A controlled trial of a high fibre, low fat and low sodium diet for mild hypertension in Type 2 (non-insulin-dependent) diabetic patients

Higher fiber higher carbohydrate diets better than lower carbohydrate lower fiber diets for diabetes management: Rapid review with meta-analyses

BACKGROUND

Some dietary recommendations continue to recommend carbohydrate restriction as a cornerstone of dietary advice for people with diabetes.

PURPOSE

We compared the cardiometabolic effects of diets higher in both fiber and carbohydrate with lower carbohydrate lower fiber diets in type 1 or type 2 diabetes.

DATA SOURCES

MEDLINE, Embase, and the Cochrane Database of Systematic Reviews up to June 24, 2024, with additional hand searching.

STUDY SELECTION

Randomized controlled trials in which both dietary fiber and carbohydrate amount had been modified were identified from source evidence syntheses on carbohydrate amount in people with diabetes.

DATA EXTRACTION

Two reviewers independently.

DATA SYNTHESIS

Ten eligible trials including 499 participants with diabetes (98% with T2) were identified from the potentially eligible 828 trials included in existing evidence syntheses. Pooled findings indicate that higher fiber higher carbohydrate diets reduced HbA1c (mean difference [MD] -0.50% [95% confidence interval -0.99 to -0.02]), fasting insulin (MD -0.99 μIU/mL [-1.83 to -0.15]), total cholesterol (MD -0.16 mmol/L [-0.27 to -0.05]) and low-density lipoprotein cholesterol (MD -0.16 mmol/L (-0.31 to -0.01) when compared with lower carbohydrate lower fiber diets. Trials with larger differences in fiber and carbohydrate intakes between interventions reported greater reductions. Certainty of evidence for these outcomes was moderate or high, with most outcomes downgraded due to heterogeneity unexplained by any single variable.

LIMITATIONS

Our predefined scope excluded trials with co-interventions such as energy restriction, which may have provided addition information.

CONCLUSIONS

Findings indicate the greater importance of promoting dietary fiber intakes, and the relative unimportance of carbohydrate amount in recommendations for people with diabetes.

Effect of calorie restriction in comparison to usual diet or usual care on remission of type 2 diabetes: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Limited evidence is available on the dose-dependent effects of calorie restriction in patients with type 2 diabetes.

OBJECTIVES

We aimed to gather available evidence on the effect of calorie restriction on the management of type 2 diabetes.

METHODS

We systematically searched PubMed, Scopus, CENTRAL, Web of Science, and gray literature until November 2022 for randomized trials >12 wk looking at the effect of a prespecified calorie-restricted diet on remission of type 2 diabetes. We performed random-effects meta-analyses to estimate the absolute effect (risk difference) at 6-mo (6 ± 3 mo) and 12-mo (12 ± 3 mo) follow-ups. Then, we performed dose-response meta-analyses to estimate the mean difference (MD) for the effects of calorie restriction on cardiometabolic outcomes. We used the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach to judge the certainty of evidence.

RESULTS

Twenty-eight randomized trials with 6281 participants were included. Using a remission definition of an HbA1c level of <6.5% without antidiabetic medication use, calorie-restricted diets increased remission by 38 more per 100 patients (95% CI: 9 more, 67 more; n = 5 trials; GRADE = moderate) at 6 mo and by 13 more per 100 patients (95% CI: 10 more, 18 more; n = 4; GRADE = moderate) at 12 mo in comparison to usual diet or usual care. Using a definition of HbA1c of <6.5% after at least 2-mo cessation of antidiabetic medications, remission increased by 34 more per 100 patients (95% CI: 15 more, 53 more; n = 1; GRADE = very low) at 6 mo and by 16 more per 100 patients (95% CI: 4 more, 49 more; n = 2; GRADE = low) at 12 mo. At 6 mo, each 500-kcal/d decrease in energy intake resulted in clinically meaningful reductions in body weight (MD: -6.33 kg; 95% CI: -7.76, -4.90; n = 22; GRADE = high) and HbA1c (MD: -0.82%; 95% CI: -1.05, -0.59; n = 18; GRADE = high), which attenuated remarkably at 12 mo.

CONCLUSIONS

Calorie-restricted diets may be effective intervention for type 2 diabetes remission, especially when coupled with an intensive lifestyle modification program. This systematic review was registered in PROSPERO as CRD42022300875 (https://www.crd.york.ac.uk/prospero/display_record.php?RecordID = 300875). Am J Clin Nutr 2023;xxx:xx-xx.

