Benefits
Blood sugar and postprandial glucose blunting
In a crossover trial in 11 adults with impaired glucose tolerance, 15 g a day of arabinoxylan for 6 weeks lowered the blood glucose, insulin and triglyceride response to a test meal. In 14 healthy adults, bread with 6 or 12 g of wheat arabinoxylan-rich fiber cut the glucose rise by about 20 and 41 percent. These are after-meal measures, not long-term blood sugar (HbA1c).
Prebiotic feeding of bifidobacteria
In a placebo-controlled crossover trial in 20 healthy adults, 10 g a day of arabinoxylan-oligosaccharides (AXOS, a shorter-chain breakdown product of wheat arabinoxylan) for 3 weeks raised faecal bifidobacteria more than placebo and lowered urinary p-cresol, a marker of protein fermentation. Shifts in butyrate producers such as Roseburia come mainly from laboratory and animal work.
Immune findings come from rice bran MGN-3, not wheat arabinoxylan
The immune evidence often linked to arabinoxylan comes from Biobran/MGN-3, an enzymatically modified rice bran arabinoxylan. In an 80-person pilot trial in adults over 55, 500 mg a day for 3 months was followed by fewer influenza-like illnesses (5.0 versus 22.5 percent), and natural killer cell activity rose in a 12-person subset tested. This has not been shown for wheat arabinoxylan or Arrabina.
Blood lipids
Some soluble fibers lower LDL cholesterol by binding bile acids, and this has been proposed for arabinoxylan. In the 3-week AXOS trial (10 g a day), blood lipids were unchanged, and the 6-week trial in impaired glucose tolerance reported a lower triglyceride response after a test meal, not a cholesterol change. A cholesterol benefit has not been shown for this fiber.
Hunger hormone ghrelin
In the 6-week trial in 11 adults with impaired glucose tolerance, arabinoxylan lowered total ghrelin after a test meal, but acylated ghrelin, the active form that drives appetite, did not change. Effects on fullness hormones such as GLP-1 and PYY, on appetite and on body weight were not reported.
Mechanism of action
Viscous gel formation and glucose diffusion barrier
Arabinoxylan dissolves in the GI tract to form a highly viscous gel that physically increases the unstirred water layer adjacent to the intestinal epithelium. This diffusion barrier slows glucose movement from the intestinal lumen to the absorptive enterocytes, reducing the rate of glucose absorption and flattening the postprandial glucose curve.
Fermentation to butyrate
In laboratory and animal work, arabinoxylan side chains are fermented by colon bacteria, including butyrate producers such as Roseburia. Butyrate is a main energy source for the cells lining the colon. Roseburia enrichment and butyrate output were not measured in the human trials cited here.
Clinical trials
Randomized, single-blind, controlled crossover intervention trial in 11 adults with impaired glucose tolerance (IGT). Subjects received placebo or 15 g/day arabinoxylan for 6 weeks with 6-week washout. Postprandial glucose, insulin, triglycerides, and ghrelin measured after liquid meal challenge. (Garcia et al. 2007, Eur J Clin Nutr)
11 adults with impaired glucose tolerance (BMI 30.1, mean age 55.5). 6-week crossover.
Compared with placebo, 6 weeks of arabinoxylan lowered the glucose, insulin and triglyceride response to a liquid test meal (P<0.05) and reduced total ghrelin by 42 pg/ml (P<0.001). Acylated ghrelin, the active appetite-related form, did not change.
Crossover study in which 14 healthy adults ate, in random order on separate mornings, three breakfasts with 75 g of available carbohydrate whose bread held 0, 6 or 12 g of wheat arabinoxylan-rich fiber. Glucose and insulin were measured over 2 hours. (Lu et al. 2000, Am J Clin Nutr)
14 healthy adults with normal blood sugar. Single-meal design.
Peak glucose was lower with 6 g (P<0.01) and 12 g (P<0.001). The glucose iAUC fell by 20 and 41 percent and the insulin iAUC by 17 and 33 percent. In a taste panel the fiber bread rated as palatable as 50 percent whole-wheat bread. The authors note that benefit in type 2 diabetes was not established.