Results

Presented in Table 1 are descriptive characteristics of the study sample stratified by supplement type. In general, there are few significant differences in the variables associated with supplement type. The means for most outcome measures appear greater among adolescents who consumed Atole during childhood, but the differences reach statistical significance 1P<0.05) for stature and radial bone width only among girls.

TABLE 1 Descriptive characteristics of the sample by gender and type of supplement¹'

	Boys		Girls
Characteristics	Atole	Fresco	Atole	Fresco
n	100	88	79	89
Age y	16.7 ± 0.4	16.7 ± 0.4	16.8 ± 0.4	16.6 ±0.4
Weight kg	44.9 ± 1.1	43.3 ± 1.2	41.8 ± 0.9	42.0 ± 1.0
Stature cm	153.6 ± 1.2	151.4 ± 1.3	148.6 ± 0.8*	145.7 ± 0.8
BMC g/cm	0.78 ± 0.02	0.77 ± 0.02	0.66 ± 0.01	0.64 ± 0.01
BW cm	1.22 ± 0.02	1.18 ± 0.02	1.06 ± 0.01*	1.03 ± 0.01
BD g/cm2	0.63 ± 0.01	0.64 ± 0.01	0.61 ± 0.01	0.62 ± 0.01
Supplement kcal	161,531 ± 17,063*	42,346 ± 4,514	161,493 ± 20,911*	50,979 ± 5,670

¹ Values are means ± SE. * P<0.05 (Atole versus Fresco). Abbreviations used: BMC, bone mineral content; BW, bone width; BD, bone density.

There are few adolescent samples available that provide mean radial density measures that may be used as comparisons. In Figure 1, the means for bone mineral content (a,b) and bone density (c,d) are plotted against age for boys (a,c) and for girls (b,d) with data for German adolescents (Runge et al. 1980). Guatemalan boys and girls have less bone mineral content and bone density compared with German adolescents but the overall pattern of age-associated changes appears similar. The Guatemalan adolescents approximate the fifth percentile of the NCHS reference data for stature and weight (Martorell et al. 1995b).

FIGURE 1 Bone mineral content (BMC) and bone density (BD) in Guatemalan and German boys and girls (Runge et al. 1980). Values are the means of BMC (a,b) and BD (c,d) over i-y age intervals plotted at each interval midpoint for boys (a,c) and girls (b,d) separately.

Effects of energy supplementation on bone mineralization, weight and stature are presented in Table 2 with the genders pooled. Presented in the first column, are estimates of the unadjusted effect of supplementation on each outcome measure. Again, the effects on each variable are measured in standard deviation units per 100 square root of kcal, (SD/100

) which translated back, means the consumption of ~10,000 kcal/41,840 kJ of supplement during childhood. As shown, early energy supplementation significantly increased each of the outcome measures to similar degrees.

TABLE 2 Effects supplementation d using early childhood on bone mineralization, weight and stature during adolescence¹

	Supplementation effects (100
Outcome measures (SD units)	Unadjusted2	Adjusted3	Adjusted4
BMC	0.198 ± 0.026*	0.072 ± 0.019*	0.076 ± 0.020*
BW	0.182 ± 0.026*	0.097 ± 0.024*	0.094 ± 0.024*
BD	0.152 ± 0.022*	0.040 ± 0.015*	0.058 ± 0.016*
Weight	0.212 ± 0.025*	0.035 ± 0.020	0.033 ± 0.021
Stature	0.220 ± 0.025*	0.054 ± 0.023*	0.028 ± 0.025

1 Values are the beta coefficients ± SE for the supplementation terms estimated using linear regression. All are expressed in SD/100
units. * P<0.05. Abbreviations used: BMC, bone mineral content; BW, bone width; BD, bone density; SD, standard deviation.

² Unadjusted effect of supplementation.
³ Effect adjusted for each subject's gender, age (see text).
⁴ Effect adjusted for gender, age and for type of supplement consumed.

In the next column of Table 2, are estimates of the effects of supplement consumed on each outcome variable after adjusting for each subject's gender and age. As stated earlier, the specification of the age variables in the models depended on the outcome of interest (see Materials and Methods for specification). The effects of supplementation are diminished by this adjustment, but significant effects of supplementation on bone mineralization can still be demonstrated. The effects of supplementation on weight and stature are reduced to a greater extent by this adjustment, and remain statistically significant at the 0.05 level only for stature. The P level for the coefficient in the weight model is 0.08, however, and is still suggestive of a supplementation effect.

Finally, in the third column of Table 2, are estimates of the effect of supplement consumed on bone mineralization, weight and stature after adjusting for the type of supplement consumed during early childhood. Differences in bone mineralization associated with village of residence (as opposed to supplement type, per se) were observed; however, after adjustment, statistically significant effects of the amount of calories from supplement consumed during childhood on bone mineralization during adolescence are still observed, irrespective of supplement type. The magnitude of these effects is similar across the three bone measures (~0.06 - 0.09 SD/

). As shown, the effects of supplementation on weight and stature become statistically nonsignificant for both weight and stature after adjusting for type of supplement consumed.

To test for bone-specific effects of the supplementation, weight and stature, were added, separately and in combination, to the regression models (Table 3). As shown here, the effects of supplement on bone mineralization are no longer statistically significant.
Interaction terms between supplement type and cumulative supplemental energy intake were not statistically significant in any models, again supporting the conclusion of energy effects per se, excluding effects due to protein, calcium or phosphorus.

TABLE 3 Effects of supplementation during early childhood on bone mineralization during adolescence: effects adjusted for current weight and stature¹

	Supplementation effects (100 )
Bone status measures (SD units)	Adjusted2	Adjusted3	Adjusted4
BMC	0.013 ± 0.016	0.015 ± 0.017	0.024 ± 0.018
BW	0.020 ± 0.023	0.017 ± 0.022	0.005 ± 0.022
BD	0.019 ± 0.014	0.024 ± 0.015	0.015 ± 0.014

1 Values are the beta coefficients (±SE) for the supplementation terms estimated using linear regression. All are expressed in SD/100
units. * P<0.05. Abbreviations used: BMC, bone mineral content; BW, bone width; BD, bone density; SD, standard deviation.

² Adjusted for each subject's gender, age, the type of supplement consumed and weight.

³ Adjusted for each subject's gender, age, the type of supplement consumed and stature.

⁴ Adjusted for each subject's gender, age, the type of supplement consumed and weight and stature.