SACN consultation on lowER carb diets & T2D

Introduction

We’re returning to our normal world this week, which I hope is refreshing if you’re a bit COVID-19 overloaded.

On March 5th, 2020, Public Health England announced, “We are seeking scientific comments on SACN’s draft report: ‘Lower carbohydrate diets for adults with type 2 diabetes’” (Ref 1). SACN stands for Scientific Advisory Committee on Nutrition. This is the body tasked with reviewing dietary policy for Public Health England.

Health was devolved in the UK in 1999, so that England, Scotland, Ireland and Wales all have their own public health bodies and chief medical officers. However, when it comes to diet, the regions tend to follow England’s lead and thus anything decreed by SACN ends up being UK wide policy.

Regarding previous reports, SACN published a report on “Carbohydrates and health” in July 2015. I reviewed it here (Ref 2). I responded to the SACN consultation on saturated fat in July 2018 (Ref 3). This had no impact on the continued damnation of saturated fat by SACN, which was published in August 2019 (Ref 4).

The consultation documents for the latest SACN review can be seen here (Ref 5). Anyone can respond. Consultation responses will be published and put on open view alongside the SACN final response. This is by no means just a UK story, as all evidence worldwide should be considered by this review and public health bodies reference each other’s policy to support their own. Indeed, this draft report references policy in Australia, Canada and the US in support of its own position.

Consultation remit

The purpose of the SACN report is to review the evidence on lowER (note lowER, not low) carbohydrate diets compared to current UK government advice for adults with type 2 diabetes (T2D). It started in 2017 when Public Health England asked SACN to review the evidence in recognition that “such diets are gaining attention and increasingly being promoted.”

The terms of reference for SACN were three fold:

i) To review the evidence on lower carbohydrate diets compared to current government advice for adults with T2D.

ii) To consider the impact, in adults with T2D, of lower compared with higher carbohydrate diets on markers and clinical outcomes of T2D including any potential adverse effects.

iii) To make recommendations based on the review of the literature.

Some markers for (ii) were well-chosen in that they are important indicators of T2D. These markers were body weight, HbA1c, fasting plasma glucose, and changes in medication and diabetes-related symptoms. Every cholesterol measurement you can think of was also included in (ii) – total cholesterol, triglycerides, LDL-cholesterol, HDL-cholesterol, and total to HDL cholesterol ratio – which reflected belief systems more than markers of T2D. For body weight outcomes, only studies with a duration of at least 12 months were considered and for all other outcomes, studies with a minimum duration of 3 months were considered.