The challenges of control groups, placebos and blinding in clinical trials of dietary interventions

Staudacher, Heidi M; Irving, Peter M; Lomer, Miranda; Whelan, Kevin

doi:10.1017/s0029665117000350

Cited by 95 publications

(75 citation statements)

References 48 publications

(90 reference statements)

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“…It is notoriously challenging to minimize bias in RCTs of dietary interventions, although numerous strategies have been recommended . Blinding to treatment allocation of participants and those delivering the intervention is rarely possible, and the nature of dietary interventions involving complex lifestyle and behaviour changes means participants are likely to have a strong preference, which may, in turn, affect adherence and attrition.…”

Section: Discussionmentioning

confidence: 99%

Carbohydrate restriction for glycaemic control in Type 2 diabetes: a systematic review and meta‐analysis

et al. 2019

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Aim To conduct a systematic review and meta‐analysis to evaluate the effect of carbohydrate restriction on glycaemic control in Type 2 diabetes. Methods We searched Medline, EMBASE and CINAHL for the period between 1976 and April 2018. We included randomized controlled trials comparing carbohydrate restriction with a control diet which aimed to maintain or increase carbohydrate intake, and that reported HbA1c as an outcome and reported the amount of carbohydrate consumed during or at the end of the study, with outcomes reported at ≥3 months. Results We identified 1402 randomized controlled trials, 25 of which met the inclusion criteria, incorporating 2132 participants for the main outcome. Definitions of low carbohydrate varied among the studies. The pooled effect estimate from meta‐analysis was a weighted mean difference of –0.09% [95% CI –0.27, 0.08 (P = 0.30); I2 72% (P <0.001)], suggesting no effect on HbA1c of restricting the quantity of carbohydrate. A subgroup analysis of diets containing 50–130 g carbohydrate resulted in a pooled effect estimate of –0.49% [95% CI –0.75, –0.23 (P <0.001); I2 0% (P = 0.56)], suggesting a clinically and statistically significant effect on HbA1c in favour of low‐carbohydrate diets in studies of ≤6 months’ duration. Conclusions There was no overall pooled effect on HbA1c in favour of restricting carbohydrate; however, restriction of carbohydrate to 50–130 g per day had beneficial effects on HbA1c in trials up to 6 months. Future randomized controlled trials should be of >12 months’ duration, assess pre‐study carbohydrate intake, use recognized definitions of low‐carbohydrate diets and examine reasons for non‐adherence to prescribed diets in greater detail.

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Section: Discussionmentioning

confidence: 99%

Carbohydrate restriction for glycaemic control in Type 2 diabetes: a systematic review and meta‐analysis

et al. 2019

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“…One challenge is the difficulty of identifying an appropriate control when evaluating foods or food patterns. 64 If control participants do not receive a placebo or a comparative intervention, there is strong potential for expectation bias (expected benefit in the intervention group versus expected lack of benefit in the control group). The Women’s Health Initiative Dietary Modification Trial, for example, compared a low fat intervention group with intensive behaviour modification counselling to increase fruit, vegetable, and grain consumption with a “usual diet” group receiving diet related education materials only.…”

Section: Potential and Limitations Of Randomised Trialsmentioning

confidence: 99%

Food based dietary patterns and chronic disease prevention

Schulze

Martínez‐González

Fung

et al. 2018

BMJ

419

341

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“…Another study reported satisfaction with symptoms in 72.1% of responders at a mean of 15.7 months follow‐up . However, these studies lacked control groups, had high attrition rates and only reported data in those who completed follow‐up appointments and questionnaires, which are common difficulties in long term follow‐up studies of dietary interventions .…”

Section: Fodmap Personalisation (Long‐term Self‐management)mentioning

confidence: 99%

“…However, a systematic review of the quality of randomised controlled trials of the low FODMAP diet identified limitations in their design, including a high risk of bias for the blinding of participants and outcome measurement, selection of control groups and objective evaluation of data . However, it is also recognised that ensuring participant blinding and identifying appropriate controls can be very challenging in dietary intervention trials .…”

Section: Introductionmentioning

confidence: 99%

The low FODMAP diet in the management of irritable bowel syndrome: an evidence‐based review of FODMAP restriction, reintroduction and personalisation in clinical practice

Whelan

Martin

Staudacher

et al. 2018

J Human Nutrition Diet

224

197

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Dietary restriction of fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAPs) is effective in the management of functional gastrointestinal symptoms that occur in irritable bowel syndrome (IBS). Numerous reviews have been published regarding the evidence for their restriction in the low FODMAP diet; however, few reviews discuss the implementation of the low FODMAP diet in practice. The aim of this review is to provide practical guidance on patient assessment and the implementation and monitoring of the low FODMAP diet. Broadly speaking, the low FODMAP diet consists of three stages: FODMAP restriction; FODMAP reintroduction; and FODMAP personalisation. These stages can be covered in at least two dietetic appointments. The first appointment focuses on confirmation of diagnosis, comprehensive symptom and dietary assessment, detailed description of FODMAPs and their association with symptom induction, followed by counselling regarding FODMAP restriction. Dietary counselling should be tailored to individual needs and appropriate resources provided. At the second appointment, symptoms and diet are re-assessed and, if restriction has successfully reduced IBS symptoms, education is provided on FODMAP reintroduction to identify foods triggering symptoms. Following this, the patient can follow FODMAP personalisation for which a less restrictive diet is consumed that excludes their personal FODMAP triggers and enables a more diverse dietary intake. This review provides evidence and practice guidance to assist in delivering high-quality clinical service in relation to the low FODMAP diet.

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The challenges of control groups, placebos and blinding in clinical trials of dietary interventions

Abstract: 25High quality placebo-controlled evidence for food, nutrient or dietary advice interventions is

Cited by 95 publications

References 48 publications

Carbohydrate restriction for glycaemic control in Type 2 diabetes: a systematic review and meta‐analysis

Carbohydrate restriction for glycaemic control in Type 2 diabetes: a systematic review and meta‐analysis

Food based dietary patterns and chronic disease prevention

The low FODMAP diet in the management of irritable bowel syndrome: an evidence‐based review of FODMAP restriction, reintroduction and personalisation in clinical practice

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