Alcohol and Nutrition
Nutrition is a process that serves two purposes: to provide
energy and to
maintain body structure and function. Food supplies energy
and provides the building blocks needed to replace worn or
damaged cells and the nutritional components needed for body
function. Alcoholics often eat poorly, limiting their supply
of essential nutrients and affecting both energy supply and
structure maintenance. Furthermore, alcohol interferes with
the nutritional process by affecting digestion, storage,
utilization, and excretion of nutrients (1).
Impairment of Nutrient Digestion and Utilization
Once ingested, food must be digested (broken down into small
components) so it is available for energy and maintenance of
body structure and function. Digestion begins in the mouth
and continues in the stomach and intestines, with help from
the pancreas. The nutrients from digested food are absorbed
from the intestines into the blood and carried to the liver.
The liver prepares nutrients either for immediate use or for
storage and future use.
Alcohol
Rehab inhibits the breakdown of nutrients into usable
molecules by
decreasing secretion of digestive enzymes from the pancreas
(2). Alcohol
impairs nutrient absorption by damaging the cells lining the
stomach and
intestines and disabling transport of some nutrients into
the blood (3). In
addition, nutritional deficiencies themselves may lead to
further absorption
problems. For example, folate deficiency alters the cells
lining the small
intestine, which in turn impairs absorption of water and
nutrients including
glucose, sodium, and additional folate (3).
Even if nutrients are digested and absorbed, alcohol can
prevent them from being fully utilized by altering their
transport, storage, and excretion
(4). Decreased liver stores of vitamins such as vitamin A
(5), and increased excretion of nutrients such as fat,
indicate impaired utilization of nutrients by alcoholics
(3).
Alcohol and Energy Supply
The three basic nutritional components found in
food--carbohydrates,
proteins, and fats--are used as energy after being converted
to simpler
products. Some alcoholics ingest as much as 50 percent of
their total daily calories from alcohol, often neglecting
important foods (3,6).
Even when food intake is adequate, alcohol can impair the
mechanisms by
which the body controls blood glucose levels, resulting in
either increased
or decreased blood glucose (glucose is the body's principal
sugar) (7). In
nondiabetic alcoholics, increased blood sugar, or
hyperglycemia--caused by impaired insulin secretion--is
usually temporary and without consequence. Decreased blood
sugar, or hypoglycemia, can cause serious injury even if
this condition is short lived. Hypoglycemia can occur when a
fasting or malnourished person consumes alcohol. When there
is no food to supply energy, stored sugar is depleted, and
the products of alcohol metabolism inhibit the formation of
glucose from other compounds such as amino acids (7). As a
result, alcohol causes the brain and other body tissue to be
deprived of glucose needed for energy and function.
Although alcohol is an energy source, how the body processes
and uses the energy from alcohol is more complex than can be
explained by a simple
calorie conversion value (8). For example, alcohol provides
an average of 20 percent of the calories in the diet of the upper third of drinking
Americans, and we might expect many drinkers who consume
such amounts to be obese. Instead, national data indicate
that, despite higher caloric intake, drinkers are no more
obese than nondrinkers (9,10). Also, wh en alcohol is
substituted for carbohydrates, calorie for calorie, subjects
tend to lose weight, indicating that they derive less energy
from alcohol than from food (summarized in 8).
The mechanisms accounting for the apparent inefficiency in
converting
alcohol to energy are complex and incompletely understood
(11), but several mechanisms have been proposed. For
example, chronic drinking triggers an inefficient system of
alcohol metabolism, the microsomal ethanol-oxidizing system
(MEOS) (1). Much of the energy from MEOS-driven alcohol
metabolism is lost as heat rather than used to supply the
body with energy.
Alcohol and the Maintenance of Cell Structure and
Function
Structure
Because cells are made mostly of protein, an adequate
protein diet is
important for maintaining cell structure, especially if
cells are being
damaged. Research indicates that alcohol affects protein
nutrition by
causing impaired digestion of proteins to amino acids,
impaired processing
of amino acids by the small intestine and liver, impaired synthesis of
proteins from amino acids, and impaired protein secretion by
the liver (3).
Function
Nutrients are essential for proper body function; proteins,
vitamins, and
minerals provide the tools that the body needs to perform
properly. Alcohol can disrupt body function by causing
nutrient deficiencies and by usurping the machinery needed
to metabolize nutrients.
Vitamins. Vitamins are essential to maintaining growth and
normal metabolism because they regulate many physiological
processes. Chronic heavy drinking is associated with
deficiencies in many vitamins because of decreased food
ingestion and, in some cases, impaired absorption,
metabolism, and utilization (1,12). For example, alcohol
inhibits fat absorption and thereby impairs absorption of
the vitamins A, E, and D that are normally absorbed along
with dietary fats (12,13). Vitamin A deficiency can be
associated with night blindness, and vitamin D deficiency is
associated with softening of the bones (6).
Vitamins A, C, D, E, K, and the B vitamins, also deficient
in some
alcoholics, are all involved in wound healing and cell
maintenance (14). In
particular, because vitamin K is necessary for blood
clotting, deficiencies
of that vitamin can cause delayed clotting and result in
excess bleeding.
Deficiencies of other vitamins involved in brain function
can cause severe
neurological damage.
Minerals. Deficiencies of minerals such as calcium,
magnesium, iron, and
zinc are common in alcoholics, although alcohol itself does
not seem to
affect the absorption of these minerals (15). Rather,
deficiencies seem to
occur secondary to other alcohol-related problems: decreased
calcium
absorption due to fat malabsorption; magnesium deficiency
due to decreased intake, increased urinary excretion,
vomiting, and diarrhea (16); iron deficiency related to
gastrointestinal bleeding (3,15); and zinc
malabsorption or losses related to other nutrient
deficiencies (17). Mineral
deficiencies can cause a variety of medical consequences
from calcium-related bone disease to zinc-related night
blindness and skin lesions.
Alcohol, Malnutrition, and Medical Complications
Liver Disease
Although alcoholic liver damage is caused primarily by
alcohol itself, poor
nutrition may increase the risk of alcohol-related liver
damage. For example, nutrients normally found in the liver, such as carotenoids, which
are the major sources of vitamin A, and vitamin E compounds,
are known to be affected by alcohol consumption (18,19).
Decreases in such nutrients may play some role in
alcohol-related liver damage.
Pancreatitis
Research suggests that malnutrition may increase the risk of
developing
alcoholic pancreatitis (20,21), but some research performed
outside the
United States links pancreatitis more closely with
overeating (21).
Preliminary research suggests that alcohol's damaging effect
on the pancreas may be exacerbated by a protein-deficient
diet (22).
Brain
Nutritional deficiencies can have severe and permanent
effects on brain function. Specifically, thiamine deficiencies, often seen in
alcoholics, can
cause severe neurological problems such as impaired movement
and memory loss seen in Wernicke/Korsakoff syndrome (23).
Pregnancy
Alcohol has direct toxic effects on fetal development,
causing
alcohol-related birth defects, including fetal alcohol
syndrome. Alcohol
itself is toxic to the fetus, but accompanying nutritional
deficiency can
affect fetal development, perhaps compounding the risk of developmental
damage (24,25).
The nutritional needs during pregnancy are 10 to 30 percent
greater than
normal; food intake can increase by as much as 140 percent
to cover the
needs of both mother and fetus (24). Not only can
nutritional deficiencies
of an alcoholic mother adversely affect the nutrition of the
fetus, but
alcohol itself can also restrict nutrition flow to the fetus
(24,25).
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