- Click here for explanation of classification scheme.

The purpose of this study targeting type 2 diabetic patients was to assess the renovascular and cardiovascular effects of replacing red meat in the diet with chicken and to assess the effects of a lactovegetarian low-protein diet.

Type 2 diabetic patients who meet the following criteria:

• Age less than 75 years
• Body mass index (BMI) (in kg/m²) less than 32
• Urinary albumin excretion rate (UAER) at least 200mcg per minute confirmed at least twice in a six-month period
• Serum triacylglycerol less than 4.52mmol per L
• Normal liver and thyroid functions
• Compliance with diabetes treatment (A_1c test less than 10%)
• Serum creatinine less than or equal to 132.6mcg per L
• Proteinuria less than 3.0g per 24 hours
• Absence of urinary tract infection (negative urine culture) or other renal diseases
• Symptomatic autonomic neuropathy
• Heart failure.

During run-in period, dislike for chicken or red meat, spontaneous regression to microalbuminuria or noncompliance with the protocol.

Recruitment

Patients were recruited through the Endocrinology Division's outpatient clinic at the Hospital de Clínicas de Porto Alegre, Brazil.  

Design

Randomized controlled trial, crossover design.

Intervention

Eligible patients entered a run-in period of approximately two months, during which they were oriented to achieve the best possible metabolic control through dietary and oral anti-diabetic agents or insulin adjustments. At the end of the run-in period, patients underwent clinical and laboratory evaluations. After the run-in period, consecutive eligible patients were randomly assigned to one of the sequences of the intervention diet (UD, usual diet; CD, chicken diet; LPD, low-protein vegetarian diet):

• UD, LPD, CD
• UD, CD, LPD
• LPD, UD, CD
• LPD, CD, UD
• CD, LPD, UD
• CD, UD, LPD.

The anti-hypertensive and anti-diabetic drugs were maintained during the study. None of the patients were using angiotensin-converting enzyme inhibitors, angiotensin receptor blockers or hypolipidemic agents during the study.

Statistical Analyses

Results were expressed as mean±SD, median (range) or mean (95% CI). Differences among diets were tested by using repeated-measures analysis of variance, which was followed by a Bonferroni adjustment test for multiple comparisons.

Timing of Measurements

After the run-in period, each diet was followed for four weeks with a four-week washout period between them. During the washout period, the patients maintained their UD. All participants were instructed to maintain their usual physical activities and not to make any changes in their lifestyles or medications throughout the study period. At the end of each diet, dependent variables were assessed.

Dependent Variables

• Laboratory measurements (blood samples were obtained after a 12-hour overnight fast):
  • GFR: Measured by using the Cr-EDTA single-injection technique
  • Urinary albumin: Measured in 24-hour timed sterile (negative urine culture) urine samples by using immunoturbidimetry
  • Urinary urea: Measured by an enzymatic ultraviolet method
  • Plasma glucose: Measured by a glucose oxidase method
  • Serum creatinine: Measured by the Jaffé reaction, A_1c test by ion-exchange HPLC
  • Fructosamine: Measured by a colorimetric method
  • Serum total cholesterol and triacylglycerol: Measured by enzymatic-colorimetric methods
  • HDL cholesterol: Measured by a direct selective inhibition method
  • LDL cholesterol: Calculated by using Friedewald's formula
  • FA composition on serum total lipids: Determined by extraction with chloroform-methanol.
• Anthropometric measurements:
  • Weight and height: Measured with an anthropometric scale
  • BMI: Calculated
  • Triceps skinfold thickness: Measured at the midpoint of the back of the upper left arm, between the acromion process and the tip of the olecranon
  • Mid-upper arm muscle area: Mid-upper arm circumference measured  at the midpoint of the back of the upper left arm and appropriate calculations according to Frisancho's indexes
  • Waist circumference: Measured midway between the lowest rib margin and the iliac crest, near the umbilicus
  • Hip circumference: Measured at the maximal gluteal protrusion (lateral view).

Independent Variables

All prescribed diets (UD, CD, and LPD) were isoenergetic, with the same proportion of lipids [30% (26% to 35%)], and the UD and the CD were isoproteic [20% (17% to 25%)]. The UD was the patient's adjusted run-in diet, and the CD was created by replacing all meat in the UD with dark chicken meat (skinless leg quarter). The protein content of the LPD was 0.5g to 0.8g per kg of body weight one per day (vegetable and dairy protein only) to achieve at least 50% reduction from the customary protein diet intake of each patient.

The content of the food was prescribed on the basis of weighed diet records performed during the run-in period and from the diabetes patients' current menu. No food was supplied to the patients.

Compliance with the diets was assessed by means of two-day weighed diet records and estimation of protein intake from 24-hour urinary nitrogen output at the end of the second and fourth weeks. The protein intake estimated by 24-hour urinary urea was calculated assuming that patients were in nitrogen balance. Dietary macronutrients and micronutrients from diet records were analyzed by using NUTRIBASE 98 Clinical Nutritional Manager software.

Initial N

40 patients entered in the run-in period, and 23 of these patients were excluded because of spontaneous regression to microalbuminuria, loss to follow-up or noncompliance with the protocol. Seventeen patients were then randomly assigned.

Attrition (Final N)

All 17 randomly assigned patients completed the study protocol and were included in the final analysis.

Age

59±11 years of age.

Other Relevant Demographics

14 of the 17 patients analyzed were men, eight were hypertensive, 10 had some evidence of diabetic retinopathy that was proliferative in four patients, four had a diagnosis of stable coronary artery disease, and only two patients were smokers. Most of the patients were treated with oral anti-diabetic agents (sulfonylurea, metformin, or both), insulin or both.

