A Dairy Delight

Milk and milk products contain a variety of important nutrients, including calcium, phosphorus, protein, potassium, riboflavin, niacin, vitamin B12, vitamin D, and vitamin A.^1,2 As a result of milk's high nutrient richness, the 2005 Dietary Guidelines for Americans recommends including 3 cups per day of fat-free or low-fat milk or equivalent milk products in the diet.³ Milk and milk products are predominantly associated with improvements in bone health.³ In addition, research links milk and/or milk products to a number of other health benefits, including regulation of blood pressure, weight maintenance, prevention of dental caries, and improved gastrointestinal health.^4–6

The health benefits of dairy foods have been attributed to a number of specific components. Protein is one component of dairy foods that has been associated with health benefits, such as increased muscle protein synthesis, satiety, weight management, and regulation of blood pressure.^7–12 Recent evidence on the benefits of higher-protein diets has resulted in considerable interest in helping Americans of all ages meet protein recommendations and reach levels that are associated with health benefits. As part of a well-balanced diet, dairy foods can serve as a major contributor to meeting protein requirements along with other protein sources. For example, consuming three glasses of milk in one day can provide almost half of the minimum protein recommendation for adults.¹³ Further, consumption of food and beverage products with value-added ingredients such as whey protein, one type of protein found naturally in cow's milk, can help individuals reach protein levels that may have positive effects on health. In addition to helping individuals meet minimum protein recommendations, the concentration of whey protein added to food and beverage products can optimize the benefits of protein on health.

Market and Food Trends
Based on recent reports from the International Food Information Council (IFIC; Washington, DC), consumer interest in foods and beverages with health benefits is on the rise. IFIC's 2008 Food and Health Survey: Consumer Attitudes Toward Food, Nutrition, and Health indicates that more than 62% of Americans believe that the "healthfulness" of foods and beverages is important.¹⁴ This increased interest in foods and beverages with added health benefits is further supported by the fact that more than 80% of consumers are including or desire to include these types of products in their diet.¹⁴ Increased interest in isolating ingredients to enhance the health benefits of foods creates a market for innovative, value-added products.

IFIC's 2008 survey also reveals that there is interest in the protein content of food products among consumers. The number of consumers who use the Nutrition Facts Panel to find information regarding protein has significantly increased from 33% in 2007 to 40% in 2008.¹⁴ Further, another survey by the NPD Group (Port Washington, NY) indicates that more than half of Americans would like to include more protein in their diet.¹⁵ Food and beverage companies have responded by using whey protein as an ingredient in a number of food and beverage products. From 2006 to 2007, there has been a 65% increase in the number of new food and beverage products that contain whey protein as an ingredient.¹⁶ Most of the new products containing whey protein are in the form of snack bars, meal replacement beverages, and spoonable yogurts.¹⁶ Other product opportunities for foods and beverages with whey protein as an ingredient include drinking yogurts, beverage mixes, hot cereals, and sports beverages.¹⁶ Although a number of food and beverage products that use whey protein as an ingredient already exist in the marketplace, there are still opportunities for new products to be developed to help meet consumers' interest in increasing the amount of protein in their diet.

Whey Protein
Among the dairy proteins, whey protein has recently received much attention from the scientific community due to its positive effects on health. Whey protein has been associated with increased muscle protein synthesis, satiety, and weight management. This dairy protein is available in several different forms, including whey powder, whey protein concentrates, whey protein isolates, reduced-lactose whey, and demineralized whey. Whey protein is a high-quality complete protein that is easily digestible. Complete proteins contain all of the essential amino acids that the body requires to build proteins. Essential amino acids are important because they cannot be synthesized from the amino acids that are already present in the body and therefore must be consumed in the diet. Whey proteins are also a rich source of branched-chain amino acids (BCAA), which are a subgroup of the essential amino acids. The BCAAs include valine, leucine, and isoleucine, and can be used as an energy source in skeletal muscle and also contribute to the synthesis of new muscle tissue.⁷ Among the BCAAs, leucine is unique, as it has been shown to be an independent stimulator of skeletal muscle protein synthesis through the regulation of gene expression.

The amino acid profile of whey protein in comparison to other protein sources demonstrates why it is a great protein source for individuals to include in their diet. Other protein sources, for example most vegetable proteins, are not complete proteins because they do not contain all of the essential amino acids. In some cases, these foods must be consumed with another protein source in order for an individual to get all of the essential amino acids. The BCAA content of whey protein is greater than other protein sources, with whey protein isolate, egg protein, soy protein isolate, and wheat protein having BCAA contents of 26, 20, 18, and 15%, respectively.⁷ Leucine content also varies across the different protein sources, with whey protein isolate, egg protein, soy protein isolate, and wheat protein containing 14, 8.5, 8, and 7%, respectively.⁷ The high content of BCAAs, and more specifically leucine, supports the inclusion of whey protein in the diet.

