Intestinal Permeability to Intact Lactose in Newborns and Adults

Abstract

Small amounts of lactose have been shown to be absorbed intact across the intestine and excreted unchanged in the urine of newborns and adults. We designed a study to quantitate the intestinal uptake and urinary excretion of this disaccharide in these age groups. Similar amounts of lactose were given orally to 17 term newborns (age: 24.8 ± 3.0 h) as a standard infant formula, and to 15 adult lactose absorbers (age: 28.1 ± 2.6 years) and 11 adult lactose malabsorbers (age: 24.7 ± 2.9 years) as a 20% water solution. Following lactose ingestion, breath was collected every 30 or 60 min for 3 h and analyzed for hydrogen concentration. Urine was also collected, and lactose and creatinine concentrations were determined. Peak hydrogen concentration was < 20 ppm above baseline in newborns and adult lactose absorbers and 85 ± 14 ppm in adult lactose malabsorbers. Urinary lactose excretion, expressed as a function of body weight (mg/ml/kg b.w.), was substantially greater in newborns (4.2 ± 0.82) than in adult lactose absorbers (0.29 ± 0.07; p < 0.001) and adult lactose malabsorbers (0.55 ± 0.04; p < 0.01). Similarly, urinary lactose excretion expressed as a ratio of urinary lactose to urinary creatinine (mg/mg) was increased (p < 0.001) in newborns (2.05 ± 0.26) when compared to adult lactose absorbers (0.11 ± 0.02) and adult lactose malabsorbers (0.20 ± 0.02). Our data demonstrate that the intestinal uptake and urinary excretion of intact lactose is significantly increased in newborns compared to adult subjects.

Human milk oligosaccharides are resistant to enzymatic hydrolysis in the upper gastrointestinal tract

“…Although high resistance to hydrolysis in the upper gastrointestinal tract has been shown, large-scale intestinal absorption of intact HMOs appears very unlikely. Even the smaller lactose units, which are an integral part of any HMOs, are not absorbed to a large extent in infants, and not absorbed at all in infants who lack lactase (35). This in turn suggests that most HMOs, the neutral as well as the acidic fraction, pass down the intestine of infants to reach the colon in intact form.…”

The role of intestinal epithelial barrier function in the development of NEC

“…[17][18][19][20][21] The initial structural barrier of the human intestinal epithelial monolayer forms in utero during the first trimester. As early as 8 weeks of gestation, enterocytes appear, eventually forming the crypt-villus architecture by 12 weeks.…”

“…15,16 The neonatal intestinal barrier is immature in the preterm neonate and has been shown to mature postnatally. [17][18][19][20][21] Multiple factors can induce postnatal intestinal maturation of this barrier including diet, [22][23][24] epidermal growth factor, 25 endogenous glucocorticoids, 26 and commensal bacteria. 17,27 Commensal bacteria, in particular, are known to induce expression of tight junction proteins that can tighten the barrier.…”

Blood lactose after dairy product intake in healthy men

“…The identification of unhydrolysed lactose in blood (lactosaemia) or urine has nevertheless been associated with specific cases, such as nursing mothers, newborns (4)(5)(6) , patients with gastrojejunostomy (7) or subjects with abnormal intestinal permeability caused by gastrointestinal disorders, for example coeliac disease (8) and rotaviral gastroenteritis (9) . In this context, Northrop et al (10) have proposed urinary lactose, after oral administration of lactose, as a marker to evaluate intestinal integrity in adults.…”