National Academies Press: OpenBook
« Previous: Dietary Fat: Total Fat and Fatty Acids
Suggested Citation:"Cholesterol." Institute of Medicine. 2006. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. Washington, DC: The National Academies Press. doi: 10.17226/11537.
×
Page 140
Suggested Citation:"Cholesterol." Institute of Medicine. 2006. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. Washington, DC: The National Academies Press. doi: 10.17226/11537.
×
Page 141
Suggested Citation:"Cholesterol." Institute of Medicine. 2006. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. Washington, DC: The National Academies Press. doi: 10.17226/11537.
×
Page 142
Suggested Citation:"Cholesterol." Institute of Medicine. 2006. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. Washington, DC: The National Academies Press. doi: 10.17226/11537.
×
Page 143

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS 140 CHOLESTEROL C holesterol plays an important role in steroid hormone and bile acid biosynthesis. It also serves as an integral component of cell membranes. Most people absorb between 40 and 60 percent of ingested cholesterol. Such variability, which is probably due in part to genes, may contribute to the individual differences that occur in plasma cholesterol response to dietary cholesterol. All tissues are capable of synthesizing enough cholesterol to meet their metabolic and structural needs. Consequently, there is no evidence for a bio- logical requirement for dietary cholesterol. Neither an Estimated Average Re- quirement (EAR), and thus a Recommended Dietary Allowance (RDA), nor an Adequate Intake (AI) was set for cholesterol. Much evidence indicates a positive linear trend between cholesterol intake and low density lipoprotein (LDL) cholesterol concentration, and therefore an increased risk of coronary heart disease (CHD). A Tolerable Upper Intake Level (UL) was not set for cholesterol because any incremental increase in cholesterol intake increases CHD risk. It is recommended that people maintain their di- etary cholesterol intake as low as possible, while consuming a diet that is nutri- tionally adequate in all required nutrients. High amounts of cholesterol are found in liver and egg yolk. The main adverse effect of dietary cholesterol is increased LDL cholesterol concentration, which could result in an increased risk for CHD. CHOLESTEROL AND THE BODY Function Cholesterol is a sterol that is present in all animal tissues. Tissue cholesterol occurs primarily as free (unesterified) cholesterol, but is also bound covalently (via chemical bonds) to fatty acids as cholesterol esters and to certain proteins. Cholesterol is an integral component of cell membranes and serves as a precur- sor for hormones such as estrogen, testosterone, and aldosterone, as well as bile acids. Absorption, Metabolism, Storage, and Excretion Cholesterol in the body comes from two sources: endogenous and dietary. All cells can synthesize sufficient amounts of cholesterol for their metabolic and

PART II: CHOLESTEROL 141 structural needs. Dietary cholesterol comes from foods of animal origin, such as eggs, meat, poultry, fish, and dairy products. Dietary and endogenous cholesterol are absorbed in the proximal jejunum, primarily by passive diffusion. Cholesterol balance studies show a wide varia- tion in the efficiency of intestinal cholesterol absorption (from 20 to 80 per- cent), with most people absorbing between 40 and 60 percent of ingested cho- lesterol. Such variability, which is probably due in part to genetic factors, may contribute to the differences seen among individuals in plasma cholesterol re- sponse to dietary cholesterol. In addition, cholesterol absorption may be re- duced by decreased intestinal transit time. In the body, cholesterol can be stored in the liver; secreted into the plasma in lipoproteins, primarily very low density lipoproteins (VLDL); oxidized and secreted as bile acids; or directly secreted into the bile. Free and esterified cholesterols circulate principally in LDL in the blood. The body tightly regu- lates cholesterol homeostasis by balancing intestinal absorption and endogenous synthesis with hepatic excretion and bile acids derived from hepatic cholesterol oxidation. Increased hepatic cholesterol delivery from the diet and other sources results in a complex mixture of metabolic effects that are generally directed at maintaining tissue and plasma cholesterol homeostasis. Observational studies have shown that increased dietary cholesterol intake leads to a net increase in plasma LDL cholesterol concentrations. DETERMINING DRIS Determining Requirements All tissues are capable of synthesizing enough cholesterol to meet their meta- bolic and structural needs. Consequently, there is no evidence for a biological requirement for dietary cholesterol. Neither an Estimated Average Requirement (EAR), and thus a Recommended Dietary Allowance (RDA), nor an Adequate Intake (AI) was set for cholesterol. However, it is recommended that people maintain their dietary cholesterol intake as low as possible, while consuming a diet nutritionally adequate in all required nutrients. The UL The Tolerable Upper Intake Level (UL) is the highest level of daily nutrient intake that is likely to pose no risk of adverse effects for almost all people. Much evidence indicates a positive linear trend between cholesterol intake and LDL cholesterol concentration, and therefore an increased risk of CHD. A UL was not set for cholesterol because any incremental increase in cho- lesterol intake increases CHD risk. Because cholesterol is unavoidable in ordi-

DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS 142 nary non-vegan diets, eliminating cholesterol in the diet would require signifi- cant dietary changes. These changes require careful planning to ensure adequate intakes of proteins and certain micronutrients. Still, it is possible to eat a low- cholesterol, yet nutritionally adequate, diet. DIETARY SOURCES Foods Foods of animal origin contain cholesterol. High amounts are found in liver and egg yolk. Moderate amounts are found in meats, some types of seafood, including shrimp, lobster, certain fish (such as salmon and sardines), and full- fat dairy products. ADVERSE EFFECTS OF CONSUMPTION The main adverse effect of dietary cholesterol is increased LDL cholesterol con- centration, which could result in an increased risk for CHD. Serum HDL con- centration also increases, although to a lesser extent, but the impact of such a diet-induced change in CHD risk is uncertain. Studies have shown that serum cholesterol concentrations increase with increased dietary cholesterol and that the relationship of blood cholesterol to the risk of CHD progressively increases. On average, an increase of 100 mg/day of dietary cholesterol is predicted to result in a 0.05–0.1 mmol/L increase in total serum cholesterol, of which ap- proximately 80 percent is in the LDL fraction. There is also increasing evidence that genetic factors underlie a substantial portion of the variation among individuals in response to dietary cholesterol. Although mixed, there is evidence that increases in serum cholesterol concen- tration due to dietary cholesterol are blunted by diets low in saturated fat, high in polyunsaturated fat, or both. No consistent significant associations have been established between di- etary cholesterol intake and cancer, including lung, breast, colon, and prostate cancers.

PART II: CHOLESTEROL 143 KEY POINTS FOR CHOLESTEROL Cholesterol plays an important role in steroid hormone and bile 3 acid biosynthesis and serves as an integral component of cell membranes. Because all tissues are capable of synthesizing enough 3 cholesterol to meet their metabolic and structural needs, there is no evidence for a biological requirement for dietary cholesterol. Neither an EAR, RDA, nor AI was set for cholesterol. 3 Much evidence indicates a positive linear trend between 3 cholesterol intake and LDL cholesterol concentration, and therefore increased risk of CHD. It is recommended that people maintain their dietary 3 cholesterol intake as low as possible, while consuming a diet nutritionally adequate in all required nutrients. A UL was not set for cholesterol because any incremental 3 increase in cholesterol intake increases CHD risk. High amounts of cholesterol are found in liver and egg yolk. 3 Meats, some types of seafood, including shrimp, lobster, and certain fish, as well as full-fat dairy products contain moderate amounts of cholesterol. The main adverse effect of dietary cholesterol is increased LDL 3 cholesterol concentration, which could result in an increased risk of CHD.

Next: Protein and Amino Acids »
Dietary Reference Intakes: The Essential Guide to Nutrient Requirements Get This Book
×
Buy Paperback | $49.95
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

Widely regarded as the classic reference work for the nutrition, dietetic, and allied health professions since its introduction in 1943, Recommended Dietary Allowances has been the accepted source in nutrient allowances for healthy people. Responding to the expansion of scientific knowledge about the roles of nutrients in human health, the Food and Nutrition Board of the Institute of Medicine, in partnership with Health Canada, has updated what used to be known as Recommended Dietary Allowances (RDAs) and renamed their new approach to these guidelines Dietary Reference Intakes (DRIs). Since 1998, the Institute of Medicine has issued eight exhaustive volumes of DRIs that offer quantitative estimates of nutrient intakes to be used for planning and assessing diets applicable to healthy individuals in the United States and Canada. Now, for the first time, all eight volumes are summarized in one easy-to-use reference volume, Dietary Reference Intakes: The Essential Reference for Dietary Planning and Assessment. Organized by nutrient for ready use, this popular reference volume reviews the function of each nutrient in the human body, food sources, usual dietary intakes, and effects of deficiencies and excessive intakes. For each nutrient of food component, information includes:

  • Estimated average requirement and its standard deviation by age and gender.
  • Recommended dietary allowance, based on the estimated average requirement and deviation.
  • Adequate intake level, where a recommended dietary allowance cannot be based on an estimated average requirement.
  • Tolerable upper intake levels above which risk of toxicity would increase. Along with dietary reference values for the intakes of nutrients by Americans and Canadians, this book presents recommendations for health maintenance and the reduction of chronic disease risk. Also included is a “Summary Table of Dietary Reference Intakes,” an updated practical summary of the recommendations. In addition, Dietary Reference Intakes: The Essential Reference for Dietary Planning and Assessment provides information about:
  • Guiding principles for nutrition labeling and fortification
  • Applications in dietary planning
  • Proposed definition of dietary fiber
  • A risk assessment model for establishing upper intake levels for nutrients
  • Proposed definition and plan for review of dietary antioxidants and related compounds

Dietitians, community nutritionists, nutrition educators, nutritionists working in government agencies, and nutrition students at the postsecondary level, as well as other health professionals, will find Dietary Reference Intakes: The Essential Reference for Dietary Planning and Assessment an invaluable resource.

  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  6. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  7. ×

    View our suggested citation for this chapter.

    « Back Next »
  8. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!