Nutrition 331: Nutrition for Health

Study Guide: Unit 3

Dietary Reference Intakes and Diet‑planning Guides


Introduction

How do you know if your diet is adequate in all the essential nutrients but is not too high in nutrients that cause health problems? What standards do health professionals and scientists use to evaluate a healthy diet? This unit summarizes the nutrition standards created for health professionals and scientists as well as the diet planning guides created for the public.

Nutritional guidance has been provided to Canadians since 1942, with the publication of Canada’s Official Food Rules. The last revision of Canada’s Food Guide, Eating Well with Canada’s Food Guide was made in 2007. During this period, many revisions of the nutrient requirements, dietary recommendations, and guidelines were made. Revisions are necessary to ensure that the Food Guide reflects advances in the knowledge of dietary requirements, changes in education techniques, and alterations in Canadian food supply and food consumption patterns. The present focus is not just freedom from nutrient deficiency, but also reduction of the risk of chronic, nutrition-related diseases and disorders such as cardiovascular disease, obesity, diabetes, and cancer.

To use or apply diet-planning guides correctly, you must understand their strengths and limitations. After completing this unit, you will begin to gain such an understanding by starting an assignment assessing the nutritional adequacy of your own diet using Eating Well with Canada’s Food Guide.


Objectives

After completing this unit, you should be able to

  1. describe the goals of Dietary Reference Intakes (DRI).
  2. describe and explain the basis for the Recommended Dietary Allowances (RDA) and Daily Values (DV), and describe the potential uses for each.
  3. describe the purpose and content of Eating Well with Canada’s Food Guide (2007), focusing on adults.
  4. discuss the reasons for including variety, moderation, calorie control, and balance in eating guidelines.
  5. identify the key nutrients found in each food group.
  6. interpret information included in a standard Nutrition Facts Table.
  7. discuss the difference between what is perceived as a serving size, a Canada’s Food Guide serving size, and the serving size included in a Nutrition Facts Table.
  8. understand what foods provide protein, carbohydrates, and fats in the diet.

Section 1 Dietary Reference Intakes

Reading Assignment

Read pages 32–37 of Chapter 2: “Nutrition Tools—Standards and Guidelines.”

Note: You will not be tested on the specific DRI values.

The first step in setting standards and guidelines is to determine the appropriate levels of required nutrients. Researchers and nutrition experts review the available scientific literature (as described in Unit 2) and create technical recommendations for use by nutrition professionals.

DRI refers to five sets of standards described on page 33 of the textbook (Table 2.1: Nutrient Standards).

Estimated Average Requirements (EARs) are used by nutrition and health professionals to plan group diets (e.g., daycares, seniors’ lodges) and for assessing the adequacy of a population’s diet.

Acceptable Macronutrient Distribution Ranges (AMDR) are established for the energy-giving nutrients (also called macronutrients). The ranges are designed to lower the risk of chronic disease. We will discuss this further in Units 5, 6, and 7.

The terms Recommended Dietary Allowances (RDAs) and Acceptable Intakes (AIs) are used interchangeably in the text and Study Guide and are the focus of this section. Factors considered in the establishment of the RDAs are outlined below.

  • The recommended nutrient levels for protein, vitamins, and minerals are set sufficiently high to meet the body’s needs and to reduce the risk of chronic diseases. The RDAs are designed to provide nutrients in recommended amounts for almost all healthy individuals, so as to cover the requirements of 97 or 98% of the population. Thus, the RDAs exceed the needs of almost all people. They are generous, yet safe and adequate.
  • In the cases of some nutrients, there is not enough scientific knowledge to conclude specifically the amount of nutrient required for 97 or 98% of the population. The new DRIs address this problem by introducing a category called Adequate Intakes (AI) for nutrients such as chromium and calcium.

When using the RDAs or AIs, you should recognize several of their limitations.

  • They are established for healthy people with normal intestinal absorption of nutrients. People suffering from an acute or chronic illness may have different nutrient needs. Modifying diets for special needs is a job for a dietitian.
  • They are set for only 38 nutrients. The body also needs other trace nutrients, which must be provided through the consumption of a wide selection of foods.
  • They are established without taking into account all nutrient interactions. For example, excess zinc will interfere with copper absorption, or excess protein may increase calcium excretion. Such nutrient interactions are of concern, especially when protein, mineral, or mega-vitamin supplements are used.
  • In spite of increased interest in the physiological changes during the aging process, only limited data are available on the nutrient requirements of the elderly. The RDAs for both youth and the elderly are extrapolated mainly from those of young adults.
  • Nutrient requirements vary with body size, growth rate, or both. The RDAs are based on the average growth rate or physiological changes according to age. For exceptional individuals who have different growth spurts, the RDAs may be inappropriate.

