A greener diet score tracked with better kidney numbers in 219 people with diabetic foot ulcers. It did not track with smaller wounds

A diabetic foot ulcer can take months of dressings, pressure relief and close follow-up, while kidney disease can quietly complicate the same person's care. Researchers in Tehran asked whether a diet score built around both health and environmental sustainability was linked to either problem. Their one-year cohort study, published in Scientific Reports on 29 October, followed adults with type 2 diabetes and a foot ulcer at one university diabetes clinic.

The score was the 150-point Planetary Health Diet Index. It gives credit across 16 components, including vegetables, fruit, whole grains, legumes and nuts, and scores moderate ranges for foods such as dairy, eggs, fish and unsaturated oils while limiting red meat, animal fat and added sugar. A trained nutritionist recorded three days of food at the start — two weekdays and one public holiday — and the researchers split the patients around the median score of 54. This was a record of what people reported eating, not a diet assigned by the study.

The participant trail matters. Of 345 people who completed the starting questionnaires, 45 were excluded, leaving 300 eligible. Another 81 did not return to the clinic, so the final analysis covered 219 people: 109 below the median diet score and 110 at or above it. That is a 27% loss from the eligible group by our division. The authors report no significant baseline differences between completers and those lost, but people who keep returning to a specialist clinic can still differ in ways a table cannot capture.

After adjustment for age, sex, energy intake, smoking, diabetes duration, body mass index, insulin and antibiotic use, cardiovascular history, HbA1c, physical activity and socioeconomic status, the higher-score group had a creatinine change 0.18 mg/dL lower than the lower-score group. Urea was 14.18 mg/dL lower and estimated glomerular filtration rate, or eGFR, 17.18 mL/min/1.73 m² higher. The confidence intervals excluded no difference: minus 0.33 to minus 0.03 for creatinine, minus 22.89 to minus 5.46 for urea, and 3.53 to 30.82 for eGFR.

Those kidney results are associations, not proof that the food pattern protected anyone's kidneys. Diet was measured only at the beginning with three recalled days, so it may not represent a whole year. Kidney disease itself, medical advice, appetite, income or the ability to shop and cook could shape what a person eats. The score also bundles many foods together, so this study cannot identify a vegetable, nutrient or food swap responsible for the differences.

The wound result was more sobering. In the adjusted comparisons, the higher diet score was not significantly related to ulcer length, width or depth. Length did fall within the higher-score group, from 1.68 cm to 1.32 cm on average, but comparing a group with its own starting point is weaker than comparing groups, and the authors say this exploratory result was not corrected for multiple testing. Only nine ulcers completely healed and five patients had an amputation. The study therefore lacked enough events to test the outcomes that matter more than a ruler measurement: complete healing, infection and limb loss.

The higher-score group reported more fibre, 18.5 g against 15.8 g a day, and more vitamin C, 141 mg against 100 mg. They also reported less energy and less red meat, poultry, dairy, animal fat and added sugar. Those contrasts help describe the pattern, but they also show why it cannot be reduced to 'eat more plants'. People with diabetes and kidney disease may need individual advice on protein, potassium, fluid and medicines, while foot ulcers need wound care and pressure offloading. A sustainable diet score may be a useful research lens; it is not a substitute for either clinic.

There are reasons to take the finding seriously enough to test again: a year of follow-up, clinical measurements from medical records and adjustment for many obvious differences. There are equally good reasons not to prescribe from it: one clinic, convenience sampling, self-reported diet, 27% attrition and very few healing or amputation events. A randomised diet trial with repeated food records and enough patients to measure healing would tell us much more.