Authors: Dr Nina Meloncelli, A/Prof Shelley Wilkinson, Dr Susie de Jersey
In a recently published review of medical nutrition therapy for gestational diabetes, the authors unpack what the research tells us about dietary interventions for managing gestational diabetes and includes emerging areas of research interest. The authors share the key points of the critical review and shows why the ‘dietary utopia’ of the perfect diet for gestational diabetes is unlikely to be found.
What is gestational diabetes and why is it important to manage?
Gestational diabetes is a common pregnancy condition that affects one in seven of all pregnancies in Australia. It is defined as ‘glucose intolerance of variable severity with onset or first recognition during pregnancy’ or put more simply, difficulty managing blood sugar levels during pregnancy. Gestational diabetes increases the risk of a baby being born too large with unhealthy fat stores (large for gestational age baby) and delivery complications (mothers needing emergency c-sections). There are also longer term risks for mother and child, such as the development type 2 diabetes. When well-managed, the risks to mum and bub are no greater than those in a pregnancy without gestational diabetes. Risk factors for developing gestational diabetes are a mother starting pregnancy above a healthy body mass index, a family history of diabetes or previous gestational diabetes, and having certain ethnic backgrounds or advanced maternal age, among others.
How important is a healthy diet in gestational diabetes?
‘Medical Nutrition Therapy’ is the term used to describe the advice delivered by a qualified dietitian to assist with managing health conditions. Along with physical activity advice and a woman doing regular blood glucose monitoring, it is the primary intervention for gestational diabetes. The goal of medical nutrition therapy is to help a woman regulate her blood glucose levels within recommended ranges, achieve a healthy rate of weight gain and change her diet, if required, to meet nutrient needs for her and her growing baby. Typically, dietary interventions for gestational diabetes have focused on the amount, type and quality of carbohydrate (carbs), the macronutrient that influences blood glucose the greatest. If medical nutrition therapy does not result in ideal blood sugar control, medication is often required, with around 50% of women diagnosed with gestational diabetes requiring ‘oral hypoglycaemic agents’ (tablets, like metformin) or insulin (injections).
Past vs present dietary advice
When women are pregnant what they eat nourishes their growing baby, as well as themselves. Sometimes this slips people’s minds when gestational diabetes enters the picture. They focus on carbs and blood glucose levels, losing sight of the bigger picture. One of the important things the science tells us not to lose sight of is the safe minimum amount of carbs to consume during pregnancy for proper fetal growth and development. For those who love numbers, this is set at 175g of carbs a day, the minimum and recommended by the Institute of Medicine.
Dietary advice for gestational diabetes used to centre on lowering the intake of carbs, often below the recommended amount of 175g of carbohydrate per day, considered important for proper fetal growth and development. However, the weight of research does not support low carb diets for gestational diabetes as the impact on pregnancy outcomes for mum and bub do not appear much different between lower and higher carbohydrate diets.
Rather than a no carb diet, it’s a slow carb diet.
Instead of cutting carbs, evidence suggests that it’s the quality of the carbs that matters. There is a trend towards women finding it easier to control their blood glucose levels with diets containing low glycaemic index (“low GI”) foods. This eating pattern is also associated with better nutrient density (a more nutritious diet) and increased fibre content (more on that soon). However, individual blood glucose responses to different carbohydrate-rich foods make it difficult to be prescriptive with carbohydrate intake, type and amount.
Any dietary intervention is better than none, and more is definitely better
Studies show that rather than focussing on a one-size-fits-all approach as the dietary pattern for women to follow when they have gestational diabetes, the amount of input from a dietitian could have greater impact on how well they can manage their gestational diabetes. There is good research both internationally and within Australia that shows a minimum of three appointments with a dietitian can improve the requirements for medication. However, the type and frequency of appointments may also be worth considering. One systematic review has demonstrated that treating gestational diabetes through dietary counselling can improve common adverse maternal and infant outcomes, regardless of the type of medical nutrition therapy delivered. There have also been trials performed using specific dietary patterns such as the well-publicised Mediterranean diet or the Dietary Approach to Stop Hypertension (DASH) diet. Improvements in outcomes have been demonstrated with both diets which focus on whole plant foods (wholegrains, fruit, vegetables, legumes and lentils) and avoid refined grains and sweets. There’s a lot going on there, but remember the need for fibre.
We have a ‘gut feeling’ there’s more to it
An exciting discovery in recent years is the influence on the microbes living inside our guts, or the ‘gut microbiota’ as it is commonly referred to. Women with gestational diabetes appear to have a gut microbiota more similar to non-pregnant people with type 2 diabetes, showing that the gut may have a large role in what goes on in the body to control blood glucose (and many other things!). Furthermore, some trials using probiotic supplementation have shown improvements in blood glucose control for gestational diabetes. However, other trials have shown that it’s not just what we take in the form of a probiotic tablet but also how we feed our gut bacteria. Once again, this is why diet is so important. The more fibre-rich foods we eat, the happier our gut bugs are. There are some suggestions that we may be on the precipice of personalised nutrition according to what resides in our guts though this is a long way off being translated into practice.
Yes, we are all individuals
In the meantime, while we await the next era of gut-directed or alternate dietary interventions, individualisation is key. We all have unique dietary preferences, lifestyles, cultural backgrounds and indeed, guts, so dietary utopia is probably just a dream, not a destination. The main point of dietary intervention is to ensure adequate, safe and appropriate advice from a qualified health professional that aims to meet the nutritional demands of pregnancy and tailors to the individual woman. Achieving blood glucose control is one goal and how we get there is not the same for everyone.
Reference:
Meloncelli N, Wilkinson SA, de Jersey S. Searching for Utopia, the Challenge of Standardized Medical Nutrition Therapy Prescription in Gestational Diabetes Mellitus Management: A Critical Review. Semin Reprod Med. 2021 Jan 11. doi: 10.1055/s-0040-1722316. Epub ahead of print. PMID: 33429445.
Dr Nina Meloncelli, Workforce Development Officer (Knowledge Translation) for Metro North Hospital and Health Service and an Accredited Practising Dietitian.
A/Prof Shelley Wilkinson is a Principal Research Fellow with the School of Human Movements and Nutrition Sciences, University of Queensland and Advanced Accredited Practising Dietitian
Dr Susie de Jersey is a Senior Research Fellow with the Centre for Clinical Research, University of Queensland and Metro North Hospital and Health Service Advanced Accredited Practising Dietitian.
