Diet and Growth in Young Vegetarians
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Feeding from Toddlers to Adolescence: edited by Angel Ballabriga, Nestle Nutrition Workshop Series, Vol. 37. Nestec Ltd., Vevey/ Lippincott-Raven Publishers, Philadelphia, © 1996. Diet and Growth in Young Vegetarians Marijke van Dusseldorp,* Pieter C. Dagnelie,** and Wija A. van Staveren* *Department of Human Nutrition, Agricultural University, Wageningen, The Netherlands; **Institute of Internal Medicine II, Erasmus University, Rotterdam, The Netherlands The popularity of vegetarianism has increased greatly over the past few years because of concern about the environment, animal welfare, and healthy eating. From a historical point of view, the pursuit of vegetarianism for reasons of physical health is a recent phenomenon. Before the nineteenth century, a diet without animal food either represented a habit justified by moral and metaphysical arguments or was due to poverty in areas where animal food was hardly available. Only as nutritional sci- ence expanded from the mid-twentieth century onward did vegetarianism acquire general recognition as a healthful diet (1-3). Although these diets offer advantages to the health of adults because of their low saturated fat and high fiber content, the adequacy of strict vegetarian diets in children has been questioned. For instance, the adoption of such diets for young children has been associated with stunting (4), and the adoption by female teenagers was associated with disorders of menstruation (5). When diets with no animal foods are used, the risk of nutrient deficiency is greatest during periods of physiologic stress and accelerated growth. Such diets may contain inadequate amounts of some nutrients, e.g., vitamin B12, vitamin D, iodine, taurine, and some long-chain polyunsaturated fatty acids such as eicosapentaenoic (20:5n-3) and docosahexaenoic (22:6n-3). Furthermore, plant foods contain compo- nents that may decrease the absorption of several minerals, such as iron, zinc, and calcium. These components occur in higher concentration in unrefined plant foods, which are favored by many vegetarians and which they also feed to their children. This may lead to iron deficiency anemia and rickets. In 1982, we conducted a study on the effects on height and weight of vegetarian diets practiced by an ecological, anthroposophic, and macrobiotic group of Dutch preschool children. The study showed that the ecological and anthroposophic groups of children were fed lacto-ovo-vegetarian diets and were somewhat lighter and shorter than a control group fed an omnivorous diet (6). The lacto-ovo-vegetarian diets con- formed better to the Dutch recommended dietary allowances (RDAs) (7) than the omnivorous and macrobiotic diets. This conforms to other and more recent findings (3,8). In contrast, height and weight of the children fed macrobiotic diets were signifi- 209 210 DIET AND GROWTH IN YOUNG VEGETARIANS cantly less than in the control group. Children fed the macrobiotic diet had a very restricted, almost vegan type of diet, consisting of grain cereals (mainly rice), vegeta- bles, and pulses with small additions of seaweeds, fermented foods, nuts, seeds, and seasonal fruits, and some fish. Intakes of calcium, riboflavin, and vitamin D recorded for children on the macrobiotic diet were substantially below the Dutch RDAs. To determine at what age growth in children on macrobiotic diets slows down, and if any return to the norm occurs later in childhood, an anthropometric study was per- formed in the Dutch macrobiotic child population aged 0-8 years (n = 243) (9). Anthropometric measurements included weight, height, mid-upper arm circumfer- ence, and triceps and subscapular skinfolds. The results showed that the age curves followed the median of the standard (10,11) until the age of 6 months, after which a marked decline was observed, reaching a minimum level (10th centile) between 1.5 and 2 years. After the age of 2 years, the anthropometric data showed only a partial return to the 50th centile. In close collaboration with macrobiotic teachers, dietary recommendations were formulated and sent in a brochure to the parents. The guide- lines included the following: 1. The addition of fat in meals as an additional source of energy. 