Consumption of whey protein increases protein synthesis, which over time can lead to the production of new muscle tissue. When routine consumption of whey protein is combined with a long-term resistance-training program in young adults, an increase in muscle can occur, which may improve body composition. For example, Candow et al. found that supplementation with 1.2 g of whey protein per kg of body weight (g/kg BW) in combination with resistance exercise resulted in a greater increase in lean muscle mass than supplementation with an isocaloric carbohydrate beverage.¹⁷ Current research supports a combination of protein intake and resistance exercise over a carbohydrate beverage and/or resistance exercise for a more effective increase in lean muscle tissue.^10,17

The older-adult population group may benefit from the routine consumption of high-quality dairy proteins. Based on early work in younger individuals and the issue of muscle loss in elderly adults, it is proposed that elderly adults could minimize the loss of muscle that occurs with aging by consuming higher amounts of high-quality dietary protein (i.e., amounts above the current RDA of 0.8 g/kg BW per day for individuals over the age of 19 years).¹⁸ The issue of muscle loss with aging, referred to as sarcopenia, is becoming an important public health concern. Maintenance of muscle mass through increased protein levels in elderly adults could extend functional capacity, independence, and quality of life.¹⁸

"While most acute studies show that older individuals are able to increase protein synthesis following consumption of dietary protein, very few longer-term, properly controlled trials have been done to determine if this can result in an increase in muscle tissue over the long term. However, several trials are under way to explore this concept," explains Matt Pikosky, PhD, RD, FACN, director of Research Transfer for Dairy Management Inc. (DMI; Rosemont, IL). Emerging research, particularly in individuals around the age of 40,¹⁸ where the decline in muscle mass becomes more pronounced, may show that individuals throughout their lifespan can benefit from a long-term increase in muscle protein synthesis.

The concept of satiety, defined as the feeling of fullness after eating, and its implications on weight management have received a lot of attention from the scientific community. It has been postulated that dietary protein may have a positive role in stimulating satiety, and research suggests that protein is more satiating than carbohydrate or fat. Studies have documented this either in the context of a single meal, or the overall diet (i.e., subjective ratings of fullness and free-access feeding energy intake after a test meal). A study on younger (21–43 years) and older (63–79 years) men found that subjects consuming low (0.5 g/kg BW per day or 63% of the RDA) and moderate amounts of protein (0.75 g/kg BW per day or 94% of the RDA) experienced a greater amount of hunger and desire to eat than subjects consuming higher amounts of protein (1.0 g/kg BW per day or 125% of the RDA; dairy protein served as one of the protein sources in this study).⁸

Skov et al. found a greater reduction in total energy intake in individuals consuming a higher-protein diet than in individuals consuming a higher-carbohydrate diet.⁹ Research also suggests that higher-protein diets compared with adequate-protein diets with equal amounts of caloric restriction may contribute to weight management by improving the quality of weight loss through preservation of lean body mass and decreasing fat mass. A study by Layman et al. supports this concept, revealing that middle-aged women who consumed a reduced-carbohydrate, higher-protein diet (1.6 g/kg BW per day of protein) for four months while participating in an exercise program had a greater total weight loss, as well as greater fat mass loss, than women on a higher-carbohydrate, lower-protein diet (0.8g/kg BW per day of protein).¹⁰ Further, there was a trend for a greater preservation of lean mass with the higher-protein group.¹⁰ This research supports evidence suggesting that protein is more satiating than other macronutrients and that the satiating effects of a longer-term, higher-protein diet may eventually lead to a reduction in body fat, thus playing a role in weight management.^{10, 11, 19}

Scientists are continually working to investigate additional potential health benefits of whey protein. In addition to improvements in muscle mass and body composition, and contributions to satiety, preliminary evidence has also suggested a benefit of whey consumption on blood pressure, immune function, and inflammation.^12,20 The scientific evidence supporting whey's role in health is still emerging and will continue to expand.

Applicability
Different forms of whey protein are used in a variety of foods and are typically suited to a particular application. According to Alan Reed, senior vice president of U.S. manufacturing and ingredients marketing for DMI,²¹ "Whey protein concentrate with a protein content of 80% and whey protein isolates are most commonly used in nutritional applications, while other types of whey-demineralized whey, reduced-lactose whey, and whey powder-are more typical in specific applications such as confections and baked goods."

Whey protein concentrate is included in a variety of food and beverage products, including confectionaries, soups, snack foods, clinical nutrition mixtures, and infant formulas.^20,22,23 Additionally, whey protein isolates are used in sports beverages and powdered beverages.²² Demineralized whey and reduced-lactose whey are used as an ingredient in some infant formulas. Although whey protein isolate contains a greater amount of protein (90%) than whey protein concentrate (35–80%), few studies distinguish the health benefits of each form to provide rationale for use of one form over the other.²² The use of whey protein concentrate instead of whey protein isolate may be due to practicality and control of functional properties as a greater amount of whey protein concentrate will be needed to match the amount of protein provided by whey protein isolate.

Conclusions
Consumer interest in healthful foods and beverages presents new opportunities for dairy components to be used as ingredients. Scientific evidence suggests that as part of a well-balanced diet, dairy products and ingredients such as whey protein can help Americans meet dietary recommendations for certain nutrients while optimizing nutritional adequacy. Furthermore, use of dairy components as ingredients can have positive effects on health. Whey protein has been found to increase muscle protein synthesis and, when combined with routine resistance exercise, build muscle tissue.

Additionally, whey protein has been shown to increase satiety. Studies have also demonstrated that higher-protein diets can improve the quality of weight loss. Future research evaluating the effectiveness of dairy proteins in decreasing blood pressure and inflammation, improving immune function, and preventing age-related muscle loss may provide additional applications for the use of whey protein as an ingredient, which could increase consumer purchase of value-added products. Increased consumer interest and scientific research suggest that the use of dairy ingredients, such as whey protein, in food and beverage products can provide positive health benefits.

References

1. G Miller, J Jarvis, and L McBean, Handbook of Dairy Foods and Nutrition. 3rd ed. (Boca Raton, FL: Taylor and Francis Group, LLC, 2007).
2. National Dairy Council, "Milk's Unique Nutrient Package: Benefits for Bones and Beyond," 2004.