Anthropometrics

• BMI of 26.2±2.6
• Blood pressure of 93.7±8.5mm Hg
• Reasonable metabolic control
  • Fasting glucose: 8.04±3.27mmol per L
  • A_1c test: 7.6%±2.6%
  • Total cholesterol: 5.34±0.93mmol per L
  • HDL cholesterol: 1.17±0.18mmol per L
  • LDL cholesterol: 3.42±0.91mmol per L
  • Non-HDL cholesterol: 4.23±1.01mmol per L
  • Triacylglycerol: 1.57 (0.88 to 3.27).

Location

Brazil.

Table One: Effect of the Diets on Renal Function, Serum Lipids, Serum Fatty Acid Composition and BMI

Variables	Usual Diet (Mean±SD)	Chicken Diet (Mean±SD)	Low-Protein Diet (Mean±SD)	P-Value
UAER	312.8 (223.7 to 1,223.7)	269.4 (111 to 128)	229.3 (76.6 to 999.3)	<0.001
GFR	81.8±22.2	83.3±26.1	81.9±25.3	0.860
Total Cholesterol (mmol per L)	5.37±1.18	5.08±0.96	5.06±0.91	0.069
HDL Cholesterol (mmol per L)	1.14±0.26	1.14±0.23	1.14±0.21	0.989
LDL Cholesterol (mmol per L)	3.89±0.99	3.64±0.91	3.55±0.84	0.123
Non-HDL Cholesterol (mmol per L)	4.23±1.06	3.92±0.99	3.92±0.93	0.042
Triaclyglycerols (mmol per L)	1.46 (0.60 to 4.73)	1.22 (0.50 to 3.88)	1.51 (0.62 to 7.35)	0.012
Total SFA	40.6±3.8	37.8±2.5	38.8±3.4	0.068
Total MUFA	22.2±2.6	22.5±2.2	21.6±3.06	0.591
Total PUFA	37.3±3.1	39.8±2.6	39.7±4.4	0.029
BMI	26.1±2.5	26.0±2.6	25.7±2.7	0.007

Effect of the Diets on Renal Function

The UAERwas significantly lower after the CD and the LPD than afterthe UD. GFR values did not change after the three diets.

Effect of the Diets on Serum Lipids

In general, the lipid profile improved after the CD and the LPD. Non-HDL cholesterol was lower after the CD andthe LPD than after the UD. Triacylglycerol was lower only afterthe CD. Total cholesterol tended to be reduced after the CDthan after the UD (P=0.099). HDL and LDL cholesterol werenot different after the diets.

Fatty Acid Composition of Serum Total Lipids after Diets

Thetotal PUFA proportion was higher after the CD and the LPD thanafter the UD. The proportion of palmitic acid was lower afterthe CD than after the UD and the LPD, and the proportion ofstearic acid was lower after the LPD than after the UD.

Effect of Diets on Glycemic Control, Blood Pressure Measurements and Anthropometric Indexes

No significant difference was observed in glycemic control indexes at the end of each diet as evaluated by fasting plasma glucose and fructosamine. Mean blood pressure measurements also did not differ significantly among the diets. BMI did not differ after the UD and the CD, but it was lower after the LPD. No other anthropometric indexes used to evaluate nutritional status differed after the diets. 

Composition of the Diets and Weighed Diet Records

• Patients' intakeof total energy was lower during the LPD than during the UDand the CD
• The intake of polyunsaturatedFAs (PUFAs) was higher with the CD and with the LPD than withthe UD
• The ratio of PUFAs to saturated FAs (SFAs) was alsohigher with the CD than with the UD, and no difference was observedbetween the LPD and the UD
• Intake of SFAs tended to be lowerafter the CD than after the UD (P=0.079)
• As expected, protein content was lower during theLPD than during the CD and the UD, but there was no differencebetween the UD and the CD
• Intakes of total fat, monounsaturated FAs (MUFAs),potassium and calcium did not differ significantly betweenthe diets
• The mean daily intake of meat recorded during the UD (75% consumedas beef) was 188±63g per day. This did not differ significantlyfrom the mean daily intake of chicken meat (skinless leg quarter)during the CD, 173±56g per day (P=0.341).Fifty percent of total protein content of the UD was from redmeat, 10% from other meats (pork, fish and mainly chicken),30% from dairy products and 10% from vegetables. During theCD, 58% of the total protein content was from chicken meat (skinlessleg quarter), 30% from dairy products and 12% from vegetables.

In this sample of macroalbuminuric type 2 diabetes patients, the CD and the LPD induced a significant reduction in UAER and an increase in the serum proportion of PUFAs. Moreover, an improvement was observed in the lipid profile. The reduction of UAER after the LPD and the CD might be related to the increase in the proportion of serum PUFAs because of the withdrawal of red meat from the diet.

Possible limitations of this study were the possibility of a carry-over effect, diet compliance, nonuse of renoprotective medications, measurement of FAs in serum total lipids and the relatively high proportion of patients not included in the study.

In conclusion, these results indicate that the withdrawal of red meat from the diet, either by replacing it with chicken or by following a lactovegetarian LPD, promotes a beneficial effect on renovascular and cardiovascular risk factors associated with diabetic nephropathy in patients with type 2 diabetes and macroalbuminuria. This benefit may be related to the concomitant reduction in albuminuria concentrations and the rise in serum PUFAs.

 

Government:	Projeto de Nucleos de Excelencia do Ministério de Ciencia e Tecnologia
University/Hospital:	Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, (Porto Alegre, Brazil)
Not-for-profit	0 Foundation associated with industry:

Relatively small sample size; however, excellent study design and methodology.