Whole grains improve gut health, cardiometabolic markers in children

Children who regularly consume wholegrain oats and rye (WG) benefit from lower serum low-density lipoprotein (LDL) cholesterol and triacylglycerol, modulated taxa, and higher beneficial metabolites, according to a recent study.

“This supports recommendations of exchanging refined grain (RG) with wholegrain oats and rye among children,” the investigators said.

Fifty-five healthy Danish children aged 8‒13 years participated in this randomized crossover trial and received WG or RG products ad libitum for 8 weeks in random order. Anthropometry, body composition, and blood pressure were measured at 0, 8, and 16 weeks.

The investigators collected fasting blood and faecal samples for analysis of blood lipids, glucose homeostasis markers, gut microbiota, and short-chain fatty acids. They also determined stool characteristics and gut symptoms using questionnaires. Finally, diet was examined using 4-day dietary records and compliance via plasma alkylresorcinols (ARs).

Of the children, 52 (95 percent) with a mean body mass index z-score of 1.5 completed the study. The participants consumed 108 g/d of WG and 3 g/d of RG, which was confirmed by a significant difference in ARs (p<0.001). [Am J Clin Nutr 2024;119:18-28]

WG, compared with RG, intake resulted in a decrease in LDL cholesterol by 0.14 mmol/L (95 percent confidence interval, ‒0.24 to ‒0.04; p=0.009) as well as in total: high-density lipoprotein cholesterol (p<0.001) and triacylglycerol (p=0.048), with no changes seen in body composition and other cardiometabolic markers.

Additionally, WG consumption led to moderation in the abundance of certain bacterial taxa; increased plasma acetate, propionate, and butyrate and faecal butyrate; and reduced fatigue with no other effects on gut symptoms.

Mechanisms

“Wholegrain oats hold a distinct physiochemical property attributed to their content of viscous β-glucans that has been suggested to improve blood lipids by reducing the absorption of lipid and carbohydrate and inhibiting bile acid reabsorption, thus upregulating de novo synthesis of bile at the cost of circulating LDL cholesterol,” the investigators said. [Cereal Chem 2020;97:20-33; Nat Rev Gastroenterol Hepatol 2021;18:101-116]

On the other hand, the mechanisms behind the beneficial effects of wholegrain rye intake could be similar to those of oats. Soluble arabinoxylans in rye also have physiochemical properties with β-glucans. In addition, wholegrain rye is capable of lowering LDL cholesterol in adults, as shown in an earlier study. [Cereal Chem 2020;97:20-33; Am J Clin Nutr 2020;111:864-876]

“In addition, due to the viscous and structural properties of their fibres, wholegrain from oats and rye possess high water-holding capacity, which may increase faecal bulk and explain the observed tendency of increased stool frequency in present study,” the investigators said.

Previous studies also reported that wholegrain rye consumption improved several markers of gut health, like stool frequency, compared with refined grain. [Cereal Chem 2020;97:20-33; Am J Clin Nutr 2003;77:967-974; J Nutr 2017;147:2067-2075]

“This study contributes to a growing body of research demonstrating the cardiometabolic benefits of replacing refined grain with wholegrain, even in children, and regardless of effects on body fat,” the investigators said.

“Further randomized trials among children, including long-term studies and trials focusing on specific wholegrain types, are necessary to gain a deeper understanding of the underlying mechanisms,” they added.