Chronic kidney disease (CKD) is a common condition and a major global cause of illness and mortality. The most common cause of kidney damage is diabetes, a condition that disrupts metabolism, leading to increased risk of damage to the kidneys and blood vessels. There is evidence suggesting that a diet with high acid load - consisting of acid-forming foods such as meat, cheese, and grain products - may contribute to this damage. People with such a diet often have poorer blood sugar control and more kidney damage. However, it is not yet well understood whether reducing dietary acid load can improve kidney function and diabetes management. Additionally, the role of ethnicity and sex in this process remains insufficiently explored.

The goal of this clinical trial is to understand how diet affects kidney function and blood sugar regulation in individuals with diabetes type 2 and chronic kidney disease, as well as to explore the role of sex and ethnicity in these effects. The main questions it aims to answer are:

Does a diet with lower acid load (e.g. less meat, cheese, and grain products) improve kidney function and blood sugar regulation in people with diabetes type 2 and chronic kidney disease?

Does the effect of diet on kidney function and blood sugar differ between ethnic groups, specifically between White-Dutch and South-Asian Surinamese descent people?

Participants will:

• be randomly assigned to follow either a high- or low-acid load diet for 8 weeks;
• Visit the study center four times (including screening)
• Complete food diaries three times per week and keep in regular contact with a dietitian;
• Collect 2x24-hour urine samples and morning feces at each visit ;
• Undergo blood sampling and an oral glucose tolerance test (OGTT).
• Spend a total of 8 hours at the study center (2 visits of 3 hours for OGTT and body composition tests, and 2 visits of 1 hour for additional assessments);
• Have up to 200 ml of blood collected during the study.

Inclusion Criteria:

• Age >18 years
• Presence of T2D and CKD stage G1-3a with albuminuria (>10mg/mmol)
• BMI≥ 25kg/m2 - Use of metformin on a stable dose (i.e. no changes in the last three months)
• Adequate knowledge of the Dutch language to comprehend the provided study information
• If incretin therapy is used, then subject must have used that for a minimum of 6 months before starting with the trial
• Use of ACE inhibitors or angiotensin II receptor blokkers
• Of white European Dutch or South-Asian Surinamese descent

Exclusion Criteria:

• Use of insulin
• serum bicarbonate < 20 mmol/L
• Use of antibiotics 3 months before inclusion
• Vegetarian diet - Presence of inflammatory bowel disease or other chronic inflammatory disease
• Alcohol consumption of more than 14 units per week in women, or more than 21 units per week in men
• Active malignancy - bariatric or other weight loss surgery in the history
• patients diagnosed with eating disorders (such as bulimia nervosa, anorexia nervosa or binge-eating disorder)
• HbA1c >9% (75mmol/mol) at screening
• Unmotivated or not able to adhere to a specific diet
• The subject is already currently involved in a clinical trial

Publication will be open access. All data is available upon resonable request from the Principal Investigator. Of note: All data will be pseudoanonymzed.