1. Efficacy and safety of low and very low carbohydrate diets for type 2 diabetes remission: systematic review and meta-analysis of published and unpublished randomized trial data (2021)

This systematic review and meta-analysis aimed to assess the efficacy and safety of low carbohydrate diets (LCDs) and very low carbohydrate diets (VLCDs) for individuals with type 2 diabetes.

Eligible trials involved randomized clinical trials assessing LCDs (<130 g/day or <26% of a 2000 kcal/day diet) and VLCDs (<10% calories from carbohydrates) for at least 12 weeks in adults with type 2 diabetes.

Primary outcomes included diabetes remission, weight loss, HbA1c, fasting glucose, and adverse events, while secondary outcomes comprised quality of life and biochemical data.

The review identified 23 trials comprising 1357 participants. LCDs showed higher rates of diabetes remission at six months compared to control diets, especially when defined as HbA1c <6.5%.

However, remission diminished at 12 months. Significant improvements were seen in weight loss, triglycerides, and insulin sensitivity at six months, but these effects lessened at 12 months.

VLCDs were less effective for weight loss at six months, attributed to diet adherence.

Adverse events and blood lipids showed no significant differences between groups at six and 12 months. The study suggests that adherence to LCDs may lead to diabetes remission without adverse effects over six months, but longer-term efficacy and safety require further investigation.

2. Diabetes UK Position Statements

Position statements as identified by Kelly et al (2020) include: Diabetes UK (2011) – “Diabetes UK support the view that low-carbohydrate diets may be considered an option for weight loss in T2DM when supported by a registered healthcare professional (Dyson, et al., 2011).

3. The Scientific Advisory Committee on Nutrition (2015) recommends that carbohydrate intake should be approximately 50% of dietary energy (SACN, 2015).

SIGN guidelines suggest a low glycaemic index is an option as well as temporarily very low consumption of carbohydrates (<50g) up to 6 months (SIGN, 2017).

4. The American Diabetes Association and European Association for the Study of Diabetes have put out consensus reports in 2018 which include low carb, low gi, high protein and DASH approaches, although they identify the Mediterranean diet may be the most effective.

5. Consensus reports by the ADA lower carbohydrate diets is a viable approach (Evert, et al., 2019).

Potential negative impacts

6. Low-carbohydrate diets have been associated with increased all-cause mortality risk including cancer and cardiovascular risk (Noto, A, Tsujimoto, & al, 2013; Fung, van Dam, Hankinson, & al, 2010; Sjogren, Becker, Warensjo, & al, 2010).

7. Sjogren et al noticed a reduction in cardiovascular risk with a Mediterranean dietary approach whereas carbohydrate restriction appeared to increase mortality.

8. Carbohydrate intake and incidence of type 2 diabetes in the European Prospective Investigation into cancer and Nutrition (EPIC)-Potsdam Study.

Schulze et al identified when carbs were switched to protein, an increased incidence of type 2 diabetes, and when fat was substituted for carbohydrate, no significant change in incidence.

Noto identifies the potential changed risk depending on the overall diet (i.e. plant-based inferred a lower risk with lower-carbohydrate method).

It is unclear whether it is the replacement with higher protein or other fats from the analyses led to increased risk, or whether it was related directly to limiting carbohydrates.

A key drawback to these studies is the understanding of ultra-processed foods in these studies is limited, and the impact of the level of processing.

Glycaemic diets - Impact on function, blood pressure and cholesterol

The focus of the program is Hba1c improvement for prediabetes and type 2 diabetes patients. The program should not lead to other negative impact on individuals’ health do not occur as a result, especially cardiovascular risk.

Diabetes management is important largely to do with its cardiovascular implications.

As identified above in meta-analyses and studies there are other benefits that are realised from taking on glycaemic related approaches. This includes positive impacts on cholesterol (Brand-Miller, Hayne, Petocz, & Colagiuri, 2003; Zafar, et al., 2019).

Low carbohydrate diets have been associated with improved renal risk factors.

9. Dr David Unwin (2021) studied the impact on 143 patients’ renal function (those with normal renal function or mild CKD) and noted an improvement of serum creatinine by mean 4.7 micromol/L

The DASH diet (Dietary Approaches to Stop Hypertension), specifically created for improving hypertension outcomes, is advocated as a diet that can help with diabetes outcomes and recommended by ADA (Davies, et al., 2018). Dr Unwin has studied the impact of a low carb approach on blood pressure.

10. Substantial and sustained improvements in blood pressure, weight and lipid profiles from a carbohydrate restricted diet: an observational study of insulin resistant patients in primary care.

154 patients studied showed reductions in blood pressure (mean reduction of systolic BP 10.9 and diastolic 6.3, alongside a mean weight reduction of 9.5kg and improved lipid profiles. These readings occurred alongside a 20% reduction in anti-hypertensive medications (Unwin, Tobin, Murray, & Delon, 2019)

Low-glycaemic index sources of food is now recommended by NICE (NICE, 2022).