Five‐Week Intake of Short‐Chain Fructo‐Oligosaccharides Increases Intestinal Absorption and Status of Magnesium in Postmenopausal Women

Fermentable carbohydrates have been shown to be nondigestible by human enzymes in the small intestine but are fermented extensively in the large bowel to short‐chain fatty acids (SCFAs), which can increase mineral absorption. It has been shown that feeding such carbohydrates including short‐chain fructo‐oligosaccharides (sc‐FOSs) increases intestinal magnesium (Mg) absorption in animals, but their beneficial impact on Mg absorption in humans still remains to be established. Therefore, this work aimed to investigate the effect of moderate daily doses of sc‐FOSs (10 g/day) on the intestinal absorption and status of Mg in postmenopausal women without hormone replacement therapy (HRT). Eleven healthy postmenopausal women aged 59 ± 6 years (mean ± SD) received for 5 weeks sc‐FOS or sucrose (placebo) treatments according to a randomized, double‐blind, crossover design separated by a washout period of at least 3 weeks. Subjects ingested 87.5 mg of stable isotope25Mg together with a fecal marker. Subsequently, feces were collected for 5–7 days. An inductively coupled plasma mass spectrometer (ICP/MS) was used for25Mg stable isotope measurements in feces, urine, and blood. Mg levels were assessed also at the beginning and at the end of each treatment in plasma, erythrocytes, and urine. These measurements allowed for the determination of net intestinal Mg absorption and Mg status. The results show that the addition of 10 g sc‐FOS to the diet increased Mg absorption by 12.3%, from 30.2 ± 5.0% (placebo treatment) to 33.9 ± 7.2% (sc‐FOS treatment; mean ± SD; p < 0.02). This increase in intestinal Mg absorption was accompanied by an increase in plasma25Mg level and led to a higher urinary25Mg excretion. This is the first time that such an effect is shown in humans. The overall conclusion of this work is that the ingestion of moderate doses of sc‐FOS did improve intestinal Mg absorption and status in postmenopausal women. Because of the important role of Mg in many cellular functions, such Mg absorption improvement may be particularly interesting when the dietary intake of Mg is limited.