Altered dietary salt intake for preventing diabetic kidney disease and its progression

BACKGROUND

There is strong evidence that our current consumption of salt is a major factor in the development of increased blood pressure (BP) and that a reduction in our salt intake lowers BP, whether BP levels are normal or raised initially. Effective control of BP in people with diabetes lowers the risk of strokes, heart attacks and heart failure and slows the progression of chronic kidney disease (CKD) in people with diabetes. This is an update of a review first published in 2010.

OBJECTIVES

To evaluate the effect of altered salt intake on BP and markers of cardiovascular disease and of CKD in people with diabetes.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 31 March 2022 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register were identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) of altered salt intake in individuals with type 1 and type 2 diabetes. Studies were included when there was a difference between low and high sodium intakes of at least 34 mmol/day.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed studies and resolved differences by discussion. We calculated mean effect sizes as mean difference (MD) and 95% confidence intervals (CI) using the random-effects model. Confidence in the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

MAIN RESULTS

Thirteen RCTs (313 participants), including 21 comparisons (studies), met our inclusion criteria. One RCT (two studies) was added to this review update. Participants included 99 individuals with type 1 diabetes and 214 individuals with type 2 diabetes. Two RCTs (four studies) included some participants with reduced overall kidney function. The remaining studies either reported that participants with reduced glomerular filtration rate (GFR) were excluded from the study or only included participants with microalbuminuria and normal GFR. Five studies used a parallel study design, and 16 used a cross-over design. Studies were at high risk of bias for most criteria. Random sequence generation and allocation concealment were adequate in only three and two studies, respectively. One study was at low risk of bias for blinding of participants and outcome assessment, but no studies were at low risk for selective reporting. Twelve studies reported non-commercial funding sources, three reported conflicts of interest, and eight reported adequate washout between interventions in cross-over studies. The median net reduction in 24-hour urine sodium excretion (24-hour UNa) in seven long-term studies (treatment duration four to 12 weeks) was 76 mmol (range 51 to 124 mmol), and in 10 short-term studies (treatment duration five to seven days) was 187 mmol (range 86 to 337 mmol). Data were only available graphically in four studies. In long-term studies, reduced sodium intake may lower systolic BP (SBP) by 6.15 mm Hg (7 studies: 95% CI -9.27 to -3.03; I² = 12%), diastolic BP (DBP) by 3.41 mm Hg (7 studies: 95% CI -5.56 to -1.27; I² = 41%) and mean arterial pressure (MAP) by 4.60 mm Hg (4 studies: 95% CI -7.26 to -1.94; I² = 28%). In short-term studies, low sodium intake may reduce SBP by 8.43 mm Hg (5 studies: 95% CI -14.37 to -2.48; I² = 88%), DBP by 2.95 mm Hg (5 studies: 95% CI -4.96 to -0.94; I² = 70%) and MAP by 2.37 mm Hg (9 studies: 95% CI -4.75 to -0.01; I² = 65%). There was considerable heterogeneity in most analyses but particularly among short-term studies. All analyses were considered to be of low certainty evidence. SBP, DBP and MAP reductions may not differ between hypertensive and normotensive participants or between individuals with type 1 or type 2 diabetes. In hypertensive participants, SBP, DBP and MAP may be reduced by 6.45, 3.15 and 4.88 mm Hg, respectively, while in normotensive participants, they may be reduced by 8.43, 2.95 and 2.15 mm Hg, respectively (all low certainty evidence). SBP, DBP and MAP may be reduced by 7.35, 3.04 and 4.30 mm Hg, respectively, in participants with type 2 diabetes and by 7.35, 3.20, and 0.08 mm Hg, respectively, in participants with type 1 diabetes (all low certainty evidence). Eight studies provided measures of urinary protein excretion before and after salt restriction; four reported a reduction in urinary albumin excretion with salt restriction. Pooled analyses showed no changes in GFR (12 studies: MD -1.87 mL/min/1.73 m², 95% CI -5.05 to 1.31; I² = 32%) or HbA1c (6 studies: MD -0.62, 95% CI -1.49 to 0.26; I² = 95%) with salt restriction (low certainty evidence). Body weight was reduced in studies lasting one to two weeks but not in studies lasting for longer periods (low certainty evidence). Adverse effects were reported in only one study; 11% and 21% developed postural hypotension on the low-salt diet and the low-salt diet combined with hydrochlorothiazide, respectively.

AUTHORS' CONCLUSIONS

This systematic review shows an important reduction in SBP and DBP in people with diabetes with normal GFR during short periods of salt restriction, similar to that obtained with single drug therapy for hypertension. These data support the international recommendations that people with diabetes with or without hypertension or evidence of kidney disease should reduce salt intake to less than 5 g/day (2 g sodium).

