Comparison of DASH With Oxalate Restricted Diet on Urine in Recurrent Stone Formers With Hyperoxaluria
Condition: Nephrolithiasis
MeSH terms: Nephrolithiasis; Kidney Calculi
Study type: Interventional

Summary: 
      Oxalate restricted diet is routinely prescribed in clinical practice of nephrolithiasis
      patients with hyperoxaluria. The effect of dietary oxalate on urinary oxalate is however
      controversial. Some studies do not implicate dietary oxalate as a major risk factor for
      nephrolithiasis. The Dietary Approaches to Stop Hypertension (DASH) diet, which is high in
      fruits and vegetables, moderate in low-fat dairy products, and low in animal protein
      represents a novel potential means of kidney stone prevention. The effect of a DASH-style
      diet on relative urinary supersaturations is however uncertain. Higher consumption of fruits
      and vegetables may increase urinary oxalate but also increases urinary citrate, an important
      inhibitor of calcium saturation.All the above data lead us to hypothesize that a DASH diet
      other than an oxalate restricted diet, which is routinely administered in clinical practice,
      might be beneficial in lowering urinary relative supersaturations of calcium oxalate in
      recurrent stone formers with hyperoxaluria.

      Recurrent stone formers with hyperoxaluria (urine oxalate>32.8) are allocated into 2 groups.
      The first group is prescribed an oxalate restricted diet. The second group are asked to
      follow a calorie-controlled DASH diet plan while drink water in the same amounts. 24-h urine
      is collected 2 times before study visits at baseline, 1 time on week 6 and 2 times at the end
      of the study.
    

Detailed description: 
      After a run-in period of 3 weeks patients are allocated into 2 groups. The first group is
      prescribed an oxalate restricted diet. They are instructed to avoid oxalate-rich foods such
      as spinach, rhubarb, beets, chocolate, cereals, nuts, tea, wheat bran, and strawberries and
      to drink water in amounts of roughly 2 L during cold weather and 3 L during warm/hot weather.
      The second group is asked to follow a calorie-controlled DASH diet plan. DASH is an eating
      pattern recommended by the 2005 Department of Health and Human Services Dietary Guidelines
      for Americans as a model of healthy eating for the majority of individuals in the population
      . This group eats a diet which includes higher fruit, vegetables, and low-fat dairy products
      and lower in saturated fat, total fat, and cholesterol, containing more whole grains and
      fewer refined grains, sweets, and red meat. The calcium, potassium, and magnesium of the DASH
      diet is higher. The DASH diet contains 2,400 mg Na per day . The servings, mentioned in the
      publication of the National Institutes of Health regarding the DASH eating plan, are used as
      a practical guideline. Lower consumption of meat and higher consumption of low-fat dairies,
      vegetable, fruit, whole-grain cereals, and legumes distinguish between the DASH trial and the
      weight-reduction diet.

      We determine the caloric needs for each person in both groups individually according to the
      Harris Benedict Formula:

      Metric BMR Formula Women: BMR= 655 + ( 9.6 × weight in kilos ) + ( 1.8 × height in cm ) - (
      4.7 × age in years ) Men: BMR= 66 + ( 13.7 × weight in kilos ) + ( 5 × height in cm ) - ( 6.8
      × age in years )

      To determine their total daily calorie needs, multiply their BMR by the appropriate activity
      factor, as follows:

      If they are sedentary (little or no exercise) : Calorie-Calculation = BMR × 1.2 If they are
      lightly active (light exercise/sports 1-3 days/week) : Calorie-Calculation = BMR × 1.375 If
      they are moderately active (moderate exercise/sports 3-5 days/week) : Calorie-Calculation =
      BMR × 1.55 If they are very active (hard exercise/sports 6-7 days a week) :
      Calorie-Calculation = BMR × 1.725 If they are extra active (very hard exercise/sports &
      physical job or 2x training) : Calorie-Calculation = BMR × 1.9

      The patients are visited in the beginning, after 6 weeks and at the end of the study; each
      session for a patient is 45-60 min. They are in touch with the nutritionist by phone every
      week. The nutritionist explains the benefits of each diet for patients and tells them if they
      continue these diets, related metabolic abnormalities might be controlled. The diets are
      individually prescribed using a calorie count system, and an exchange list is given to each
      patient for exchanging food items and counting the calories. A nutritionist educates subjects
      on how to use the exchange list. Patient compliance to diet is evaluated by a detailed food
      recall for 3 days which are collected from 2 weekdays and 1 weekend day in week 1 and week 12
      as well as evaluation of the urinary excretion of sodium, inorganic sulfate and total
      nitrogen. The food recalls are reviewed by a nutrition PhD when they are submitted and then
      are analyzed using nutritionist IV software. 24-h urine is also collected 2 times before
      study visits at baseline, and 2 times at the end of the study on the day food recalls are
      filled. Urinary supersaturation of calcium oxalate, calcium phosphate and uric acid also is
      calculated at the beginning and end of the study. Because this is a dietary intervention,
      patients are not blinded.

      Clinical measurements included blood pressure, weight, height, and waist circumference. Blood
      pressure measurements are the average of 2 measurements and are taken using an automated
      system after the subjects are seated for 5 minutes. Participants are weighed wearing minimal
      clothing and without shoes. Height is measured in a standing position, without shoes. Waist
      circumference is measured where the waist is narrowest over light clothing. Body mass index
      (kg/m2) is calculated as weight (kg) divided by height squared (m2) We use General Linear
      Models (paired t tests) to globally compare means of all variables at the end of the 2
      different diet periods with and without adjustment for weight. We calculate the percent
      change for each variable using the formula (E- B/B)×100, where E was the end of treatment
      value and B was the baseline value. Groups are compared using the percent change in the
      General Linear Model (paired t test)analyses. We use ANCOVA to compare adjusted means of end
      values and percent changes while weight change was included as a covariate. Results are
      considered significant if the 2-tailed P-value is<,0.05. Statistical analyses are performed
      using STATA 15.0.
    

Intervention name(s): diet
Intervention type(s): Behavioral
Intervention description(s): When the first set of urine samples confirmed hyperoxaluria (urine oxalate>32.8), the patients will enter the study. After a run-in period of 3 weeks patients are allocated into 2 groups that I already explained in the arms section.The patients are visited in the beginning, after 6 weeks and at the end of the study
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Prevention
Keywords: Nephrolithiasis; Recurrent stone former; DASH; Urine oxalate; Urine calcium oxalate supersaturation