) and the Na-

tional Institutes of Health (HD26715).3 Address reprint requests to L Canfield, the Department of Biochem-

istry, University of Arizona, Tucson, AZ 85721.Receivedluly 14, 1993.Accepted for publication December 14, 1993.

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protected, hermetically sealed, screw-top vial, and stored at -20

OC until it could be transported to the University of Arizona.

The children were divided at random into four groups for sup-

plementation: group 1, placebo (n = 17); group 2, retinyl pal-

mitate (n = 17); group 3, /3-carotene in carrots (n = 17); and

group 4, /3-carotene supplements (n = 16). Subjects in group I

were administered a placebo (330 mg cellulose microcrystals)

three times per week (Monday, Wednesday, and Friday). Cap-

sules were either administered whole or the capsule opened and

the contents poured into the child’s mouth. Each subject in group

2 was administered retinyl palmitate [1000 retinol equivalents

(RE)1 in oil, orally each day by syringe. Each day subjects in

group 3 received 60-g portions of carrots that had been cooked

in oil, frozen, and reheated in a microwave. This serving con-

tamed so g carrot and 10 g absorbed vegetable fat. The mean

concentration of /3-carotene in the carrots was determined to be

120 �zg/g (9). Subjects in Group 4 received daily, by visual de-

termination, one-half of a 12.6-mg capsule containing 10% /3-

carotene as water-miscible beadlets (Hoffmann La-Roche, Nut-

Icy, NJ) and 286 mg cellulose microcrystals. Beta-carotene cap-

sules were shown by HPLC analysis in a related study (10) to

provide within 95% of the stated dose. The capsules were opened

and one-half of the contents mixed into a glass of ‘ ‘horchata,’ ‘ a

rice-based beverage (5). After the supplement, to provide fat to

aid in absorption, children received an ‘ ‘empanada,’ ‘ (baked fruit

turnover), prepared by the school baker using a recipe and sup-

plies furnished by CeSSIAM. Each turnover contained 23 g fat

as shortening. Children were required to consume the entire

snack before leaving. Additional horchata was served upon re-

quest. Retinyl palmitate, /3-carotene, and placebo capsules were

stored at 4 #{176}C.To aid in subject compliance, children were re-

warded with small gifts, eg, crayons, pens, and pencil sharpeners,

for completing the period of supplementation. Sixty-five of the

original 67 subjects completed the study.

Dietary intake

Dietary intake of vitamin A sources was estimated as previ-

ously described (5), by using both a food-frequency question-

naire to ascertain relative usual intake and a quantitative food-

frequency instrument focusing on the previous 7 d to estimate

recent intake quantitatively. For both methods, we utilized food-

composition data from the Food Composition Table for Use in

Latin America (1 1), supplemented with the current revision of

the US Department of Agriculture Handbook No 8 (12). In the

present study, dietary ‘ ‘vitamin A’ ‘ denotes ‘ ‘retinol’ ‘ from the

Latin American table, or ‘ ‘vitamin A’ ‘ from the US Department

of Agriculture table and ‘ ‘/3-carotene’ ‘ denotes /3-carotene from

the Latin American table, or ‘ ‘carotenes’ ‘ from the US Depart-

ment of Agriculture table. Dietary questionnaires were adminis-

tered by a single research dietitian (JQS). The food-frequency

data were adjusted to standard portion sizes by using the US

Department of Agriculture’s ‘ ‘average portion sizes,’ ‘ and esti-

mates of nutrient composition per serving were then calculated

as previously described (5).

Recent intake of vitamin A in foods (over the past week) was

estimated by using a quantitative food-frequency instrument de-

veloped at CeSSIAM as previously described (5). This instru-

ment includes 39 vitamin A-rich items, each containing > 30

;.ig vitamin A (dietary vitamin A and /3-carotene) per 100 g edible

portion. The number of times and portion sizes of each item for

the previous 7-d period was recorded, and the responses con-

BULUX ET AL

verted to REs by using the aforementioned food composition

tables. The value was divided by seven to provide daily estimates

of total intakes of dietary vitamin A and /3-carotene.