Effect of different dietary approaches compared with a regular diet on systolic and diastolic blood pressure in patients with type 2 diabetes: A systematic review and meta-analysis

AIMS

We aimed to investigate the effect of different dietary approaches on systolic and diastolic blood pressure (SBP and DBP) in Type II diabetes (T2D).

METHODS

A systematic search was performed in Web of Science, PubMed, Scopus and Cochrane library without any language and time restriction up to December 2018, to retrieve the randomized controlled trials (RCTs) which examined the effects of different dietary approaches on SBP and DBP in T2D patients. Meta-analyses were carried out using a random effects model. I2 index was used to evaluate the heterogeneity.

RESULTS

Twenty four RCTs with 1130 patients were eligible. The dietary modifications were more effective in reducing both SBP and DBP vs. control diet. The Low-sodium, High-fiber, DASH, Low-fat, Low-protein and Vegan dietary approach were significantly more effective in reducing SBP compared to a control diet. The High-fiber, Low-fat, Low-protein and Vegan diet were significantly more effective in reducing DBP. The Low-sodium and High fiber diets had the greatest lowering effect on SBP and DBP in T2D patients.

CONCLUSIONS

Adopting healthful dietary modifications were more effective in reducing both SBP and DBP vs. control. The High-fiber and Low-sodium diets had the greatest lowering effect on SBP and DBP in T2D.

Dietary fibre and whole grains in diabetes management: Systematic review and meta-analyses

BACKGROUND

Fibre is promoted as part of a healthy dietary pattern and in diabetes management. We have considered the role of high-fibre diets on mortality and increasing fibre intake on glycaemic control and other cardiometabolic risk factors of adults with prediabetes or diabetes.

METHODS AND FINDINGS

We conducted a systematic review of published literature to identify prospective studies or controlled trials that have examined the effects of a higher fibre intake without additional dietary or other lifestyle modification in adults with prediabetes, gestational diabetes, type 1 diabetes, and type 2 diabetes. Meta-analyses were undertaken to determine the effects of higher fibre intake on all-cause and cardiovascular mortality and increasing fibre intake on glycaemic control and a range of cardiometabolic risk factors. For trials, meta regression analyses identified further variables that influenced the pooled findings. Dose response testing was undertaken; Grading of Recommendations Assessment, Development and Evaluation (GRADE) protocols were followed to assess the quality of evidence. Two multicountry cohorts of 8,300 adults with type 1 or type 2 diabetes followed on average for 8.8 years and 42 trials including 1,789 adults with prediabetes, type 1, or type 2 diabetes were identified. Prospective cohort data indicate an absolute reduction of 14 fewer deaths (95% confidence interval (CI) 4-19) per 1,000 participants over the study duration, when comparing a daily dietary fibre intake of 35 g with the average intake of 19 g, with a clear dose response relationship apparent. Increased fibre intakes reduced glycated haemoglobin (HbA1c; mean difference [MD] -2.00 mmol/mol, 95% CI -3.30 to -0.71 from 33 trials), fasting plasma glucose (MD -0.56 mmol/L, 95% CI -0.73 to -0.38 from 34 trials), insulin (standardised mean difference [SMD] -2.03, 95% CI -2.92 to -1.13 from 19 trials), homeostatic model assessment of insulin resistance (HOMA IR; MD -1.24 mg/dL, 95% CI -1.72 to -0.76 from 9 trials), total cholesterol (MD -0.34 mmol/L, 95% CI -0.46 to -0.22 from 27 trials), low-density lipoprotein (LDL) cholesterol (MD -0.17 mmol/L, 95% CI -0.27 to -0.08 from 21 trials), triglycerides (MD -0.16 mmol/L, 95% CI -0.23 to -0.09 from 28 trials), body weight (MD -0.56 kg, 95% CI -0.98 to -0.13 from 18 trials), Body Mass Index (BMI; MD -0.36, 95% CI -0·55 to -0·16 from 14 trials), and C-reactive protein (SMD -2.80, 95% CI -4.52 to -1.09 from 7 trials) when compared with lower fibre diets. All trial analyses were subject to high heterogeneity. Key variables beyond increasing fibre intake were the fibre intake at baseline, the global region where the trials were conducted, and participant inclusion criteria other than diabetes type. Potential limitations were the lack of prospective cohort data in non-European countries and the lack of long-term (12 months or greater) controlled trials of increasing fibre intakes in adults with diabetes.

