Enhanced lumbar spine bone mineral content and bone mineral density in SGA piglets fed arachidonic acid and docosahexaenoic acid are modulated by birth weight

The infant born small size for gestational age (SGA) has low bone mass. Dietary arachidonic acid (AA) and docosahexaenoic acid (DHA) enhance bone mass in normal birth weight (BW) piglets; however, the benefits in the SGA neonate are unknown. In this 15 d study, two levels of dietary AA + DHA (0.6 or 1.2 g/100 g of fat as AA plus DHA as 0.1 or 0.2 g/100 g of fat) versus control diet were tested for effects on growth, fatty acid status, bone mass and metabolism in SGA piglets categorized as either very low BW (≤ 1.0 kg) or low BW (1.1 to 1.2 kg). Differences in outcomes for each BW category were detected by one-way ANOVA with post-hoc Bonferroni tests. Growth did not respond to diet, yet the low BW piglets fed 0.6:0.1 AA + DHA as g/100 g of fat had elevated bone mass in the spine, whereas the very low BW piglets had higher bone mass of the spine if fed the higher intake of AA + DHA. In both BW categories, the higher intake of AA + DHA lowered bone resorption relative to controls, but bone formation was unchanged. Fatty acid concentrations reflected dietary AA in all tissues, without a decline in DHA status. This study provides evidence that bone mass is enhanced by both levels of AA + DHA in the SGA piglet in a manner determined by the severity of growth restriction at birth. Interventions are needed to determine if AA + DHA can improve bone mass of the human infant born SGA.