THE ADVANTAGES OF A LOW GLYCEMIC INDEX DIET FOR WOMEN WITH GESTATIONAL DIABETES
Disorders
of blood glucose levels in pregnancy are relatively common. In a
representative Australian population about 1-2% of women with
pre-existing diabetes become pregnant. This type of diabetes is usually
insulin treated type 1 diabetes or type 2 diabetes with various
treatments ranging from diet alone, oral hypoglycaemic agents
(tablet(s)) to insulin.
However, relatively minor
elevations of glucose levels during pregnancy, a condition called
gestational diabetes mellitus (GDM) are associated with a range of
adverse maternal and fetal outcomes. The most common problems are a
large for gestational age baby leading to birthing problems, an
increased rate of caesarean section and an increased rate of admissions
to a special care nursery. Evidence is now accumulating that problems in
childhood may be related to the effects of intrauterine programming
linked to high glucose levels in the mother. It is not only the
“average” maternal glucose level that is associated but also the
fluctuations (usually highs) that can happen in the mother, invariably
related to diet.
It is recommended that all women are
tested for diabetes in every pregnancy. Conventionally this is around 28
weeks gestation, but early testing is recommended for women with risk
factors – a family history of diabetes, previous GDM, high risk ethnic
groups, etc...
In Australia, the majority of women
diagnosed with GDM are referred to a specialist Diabetes Centre and a
see a diabetes educator and a dietitian. The diabetes educator will
usually arrange for access to a lancing device (finger pricker) and home
blood glucose meter and give instruction on its use. Women are all
asked to measure their fasting glucose level, either one or two hours
after each of the three major meals. There are strict criteria about the
upper range of the glucose levels. If either the fasting level or the
after-meal level (post prandial) are exceeded, then it is usual to
advise the use of insulin injections. Clearly this is a situation and
recommendation that most women would like to avoid.
The dietitian has two major roles. The first is to
ensure that the overall diet for the pregnancy is suitable and
nutritionally sound for both the mother and the developing fetus. The
second is to ensure that the glucose targets fasting and after meals are
not exceeded. It is here that knowledge and application of a low GI
diet is critical.
The dietitian will ensure that the
diet contains an adequate amount of low GI carbohydrates and that this
is distributed as evenly as possible throughout the day. A common
example is to advise women to have two carbohydrate exchanges (15 g
each) at the three major meals and to have one exchange with snacks. A
15 g exchange might include a slice of bread, or an apple, or a medium
potato. For some women this might involve a redistribution of their
daily food intake, especially with the evening meal.
With
strict attention to the diet, most women will avoid the need to use
insulin to help lower their glucose levels. The low GI diet choices
really work. In a major clinical trial, women with GDM were randomised
to either a low GI diet or a conventional diet in pregnancy and
observed.
Women on a conventional diet were far more
likely to meet the criteria to commence on insulin. However, if they
were then changed to a low GI diet, about half could avoid having to use
insulin.
Low GI dietary advice is not just suitable
for women with GDM. While women with GDM are an obvious choice for
intervention, normal pregnant women with glucoses in the higher range
have more adverse pregnancy outcomes than women in the lower range –
hence a low GI diet is suitable and advantageous for all women in every
pregnancy.
A low GI diet makes common sense for
everybody. It is especially relevant in pregnancy where it has been
shown to improve pregnancy outcomes.
Read more:
- Carbohydrates, glycemic index, and pregnancy outcomes in gestational diabetes
- Can a low-glycemic index diet reduce the need for insulin in gestational diabetes mellitus? A randomized trial
PROFESSOR ROBERT MOSES, OAM is an international authority on diabetes and its treatment. Since opening an endocrinology practice in Wollongong in 1975, his interest and referral base has developed to focus on diabetes and problems that can arise during pregnancy, particularly gestational diabetes.
Contact: Illawarra Health and Medical Research Institute