CONCLUSIONS

Higher-fibre diets are an important component of diabetes management, resulting in improvements in measures of glycaemic control, blood lipids, body weight, and inflammation, as well as a reduction in premature mortality. These benefits were not confined to any fibre type or to any type of diabetes and were apparent across the range of intakes, although greater improvements in glycaemic control were observed for those moving from low to moderate or high intakes. Based on these findings, increasing daily fibre intake by 15 g or to 35 g might be a reasonable target that would be expected to reduce risk of premature mortality in adults with diabetes.

Effect of longer-term modest salt reduction on blood pressure

BACKGROUND

A reduction in salt intake lowers blood pressure (BP) and, thereby, reduces cardiovascular risk. A recent meta-analysis by Graudal implied that salt reduction had adverse effects on hormones and lipids which might mitigate any benefit that occurs with BP reduction. However, Graudal's meta-analysis included a large number of very short-term trials with a large change in salt intake, and such studies are irrelevant to the public health recommendations for a longer-term modest reduction in salt intake. We have updated our Cochrane meta-analysis.

OBJECTIVES

To assess (1) the effect of a longer-term modest reduction in salt intake (i.e. of public health relevance) on BP and whether there was a dose-response relationship; (2) the effect on BP by sex and ethnic group; (3) the effect on plasma renin activity, aldosterone, noradrenaline, adrenaline, cholesterol, low-density lipoprotein (LDL), high-density lipoprotein (HDL) and triglycerides.

SEARCH METHODS

We searched MEDLINE, EMBASE, Cochrane Hypertension Group Specialised Register, Cochrane Central Register of Controlled Trials, and reference list of relevant articles.

SELECTION CRITERIA

We included randomised trials with a modest reduction in salt intake and duration of at least 4 weeks.

DATA COLLECTION AND ANALYSIS

Data were extracted independently by two reviewers. Random effects meta-analyses, subgroup analyses and meta-regression were performed.

MAIN RESULTS

Thirty-four trials (3230 participants) were included. Meta-analysis showed that the mean change in urinary sodium (reduced salt vs usual salt) was -75 mmol/24-h (equivalent to a reduction of 4.4 g/d salt), the mean change in BP was -4.18 mmHg (95% CI: -5.18 to -3.18, I (2)=75%) for systolic and -2.06 mmHg (95% CI: -2.67 to -1.45, I (2)=68%) for diastolic BP. Meta-regression showed that age, ethnic group, BP status (hypertensive or normotensive) and the change in 24-h urinary sodium were all significantly associated with the fall in systolic BP, explaining 68% of the variance between studies. A 100 mmol reduction in 24 hour urinary sodium (6 g/day salt) was associated with a fall in systolic BP of 5.8 mmHg (95%CI: 2.5 to 9.2, P=0.001) after adjusting for age, ethnic group and BP status. For diastolic BP, age, ethnic group, BP status and the change in 24-h urinary sodium explained 41% of the variance between studies. Meta-analysis by subgroup showed that, in hypertensives, the mean effect was -5.39 mmHg (95% CI: -6.62 to -4.15, I (2)=61%) for systolic and -2.82 mmHg (95% CI: -3.54 to -2.11, I (2)=52%) for diastolic BP. In normotensives, the mean effect was -2.42 mmHg (95% CI: -3.56 to -1.29, I (2)=66%) for systolic and -1.00 mmHg (95% CI: -1.85 to -0.15, I (2)=66%) for diastolic BP. Further subgroup analysis showed that the decrease in systolic BP was significant in both whites and blacks, men and women. Meta-analysis of hormone and lipid data showed that the mean effect was 0.26 ng/ml/hr (95% CI: 0.17 to 0.36, I (2)=70%) for plasma renin activity, 73.20 pmol/l (95% CI: 44.92 to 101.48, I (2)=62%) for aldosterone, 31.67 pg/ml (95% CI: 6.57 to 56.77, I (2)=5%) for noradrenaline, 6.70 pg/ml (95% CI: -0.25 to 13.64, I (2)=12%) for adrenaline, 0.05 mmol/l (95% CI: -0.02 to 0.11, I (2)=0%) for cholesterol, 0.05 mmol/l (95% CI: -0.01 to 0.12, I (2)=0%) for LDL, -0.02 mmol/l (95% CI: -0.06 to 0.01, I (2)=16%) for HDL, and 0.04 mmol/l (95% CI: -0.02 to 0.09, I (2)=0%) for triglycerides.

AUTHORS' CONCLUSIONS

A modest reduction in salt intake for 4 or more weeks causes significant and, from a population viewpoint, important falls in BP in both hypertensive and normotensive individuals, irrespective of sex and ethnic group. With salt reduction, there is a small physiological increase in plasma renin activity, aldosterone and noradrenaline. There is no significant change in lipid levels. These results provide further strong support for a reduction in population salt intake. This will likely lower population BP and, thereby, reduce cardiovascular disease. Additionally, our analysis demonstrates a significant association between the reduction in 24-h urinary sodium and the fall in systolic BP, indicating the greater the reduction in salt intake, the greater the fall in systolic BP. The current recommendations to reduce salt intake from 9-12 to 5-6 g/d will have a major effect on BP, but are not ideal. A further reduction to 3 g/d will have a greater effect and should become the long term target for population salt intake.

