Diabetes is a dangerous condition that causes millions of deaths every year due to complications (Diabetes Control and Complications Trial (DCCT) and Epidemiology of Diabetes Interventions and Complications (EDIC) Study Research Group, 2016). In 2017, there were 425 million adults aged 20 to 79 years with type 1 diabetes worldwide, while over 1 million children and adolescents had type 1 diabetes. The expectation is that the number of adults will increase to 629 million by 2045, according to the International Diabetes Federation (Cho et al, 2018).
The World Health Organization (WHO) (2016) has described diabetes as a serious chronic disease that occurs when the pancreas neither produces enough insulin nor uses it well. Without insulin, the body cannot store glucose as fat or convert it into energy. Hence, the glucose accumulates in the blood, causing hyperglycaemia. At high levels, blood glucose is toxic and damages cells and organs, causing serious short- and long-term health complications, including heart attack, stroke, hypertension, blindness and other eye problems, kidney disease, nervous system complications, foot problems sometimes leading to amputations, dental disease, pregnancy complications, mental health problems, such as depression and dementia, and skin issues.
Before the advent of insulin therapy, dietary restriction of carbohydrates was the recommended treatment. Currently, the nutritional recommendation of a low-fat, high-carbohydrate diet for people with diabetes is dramatically different (Yancy et al, 2005). Studies have shown that the current recommendation of an unrestricted diet together with bolus insulin, such as that recommended by the Dose Adjustment For Normal Eating Study Group (DAFNE) (2002), is ineffective in achieving normal glycated haemoglobin (HbA1c) (which indicates the average plasma glucose concentration over the past 2–3 months) and reducing blood glucose variability, even with the use of an insulin pump and glucose monitoring sensors (Action to Control Cardiovascular Risk in Diabetes Study Group (ACCORD) et al, 2008; Foster et al, 2018; Foster et al, 2019). In addition, carbohydrate counting recommendations, based on matching insulin doses with food choices, are not well evidenced in the literature and further studies are required (Bell et al, 2014). Even with carbohydrate counting, it is still very difficult to achieve accuracy, predictability, and to avoid mistakes (Kawamura et al, 2015).
Therefore, monitoring of carbohydrate intake, a major determinant of postprandial blood glucose, is a key strategy for achieving good blood glucose control and preventing complications (Wolever and Bolognesi, 1996).
Carbohydrates can be found in simple forms, such as sugars, and in complex forms, such as starch and fibre (American Diabetes Association (ADA), 2014). Different types of carbohydrate may have different effects on blood glucose and insulin levels. For this reason, the glycaemic index, a value assigned to foods based on how slowly or how quickly they cause increases in blood glucose levels, was created. A person with diabetes should choose low-glycaemic-index and nutrient-dense foods because they will not cause blood glucose levels to increase much (Thomas and Elliot, 2009). Despite whole grains being regarded as an important source of dietary fibre, and their consumption being encouraged, they also have high glycaemic index, and substitution of white-wheat for wholemeal wheat in bread and pasta does not lead to reduced postprandial blood glucose levels (Musa-Veloso et al, 2018). In contrast, a very low carbohydrate diet (VLCD) is an easy way to control glucose levels because it causes only a small increase in blood glucose levels at each meal (Leow et al, 2018).
In October 2018, the ADA concluded that a low carbohydrate diet may result in lower blood glucose levels, lower doses of insulin and other medications required, and weight loss, and approved the therapy for adults with type 2 diabetes (Davies et al, 2018). Although the benefits of a VLCD seem logical for people with diabetes (Feinman et al, 2015), the new Standards of Medical Care in Diabetes by the ADA (2019a) still do not recommend a low-carbohydrate diet for type 1 diabetes due to insufficient dietary research to support one food plan over another. Thus, the present case study provides additional data about the use of a VLCD in the treatment of children with type 1 diabetes and its benefits.
Case study
The patient was a 5-year-old boy who was diagnosed with type 1 diabetes at the age of 4 years and 9 months. Before being hospitalised, he showed symptoms of diabetic ketoacidosis (DKA), such as thirst, polyuria, vomiting, and fast weight loss. Symptoms appeared about 1 month before the diagnosis. At his diagnosis, on 27 August 2018, his blood glucose was above 600 mg/dL (33.3 mmol/L), and his C-peptide level was at 0.3 ng/ml. He was put on insulin-replacement therapy to cover 50 g of carbohydrate per meal plus 10-15 g of carbohydrate at each snack. The recommendation was to use 0.5 units of rapid-acting insulin to cover every 20 g of carbohydrate, combined with a daily 5.5-unit dose of basal insulin. He was discharged from the hospital on 30 August.
On 4 September, at his first appointment with the nurse diabetes educator, his blood glucose was 176 mg/dL (9.7 mmol/L) and his HbA1c 10.9%. After 2 weeks unsuccessfully following the physician's recommendations, his mother was inspired by an article by Lennerz et al (2018), which showed excellent blood glucose control with a VLCD of 30 g of carbohydrate a day, and decided to reduce his carbohydrate intake accordingly.
