A Brief Look At The Impact Of The Low Carb Diet And Very Low Carb Diet On People Living With Diabetes
How does a low or very low carbohydrate diet affect people living with type 1 diabetes? The first step is to be clear what is understood about the definition of Low Carb Diets (LCD) and Very Low Carb Diets (VLCD).
The table below is one common consensus used when looking to describe and compare evidence for LCD and VLCD.
Table 1 The consensus description on different levels of carbohydrate diets
Low carbohydrate diets are one of the most researched dietary topics in diabetes. However, it should be noted that a majority of the research relates to people living with type 2 diabetes and therefore caution should always be taken when relating this to people living with type 1 diabetes.
Recent studies in the last few years have started to question whether carbohydrates should play such a central role in diets, for people living with or without diabetes. For people living with type 2 diabetes, LCD may help to lower cholesterol, HbA1c and weight. Additionally, following an LCD could reduce the risk of developing type 2 diabetes.
One of the reference bodies, the American Diabetes Association (ADA)1, has already included low-carbohydrate diets in its recommendations as a possible eating pattern. In the most recent UK guidance from Diabetes UK, LCD is suggested as an option. However, Diabetes UK has also shared that currently, there is not enough strong evidence to make it clear that the long-term benefits of LCD are more or less effective than any other dietary regime.
LCD and type 1 diabetes
The impact of LCD for people living with type 1 diabetes is debatable for many reasons. In general, there are not enough studies to clearly indicate that LCD brings greater benefits to people living with type 1 diabetes.
Additionally, there is much less evidence for LCD in Type 1 and hardly any of good enough data in children and pregnancy.
At the end of 2018, a medical publication2 was published by a group of experts in nutrition and type 1 diabetes. In this article, all published articles on the subject were reviewed. This review found that the low-carbohydrate diet has beneficial effects on glycaemic control, although more studies are needed to clearly ensure this. In conclusion, it seems that there might be positive effects on glycaemic control, but more studies need to be developed to be conclusive.
VLCD and type 1 diabetes
Another name for VLCD is Very Low Carb Ketogenic Diets. This is because by nature if the body has insufficient access to carbohydrates for energy it will break down the body’s protein and fat stores. Fat breakdown for energy produces the by-product of ketones. To a person living without diabetes, these ketones are usually not harmful, but to a person living with type 1 diabetes, the production ketones can be dangerous and indeed, life-threatening if levels are allowed to rise due to insufficient insulin administration.
In May 2019, another paper was published in the journal Pediatrics3 about a study on a low-carbohydrate diet in type 1 diabetes treatment. This study suggested that those children and adults who followed a very low carbohydrate diet maintained a particularly good glycaemic control, with an HbA1c of 5.7% (60mmol/mol) and notably decreasing the frequency of hypoglycaemic incidents. The idea is that decreasing the amount of consumed carbohydrates, reduced glucose variability after meals. It also decreased the amount of insulin needed and individuals in this study reported a lower frequency of hyperglycaemia by maintaining lower blood insulin levels during the day. Although the results of this study show benefits, it should be looked at with caution as this was a particularly motivated group of people living with type 1 diabetes and the individuals self-reported their dietary intake.
Moreover, there is extensive literature on the adverse effects of this type of diet in people living with diabetes2. These include, for example, decreased growth rates, alterations in blood lipids, increased risk of hypoglycaemic incidents and ketoacidosis, and lack of adherence to dietary monitoring.
A VLCD should not be generalised for everyone and is suggested to speak with your diabetes healthcare team before starting a VLCD.
In conclusion, there is some consensus between the definition of an LCD and VLCD, but this is not always obvious in the literature. Some studies indicate dramatic reductions in HbA1c, even reducing the frequency of hypoglycaemic incidents and increasing the time in range. However, evidence on efficacy and safety is still pending. For people living with type 1 diabetes and there is some concern about the risk of DKA as well as a potential impact on growth in children living with type 1. Adherence to either a VLCD or LCD involves motivation and commitment to sustain long term. We would always suggest you speak with your diabetes healthcare team before embarking on this type of dietary regime.
1. Feinman RD, Pogozelski WK, Astrup A, et al. Dietary carbohydrate restriction as the first approach in diabetes management: critical review and evidence base [published correction appears in Nutrition. 2019 Jun;62:213]. Nutrition. 2015;31(1):1-13.
2. Seckold R, Fisher E, de Bock M, King BR, Smart CE. The ups and downs of low-carbohydrate diets in the management of Type 1 diabetes: a review of clinical outcomes. Diabet Med. 2019;36(3):326-334.
3. Lennerz B, Barton A, Bernstein R et al. Management of Type 1 Diabetes With a Very Low–Carbohydrate Diet. Pediatrics. 2018;141(6):1-12
4. Diabetes UK, 2019. Low-Carb Diet And Meal Plan. [online] Diabetes UK. Available at: <https://www.diabetes.org.uk/guide-to-diabetes/enjoy-food/eating-with-diabetes/meal-plans-/low-carb> [Accessed 19 September 2020].
5. Evert A, Dennison M, Gardner C et al. Nutrition Therapy for Adults With Diabetes or Prediabetes: A Consensus Report. Diabetes Care. 2019;42(5):731-754