The relationships of plasma retinol, retinol-binding protein (RBP), beta-carotene, and alpha-tocopherol with their potential determinants, plasma cholesterol and triglyceride, body fat, dietary intake, stages of pubertal development, and drugs, were examined in a French sample of 263 boys and 246 girls aged 10-15 y. By use of multiple-regression analysis, plasma retinol concentration was positively related to plasma cholesterol and triglyceride, sexual-maturation index, body fat, and being male. For plasma RBP the same predictors were identified. Plasma beta-carotene was positively related to plasma cholesterol and beta-carotene nutrient density and negatively related to body fat and plasma triglyceride. Three predictors of plasma alpha-tocopherol were identified: plasma cholesterol and vitamin E nutrient density, which were positively related to its concentration, and sexual-maturation index, which was negatively related. These results confirm that physiological developmental age should be considered in epidemiologic studies of plasma fat-soluble vitamins in adolescents.

A segregation analysis using a regressive model with generation- and age-dependent effects was applied to familial data of height-adjusted weight to investigate the major gene hypothesis. The sample included 629 nuclear families with 2,534 members volunteering for a free health check-up in the Preventive Medicine Center of Vandoeuvre-lès-Nancy, France. The familial correlations were 0.094 +/- 0.040 between spouses, 0.198 +/- 0.023 between parent and offspring, and 0.327 +/- 0.034 between siblings. The variability of the trait was higher in parents than in offspring. The most parsimonious genetic model indicated a codominant major effect increasing with age in childhood, then stabilizing in adulthood. The same data were analyzed using the classical mixed model, assuming equality of variances between parents and offspring, no resemblance between spouses, similar parent-offspring and sib-sib correlations, and identical effects in parents and offspring. This analysis indicated a recessive solution. In both analyses, mendelian transmission was rejected. However, the mixture of two distributions in the recessive model, instead of three in the codominant one, was less constraining with respect to the test of transmission probabilities, and the rejection of mendelian transmission was due to a single family in the recessive case, instead of several families in the codominant one. This could possibly explain why previous studies, all using the mixed model, found evidence for a recessive major gene. Although the major gene hypothesis cannot be definitely ruled out from our results, the mechanism appears more complex than the effect of one single gene.

The dietary history method was used to determine the total energy and macronutrient intake, the distribution of daily energy from the different meals and the energy contribution of various food groups, in a population of 299 boys, aged between 10 and 15 years. The effects of age, the social status of the father (SPS), the ponderal index, the importance of breakfast or lunch, and the level of energy intake on dietary indicators, were studied. In our population, energy intake increased with increasing age but the energy contribution of macronutrients did not vary. The diet of boys whose fathers were in the upper SPS classes differed from the diet of those boys whose fathers were manual workers: for example they consumed less energy and pastries, but more animal protein (in percentage of energy intake), more dairy products, and more fruit. The ponderal index was negatively related to energy intake but positively related to protein intake, especially from meat and meat products. The energy intake from protein, animal protein and the energy contribution of dairy products, meat and meat products, fish and vegetables was lower among large eaters than among small eaters. The energy contribution of pastries, sugar and sweets was higher among large eaters. Similarily, the energy intake from morning and evening snacks was also higher among large eaters. It should be noted that boys who had a substantial breakfast took in less energy from all other meals (including snacks and main meals). Such informaton is necessary in order to develop an effective health programme.

The comparison of various adiposity indices in children and adolescents shows that there is a great similarity between the indices, and also between their ability to distinguish extreme groups. The adiposity indices used are highly correlated with weight and subscapular skinfold thickness, and are not generally independent of height. Differences in these correlations appear during the period of puberty. Discrimination of obese and non-obese subjects by the indices and by clinical opinion agrees in 65%-75% of instances, with no one index agreeing better than the others.

The relationships of diet, development, and maturation indices to the status of blood iron and folate indicators were studied among 233 adolescent girls aged 10-16 years. Statistically significant associations between total iron intake and hemoglobin, plasma iron,