Please note: In 2003, the CTF updated its Grades of Recommendations to include an "I Recommendation" for situations where insufficient evidence exists to allow a recommendation to be made. (Formerly, these situations were captured under a "C Recommendation".) This change is not retroactive, and all "C Recommendations" made prior to 2003 have not been reevaluated in light of the new "I" recommendation grade. For a discussion of these recommendation grades, please link to the 2003 article in the Canadian Medical Association Journal here.
Contents
Objective Burden
of SufferingDiseases associated with dietary excess and imbalance rank among the leading causes of illness and death in the western world. Major diseases in which diet plays a role include coronary artery disease, some cancers (colorectal, breast and prostate) and cerebrovascular disease, which account for 46,600, 15,500 and 13,900 annual deaths, respectively. Caloric intake exceeding energy expenditure can lead to obesity, which in turn is a risk factor for both hypertension and type II diabetes mellitus. vascular disease, renal failure and blindness. Major disparities between recommended dietary practices and actual consumption are most notable in intakes of fat (30% vs. 38%) and complex carbohydrates (55% vs. 48%.) There is also concern about excessive consumption of inappropriate vitamin and mineral supplements. Excessive vitamin C has been associated with B12 absorption interference, Vitamin A with bone and joint pains, and Vitamin D with hypercalcemia and skeletal decalcification.
Deficiency Disorders
Nutritional factor deficiencies have been linked to osteoporosis, diverticular disease, constipation, and iron deficiency anemia. An estimated 40% of North American women will suffer from osteoporosis-related fractures by the time they reach age 70. Deficiency of dietary fibre has been implicated in constipation and other gastrointestinal disorders such as diverticulosis. Iron deficiency is common in menstruating women whose diet is deficient in foods containing available iron, especially meats. Pregnant women, and those who nurse for a prolonged period of time are also at risk for iron deficiency. Up to 63% of people over age 60 have been documented to have deficient iron intakes. Chronic alcoholics and strict vegetarians are also at risk for deficiency disorders. An additional concern is malnutrition, which is associated with an increased prevalence of complications and high mortality among hospitalized patients. While those living alone are at risk, institutional care is associated with malnutrition in as many as 52-85%.
Options Outcomes EvidenceRecommendations were graded as:
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Good evidence to support the recommendation that the condition be specifically considered in a PHE. |
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Fair evidence to support the recommendation that the condition be specifically considered in a PHE. |
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Poor evidence regarding inclusion or exclusion of the condition in a PHE, but recommendations may be made on other grounds. |
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Fair evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE. |
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Good evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE. |
Quality of evidence was rated according to 5 levels:
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Evidence from at least 1 properly randomized controlled trial (RCT). |
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Evidence from well-designed controlled trials without randomization. |
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Evidence from well-designed cohort or case-control analytic studies, preferably from more than 1 centre or research group. |
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Evidence from comparisons between times or places with or without the intervention. Dramatic results in uncontrolled experiments could also be included here. |
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Opinions of respected authorities, based on clinical experience, descriptive studies or reports of expert committees. |
ValuesBackground papers providing critical appraisal of the evidence and tentative recommendations prepared by the chapter author were pre-circulated to the members. Evidence for this topic was presented and deliberated upon in 1- to 2-day meetings, 2 to 3 times per year from January 1993 to June 1993. Consensus was reached on final recommendations.
Benefits,
Harms, and CostsNo evidence shows a screening benefit for elderly persons or alcoholics. Controversy exists regarding the benefit of supplementation for individuals who have an inadequate dietary intake of specific nutrients, have serum levels below accepted normal levels and no characteristics of classic deficiency syndromes.
The results of RCTs support that counselling by non-physicians can lead to changes in dietary habits. A study of adults with hypercholesterolemia found that those who received counselling and printed materials decreased their cholesterol and increased their fibre intakes. Another study found that middle-aged women who received individual and group nutritional counselling reduced the percentage of energy derived from dietary fat from 39% to 21%; no change occurred in the control group. In a study of men recovering from myocardial infarction, those who received individual and group counselling reported changes in fat intake which persisted for up to 24 months. A study of an intervention comprised of a 5-minute interview with a nurse, generic self-help materials and a follow-up phone call reported small but significant improvements in dietary fat and fibre intakes, but only for those with responsibility for meal production.
Controlled trials have shown decreases in the incidence of myocardial infarction and sudden death, but not all-cause mortality in asymptomatic middle-aged men with selected cardiac risk factors who were given diets low in saturated fat. No evidence exists that changes in fat intake reduce the incidence of various malignancies. Case-control studies report inconsistent results about the association between fibre intake and colon cancer, but meta-analyses of these studies suggest an overall benefit. Adverse effects associated with changes in dietary intake of specific nutrients were identified but not quantified.
Recommendations ValidationThe Canada Food Guide recommends eating a variety of foods and choosing lower fat foods, and makes recommendations on daily adult intakes for specific food groups. The 1989 U.S. Preventive Services Task Force recommended consumption of foods high in complex carbohydrates and fibre, and periodic counselling regarding dietary intakes of calories, fat, cholesterol, complex carbohydrates, fibre and sodium. The American Medical Association, American College of Physicians and American Heart Association make specific recommendations about nutritional counselling.
Sponsors Selected
References
Link to Full Text of this review
Link to Summary Table of Recommendations of this review
Link to Selected References list of this review
Copyright © 1997 Canadian
Task Force on Preventive Health Care
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Last modified: June 10, 1998.
