Dietary Assessment Health Article

Definition

A dietary assessment is an estimation of food and nutrients eaten over a particular time point. There are a number of dietary assessment tools used by dietitians, nutritionists, and doctors that aid in dietary counseling. These include:

• food records or diaries (including weighed intakes)
• dietary recalls• food frequency questionnaires (FFQs)
• dietary histories
• observed intakes
• chemical analyses of duplicate collections of foods consumed
• biological assessments (e.g. doubly-labelled water, plasma carotene, etc.)

Purpose

A dietary assessment is often conducted to determine the macronutrient (energy or caloric, protein, and fat) content and the micronutrient (vitamin and mineral) content of the diet to assist in providing dietary counseling. The validation of dietary assessment instruments is important to evaluate the diet in terms of a chronic disease risk factor. It is often used as a tool to help the patient lose weight, or to prevent or treat conditions or diseases that are influenced by food intake and nutritional status (i.e. cardiovascular disease, cancer, obesity, diabetes, hyperlipidemia).

A guide to the amount an average person needs each day to remain healthy has been determined for each vitamin and mineral as well as macronutrients. In the United States, this guide is called the recommended daily allowance (RDA). Consumption of too little or too much of certain vitamins and minerals may lead to a nutrient deficiency or a nutrient toxicity respectively. The RDA suggests a level of vitamin and minerals that is adequate for approximately 98% of healthy people in the population. The dietitian may use the dietary assessment to compare it to population requirements for nutrients (such as the RDA) to ensure the diet has proper intakes of energy, protein, fat, vitamins, and minerals. The RDA is under revision and will become the Dietary Reference Intakes, and will be applicable to Canadians and Americans.

Precautions

Dietary assessments are estimations based on an intake of a particular time point and cannot generalize that the diet is adequate or inadequate since intake varies day to day. For example, fruit and vegetables may be lacking on a day that was surveyed for the dietary assessment while overall the diet may be adequate in fruit and vegetable intake. Thus, care must be taken regarding generalizations about deficiencies or adequacy of nutrient intake. Intake of energy, carbohydrates, and protein varies less from day to day and may be estimated more closely than vitamin and mineral intakes.

Description

Some of the most common tools that assist in providing dietary advice include food records, 24 hour dietary recalls, food frequency questionnaires, diet histories, and several other methods including biochemical indices. These tools are explained in greater detail below. Furthermore, a scientific assessment of nutritional status may be made by using a combination of the information collected from clinical evaluations, biochemical tests, and dietary information. The clinical evaluation includes measurements of various anthropometric parameters such as height, weight, and percent body fat (determined by skinfolds or hydrostatic weighing). In addition, a clinical evaluation may also include observations for signs of nutrient deficiencies in the mouth, skin, eyes, and nails. The information collected from a clinical evaluation can be compared with that obtained from the dietary assessment and biochemical tests to provide a comprehensive picture of the patient's current nutritional status and relative risk factors for diet-related illnesses.

Food records

This method instructs subjects to record at the time of consumption all foods and beverages consumed for a specified duration, typically one to seven days, in order to quantify intake. Three or seven day food records are the most common. Food records can be estimated or weighed, the latter providing a more precise measure of intake. Portion sizes can be obtained through the use of household measures, cups, spoons, and scales. All days of the week should be proportionally included to avoid day of the week effects on nutrient and compositional intake. The weighed food record is the preferred method for assessing individual requirements because of its ability to determine intake quantitatively. Disadvantages of the method are that it is laborious and it may be a considerable burden to correctly measure and record intake.