Lactose, calcium source and age affect calcium bioavailability in rats.

Area of Science:

• Nutritional Science
• Biochemistry
• Physiology

Background:

• Calcium is essential for bone health and numerous physiological functions.
• Dietary factors, including carbohydrates like lactose, can influence calcium absorption.
• Understanding calcium bioavailability is crucial for optimizing dietary calcium intake.

Purpose of the Study:

• To investigate the effect of lactose on calcium bioavailability in rats.
• To determine if lactose's impact on calcium absorption varies with age, calcium source, or dietary calcium levels.

Main Methods:

• Experiment 1: Rats of different ages (21, 40, 100 days) were fed diets with varying calcium levels and sources (CaCO3, calcium citrate-malate, milk, cheese), with or without lactose. Calcium-45 retention in tibias was measured.
• Experiment 2: Suckling rats (7, 12, 17 days) were gavaged with calcium-47 labeled milk (with or without lactose) or a calcium chloride-casein mixture with different sugars. Calcium-47 retention in carcasses was measured.

Main Results:

• Lactose significantly increased calcium bioavailability from control and milk diets in all age groups.
• The enhancement of calcium bioavailability by lactose was observed in younger rats (21 days) for calcium citrate-malate and CaCO3, but not cheese.
• Lactose and glucose + galactose increased calcium bioavailability compared to sugar-free diets in suckling rats.

Conclusions:

• Lactose enhances calcium bioavailability across various developmental stages in rats.
• The positive effect of lactose on calcium absorption is maintained even with high dietary calcium.
• The magnitude of lactose's effect on calcium bioavailability can vary depending on the calcium source.