Carbohydrates and Health

A7.21 A study conducted in 1698 women in the USA assessed maternal diet in the
second trimester in relation to the risk of developing gestational diabetes mellitus
or impaired glucose tolerance (Saldana et al., 2004). The authors observed
that women defined as having developed gestational diabetes mellitus (n=89)
consumed a lower percentage of energy from carbohydrates and a higher
percentage of energy from fat than the women who maintained normal glucose
tolerance. Modelling showed that adding 100 kcal from carbohydrates to the
diet was associated with a decrease in the risk of gestational diabetes mellitus
(RR 0.9, 95% CI 0.85, 0.98, p=0.01). A theoretical substitution model was devised
which substituted one macronutrient for another. It was found that substituting
fat for carbohydrates (per each 1% of total dietary energy) resulted in a significant
increase in the risk of gestational diabetes mellitus (RR 1.10, 95% CI 1.02, 1.12 and RR
1.10, 95% CI 1.02, 1.10, respectively). Predicted probabilities of gestational diabetes
mellitus were reduced by one half with a 10% decrease in dietary fat and a 10%
increase in carbohydrate.
A7.22 A study conducted in 1722 women in the USA assessed maternal diet in early
pregnancy in relation to the risk of developing gestational diabetes mellitus
(Radesky et al., 2008). The percentage energy from carbohydrate was not
associated with risk of developing gestational diabetes mellitus (OR 1.00, 95%
CI 0.96, 1.03) in this cohort. Unlike the findings reported by Saldana et al. (2004)
there was no evidence that adding fat or carbohydrates to the diet, or substituting
fat for carbohydrates, fat for protein, or carbohydrates for protein was associated
with altered risk for gestational diabetes mellitus.
A7.23 A smaller study in 205 women in Canada assessed maternal diet in the second
trimester in relation to the risk of developing gestational diabetes mellitus (Ley
et al., 2011). A decreased risk of gestational diabetes mellitus was associated with
higher carbohydrate intake as a percentage of energy (OR 0.60, 95% CI 0.40, 0.90
per 1 standard deviation change in intake).
A7.24 A study conducted in 13,110 women in the USA assessed maternal diet prepregnancy
in relation to the risk of developing gestational diabetes mellitus (Zhang
et al., 2006). There was no association observed between total carbohydrate
intake as a percentage of energy pre-pregnancy and gestational diabetes mellitus
risk (RR 1.00, 95% CI 0.62, 1.63) for the highest versus lowest quartile of intake.
In this study, higher carbohydrate intake pre-pregnancy was associated with
lower gestational diabetes mellitus risk after adjustment for age and BMI, but
this association disappeared after additional adjustment for lifestyle and other
dietary factors (Zhang et al., 2006). One of the studies in which it was observed
that higher total carbohydrate intake as a percentage of energy was associated
with decreased risk of gestational diabetes mellitus only adjusted risk for age,
race and BMI (Saldana et al., 2004) and none of the studies assessing diet during
pregnancy adjusted for other dietary factors. Overall, there is little indication of an
association between total carbohydrate intake as a percentage of energy and risk
of gestational diabetes mellitus.
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