Bray et al.102 noted that the average American
older than 2 years consumes 553 kJ(132 kcal) per day from high fructose corn
syrup (the sole sweetener in US soft drinks)
and that intake of this sweetener rose 1000%
between 1970 and 1990. These authors proposed
that fructose is digested, absorbed, and
metabolized differently than glucose in ways
that favor de novo lipogenesis and do not
stimulate insulin secretion or enhance the production
of leptin, both afferent signals in the
regulation of food intake and body weight.
One would expect a weaker relationship of
soft drink consumption with body weight than
with energy intake because soft drinks are not
the only source of energy in the diet. In addition,
higher intake of diet drinks among people
with elevated BMIs could reduce or cancel
out a relationship between intake of soft
drinks overall and body weight. Indeed, crosssectional
and longitudinal studies showed only
small positive associations between soft drink
consumption and BMI (rs=0.05 and 0.09, respectively).
More impressive, however, is the
fact that a moderate effect size (r =0.24) was
observed for experimental studies that controlled
for many extraneous variables.
In addition to effects on energy intake and
weight, it is important to know whether soft
drinks displace essential nutrients and contribute
to overall poorer diets. Our review
showed that increased soft drink intake is related
to lower consumption of milk and calcium,
but average effect sizes were small. Soft
drink consumption was also related to higher
intake of carbohydrates, lower intakes of fruit
and dietary fiber, and lower intakes of a variety
of macronutrients in cross-sectional, longitudinal,
and longer-term experimental studies.
Interpreting the association between soft
drink consumption and nutrient intake is
complex. Soft drink intake could be a marker
for poor nutrition, with individuals who consume
more sweetened beverages eating
poorer diets in general. Soft drinks might also
stimulate people’s appetite for other nonnutritious
foods. One study showed that individuals
who consumed more soft drinks consumed
diets with higher overall glycemic
indexes,17 supporting the prediction that consumption
of foods with high glycemic indexes
(such as soft drinks) might stimulate intake of
other such foods.22 Other studies showed that
soft drink consumption is positively related to
the consumption of foods such as hamburgers
and pizza54 and negatively related to an overall
healthy eating index.16
A number of studies suggest links between
soft drink intake and medical problems. The
issues of greatest concern are elevations in
blood pressure and increased risk of diabetes.
The most striking finding, in a study of
91249 women followed for 8 years, was that
those who consumed 1 or more servings of
soft drinks per day (less than the US national
average) were at twice the risk of developing
diabetes as those who consumed less than 1
serving per month.17 This result alone warrants
serious concern about soft drink intake,
particularly in light of the unprecedented rise
in type 2 diabetes among children.