Data management and analysis

All data were entered with DBASE III, and analyses were ac-

complished on STATA-PC software on IBM-compatible micro-

computers (STATA, Inc. Santa Monica, CA). HPLC data were

reduced, analyzed, and charted by using Graphpad(ISI Software,

Philadelphia) and Quattro (Borland International, Scotts Valley,

CA) software programs. Statistical analyses included linear re-

gression, Student’s t test, and analysis of variance (ANOVA).

Carotenoid content of carrots

Concentrations of /3-carotene in carrots were determined as

previously described (9, 13). Carrots were extracted with tetra-

hydrofuran (THF) containing 0.25 g /3-hydroxytoluene (BHT)IL

by using nonapreno-/3-carotene (C45 /3-carotene), a gift of Gary

Beecher (Nutrient Composition Laboratory, US Department of

Agriculture) of known concentration as an internal standard. Ca-

rotenoids were extracted into the organic phase, evaporated to

dryness, reextracted with petroleum ether and water ( 1 : 1 vol/vol)

containing 0.5 g NaC1 and filtered over Na2SO4 . The eluent was

again evaporated to dryness before dissolving in THF containing

0.25 g BHT/L. Extracts were flushed with argon and stored at

-70 #{176}Cuntil analysis.

Beta-carotene and retinol content in plasma

Samples were transported on dry ice to the University of Ar-

izona and stored at -70 #{176}Cuntil assayed. Six of the plasma sam-

ples were damaged or lost in transit. Before assay, the samples

were thawed and held at room temperature for 10 mm. Beta-

carotene and retinol were extracted from plasma by using a mod-

ification of previously described procedures (14). Plasma (0.25

mL) was added to 0.25 mL methanol containing /3-apo-8 caro-

tenal and vortexed for 30 s. Hexane (0.5 mL) was added and the

solution was then mixed with vortexing and centrifuged at 16 000

x g (model E Microfuge; Beckman Instruments, Inc. Palo Alto,

CA) for 2 mm. The hexane layer was removed and the pellet

reextracted with an additional 0.5 mL hexane. The hexane layers

were evaporated under nitrogen and the extracted carotenoids

resuspended in 0.075 mL HPLC running solvent (see below). Of

this, 0.05 mL was injected onto a Waters Resolve reversed-phase

C18 !O-�t column (4.6 mm internal diameter x 100 mm). HPLC

analysis was performed by using a Waters pump (model 510;

Waters Assoc, Milford, MA) with a Milton Roy programmable

detector (model SM 4000; Riviera Beach, FL). The running sol-

vent was acetonitrile:methylene chloride (80:20 vol/vol) contain-

ing 0.1% cyclohexene and 0.25 g BHTIL. Quantitation was by

external standardization as previously described (15). Standard

curves for HPLC were prepared daily from injections of at least

three different concentrations of authentic retinol and /3-carotene.

Values of both retinol and /3-carotene were corrected for recov-

cry, estimated at 82% by comparison with an internal standard

of apo-8 carotenal (n = 198). Data are reported only for samples

in which the detected response was � 3 X baseline signal (5).

Limits of detection for our assay were 0.06 j�mol/L for /3-caro-

tene and � 0.35 j.zmol/L for retinol.

Analysis for intestinal parasites

A fresh stool sample was collected on the day of the first blood

draw. Stools were processed on the same day by using a modi-

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/3-CAROTENE BIOAVAILABILITY 1371

TABLE 1

Parasite load by treatment group’

Retinyl

Parasite

Place(n =

bo17)

palmitate Carrots(n = 17) (n = 17)

/3-Caro(n =

tene16)

% of subjects

Ascaris eggs present 59 22 29 20Tricharis infection 71 61 65 53

‘ Intensity of infection was assessed as described in Methods on freshstool samples collected at the time initial blood samples were obtained.

fication of the Kato-Katz method (16). The number of eggs

counted was used to assess prevalence and intensity of infection.