Finally, a common mistake is to interpret intakes that are less than the RDA as a “deficiency,” rather than an indication of a possible inadequacy, with the probability of deficiency increasing as the intakes fall. The RDAs are only “best guesses” of the nutrient levels people require. Consequently, adequate intakes are achieved when the diet has 95% of the RDAs or more. The further below 95% of the RDA a nutrient is, the more likely the person is to have low nutrient stores, which may lead to poor health and nutrient deficiency symptoms.

An excess of nutrients obtained from ordinary foods seldom poses a problem, because the body can absorb less, or can store or excrete the excess, without harm. However, if nutrient intake is substantially too high (e.g., from the use of supplements), adverse effects may occur. The Tolerable Upper Intake Levels (UL) serves as a guide for what intakes are considered excessive and hazardous to health.

Note: RDAs, AIs, and ULs are found on the inside front cover of the textbook (pages A, B, and C).

Energy requirements are compiled slightly differently from RDAs. The Estimated Energy Requirements (EERs) are described on pages 36–37 of the textbook. It’s important that estimated energy requirements are not too high, as they could encourage overeating and obesity. Therefore, energy recommendations are based on average needs, rather than estimations for the highest needs.

In summary, the DRIs are designed for people of all ages—from infants to senior citizens. They are separated into 18 age-gender categories, plus five categories for stages of pregnancy and lactation. They are technical guidelines describing nutrients that are used by scientists researching nutrition and by health professionals to assess diets and provide nutrition advice.


Section 2 Eating Well with Canada’s Food Guide

Reading Assignment

Read pages 38–54 of Chapter 2: “Nutrition Tools—Standards and Guidelines.”

Note: Pages 46–47 explain the concept of discretionary calorie allowance. While this is a useful concept, it is not used in this course.

You will not be tested on the details of Figure 2.8 (pages 51–52). Read pages 9–10 of Chapter 1: “Food Choices and Human Health.”

A Healthy Eating Pattern for Canadians

Eating Well with Canada’s Food Guide describes what amount of food people need and what type of food is part of a healthy eating pattern. The eating pattern in Canada’s Food Guide includes foods from each of the four food groups—Vegetables and Fruit, Grain Products, Milk and Alternatives, and Meat and Alternatives—plus a certain amount of added oils and fats.

Following the eating pattern in Canada’s Food Guide will help people

  • get enough vitamins, minerals, and other nutrients.
  • reduce the risk of obesity, type 2 diabetes, heart disease, certain types of cancer, and osteoporosis.
  • achieve overall health and vitality.

The healthy eating pattern is based on extensive scientific evidence. It was developed by looking at different combinations of amounts and types of food to find an eating pattern that meets nutrient needs. The eating pattern was also evaluated against evidence that links certain foods with reduced risk of chronic diseases. The eating pattern meets the nutrient standards called Dietary Reference Intakes (DRIs). The DRIs summarize research findings about the amount of each nutrient and calories needed for good health and the prevention of chronic disease, while avoiding the negative effects of consuming too much of any individual nutrient. The eating pattern in Canada’s Food Guide falls within the DRIs’ Acceptable Macronutrient Distribution Ranges (AMDRs) for carbohydrate, protein, and fat in the diet.

Canada’s Food Guide groups people into nine categories based on age and gender (p. 40). For this course, you need to remember the recommendations for adults. The recommended number of servings represents an average that should be consumed each day. People who are at a healthy weight and are very active may need more than the recommended number of servings to meet their energy needs. They simply need to choose extra servings from all four food groups. For those who are overweight, the Food Guide can serve as a basis for a weight loss diet. To encourage normal weight levels, the Food Guide encourages people to regularly engage in moderate or vigorous physical activity (p. 44). This is important in order to help maintain normal body weight, enhance health, and prevent disease.

What Type of Food Should People Choose?

The Food Guide gives a number of directive statements that can help consumers choose the most nutritious choices—those that are lower in fat, sugar, and salt. These are shown on p. 42 of the textbook and the right side of the printed Food Guide.

For example, the first statement advises “Eat at least one dark green and one orange vegetable each day.” Vegetables with these features are mentioned specifically because they are rich in folate and vitamin A, respectively. Dark green vegetables include asparagus, broccoli, Brussels sprouts, collards, fresh parsley, green peas, mustard greens, romaine lettuce, and spinach. The most common lettuce used, iceberg lettuce, is not a dark green vegetable. The nutrient values back this up: compared to Romaine or dark green leafy lettuce, iceberg lettuce has very small amounts of vitamins and minerals.

