INS and type 2 diabetes mellitus: A later systematic review of both randomised controlled trials and observational studies in adults with prediabetes, Type 1 diabetes, or Type 2 diabetes showed that increased intake of soluble dietary fibre and wholegrain led to decreased levels of FPG, HbA1c, and insulin in randomised controlled trials (with an average duration of 6 to 12 weeks) as well as with reduced all-cause mortality in prospective observational studies (with a mean follow-up of 8.8 years) [10].