The present study examines the effect of animal-source-food (ASF) intake on arm muscle area growth as part of a larger study examining causal links between ASF intake, growth rate, physical activity, cognitive function and micronutrient status in Kenyan schoolchildren. This randomised, controlled feeding intervention study was designed with three isoenergetic feeding interventions of meat, milk, and plain traditional vegetable stew (githeri), and a control group receiving no snack. A total of twelve elementary schools were randomly assigned to interventions, with three schools per group, and two cohorts of 518 and 392 schoolchildren were enrolled 1 year apart. Children in each cohort were given feedings at school and studied for three school terms per year over 2 years, a total of 9 months per year: cohort I from 1998 to 2000 and cohort II from 1999 to 2001. Food intake was assessed by 24 h recall every 1–2 months and biochemical analysis for micronutrient status conducted annually (in cohort I only). Anthropometric measurements included height, weight, triceps skinfold (TSF) and mid-upper-arm circumference (MUAC). Mid-upper-arm muscle area (MAMA) and mid-upper-arm fat area (MAFA) were calculated. The two cohorts were combined for analyses. The meat group showed the steepest rates of gain in MUAC and MAMA over time, and the milk group showed the next largest significant MUAC and MAMA gain compared with the plain githeri and control groups (P< 0·05). The meat group showed the least increase in TSF and MAFA of all groups. These findings have implications for increasing micronutrient intake and lean body mass in primary schoolchildren consuming vegetarian diets.

Foetal development may permanently affect muscle function. Indian newborns have a low mean birthweight, predominantly due to low lean tissue and muscle mass. We aimed to examine the relationship of birthweight, and arm muscle area (AMA) at birth and post-natal growth to handgrip strength in Indian children. Grip strength was measured in 574 children aged 9 years, who had detailed anthropometry at birth and every 6–12 months post-natally. Mean (standard deviation (s.d.)) birthweight was 2863 (446) g. At 9 years, the children were short (mean height s.d. −0.6) and light (mean weight s.d. −1.1) compared with the World Health Organization growth reference. Mean (s.d.) grip strength was 12.7 (2.2) kg (boys) and 11.0 (2.0) kg (girls). Weight, length and AMA at birth, but not skinfold measurements at birth, were positively related to 9-year grip strength (β = 0.40 kg/s.d. increase in birthweight, P < 0.001; and β = 0.41 kg/s.d. increase in AMA, P < 0.001). Grip strength was positively related to 9-year height, body mass index and AMA and to gains in these measurements from birth to 2 years, 2–5 years and 5–9 years (P < 0.001 for all). The associations between birth size and grip strength were attenuated but remained statistically significant for AMA after adjusting for 9-year size. We conclude that larger overall size and muscle mass at birth are associated with greater muscle strength in childhood, and that this is mediated mainly through greater post-natal size. Poorer muscle development in utero is associated with reduced childhood muscle strength.