Orange vegetables are rich in carotenoids, such as beta-carotene, that the body converts to vitamin A. These include carrots, pumpkins, orange-coloured squash, and sweet potatoes.

Oils and Fats

The 2007 Canada’s Food Guide, for the first time in its history, recognizes that a small amount of certain types of oil or fat is essential and desirable in the daily diet. These supply calories and essential fatty acids, and they help the body absorb fat-soluble vitamins. Beneficial fats come primarily from unsaturated fat sources such as vegetable oils (canola, olive, and soybean), soft, non-hydrogenated margarines, and nuts, seeds, and fatty fish. The Nutrition Facts label, now found on the majority of processed foods in Canada, is a valuable tool in helping to choose margarine low in saturated fat with no trans fat. Thus, the new recommendation for oils and fats is to include a small amount of unsaturated fat each day.

Limited Foods

In addition to the directive statements (p. 42 of the textbook and the right-hand side of the printed Food Guide), the Guide describes the kinds of foods that should be limited in the diet (see “Eat Well,” shaded purple, p. 44). This list includes foods high in calories, fat, sugar, and salt (sodium). These foods are often called junk foods. It’s important to remember that the overall quality of the diet is more important than the relative number of “Limited Foods” that a person consumes each day.

Many foods classified as “limited” may surprise you, in part because of advertising and nutrient claims on the packaging. Such foods have low nutrient density (i.e., a low level of nutrients per calorie of food). For example, baked goods such as cakes, croissants, doughnuts, pastries, pies, and many muffins add extra calories, fat, sugar, or salt (sodium) to the diet and therefore should be limited. The labels of some baked items state “low fat” or “source of fibre,” but this can be misleading. Such items may still provide more calories than many other Grain Products. Popcorn, a Grain Product, is considered a Limited Food if it has a significant amount of added salt and fat (usually true for microwaveable brands). Likewise, most cookies are Limited Foods, but some—those made mainly from flour are considered Grain Products. Some of the higher fat Milk and Alternatives should be limited due to their high fat content; examples include ice cream, regular sour cream, and cream.

Many beverages should be classified as Limited Foods. The few that fit into the food groups are fluid milk and fruit juice. Beverages rich in sugar or fat include sports and energy drinks, hot chocolate, and many specialty coffee drinks. Alcoholic beverages are also categorized as Limited Foods. If a label describes a beverage as punch, beverage, or cocktail, it is a Limited Food. While some fruit-flavoured beverages can claim to be a “source of vitamin C” (supplemented), fruit juices have a higher content of other nutrients, such as potassium, folate, and possibly vitamin A.

Key Nutrients Found in Each Food Group

Within a food group, foods can vary greatly in their nutrient content. Because different people prefer different foods, each food group has many different choices. Eating a variety of foods from each food group usually ensures that people get the nutrients that they require. The table below demonstrates how different key nutrients distribute themselves over the four food groups so that a diet based on the Food Guide forms a healthy pattern of eating.

Key Nutrient Vegetables and Fruit Grain Products Milk and Alternatives Meat and Alternatives Oils and Fats
Protein      
Fat      
Essential Fatty Acids      
Carbohydrate    
Fibre      
Thiamin      
Riboflavin    
Niacin      
Folate      
Vitamin B6      
Vitamin B12      
Vitamin C        
Vitamin A      
Vitamin D        
Vitamin E    
Calcium        
Iron      
Zinc    
Magnesium  
Potassium  

Adapted from Health Canada, 2007.

Classifying Foods

The following foods are often classified incorrectly:

Food Correct Food Group
potatoes Vegetables and Fruit
eggs Meat and Alternatives
dried peas, beans, lentils (e.g., brown beans or split pea soup) Meat and Alternatives
nuts and seeds Meat and Alternatives
drinks, punches, cocktails (e.g., cranberry cocktail) Limited Foods

One simple method to determine whether a convenience or processed food belongs to a particular food group is to read the list of ingredients. Ingredients are listed by weight, in descending order of predominance. If two of the first four ingredients fit into a specific food group, the food likely contains the nutrient in a significant amount. If sugar or fats are listed as the predominant ingredients, the product should be classified as a Limited Food.