Altered dietary salt intake for preventing and treating diabetic kidney disease

BACKGROUND

There is strong evidence that our current consumption of salt is a major factor for increased blood pressure (BP) and a modest reduction in salt intake lowers BP whether BP levels are normal or raised. Tight control of BP in diabetics lowers the risk of strokes, heart attacks and heart failure and slows the progression of diabetic kidney disease (DKD). Currently there is no consensus in restricting salt intake in diabetic patients.

OBJECTIVES

To evaluate the effect of altered salt intake on BP and markers of cardiovascular disease and DKD.

SEARCH STRATEGY

In January 2010, we searched the Cochrane Renal Group's Specialised Register, CENTRAL (in The Cochrane Library), MEDLINE (from 1966) and EMBASE (from 1980) to identify appropriate articles.

SELECTION CRITERIA

We included all randomised controlled trials of salt reduction in individuals with type 1 and type 2 diabetes.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed studies and resolved differences by discussion with a third independent author. We calculated mean effect sizes using both the fixed-effect and random-effects models.

MAIN RESULTS

Thirteen studies (254 individuals) met our inclusion criteria. These included 75 individuals with type 1 diabetes and 158 individuals with type 2 diabetes. The median reduction in urinary sodium was 203 mmol/24 h (11.9 g/day) in type 1 diabetes and 125 mmol/24 h (7.3 g/day) in type 2 diabetes. The median duration of salt restriction was one week in both type 1 and type 2 diabetes. BP was reduced in both type 1 and type 2 diabetes. In type 1 diabetes (56 individuals), salt restriction reduced BP by -7.11/-3.13 mm Hg (systolic/diastolic); 95% CI: systolic BP (SBP) -9.13 to -5.10; diastolic BP (DBP) -4.28 to -1.98). In type 2 diabetes (56 individuals), salt restriction reduced BP by -6.90/-2.87 mm Hg (95% CI: SBP -9.84 to -3.95; DBP -4.39 to -1.35). There was a greater reduction in BP in normotensive patients, possibly due to a larger decrease in salt intake in this group.

AUTHORS' CONCLUSIONS

Although the studies are not extensive, this meta-analysis shows a large fall in BP with salt restriction, similar to that of single drug therapy. All diabetics should consider reducing salt intake at least to less than 5-6 g/day in keeping with current recommendations for the general population and may consider lowering salt intake to lower levels, although further studies are needed.

Glomerular function reserve and sodium sensitivity

In clinical nephrology, the glomerular filtration rate (GFR) has been recognized as the golden standard to assess renal function. However, a normal GFR does not necessarily mean normal filtration capability of the kidneys, because impaired filtration capability can be compensated for by elevating glomerular hydraulic pressure. Therefore, an early phase of glomerular dysfunction cannot be detected by the baseline GFR alone. On the other hand, glomerular capillary hypertension is widely recognized as one of the strong risk factors for the progression of nephropathies. Now, it is very important to imagine glomerular hemodynamics in each patient with nephropathy for detecting early dysfunction, as well as for evaluating risk factors. Here, I would like to summarize the current status of how an early phase of renal dysfunction can be detected in clinical practice. I truly anticipate that new methods to assess glomerular hemodynamics in humans will be developed in the near future.

Carbohydrate and Fiber Recommendations for Individuals with Diabetes: A Quantitative Assessment and Meta-Analysis of the Evidence

To review international nutrition recommendations with a special emphasis on carbohydrate and fiber, analyze clinical trial information, and provide an evidence-based recommendation for medical nutrition therapy for individuals with diabetes. Relevant articles were identified by a thorough review of the literature and the data tabulated. Fixed-effects meta-analyses techniques were used to obtain mean estimates of changes in outcome measures in response to diet interventions. Most international organizations recommend that diabetic individuals achieve and maintain a desirable body weight with a body mass index of </=25 kg/m(2). For diabetic subjects moderate carbohydrate, high fiber diets compared to moderate carbohydrate, low fiber diets are associated with significantly lower values for: postprandial plasma glucose, total and low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and triglycerides. High carbohydrate, high fiber diets compared to moderate carbohydrate, low fiber diets are associated with lower values for: fasting, postprandial and average plasma glucose; hemoglobin A(1c); total, LDL-cholesterol, HDL-cholesterol and triglycerides. Low glycemic index diets compared to high glycemic index diets are associated with lower fasting plasma glucose values and lower glycated protein values. Based on these analyses we recommend that the diabetic individual should be encouraged to achieve and maintain a desirable body weight and that the diet should provide these percentages of nutrients: carbohydrate, >/=55%; protein, 12-16%; fat, <30%; and monounsaturated fat, 12-15%. The diet should provide 25-50 g/day of dietary fiber (15-25 g/1000 kcal). Glycemic index information should be incorporated into exchanges and teaching material.

