Design: Randomised controlled feeding trial, four-period crossover, secondary analysis
Population: 101 adults with type 2 diabetes, mean age 67, 87% Black adults
Primary outcome: Fructosamine, fasting glucose and HbA1c at end of each five-week feeding period
Effect: Fructosamine −5.6 μmol/L (P = 0.002); fasting glucose −4.5 mg/dL (P = 0.02); HbA1c −0.09 percentage points (P = 0.04)

In a controlled feeding trial, 101 adults with type 2 diabetes ate four diets in random order over five-week periods: a DASH diet tailored for diabetes and a comparison diet representative of typical American eating, each at higher and lower sodium. Participants had a mean age of 67; 65% were female and 87% were Black adults.

Against the comparison diet, the DASH4D diet lowered fructosamine by 5.6 μmol/L (P = 0.002), fasting glucose by 4.5 mg/dL (P = 0.02) and HbA1c by 0.09 percentage points (P = 0.04). All three moved in the same direction, which is the useful part; the size of each is small.

Controlled feeding is the strongest design available for a dietary question and the weakest guide to what happens outside it — food was provided, so this measures the diet's efficacy, not a patient's ability to follow it. An HbA1c difference of 0.09 points will not on its own change a prescribing decision. What it supports is recommending a DASH-style pattern to a patient who already has hypertension to manage, where the blood pressure benefit is the main event and the glycaemic effect is a bonus that at least points the right way.

Offer a DASH-style pattern first to patients with both type 2 diabetes and hypertension, where it does two jobs.
Set expectations honestly: this is not a substitute for a glucose-lowering drug.
Refer to a dietitian for the adaptation — the Indian equivalent of a DASH pattern is not the American menu translated.
Recheck HbA1c at three months rather than expecting a visible change sooner.

Why it matters

Diet advice for diabetes is usually given without a number attached — this one has a number, and it is modest.

The statistics, in plain English

These are P values without confidence intervals, so the precision of each estimate is not stated — statistical significance here tells you the direction is probably real, not that the effect is large. A 0.09 percentage-point fall in HbA1c is well inside what day-to-day variation in the assay can produce in one person; it is detectable across 101 people, not in one.