Infected children were given a treatment course of the indicated

antiparasitic drug free of charge and supervised by CeSSIAM

physicians.

Results

Our subjects had significant intestinal parasite infestation, with

the highest intensity in the group receiving placebos (Table 1).

Numbers of children with parasite load varied from 20% to 59%

for ascariasis and 53% to 71% for trichuriasis. Parasite load var-

ied widely from 2000 to 18 000 eggs (Ascaris lumbricoides) and

650 to 1542 parasites (Trichuris trichura).Plasma concentrations of /3-carotene and retinol before initia-

tion of the study (Table 2) were not different among the treatment

groups (P > 0.05). The overall mean plasma retinol concentra-

tion was in the low-normal range: 1 .23 ± 0.35 �.tmol/L. Only four

subjects had initial plasma concentrations that could be considered

vitamin A deficient (< 0.7 j.�molJL). However, when measured by

groups (Table 3), 15-29% of the children were consuming diets

containing less than two-thirds of the RDA for vitamin A.

Initial /3-carotene concentrations varied from 0.06 to 0.73

�.tmol/L. In agreement with our previous reports (5, 6) and those

of others (17-34), variations in initial plasma concentrations

were large. In addition, individual responses to /3-carotene sup-

plements varied widely: from 0.09 to 2.5 jzmol/L (1 .4- to 1 1.6-

fold) at 10 d and from 0.05 to 2.6 �.tmolJL (1.3- to 12.1-fold) at

20 d.

In subjects supplemented with /3-carotene capsules, plasma /3-

carotene was elevated by 0.59 and 0.65 �mol/L after 10 and 20

d, respectively, an approximately threefold increase. The equiv-

alent dosage of /3-carotene (6 mg/d) taken in the diet as carrots

resulted in no statistically significant rise in serum /3-carotene by

either 10 or 20 d in our subjects (Fig 1).

To assess effects of diet on the response of plasma /3-carotene

to carotene supplementation, we compared the serum response

both to dietary /3-carotene and total vitamin A intake by individ-

ual and by quartile. With use of our food-frequency and 24-h

recall instruments with the available databases (1 1, 12), neither

dietary intake of /3-carotene nor retinol was predictive of the rise

of serum /3-carotene concentration after /3-carotene supplemen-

tation (data not shown).

Subjects with higher initial serum /3-carotene had higher serum

/3-carotene concentrations after supplementation with /3-carotene

for 20 d (r = 0.428; Fig 2). Thus, with the exception of a single

subject, ranking was maintained, and micromoles of /3-carotene

TABLE 2Initial concentrations of plasma /3-carotene and retinol by treatment

group’

Placebo

(n = 17)

Retinyl

palmitate

(n = 17)

Carrots

(n = 17)

/3-Carotene

(n = 16)

MmoL/L

/3-Carotene 0.27 ± 0.22 0.27 ± 0. 18 0.25 ± 0. 18 0.27 ± 0.16Retinol 1.22 ± 0.37 1.23 ± 0.32 1.26 ± 0.37 1.20 ± 0.38

‘ .1 ± SD. Determined by HPLC analysis of hexane extracts of frozen

samples as described in Methods.

increase was comparable across this population in response to

this dosage. We found no relationship between changes in plasma

/3-carotene and initial retinol concentrations (data not shown).

In response to retinyl palmitate supplementation (1000 REId),

plasma /3-carotene was slightly increased over baseline in our

subjects, however, differences were not statistically significant

from those of subjects receiving placebo (Fig I ). We were unable

to detect any significant changes in the average plasma retinol

concentrations in response to any of the treatments (Fig 3).

