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Low carb diets for diabetes? An interview with Dr Carmel Smart

For adults with Type 2 diabetes, there’s evidence that a low carb diet can help reduce blood glucose levels, at least in the short term - but what about children with Type 1 diabetes?

 “Some families are interested in a low carb diet for children with Type 1 but it’s important to carefully monitor nutrient and saturated fat intakes because restricting high quality carbohydrate (fruit, wholegrains, low fat dairy) can lead to potentially adverse health outcomes,” says  Carmel Smart, co-author of a recent review , of research into low carb diets and Type 1 diabetes published in Diabetic Medicine. 

 “Another issue is that a low carb diet might not deliver enough kilojoules for active children because the high fat and protein content is so satiating. This may have an impact on their growth,” says Dr Smart, a paediatric dietitian and clinical researcher with the Hunter Medical Research Institute in NSW. 

“We’ve published a case series of six children with type 1 diabetes where carbohydrates were restricted, resulting in energy deficits. These children did not grow well until carbohydrate foods such as cereals and milk were re-introduced. (De Bock et al). Iron deficiency has also been linked to high fat diets because iron absorption is reduced via hepacidin-independent reduction of duodenal iron absorption.

“It’s understandable  that some parents worry if they see their children’s blood glucose levels spiking after eating carbohydrate but this can be helped by choosing lower GI carbohydrate foods with protein like milk and yogurt instead of fruit juice and white bread - and to match the insulin dose to the amount of carbohydrate.” 

But fat and protein can also affect blood glucose levels and increase the risk of delayed hyperglycaemia.   

“Our studies have shown that for most people, meals with more than 30g of protein and 20 grams of fat can result in higher blood glucose values later on,” she adds.  

 The idea that fat and protein in meals should also be considered in dosing meal-time insulin is now  included in the latest American Diabetes Association Clinical Guidelines, says Dr Smart who’s developing a family friendly app to make it easier to calculate protein and fat as well as carbohydrate in meals.

“Another benefit of calculating the fat content of meals is that it makes families more aware of how much fat there is in some meals, especially fast food, and this can help prevent hyperlipidemia,“ she says.

The Hunter region where she works is a Type 1 diabetes hot spot, with the highest rate of the disease in Australia.  

It’s a challenging condition, but a program developed by Carmel Smart and the diabetes team at the John Hunter Children’s Hospital that aimed for tighter blood glucose control lead to a drop in the average HbA1c levels of children attending the hospital between 2004 and 2016 (Phelan et al). 

Instead of standard therapy of twice daily insulin injections, all children used intensive insulin therapy (insulin pump or multiple daily injections), plus diabetes education, dietary advice and psychological support. The result: 83 per cent of   young children achieved target glycaemia without an increase in severe hypoglycaemia or diabetes.

“I love working with children with Type 1. If you start with a toddler and help them manage their condition well, they can go on to do everything they could have done if they hadn’t had this diagnosis - I’ve worked with people who are now cycling competitively in Europe.” she says.

“But we need more specialist dietitians, especially those with an interest in Type 1 and sport. There are sports dietitians and dietitians specialising in Type 1 but we need dietitians who can combine both specialties.“

What if parents want their child to follow a low carb diet?

Ask what they mean by ‘low carb’ first - it means different things to different people. If it means avoiding cake and sweets that’s good, but it can be difficult if it means avoiding core foods, says Carmel Smart.  Other tips:

• Ask what the child’s carbohydrate intake is - and what alternative foods are substituted.
• Discuss strategies to decrease postprandial glycaemic excursions, with a focus on carbohydrate quality and glycaemic load, meal structure and prandial insulin calculation and timing; discuss the need for extra monitoring of growth, lipids, nutrient intakes and iron levels for children on a low carbohydrate diet (<60g/day).  This provides a framework for discussing any potential problems in a non-confrontational way.
• Listen to parents. Find out what their motivations are and try to build a trusting relationship.

Dr Smart, a Conjoint Senior Lecturer with the University of Newcastle, is a lead author of the American Diabetes Association Clinical Nutrition Guidelines and co-author of the International Society of Paediatric and Adolescent Diabetes Preschool Guidelines