Dietary advice given by a dietitian versus other health professional or self-help resources to reduce blood cholesterol

BACKGROUND

The average level of blood cholesterol is an important determinant of the risk of coronary heart disease. Blood cholesterol can be reduced by dietary means. Although dietitians are trained to provide dietary advice, for practical reasons it is also given by other health professionals and occasionally through the use of self-help resources.

OBJECTIVES

To assess the effects of dietary advice given by a dietitian compared with another health professional, or the use of self-help resources, in reducing blood cholesterol in adults.

SEARCH STRATEGY

We searched The Cochrane Library (to Issue 2 1999), MEDLINE (1966 to January 1999), EMBASE (1980 to December 1998), Cinahl (1982 to December 1998), Human Nutrition (1991 to 1998), Science Citation Index, Social Sciences Citation Index, hand searched conference proceedings on nutrition and heart disease, and contacted experts in the field.

SELECTION CRITERIA

Randomised trials of dietary advice given by a dietitian compared with another health professional or self-help resources. The main outcome was difference in blood cholesterol between dietitian groups compared with other intervention groups.

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data and assessed study quality.

MAIN RESULTS

Eleven studies with 12 comparisons were included, involving 704 people receiving advice from dietitians, 486 from other health professionals and 551 people using self-help leaflets. Four studies compared dietitian with doctor, seven with self-help resources, and one compared dietitian with nurse. Participants receiving advice from dietitians experienced a greater reduction in blood cholesterol than those receiving advice only from doctors (-0.25 mmol/L (95% CI -0.37, -0.12 mmol/L)). There was no statistically significant difference in change in blood cholesterol between dietitians and self-help resources (-0.10 mmol/L (95% CI -0.22, 0.03 mmol/L)). No statistically significant differences were detected for secondary outcome measures between any of the comparisons with the exception of dietitian versus nurse for HDLc, where the dietitian groups showed a greater reduction (-0.06 mmol/L (95% CI -0.11, -0.01)). No significant heterogeneity between the studies was detected.

REVIEWER'S CONCLUSIONS

Dietitians were better than doctors at lowering blood cholesterol in the short to medium term, but there was no evidence that they were better than self-help resources. The results should be interpreted with caution as the studies were not of good quality and the analysis was based on a limited number of trials. More evidence is required to assess whether change can be maintained in the longer term. There was no evidence that dietitians provided better outcomes than nurses.

Dietary fiber prevents carbohydrate-induced hypertriglyceridemia

Plant foods rich in carbohydrate and dietary fiber have many health benefits. One concern often expressed about higher carbohydrate, lower fat diets is that they may increase fasting serum triglycerides. Recently the importance of hypertriglyceridemia as an independent risk factor for coronary heart disease has been reaffirmed. For 40 years, clinicians have noted "carbohydrate-induced hypertriglyceridemia" when persons were fed high-carbohydrate, low-fiber diets. The role of fiber in protecting from carbohydrate-induced hypertriglyceridemia has not been discussed by many reviewers. Systematic review of the literature documents that high fiber intakes clearly protect from carbohydrate-induced hypertriglyceridemia. These are reviewed. Thus, recent and earlier research indicates that use of a higher carbohydrate, higher fiber diet compared with a lower carbohydrate, higher fat diet is associated with a small reduction in fasting serum triglyceride values.

Screening, prevention, counseling, and treatment for the complications of type II diabetes mellitus. Putting evidence into practice

PURPOSE

To summarise current knowledge of interventions that should improve the care of patients with type II diabetes mellitus. Interventions lie within the realms of preventions, screening, and treatment, all of which are focused on office practice.

METHODS

Review of the literature by a multidisciplinary team involved in the care of patients with diabetes, followed by synthesis of the literature into a clinical care guideline. Literature was identified through consultation with experts and a focused MEDLINE search.

MAIN RESULTS

An algorithm-based guideline for screening and treatment of the complications of diabetes was developed. The emphasis is on prevention of atherosclerotic disease, and prevention, screening, and early treatment of microvascular disease. Implementation of these practices has the potential to significantly improve quality of life and increase life expectancy in patients with type II diabetes mellitus.

