Current Knowledge of the Health Effects of Sugar Intake

Current Knowledge of the
Health Effects of Sugar Intake
Anne L. Mardis, MD, MPH1
Twenty years ago, the common
themselves or from corresponding
Center for Nutrition Policy
perception was that sugar intake was
simple sugars added to foods during
and Promotion
associated with several chronic
processing. Within the body, most
diseases: Diabetes, coronary heart
dietary sugars are converted to glucose,
disease, obesity, and hyperactivity in
a major fuel used by all cells and the
children. Sugar was also thought to be
primary fuel required by brain tissue
the sole cause of dental caries. Recent
for normal function. Low levels of
advances in scientific knowledge,
glucose in the blood will impair the
however, have shed some light on the
brain and cause permanent mental
role of sugar in chronic diseases and
impairment or worse—coma or death.
dental caries. The evidence indicates
The body can store a limited amount
that sugar is not in itself associated
of glucose as glycogen, which it can
with the aforementioned chronic
draw upon for less than a day. After
diseases and is not the sole offender
this, other sources such as proteins,
in the development of dental caries.
from the breakdown of body tissues,
This research brief discusses current
must be used to synthesize glucose
scientific knowledge of the health
for the cells (15).
effects of sugar.
Diabetes
Physiology
The relationship between dietary
Despite having been labeled as “empty
carbohydrates and insulin resistance
calories,” sugars are truly important
(a risk factor for diabetes mellitus,
compounds from the perspective of
ischemic heart disease, and hyper-
the human organism. Humans have
tension) is not clear based on available
retained the ability to synthesize all
research (7). In two studies based on
forms of carbohydrates the body needs
a large, prospective study of U.S.
from simple sugars. This is not the case
women, sucrose and carbohydrate
with the other dietary macronutrients,
intake were not associated with an
fats, and proteins. Following ingestion,
increased risk of diabetes (6,27).
all digestible complex dietary carbohy-
However, based on the same popula-
drates are broken down in the gut to
tion, associations were found between
simple sugars before they are absorbed
a diet with high glycemic load2 (26)
into the body. Because simple sugars
and high intake of refined grains (21)
are all identical chemically, the
and the risk of diabetes. The general
absorption process cannot distinguish
consensus, based on epidemiological
1
simple sugars resulting from the
studies, is that sugar intake alone is not
Currently at the National Institute for
Occupational Safety and Health, Centers
breakdown of complex dietary carbo-
for Disease Control and Prevention,
hydrates from corresponding simple
2
Morgantown, WV.
sugars occurring naturally in the foods
Glycemic load is a function of the effect of a
carbohydrate meal on glucose levels in the blood
(3).
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associated with the development of
study of 32 hypertriglyceridemic
Hyperactivity
diabetes mellitus. Sugars fed at levels
patients provided evidence that an
equivalent to those consumed by the
“extrinsic sugar-free” diet significantly
Many people still believe that sugar
U.S. population do not produce adverse
lowers abnormally elevated plasma
intake in children causes hyperactivity.
glycemic effects in non-diabetics (23).
triglyceride levels (28). Evidence also
A meta-analysis, however, of 16
The effects of sugar intake on glucose
suggests that insulin resistance and
different reports from 23 separate
tolerance, insulin levels, and plasma
compensatory hyperinsulinemia5 have
studies with 560 subjects showed
lipids are confounded by other dietary
major roles in the regulation of blood
virtually no effect of sugar intake on
components. The American Diabetes
pressure in subjects predisposed to
the hyperactivity in children (30). In a
Association has also acknowledged,
hypertension due to hereditary or
review of the literature, Krummel et al.
in its nutrition recommendations for
environmental factors, possibly
(19) reported that in 12 double-blind,
people with diabetes, that there is no
mediated by activity of the sympathetic
placebo-controlled studies, no associa-
evidence that refined sugars such as
nervous system. But there are multiple
tion was found between sugar intake
sucrose behave any differently from
metabolic abnormalities associated
and hyperactive behavior. Thus, despite
other types of simple carbohydrates (1).
with hyperinsulinemia in hypertensive
numerous anecdotal perceptions to the
patients that increase the risk of
contrary, systematic, controlled studies
coronary heart disease (24).
show that sugars do not cause hyper-
Heart Disease
activity.
The Sugars Task Force of the U.S.