Discussion

Although plasma response to /3-carotene supplementation

from both foods and purified supplements have been studied sep-

arately (5, 17, 34) the present report is the first direct comparison

of this response in children. Because the optimal long-term so-

lution to the problem of vitamin A deficiency in Third World

children is to provide a source of vitamin A in the diet, these

studies were designed to compare the effects of short-term dietary

supplementation of /3-carotene with an equivalent amount of a

purified supplement on plasma concentrations of /3-carotene and

retinol. /3-Carotene was administered in an amount calculated to

TABLE 3Estimated daily dietary vitamin A intake by treatment group’

Retinyl

Placebo(n = 17)

palmitate

(n = 17)

Carrots

(n = 17)

/3-Carotene(n = 16)

Total vitamin A(RE)2 673 ± 418-’ 743 ± 643 408 ± 301 803 ± 447

Preformed

vitamin A

(RE) 206 ± 228 251 ± 350 109 ± 124 200 ± 13

/3-Carotene (RE) 383 ± 229 419 ± 330 260 ± 231 492 ± 333

Other carotenoids(RE) 83 ± 59 73 ± 58 51 ± 49 99 ± 71

< Two-thirds

RDA(%) 29 18 17 15

‘ Dietary intake of vitamin A sources was measured by using food

frequency instruments to estimate usual and recent (previous 7 d) intake.Vitamin A in foods was estimated by using the Food Composition Table

for Use in Latin America (10) and US Department of Agriculture hand-

book no. 8 (1 1). RE, retinol equivalents.

2 Retinol and carotenoids.�1± SD.

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BULUX ET AL

Although, with the exception of four subjects (Table 2), plasma

retinol concentrations of our subjects were not in the vitamin A-

deficient range (� 0.7 �mol/L or 20 �g/dL), a substantial number

of the children in the sample, (15-29%, expressed by groups,

Table 3) were consuming diets containing less than two-thirds of

the RDA for vitamin A. Vitamin A consumption at these con-

centrations or below is common in developing countries and has

recently been reported in southwestern Kenya (37). Recent data

(38) show that populations in which individuals have plasma ret-

inol concentrations � 1.05 �mol/L (30 �gIdL) benefit from an

increased intake of vitamin A as demonstrated by a shift in the

population distribution to increased serum vitamin A concentra-

tions. Although individually these children may not be diagnosed

as vitamin A deficient by their response to the relative-dose-re-

sponse assay, the most logical biological explanation of these

data is that they have suboptimal vitamin A stores that are being

replenished by vitamin A supplementation. In this event, they are

at risk for subclinical effects of low vitamin A, eg, respiratory

and gastrointestinal disease. Of our subjects, 31.7% fall in this

category. Given the significant threat to child health from gastro-

intestinal and respiratory infection in children (1 -4), the urgency

of identifying an appropriate vehicle for vitamin A administration

to these children cannot be overestimated.

The approximately three-fold increase in serum concentrations

in response to purified /3-carotene supplements that we observed

is comparable with the twofold rise in plasma /3-carotene in chil-

dren by 24 h, which we previously reported in response to a

single 30-mg supplement (5). In the present study, plasma /3-

carotene concentrations after 10 and 20 d were not statistically

, , ,0 1 0 2 0

different from each other, indicating that the maximum increase

in plasma concentrations occurs within the first 10 d.

The differences in response of serum concentrations to sup-

plementation with purified supplements and with foods that we

observed here is similar to that observed by others in human (23-

25) as well as animal studies (26, 39). In adults, either single (24)

or chronic (23) doses (30 mg) of /3-carotene capsules were five

to six times as effective as the equivalent amount of /3-carotene

in carrots. Interestingly, in chronic supplementation studies (23),

plasma lutein was decreased over control in response to /3-caro-

tene supplementation, suggesting a competition between these

FIG 1. Changes in plasma /3-carotene concentrations (±SEM) before

treatment (day 0) and after treatment for 10 and 20 d of 17 children withplacebo (0), 17 with retinyl palmitate (0), 17 with carrots, (#{149})and 16with /3-carotene (#{149}).*Significantly different from day 0 at P � 0.005.

be equivalent to 1000 RE of retinyl palmitate, ie, 6 mg purified

supplement, 50 g carrots, or 1000 �ig retinyl palmitate. The Beta-

amount of /3-carotene provided by the carrots was estimated

based on previous studies (9), in which we determined the con-

Carotene�umoVL)

�

centration of /3-carotene in cooked carrots obtained in Guate-

malan markets (120 �igIg).