Very low carbohydrate diet
The VLCD described in Lennerz's article consists of 30 g of carbohydrate daily derived from fibrous vegetables and nuts with a low glycaemic index. In this case, high-protein foods with associated fat were substituted for carbohydrates and adjusted on the basis of outcomes, including glycaemic control and weight. To ensure adequate nutrient intake, the amount of protein was increased until the child felt satisfied after meals. The macronutrient distribution of the child's diet became: 70 g of protein, 30 g of carbohydrate and 55 g of fat per day.
The latest Dietary Guidelines for Americans (US Department of Health and Human Services and US Department of Agriculture, 2015) recommend that male children aged 4 to 8 years should eat 19 g of protein, 130 g of carbohydrate and 25%-35% of total fat in a diet of 1400-1600 kcal daily. Compared with the guidelines, the child in the case study consumed more than 3 times the amount of protein.
Initially, a diet of 30 g of carbohydrate a day was not possible because the prescribed insulin was too potent, and no diluted version was available. On 1 October, after obtaining the diluent and testing a few ratios of insulin dilution, a concentration compatible with the new amount of carbohydrates contained in a VLC and high protein diet was reached. From that time on, the child ate approximately 6 g of carbohydrate for breakfast, 12 g for lunch and 12 g for dinner, as suggested by Lennerz et al's (2018) study. Additionally, he took vitamin D and omega-3 oil supplements. The child adapted very well to the new diet and had gained 3.6 kg since the diagnosis, reaching 17.4 kg in weight. He had also grown taller over the previous 5 months and was now in the 53rd percentile for height.
The average amount of carbohydrates consumed in the first two weeks after the diagnosis was 76.5 g/day (46.0 g–104.3 g). After 1 October, when the VLCD was introduced, the average carbohydrate intake decreased to 29.9 g per day (CHO 20.5 g–45.4 g) (Figure 1).
The permitted 30 g of carbohydrates in the diet were consumed from foods such as asparagus, avocados, bell peppers, berries, broccoli, brussels sprouts, carrots, cauliflower, celery, coconut chips, coconut flour, cucumber, endive, flax seeds, green beans, hearts of palm, jicamas, kale, psyllium husks, pumpkin seeds, radishes, red cabbage, seaweed and sugar snap peas. Processed foods, refined carbohydrates and grains were withdrawn from the diet. Snacks were limited to a single meal during school time. A meal at bedtime (supper) was introduced to avoid the risk of nocturnal hypoglycaemia. Despite a newly discovered allergy to nuts (Brazil nuts and almonds) and stevia (sweetener), the child diligently followed the diet and was offered enough food options. No others side effects were observed.
During the first 2 weeks after the diagnosis, and before the VLCD diet was introduced, blood glucose levels were like a roller-coaster, averaging 137.3 mg/dL (7.6 mmol/L), within a range between 65 and 330 mg/dL (3.6 mmol/L–18.5 mmol/L), and with a standard deviation of 57.3 mg/dL (3.1 mmol/L). Under a VLCD diet, average blood glucose levels were drastically reduced to 87.5 mg/dL (4.8 mmol/L). Range stayed within 57-189 mg/dL (3.1 mmol/L–10.4 mmol/L), and standard deviation at 14 mg/dL (0.7 mmol/L). On 29 September, a spike occurred in the patient's blood glucose because he ate a small piece of banana bread (see Figure 2).
The child's basal insulin was reduced from 3.8 units to 0.4 unit per day, on average. His rapid-acting insulin average daily dosage, originally at 1.4 units, was reduced by half, by simply switching from an undiluted to a diluted dose of 1:1 ratio. As a result, HbA1c decreased from 10.9% to 4.8% during the first 3 months (see Figure 3).
Data from continuous glucose monitoring (CGM), introduced on 26 November 2018, showed a marked reduction of average daily blood glucose variability and maintenance of blood glucose levels in a range of 70–180 mg/dL (4 mmol/L–10 mmol/L) 95.3% of the time (see Figure 4). In addition, the child's parents observed an improvement in his speech and behaviour, especially at school.
Data collection
The carbohydrate content of every meal, as well insulin intake, were documented from August 2018 to February 2019 on an Excel spreadsheet. Blood glucose readings (mg/dL) were recorded using a Dexcom G6 (a CGM) and a Freestyle Lite glucometer. HbA1c values were obtained from routine clinical monitoring. The app FatSecret was used to collect information about carbohydrate counting. The case study was approved by the Ethics Committee of the University of Campinas (CAAE: 09131319.7.0000.5404). Both parents provided written informed consent for the study and publication of this article.
Discussion
This case study concerned a recently diagnosed child with type 1 diabetes, whose HbA1c decreased from 10.9% to 4.8% in 3 months after the diagnosis. Unfortunately, that is not the usual outcome observed in other cases. Despite an increase in the use of insulin pumps and CGM devices over a 5-year timeframe among participants of a US type 1 diabetes study, there was an increase in HbA1c from 7.8% in 2010-2012 to 8.4% in 2016-2018 (Foster et al, 2019). These levels are higher than those the ADA (2019b) considers normal for children with type 1 diabetes, ie HbA1c <7.5%. Furthermore, between 2016 and 2018, only 17% of all youngsters with type 1 achieved HbA1c <7.5% (Foster et al, 2019).