Obesity
Food and Drug Administration (29)
Dental Caries
presented a comprehensive review of
Despite popular belief that sugar causes
epidemiological, clinical, and animal
obesity, a number of studies show an
Dental caries is a chronic disease that
studies dealing with the relationship
inverse relationship between reported
has many causes. Sugar is involved in
between sugar intake and heart disease
sugar consumption and degree of
tooth decay, but it is one of many
or risk factors for heart disease (14).
overweight (10,11,20,25). An increase
factors, including oral bacteria, saliva,
The report concluded that at current
in the percentage of calories from sugar
tooth enamel, food substrate, and host
levels of consumption, sugar is not
is, by definition, associated with a
susceptibility. All fermentable carbohy-
an adverse risk factor in heart disease.
decreased consumption of calories
drates are potentially cariogenic. Other
The same conclusion was made by the
from fat. Obesity is basically a conse-
dietary factors such as the retention of
National Research Council in its report
quence of higher energy intake than
food in the mouth affect cariogenic
on chronic disease risk (23). There is
energy expenditure, where excess
potential. Even starches, which may
no conclusive evidence that dietary
calories are stored as fat (5). The type
not taste sweet, are chains of glucose
sugar is an independent risk factor for
of calories consumed is the subject of
and are broken down to glucose in the
coronary artery disease in the general
much study in obesity research. For
mouth. Good oral hygiene, good genes,
population. However, hypertrigly-
instance, extra calories consumed as
fluoridation of water, and restricting
ceridemia3 and central fat distribution,4
sugar cause an appropriate compensa-
snacks between meals can prevent
consequences of abnormal glucose
tory increase in carbohydrate oxidation
tooth decay, no matter how high the
tolerance and diabetes mellitus, are
(metabolism of carbohydrates for
sugar consumption (13,18,25).
independent risk factors for coronary
energy), whereas extra calories
heart disease (8). A 1996 randomized
consumed as fat do not (17). Simply
stated, obesity results from energy
Nutrient Displacement
intake in excess of energy require-
3Elevated blood levels of triglycerides: a form of
ments. Many factors contribute to
fatty acid found in animal and vegetable fats.
obesity, but evidence does not single
Research on the effects of sugar intake
4
and nutrient displacement in the diet of
A type of body fat distribution with a high ratio
out dietary sugar as a cause (25).
of waist or abdominal circumference to hip or
children is inconclusive. In a review of
gluteal circumference that is epidemiologically
the literature, Ruxton et al. (25) found
associated with heart disease and diabetes.
5An increase in pancreatic secretion of insulin to
that higher intake of sugar did not
compensate for cellular resistance to insulin.
negatively affect micronutrient intake.
Gibney et al. (10) found, in an analysis
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of the 1987-88 USDA Nationwide
But, the nutritional quality of the diet
Food Consumption Survey, that high
of children with higher sugar intake
consumption of sugars was not
appeared to be adequate regarding
associated with a poorer quality diet.
vitamin and mineral intakes and were
In a study of 143 children ages 11 and
closer to meeting current recommenda-
12 years, a 7-day weighed and recorded
tions for dietary fat. Nevertheless, a
food inventory revealed that as the
relationship between the consumption
proportion of energy from sugars
of sugars and nutrient displacement has
increased, there was no decline in
not been observed consistently nor has
dietary fiber or micronutrient intake,
there been consistency among the
with the exception of niacin, which
specific nutrients displaced when a
exceeded recommended levels (22).
relationship has been found. Thus, this
However, Linseisen et al. (20) and
issue remains unsettled and requires
Gibson (12) did demonstrate intake
additional data from primary research.
of many micronutrients below recom-
mended levels in persons in Germany
and the United Kingdom who con-
Conclusion
sumed high (energy-adjusted) amounts
of sugar. In addition, high consumption
Recent evidence shows that aside
of non-diet soft drinks, a significant
from dental caries, the intake of added
source of added-sugar intake in
sugars is not directly related to diabe-
children, is associated with lower
tes, heart disease, obesity, and hyperac-
consumption of milk and fruit juice
tivity, as was previously thought. This
and lower intake of riboflavin, vitamin
conclusion was also reached in a 1997
A, calcium, phosphorus, and the ratio
review of the literature on the health
of calcium to phosphorus, which may
effects of sugar intake (2). Because
be considered markers for milk
high intake of sugars along with other
consumption (16).
factors can affect oral health and can
displace important foods and nutrients
In an analysis of the Continuing Survey
in the diets of children when consumed
of Food Intakes by Individuals (1994-
as soft drinks, it seems prudent to limit
96), Bowman found that compared
excessive intake. But the focus on
with Americans over 2 years of age
sugar as an independent risk factor
with lower added sugar consumption
for chronic disease and hyperactivity
as a percentage of total energy, indi-
should be de-emphasized.
viduals consuming greater than 18
percent of their total energy from added
sugars did not meet the Recommended
Daily Allowance (RDA) for many
micronutrients (4). Farris et al. reported
that as total sugar intake increased, a
significant linear decrease occurred in
mean intake of protein, fat, saturated
fat, starch, cholesterol, sodium,
vitamins B and E, thiamin, niacin,
6
iron, and zinc. Also, as total sugar
intake increased, a significant linear
increase occurred in mean intake of
carbohydrate, fructose, lactose,
sucrose, vitamin D, and calcium (9).
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