Intestinal parasite load must be considered in relationship to

the intestinal handling of dietary carotenes. Investigators in Pan-

ama (35) and Indonesia (36) have provided evidence for an as-

t �

sociation between intestinal helminths and poor vitamin A status

or impaired bioavailability. We have no explanation for the im-

balance in initial distributions among treatment groups, but be-

cause the placebo group had the greater intensity of parasite in-FIG 2. Comparison by regression analysis of plasma /3-carotene con-

centrations before supplementation (t = 0) and after 20 d of supplemen-fection, the differences in response to the various supplements- tation with /3-carotene. (r = 0.428). *> 2 SDs above the mean: excludingtion treatments cannot be attributed to this variable. this value, r = 0.945.

Days of Treatment

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Days of Treatment

FIG 3. Changes in plasma retinol concentrations (±SEM) before treat-ment (day 0) and after treatment for 10 and 20 d of 17 children with

placebo ([:J), 17 with retinyl palmitate (0), 17 with carrots (U), and 16

with /3-carotene (U).

two carotenoids at the level of intestinal absorption. Our estimate

of the carotene content of our preparation was based on analyses

of samples of cooked carrots from the same region prepared by

using the same recipe (9). On two earlier occasions we analyzed

carrots from this region of Guatemala and found their content to

be similar to that from two Arizona markets. Other carotenoids

in carrots, eg, a-carotene and cryptoxanthin have provitamin A

activity (40, 41). Thus, because we considered only /3-carotene

in our estimates, subjects consuming carrots actually consumed

more provitamin A activity than those administered purified sup-

plements.

If the objective is to achieve a pharmacologic response of se-

rum /3-carotene to supplementation, the present data in children

as well as that of others in adults (17, 23, 24) clearly show that

purified supplements are more effective than the same quantity

of carotenoids in foods. However, foods provide other nutrients

not present in micronutrient supplements that are important for

the health and well-being ofchildren and are the vehicle of choice

for carotenoid ingestion if they result in increased carotenoid

absorption. Studies of carotenoid metabolism and the factors reg-

ulating its bioavailability from foods are needed to formulate

meaningful recommendations for carotenoid consumption by

children.

Possible explanations for the preferential response of plasma

/3-carotene to purified /3-carotene supplements as compared with

carotene-containing foods include binding to proteins in foods,

interference by other dietary components, eg, fiber or other lipids

including carotenoids (23), or suboptimal concentrations of fat

in the diet (25, 27). Indeed, over a 2-wk period, administration

of carrot juice, which contains less fiber, resulted in a three- to

fourfold increase in plasma /3-carotene in 10 adults (28). In ad-

dition, cooking leads to isomerization of plant carotenoids (41)

and recent studies have documented that the various carotenoid

isomers are not handled equally in the intestine. On feeding a

mixture of cis and trans isomers of /3-carotene, the trans isomer

preferentially accumulates in human serum (40) and in ferret Se-

rum and liver (39). Alternatively, carotenoid isomers may be

cleared from plasma at different rates. Thus, if foods contain

higher concentrations of a biologically active form than do sup-

plements, this form could be more rapidly cleared from plasma,

giving the appearance of lower absorption when in fact absorp-

tion of specific isomers could be increased. It is also possible that

supplementation with food must be continued for longer periods

of time than those in the present study to produce significant

effects on plasma carotenoid concentrations. In any case, in in-

terpreting these effects, as previously discussed (5), increases in

plasma concentrations of carotenoids cannot be assumed to di-

rectly reflect increased carotenoid absorption. Plasma carotene

concentrations are the result of a complex interaction of absorp-

tion, export from body stores and uptake by target tissues. In

individuals with low body stores of vitamin A, as discussed

above, disappearance from plasma could in fact, reflect more

rapid mobilization to target tissues.