Fortunately, there is evidence of alternative approaches that have resulted in consistently lower HbA1c levels. In the study by Lennerz et al (2018), the mean HbA1c achieved by study participants was 5.67 % (36 g of carbohydrate daily). In addition to improved HbA1c rates, other benefits were observed, such as fewer hospitalisations (only 2% over the previous 12 months), lower numbers of hypoglycaemic events, much lower rates of complications, much lower usage of insulin and other medications, and higher levels of satisfaction with health and diabetes control.
Although HbA1c is not considered a good marker in isolation from glucose variability (Hirsch and Brownlee, 2005), it is considered a good marker for many diseases, including heart disease. In adults with diabetes, the most common causes of death are heart disease and stroke (National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), 2019). In a study of people without diabetes, the chance of cardiovascular disease more than doubled as HbA1c rose from 5% to 6% (Ikeda et al, 2013). Another study of patients undergoing coronary artery bypass surgery found a near-zero prevalence of patients without diabetes with HbA1c <5% (Engoren et al, 2008).
Unrestricted consumption of carbohydrates, even covered by a corresponding insulin dosage, is proving to be a dangerous and ineffective way of lowering HbA1c. One study sought to determine whether lowering HbA1c to 6%, lower than the 7% recommended by the ADA, could prevent heart attacks. It resulted in increased mortality and no significant reduction of major cardiovascular events over 3.5 years. The authors (ACCORD et al, 2008) suggested that these findings might be a result of the approach used of rapidly lowering glycated haemoglobin levels using larger doses of insulin and medication. Thus, increasing the amount of insulin and medication does not appear to be a safe solution.
By contrast, another positive outcome observed in this case study was the reduction in the requirement of insulin. The child's daily average dosages of basal and rapid-acting insulin were reduced from 3.8 to 0.4 units, and from 1.4 to 0.7 units, respectively, with the use of a VLCD. Authors of another two studies suggested that, with the use of the palaeolithic-ketogenic diet, it was possible to completely withdraw insulin by extending the ‘honeymoon period’ (when the pancreas is still able to produce some insulin after blood sugar levels become nearly normal) (Tóth and Clemens, 2014; 2015).
Although no specific diet for people with diabetes exists, avoiding refined sugar and processed foods, and lowering carbohydrate intake have been shown to be an excellent alternative to intensive insulin therapy.
The use of the unrestricted carbohydrate diet assumes that changing dietary habits is often unsuccessful in the long run because people would eventually return to their usual macronutrient distribution (Leow et al, 2018). To avoid that outcome, in this case study, the child was encouraged to choose his preferred low-carbohydrate foods at each meal. Once the preferred foods were established, the menu was followed closely, even past the 6-month period of this study. Family involvement is a vital component of optimal diabetes management throughout childhood and adolescence. The change in the child's diet was successful largely because the entire family also adopted the new diet.
Another important finding of the case study was the immediate glycaemic stability achieved by reducing carbohydrates and insulin doses. According to the CGM, the child's blood glucose stayed in the range of 70–180 mg/dL (4 mmol/L–10 mmol/L) 95% of the time. A range of 70–180 mg/dL (4 mmol/L–10 mmol/L) 70% of the time is equivalent to HbA1c of 7%, an acceptable level for clinical practice (Beck et al, 2019). However, that goal is not always achieved. A study with DirectNet data showed that 50 % of children achieved blood glucose levels of >180 mg/dL (10 mmol/L) for >12 hours/day and >205 mg/dL (11.3 mmol/L) for >6 hours/day (Tansey et al, 2016).
Keeping blood glucose within target levels is important because ineffective glycaemic control can cause several complications. A review study found that cognitive functions and brain structure were impacted in children and adolescents with type 1 diabetes who experienced glycaemic extremes (severe hypoglycaemia, chronic hyperglycaemia, and diabetic ketoacidosis) (Cato and Hershey, 2016). One way to minimise these problems is by achieving tighter glycaemic control early in childhood. In the present case that was possible with a simple change in the composition of macronutrients in the diet.
Limitations
This is a case study of one child. There is no long-term evidence of the benefits and risks of management of type 1 diabetes in children with a VLCD or ketogenic diet.
Conclusion
This study demonstrated that a VLCD diet had a positive sustained impact on glycaemic control in a 5-year-old child with type 1 diabetes without causing side effects. The diet normalised HbA1c and stabilised and kept blood glucose fluctuations in range more than 95% of the time.
Currently, no randomised controlled trials suggest an ideal daily amount of carbohydrate for a child with type 1 diabetes that could justify a change in diabetes management. Therefore, further studies are needed to follow children of different ages, to verify how a VLCD diet impacts child development, and to establish a protocol that can be safely followed by a broader population in the future.