Intestinal dysfunction in chronic disease

Short-chain fatty acid kinetics and concentrations are higher after inulin supplementation in young and older adults. A randomized trial

BACKGROUND

Beneficial short-chain fatty acids (SCFAs) are produced through intestinal microbial fiber fermentation. Using stable tracer methodology and compartmental modeling, we observed lower SCFA production in older than young adults in both an accessible (i.e. systemic circulation; whole-body production (WBP)) and inaccessible (potentially representing intestine absorbing microbially produced SCFAs (U2)) pool.

OBJECTIVES

We now investigated if fiber supplementation increases SCFA production in older adults and if concentrations reflect production rate changes.

METHODS

In this randomized, placebo controlled, double-blind crossover study, 21 young (YA: 20-29y) and 40 older (OA: 59-87y) adults, were supplemented with inulin or placebo (maltodextrin) for 7d (final intake: 30 g/d). Before and after interventions, participants collected stool and received an intravenous pulse containing [U-13C]-labeled SCFAs followed by blood draws. We measured plasma tracer enrichments, plasma and fecal concentrations by GC-MS and performed compartmental analysis. Data are mean [95% CI].

RESULTS

Inulin evoked a 44% increase in butyrate production (μmol/min) in the inaccessible pool (YA: 28 to 44 (+16.2 [4.3, 28.1]; p=0.038), OA: 14 to 20 (+6.1 [2.2, 9.9]; p=0.011) and were not different between young and older adults. In addition, a 34% increase in propionate production in YA only. We found a 50-60% increase in fecal acetate, propionate and butyrate and a 34% increase in plasma butyrate in OA, while in YA only 34% increase in fecal acetate. Plasma but not fecal concentrations correlated positively with SCFA production in the inaccessible pool (R2 = 0.20-0.45; p<0.001).

CONCLUSION

Older adults have a lower SCFA production. Inulin intake increases SCFA production. Tracer pulse approach detects SCFA metabolism changes more sensitively than plasma or fecal concentration measurements (NCT04459156).

The importance of protein sources to support muscle anabolism in cancer: An expert group opinion

This opinion paper presents a short review of the potential impact of protein on muscle anabolism in cancer, which is associated with better patient outcomes. Protein source is a topic of interest for patients and clinicians, partly due to recent emphasis on the supposed non-beneficial effect of proteins; therefore, misconceptions involving animal-based (e.g., meat, fish, dairy) and plant-based (e.g., legumes) proteins in cancer are acknowledged and addressed. Although the optimal dietary amino acid composition to support muscle health in cancer is yet to be established, animal-based proteins have a composition that offers superior anabolic potential, compared to plant-derived proteins. Thus, animal-based foods should represent the majority (i.e., ≥65%) of protein intake during active cancer treatment. A diet rich in plant-derived proteins may support muscle anabolism in cancer, albeit requiring a larger quantity of protein to fulfill the optimal amino acid intake. We caution that translating dietary recommendations for cancer prevention to cancer treatment may be inadequate to support the pro-inflammatory and catabolic nature of the disease. We further caution against initiating an exclusively plant-based (i.e., vegan) diet upon a diagnosis of cancer, given the presence of elevated protein requirements and risk of inadequate protein intake to support muscle anabolism. Amino acid combination and the long-term sustainability of a dietary pattern void of animal-based foods requires careful and laborious management of protein intake for patients with cancer. Ultimately, a dietary amino acid composition that promotes muscle anabolism is optimally obtained through combination of animal- and plant-based protein sources.