Page 510 - Nutrition Essentials for Nursing Practice

498 U N I T 3 Nutrition in Clinical Practice

G lucose circulating in the blood is a source of ready fuel for body cells. It comes primarily
from recently absorbed dietary carbohydrates and liver glycogen, although glucose is
available from some amino acids and the glycerol portion of fatty acids. All body cells use
glucose for energy to some extent; under normal conditions, cells of the brain and the rest
of the nervous system rely solely on glucose for energy.

The amount of carbohydrate and, to a lesser extent, the type of carbohydrate consumed
are the primary determinants of how quickly and how high blood glucose levels rise after
eating. A rise in postprandial blood glucose levels stimulates the pancreas to secrete insu-
lin. As an anabolic hormone, insulin promotes the formation of glycogen, the storage of
fat, and protein synthesis; conversely, it inhibits the breakdown of stored macronutrients.
Its most well-known role is facilitating glucose uptake from the blood into the cells. The
amount and effectiveness of circulating insulin determines how quickly blood glucose levels
return to normal after eating.

When insulin secretion is absent or deficient, or circulating insulin is ineffective, glu-
cose levels remain high after eating. Fasting blood glucose levels Ն126 mg/dL indicate
diabetes. This chapter presents nutrition therapy aimed at preventing diabetes, managing
existing diabetes, and preventing or forestalling diabetes complications.

DIABETES

Diabetes Mellitus: Diabetes mellitus is a group of metabolic diseases characterized by hyperglycemia related
a chronic heteroge- to inadequate insulin secretion, diminished insulin effectiveness, or both. Over time, hy-
neous disorder charac- perglycemia damages blood vessels, nerves, and tissues. Diabetes also alters protein and fat
terized by elevated metabolism, resulting in muscle wasting and elevated serum triglyceride levels, respectively.
blood glucose levels Table 19.1 summarizes the actions of insulin and effects of its insufficiency.
(hyperglycemia) related
to a relative or absolute Diabetes is one of the most costly and burdensome chronic diseases of our time and
deficiency of insulin. is increasing in epidemic proportions. Every 17 seconds, an American is diagnosed with
diabetes; if the current trend continues, one in three Americans will have diabetes by 2050

Table 19.1 Actions of Insulin and Effects of Its Insufficiency

Nutrient Action of Insulin Results of Insulin Insufficiency

Glucose Promotes uptake of glucose into cells Decreases uptake of glucose into muscle and
Promotes formation of glycogen in the adipose
Protein
Fat liver and muscle Decreases glycogen formation in liver and
Promotes conversion of excess glucose muscle

into triglycerides for storage Increases glycogen breakdown in liver and
muscle
Promotes uptake of amino acids into
tissue protein Increases gluconeogenesis (the formation of
glucose from a noncarbohydrate source, such
Promotes formation of adipose from as amino acids or glycerol)
excess fat
Hyperglycemia

Decreases uptake of amino acids into muscle
Decreases protein synthesis
Increases protein breakdown

Increases production of ketones in the liver
Decreases formation of triglycerides in adipose
Increases triglyceride breakdown in adipose
Increases serum triglyceride and fatty acid levels