Dietary Variety

Dietary variety may be described in a number of ways. The most basic definition is the number of different food or beverage items consumed in a meal, a day, or over a longer period of time such as a month or a year. In the United States, the average adult consumes approximately 17 or 18 unique food or beverage items per day; however, many of these items may be repeated over time on other days. Dietary variety can be classified into different types, including total dietary variety, variety within food groups, and sources of variety that are dense or weak in vitamins and minerals or energy. Variety can also be described on a food level (food variety) or an ingredient level (ingredient variety). It should be noted that there is no consensus among researchers on a standard definition for dietary variety. Table 1 lists and defines several examples of different classifications of dietary variety that have been described to date.

Dietary variety influences nutrient intake, with the relative amounts of specific types of variety in the diet affecting overall dietary quality. Adults who consume a greater number of micronutrient-dense foods have higher vitamin and mineral intakes. In contrast, those who consume a greater number of energy-dense foods, many which tend to be “empty calorie” sources that are low in micronutrients, have lower vitamin and mineral intakes. Several studies show that selecting a diet higher in micronutrient-dense variety is associated with reduced morbidity and mortality. However, those studies do not generally take into account micronutrient-dense variety and energy-dense variety at the same time. Therefore, whether consuming a diet lower in energy-dense variety is also associated with those variables is not known.

Dietary variety also influences caloric intake and hence body weight status. People consume approximately 25% more calories in a meal when they are served a greater variety of foods that differ in sensory properties such as flavor, texture, and appearance. For example, when sandwiches with three different fillings are served, more calories are consumed than when one sandwich type is served. The same is true for different yogurt flavors or pasta shapes. The effects of dietary variety on consumption appear to extend beyond a single meal. Adults who consume a greater variety from different food groups over several days or months consume more calories from each of those groups. However, variety may have either beneficial or detrimental effects on body weight, depending on the food group. More variety from energy-dense groups, such as sweets, snacks, condiments, entrees, and carbohydrate-based foods, is consumed by people who have higher than desirable body weights, whereas more variety from energy-weak vegetables, fruits, and legumes is consumed by people who have lower healthier body weights. Reducing energy-dense variety and increasing energy-weak and micronutrient-dense variety may help reduce excess body fat. One way commercial and popular diets may work to reduce calorie intake is by limiting food variety.

The effects of variety on caloric intake and body weight are not limited to humans. Laboratory animals (e.g., rats, cats, hamsters) also consume approximately 25% more calories and gain more weight when fed different flavored chows. The fact that variety stimulates consumption in several species suggests a [Page 155]role for dietary variety in evolution; during prehistoric times, a more varied diet would have helped to maximize calorie, vitamin, and mineral consumption during times when food was plentiful, in turn helping to maintain or minimize depletion of body stores during times of starvation.

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