Insulin resistance--not hyperinsulinemia--is pathogenic in essential hypertension

A correlation between essential hypertension and insulin resistance/hyperinsulinemia is well documented, and there is adequate reason to believe that this association is causal. The common presumption that hyperinsulinemia mediates this connection is based on studies demonstrating various pressor effects of insulin, such as sodium retention, activation of the sympathetic nervous system, and stimulation of renin output. However, a consideration of physiological parameters in essential hypertensives indicates that these insulin-mediated pressor effects are unlikely to play a crucial pathogenic role in most cases of essential hypertension. Moreover, physiological elevation of insulin following a meal is typically associated with a reduction of blood pressure in hypertensives and the elderly. Euglycemic insulin clamps tend to reduce blood pressure in elderly subjects, and prolonged maintenance of hyperinsulinemia in animals does not raise blood pressure. In fact, insulin has long been known to have direct vasodilatory or antipressor effects on resistance vessels, and there is recent evidence that insulin reduces vascular resistance in skeletal muscles to facilitate glycogen storage after a meal. I propose that essential hypertensives experience a net deficit of insulin activity in vascular muscle, and that, in conjunction with other genetic or acquired defects of electrolyte transport, this leads to an increase in basal vascular tone and a hypersensitivity to pressor agents. Correction of insulin resistance usually aids blood pressure control, and in addition may mitigate the excess cardiovascular risk associated with hypertension.

Dietary fats, fish, and blood pressure

In humans any effects of dietary saturated fats or omega-6 polyunsaturates on blood pressure appear to be mediated by changes in caloric intake and long-term weight changes. In contrast, omega-3 fatty acids have a mild antihypertensive effect which is seen most clearly in untreated subjects with higher blood pressures, in older people, and during sodium restriction. The mechanism may be due to a combination of effects consequent to incorporation of omega-3 fatty acids into vascular phospholipids, leading to reduced formation of endothelial contractile substances in larger vessels and impairment of sympathetic neuroeffector and other vasoconstrictor mechanisms in resistance vessels.

A controlled trial of a low sodium, low fat, high fibre diet in treated hypertensive patients: the efficacy of multiple dietary intervention

An 8-week combination low sodium, low fat, high fibre diet was compared to the individual components of this diet in a controlled trial using 193 patients already on treatment for essential hypertension. No significant changes were observed in the high fibre group. The low sodium group showed a decrease in systolic blood pressure which was close to significance. The low fat group showed a small but significant decrease in seated diastolic blood pressure and weight. The combination group showed larger and highly significant decreases in seated and standing systolic blood pressures, seated diastolic blood pressure and weight, as well as a significant reduction in standing diastolic blood pressure. We conclude that multiple dietary intervention in this case in the form of a low sodium, low fat, high fibre diet, is more effective than any single dietary intervention and is useful in patients already on medication.

Sodium restriction and blood pressure in hypertensive type II diabetics: randomised blind controlled and crossover studies of moderate sodium restriction and sodium supplementation

OBJECTIVE

To determine the effect of moderate dietary sodium restriction on the hypertension of non-insulin-dependent (type II) diabetes.

DESIGN

Randomised parallel controlled study of moderate sodium restriction for three months compared with usual diabetic diet, followed by randomised double blind crossover trial of sustained release preparation of sodium for one month versus placebo for one month in patients continuing with sodium restriction.

SETTING

Patients attending diabetic outpatient clinic of city hospital.

PATIENTS

Thirty four patients with established type II diabetes complicated by mild hypertension (systolic blood pressure greater than 160 mm Hg or diastolic pressure greater than 95 mm Hg on three consecutive occasions). Patients already taking antihypertensive agents (but not diuretics) not barred from study provided that criteria for mild hypertension still met. Conditions precluding patients from study were diabetic or hypertensive nephropathy, cardiac failure, and pregnancy.

INTERVENTIONS

After run in phase with recordings at seven weeks, three weeks, and time zero patients were allocated at random to receive moderate dietary sodium restriction for three months (n = 17) or to continue with usual diabetic diet. Subsequently nine patients in sodium restriction group continued with regimen for a further two months, during which they completed a randomised double blind crossover trial of sustained release preparation of sodium (Slow Sodium 80 mmol daily) for one month versus matching placebo for one month.

END POINT

Reduction in blood pressure in type II diabetics with mild hypertension.

