Objective To investigate whether a whole grain diet
alters the gut microbiome and insulin sensitivity, as well
as biomarkers of metabolic health and gut functionality.
Design 60 Danish adults at risk of developing
metabolic syndrome were included in a randomised
cross-over trial with two 8-week dietary intervention
periods comprising whole grain diet and refined grain
diet, separated by a washout period of ≥6 weeks. The
response to the interventions on the gut microbiome
composition and insulin sensitivity as well on measures
of glucose and lipid metabolism, gut functionality,
inflammatory markers, anthropometry and urine
metabolomics were assessed.
Results 50 participants completed both periods with a
whole grain intake of 179±50 g/day and 13±10 g/day
in the whole grain and refined grain period, respectively.
Compliance was confirmed by a difference in plasma
alkylresorcinols (p<0.0001). Compared with refined
grain, whole grain did not significantly alter glucose
homeostasis and did not induce major changes in the
faecal microbiome. Also, breath hydrogen levels, plasma
short-chain fatty acids, intestinal integrity and intestinal
transit time were not affected. The whole grain diet did,
however, compared with the refined grain diet, decrease
body weight (p<0.0001), serum inflammatory markers,
interleukin (IL)-6 (p=0.009) and C-reactive protein
(p=0.003). The reduction in body weight was consistent
with a reduction in energy intake, and IL-6 reduction was
associated with the amount of whole grain consumed, in
particular with intake of rye.
Conclusion Compared with refined grain diet, whole
grain diet did not alter insulin sensitivity and gut
microbiome but reduced body weight and systemic low-
grade inflammation.
Trial registration number NCT 01731366; Results.