Canada’s Food Guide (2007): Strengths and Weaknesses

Strengths of the 2007 Food Guide include the following:

  • It is a simple, yet comprehensive guide that is easy to teach, learn, and remember.
  • The Guide is designed to help plan and assess the diets of all healthy Canadians over 2 years of age. It provides specific guidance for various age groups and recognizes the different needs of females and males.
  • It provides a total diet approach that helps Canadians meet their nutritional requirements and achieve overall health and vitality.
  • It has incorporated current scientific evidence relating intake of certain beneficial foods to reducing risk of chronic diseases.
  • It has been updated to reflect current eating patterns of Canadians and the changing food supply.
  • It can accommodate ethnic foods and special dietary needs such as low salt, low fat, and low calories.
  • It has included a recommendation for daily moderate physical activity as a step towards better health and a healthy body weight.
  • It is available in 12 or more languages, and it has been adapted for First Nations, Inuit, and Métis peoples.

Weaknesses still inherent in the Guide include the following:

  • Based on the considerable variation in nutrient values of foods, it may be possible to consume the recommended numbers of servings, yet have inadequate nutrient intake (below DRI values), particularly if a person often chooses foods with a low nutrient density.
  • Combination foods like casseroles continue to be difficult to break down into individual components.
  • Eating out and using prepared foods may make estimating serving size difficult.

Section 3 Nutrition Facts and Claims on Food Labels

Reading Assignment

Read page 37, “Why Are Daily Values Used on Labels?”

Read pages 55–60, “Consumer Corner: Checking out Food Labels.”

Table 2.7 (p. 59) is background information only. You will not be tested on this information. You are encouraged to read Nutrition Facts and Ingredient lists on actual foods throughout this course. Start with foods in your refrigerator and cupboards and then read labels while grocery shopping. While you are not required to memorize the amounts of nutrients in different foods, it is helpful for you to become familiar with foods that are high or low in specific nutrients.

Food labels list the ingredients of a product in descending order, by weight. This list is invariably written in small print. Often, a food label will have words in much larger print that imply something that is not quite accurate. For example, a fruit juice may say (in large letters), “made with blueberries,” but the list of ingredients (in small print) reveals that berries are the second or third ingredient, behind cheaper fruit juices, such as apple juice. As the label does not state the actual amount of each ingredient, it is impossible to determine whether blueberry juice is a major ingredient (say, 30%) or a minor ingredient (say, 3%). To make it even more confusing, the label may have a large image of blueberries, not apples!

It is important to carefully read the serving size on a Nutrition Facts table. One reason for this is that serving sizes used on food labels are often quite different from those used in Canada’s Food Guide. Also, a quick glance at a Nutrition Facts label might give a misleading impression. For example, the label on a bag of potato chips may indicate that a single serving has 150kcal. However, a “serving” may be defined as only a quarter of a bag. Serving sizes often vary between similar products. For example, the serving size on one can of sardines may be 58 grams (half a can) but for another can it may be 106 grams (the whole can). Accordingly, if you wish to compare two brands of a particular food (e.g., breakfast cereals), you must compare them using the same serving sizes.

Consumers can also use % Daily Value as a guide for comparing foods (p. 58 of the textbook). The % Daily Value indicates, at a glance, whether there is a lot or a little of a nutrient per serving of food (relative to the daily amount required). This topic is discussed in more detail at the following website: http://www.hc-sc.gc.ca/fn-an/label-etiquet/nutrition/cons/dv-vq/index-eng.php

Percent DV for fat and carbohydrate cannot be interpreted as percent of calories or percent of the weight of the food. For example, a Nutrition Facts table with 20% DV for fat means the food is high in fat. Some interpret this to mean that the food is 20% by weight, but that is not correct.

Nutrition and diet-related health claims usually highlight one nutrient of a food and are optional. Some evidence suggests that food products with nutrition and diet-related health claims may cost more than products of comparable nutritional value that do not include a claim (Riciutto & Tarasuk, 2005). To assess the overall value of a food, read the Nutrition Facts and the ingredient list, and check comparable foods. For example, a product that is low in sodium or high in fibre may still be high in fat and calories.


Section 4 Looking at the Whole Diet

Reading Assignment

Read pages 60–63 “Food Feature: Getting a Feel for the Nutrients in Foods.”

Assignment

After taking the Unit Quiz, begin Assignment 1: Diet Analysis. Continue working on the course as you conduct your “Assessment of Nutrient Intakes Using Eating Well with Canada’s Food Guide.

Review Questions

See textbook, page 28, “Self-Check” questions 3 and 4, and page 73, questions 1–9.