MEASUREMENTS AND MAIN RESULTS

Supine and erect blood pressure, body weight, and 24 hour urinary sodium and potassium excretion measured monthly during parallel group and double blind crossover studies. After parallel group study sodium restriction group showed significant reduction in systolic blood pressure (supine 19.2 mm Hg, erect 21.4 mm Hg; p less than 0.001) and mean daily urinary sodium excretion (mean reduction 60 mmol/24 h). There were no appreciable changes in weight, diabetic control, or diastolic pressure. No significant changes occurred in controls. In double blind crossover study mean supine systolic blood pressure rose significantly (p less than 0.005) during sodium supplementation (to 171 mm Hg) compared with value after three months of sodium restriction alone (159.9 mm Hg) and after one month of placebo (161.8 mm Hg).

CONCLUSIONS

Moderate dietary restriction of sodium has a definite hypotensive effect, which may be useful in mild hypertension of type II diabetes.

Hypertension

The awareness of hypertension as one of the major risk factors for mortality and morbidity in NIDDM has increased greatly in the past few years. It is now accepted practice to measure BP at least yearly in all such patients. Unfortunately, one cannot yet be sure to what extent diabetics benefit from anti-hypertensive therapy, and the simple assumption that treatment of the increased risk reduces that risk must be constantly questioned. No specific data are yet available for NIDDM, though it would be remarkable if the benefits of decreased cerebrovascular mortality and probable reduced total mortality (Sleight, 1987) did not apply to the higher-risk diabetic subject, at least at the higher levels of diastolic pressure (greater than 105 mm Hg). There is, though, no evidence that mortality or morbidity of coronary artery disease, the major killer in NIDDM, is reduced even in non-diabetics and the present author does not consider there to be any evidence suggesting that thresholds for treatment of hypertension in uncomplicated patients with NIDDM should be lower than those for non-diabetics, unless progressive nephropathy is present. Current advice in the non-diabetic is that levels of blood pressure in adults consistently above 95 mm Hg warrant therapy, aiming to reduce it below 90 mm Hg (World Health Organization, 1986). While the importance of hypertension should not be underestimated, it should not deflect attention from the other risk factors. Cessation of smoking, and by implication its reduction, will, for all smoking patients but the most hypertensive, produce a greater reduction in cardiovascular and total mortality risk than will anti-hypertensive therapy. There are also early signs that effective dietary and/or drug treatment of significant hyperlipidaemia lowers cardiovascular mortality. Choice of anti-hypertensive therapy is especially important, not only for efficacy but also for quality of life, in patients who already suffer major restrictions on diet, freedom and life expectancy. While controlled trials in the subject are of immense importance in determining optimum therapy, there is currently no evidence to favour any particular group of drugs, and an individual patient's therapy should be decided on the basis of their own circumstances.

Dietary sugars and carbohydrate metabolism in type II diabetes

Diabetes, the most common metabolic disease, is responsible for the deaths of over 300,000 Americans annually. The incidence of the disease increases with age and since the U.S. population is graying, prevalence is also increasing. Obesity and family history are strong predictors of diabetes. The etiology of Type II diabetes is heterogeneous. The hyperglycemia of Type II diabetes can result from a variety of metabolic defects including impaired beta cell secretion, receptor deficiencies, or abnormal hepatic production or uptake of glucose. Other glucoregulatory hormones such as glucagon, growth hormone, cortisol, thyroid hormones, somatostatin, and gastric inhibitory polypeptide may contribute to the aberrations of carbohydrate metabolism. Environmental factors including stress, diet, and exercise may also contribute to the disease. Since most diabetics are obese, weight loss should be the first priority in improving status. A variety of diet and exercise regimens may help achieve this goal or even improve glucose control without weight loss. Due to the heterogeneity of the disease individualized treatment must be used to improve status of patients with the various metabolic defects of Type II diabetes.

[Nutritional behavior of insulin-dependent diabetes patients studied with the KALI 2.1.2 computer program]

We investigated the levels of intake of essential nutrients in 51 patients with insulin dependent diabetes mellitus. The mean daily intake in males was 223 +/- 55 g carbohydrates, 111 +/- 22 g fat and 112 +/- 27 g protein. In females the mean daily intake was 166 +/- 36 g carbohydrates, 78 +/- 23 g fat and 97 +/- 25 g protein. the percentage of calories from carbohydrates, fat and protein was for males 36:40:18 and for females 37:39:21 respectively. The daily intake of dietary fiber was 32.5 +/- 8.0 g in men and 28.3 +/- 6.4 g in women. The mean linoleic acid intake was 12 +/- 5 g/day in men and 9 +/- 4 g in women. A marginal deficiency of linoleic acid was found in 15% of men and in 25% of women. The P/S ratio of the diet was 0.35. The consumption of vitamins, minerals and trace elements differed considerably from the recommended dietary allowances.