2. The inclusion of 100-150 g of fatty fish as an extra supply of vitamins B12 andD. 3. Addition of at least one serving of dairy products in the diet as a source of calcium, vitamin B2, and protein. For followers of the macrobiotic diets, this was the most difficult recommendation to adopt. The present chapter will discuss results of a follow-up study conducted 2 years after the first cross-sectional study and 6 months after the parents had received the instructional brochure. In addition, data on a subgroup of children contacted again in 1993 will be reported. Parts of the follow-up study and an in-depth mixed longitudi- nal study on diet and growth during the weaning period in children on macrobiotic diets have been published earlier (12-15). CHANGES IN DIET AND GROWTH IN CHILDREN AGED 2-9 YEARS ON MACROBIOTIC DIETS Subjects One hundred and ninety-four children (98 boys and 96 girls) participated in the study. This is 80% of the original population. Nonresponse was due to refusals (4%), removals (1%), children younger than 2 years (1%), children no longer fed a macrobi- otic diet (12%), and not all measures being completed (6%). Methods For an extensive description of the methods, see Dagnelie et al. (9). DIET AND GROWTH IN YOUNG VEGETARIANS 211 Anthropometry Body weight was measured using a SECA 707 electronic scale with the child wear- ing light clothing. Standing height was measured with a flexible steel tape, which was attached to a metal bottom and top board. The measurements were performed by four trained observers. Quality control with a reference observer showed an over- estimation in height of 0.4 cm (p < 0.001). Reference Values Data from The Netherlands third nationwide survey (1980) were used as a refer- ence (10). Questionnaire Food habits of the participants were checked by a structured questionnaire, which was filled in by a parent, usually the mother. It was the same questionnaire that was used in the baseline study, with some extra questions about foods recommended in the brochure. The food questionnaire is a frequency list (a 6-point scale ranging from "never" to "daily") of foods typical or atypical for the macrobiotic diet. Questions were also asked about changes in dietary pattern. Data Analysis In order to make the data on anthropometric development independent of the children's age and sex, standard deviation (SD) scores were calculated from the median (P50) and standard deviation of the reference data as follows: SD score (a) = (a - median of reference)/(SD of reference) For this purpose, the P50 and the SD of the reference were interpolated to each child's exact age. To correct for a skewed distribution of the reference data of body weight for girls from 4 years onward, the observed weight and the reference data for this group were first transformed to achieve normal distribution by means of the equation: X = log (weight - 3.663 x age + 14.758) From the results of the baseline study in 1985, children were classified in three age groups: (a) a 2-year-old group, because some of the children in this age group will still be breast-feeding; (b) a 3-5 years group, because catch-up growth was ex- pected in this age category; (c) 6 years and older, because it was expected that from 6 years onward growth would follow a reference growth percentile. Student's t test was used to test for significant differences or changes. 212 DIET AND GROWTH IN YOUNG VEGETARIANS SOS score weight o -0.5 - -1.5 - FIG. 1. Standard deviation scores (SDS) of weight for age of macrobiotically fed children in 1985 (n = 243) and 1987 (n = 194). (Reproduced from T Soc Gezondheidszorg, 1992; 70: 227-33, with permission.) Results Anthropometry Figures 1 and 2 show a cross-sectional comparison of SD scores by sex for weight and height. Although there was a tendency to less negative scores in 1987, none of the differences was statistically significant. SDS score height o -0.5 - -1.5 - FIG. 2. Standard deviation scores (SDS) of height for age of macrobiotically fed children in 1985 (n = 243) and 1987 (n = 194). (Reproduced from T Soc Gezondheidszorg, 1992; 70: 227-33, with permission.) DIET AND GROWTH IN YOUNG VEGETARIANS 213 TABLE 1. Change in standard deviation score per year of macrobiotic children in different age groups Change in SDS per year (mean ± SD) Current age (1987) 2 y 3-5 y 6-9 y Boys (n =•• 25) (n = 40) (n = 33) Weight -0.17 :t 0.11 0.14 ± 0.05* -0.01 d: 0.02 Height -0.44 :t 0.09" 0.09 ± 0.04*" 0.04 i: 0.04 Girls (n =-• 18) (n = 48) (n = 30) Weight -0.15 ± 0.12 0.16 ± 0.05* 0.08 d: 0.06 Height -0.55 :t 0.11* 0.14 ± 0.04* 0.11 ± 0.03* From Smeets ef al. (12). SDS, standard deviation score. * p <0.01; "p < 0.001; *"p < 0.05 (paired f test) Growth velocity, expressed as change in SD score of the macrobiotically fed chil- dren in various age groups, is presented in Table 1. A marked growth depression for height was observed in the children who at the time of follow-up were 2 years old. For children aged 3-5 years, a slight but significant positive change had occurred for both weight and height. In children aged 6-9 years, no changes in SD score occurred except for a slight but significant positive trend toward the 50th centile for height in girls. Diet Few changes were found in the frequency of consumption of foods typical of the macrobiotic diet, but there were some changes in the consumption of animal products, especially dairy products and fish, as well as vegetables and vitamin D supplements.