In this study, dietary intake of /3-carotene was not predictive

of the response of plasma carotene to carotene supplementation.

However, the database for Guatemalan foods that we used ( I 1)

was compiled by using data collected before the introduction of

modern HPLC methods and may not be accurate for specific

carotenoids in Guatemalan foods. In contrast, initial serum car-

otene concentrations were strongly predictive of final carotene

concentrations. Similarly, in a large study of men (n = 222) a

strong correlation (0.64) was observed between baseline serum

/3-carotene and increases in /3-carotene after /3-carotene supple-

mentation for 2 mo (42). Taken together, these data suggest that

intestinal absorption of pharmacological doses of /3-carotene is

not stringently controlled. Further work on the factors regulating

/3-carotene absorption is needed.

With respect to vitamin A status as a predictor of /3-carotene

uptake, we found no relationship between changes in plasma /3-

carotene and initial retinol concentrations. Similar results have

been reported by others (19) and are in agreement with our earlier

studies of single carotene doses in children (5).

Because carotenes are apparently first metabolized to retinol

in the intestine and then esterified to retinyl esters for export to

the liver, postprandial serum retinyl palmitate may provide a sen-

sitive measure of the effectiveness of /3-carotene as a source of

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1374

retinol in vitamin A-deficient children (43). In Egyptian chil-

dren, carrots in the diet in amounts similar to those used here

were sufficient to increase plasma retinol concentrations in vita-

mm A-deficient children (44, 45). Similarly, two subjects in our

study with low initial plasma retinol concentrations (0.65 and

0.8 1 �molIL) who received the carrot supplement showed almost

twofold increases in plasma retinol (1 . 16 and 1.51 �.imol/L, re-

spectively) after 20 d. In addition, we presented preliminary data

(6) showing that plasma retinyl ester concentrations in vitamin

A-low-to-deficient children (plasma concentrations of 0.7-1.!

�tmol/L) were increased relative to control subjects in response

to single doses of carotene capsules. We were unable to detect

any significant changes in the average plasma retinol concentra-

tions of any of the groups (Fig 3). However, plasma retinol is an

insensitive index of vitamin A status because it is only responsive

at the extremes of deficiency and toxicity (46). Because our pop-

ulation was not frankly vitamin A-deficient, the duration and

dosage used here may not be sufficient to produce a statistically

significant response in this sample size.

The effect of varying vitamin A status on carotene supple-

mentation, particularly in children, deserves further study. Recent

data generated using stable isotopes indicate that, in contrast to

pharmacological doses such as those used here, /3-carotene in the

amounts commonly consumed in the diet (< 6 mgld) is essen-

tially converted to retinyl palmitate in the intestine (47). Thus

under physiological (dietary) conditions, /3-carotene may be me-

tabolized in the intestine to supply the body’s need for retinol,

but when these needs are met, ie. in pharmacological doses, or

in retinol-replete subjects, carotene may be absorbed intact.

In summary, in this population of children (initial plasma ret-

inol 1 .23 ± 0.35 pmollL), short-term administration of /3-caro-

tene capsules (6 mgld) produced a threefold increase in plasma

/3-carotene by 10 d. Equivalent /3-carotene intake in carrots re-

suIted in no significant changes in plasma /3-carotene. The

differences may reflect lower bioavailability of /3-carotene from

foods as compared with capsules. There is substantial individual

variation in plasma carotene concentrations and in the response

to supplementation, although rank order is maintained after sup-

plementation relative to baseline plasma /3-carotene. We were

unable to demonstrate a relationship of plasma /3-carotene con-

centrations to diet in this population. Preliminary data in our lab-

oratory indicate that vitamin A deficiency may enhance both car-

otene absorption and its conversion to retinol. Experiments are

in progress to test this hypothesis. U

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