June 2015 Issue
By Densie Webb, PhD, RD
Vol. 17 No. 6 P. 22
Studies show high-quality protein can improve satiety, help manage weight, and prevent chronic disease.
It seems as though snacking may have replaced baseball as America's favorite pastime. National dietary surveys have found that about 90% of adults,1 83% of adolescents,2 and 97% of children3 snack every day, sometimes several times per day. Whether or not that's a good thing largely depends on the quality of the snacks being consumed. Many of the most common snacks, such as chips and soda, are high in both salt and sugar. It's no coincidence then that increased snacking is associated with decreased protein intake.4 However, there's much research to suggest that choosing snacks high in protein, rather than high in salt and sugar, could provide a host of health benefits.
Satiety and Weight Management
Jessica Crandall, RD, CDE, a Denver-based nutrition counselor and national spokesperson for the Academy of Nutrition and Dietetics (the Academy) says, "High-protein snacks, as well as balanced meals, have been linked to increased satiety."
Indeed, several studies have suggested that protein-rich snacking may boost satiety and facilitate weight loss. In a longitudinal study, researchers gave 17 men and women with type 2 diabetes moderately high-protein morning and afternoon snacks (7 g to 12 g of protein) for four weeks, and compared the results with their normal eating habits for four weeks. The subjects who ate the two high-protein snacks lost a modest but significant amount of weight (1 kg) during the four-week period. Researchers noted that the subjects' weight reduction occurred without changes in total energy intake.5
In a study that examined the effect of high-protein snacking on satiety and appetite control, researchers found that healthy women who ate a high-protein yogurt snack (14 g of protein) in the afternoon experienced improved appetite control, satiety, and reduced subsequent food intake compared with eating other common, energy-dense, high-fat snacks.6 However, the women didn't feel a greater sense of fullness after eating the yogurt compared with consuming the high-fat snacks.
In other studies, it's difficult to interpret the findings of the effects of protein snacking on weight in populations, as the definition of snacking often is broad.7
Population studies may look at protein intake at meals, but they seldom zero in on the specific effect of protein-rich snacks.8 Many of the snacking studies depend on self-reporting of both the frequency and the types of foods that are eaten as snacks.
Underreporting of food intake is a well-documented problem in population studies, especially among overweight and obese adults, casting doubt on some of the findings.9 In addition, there are several factors that affect the impulse to snack and the composition of snacks, including television watching, alcohol intake, and lack of sleep, making it even more difficult to know if snacking, specifically snacking on protein-rich foods, is the factor affecting appetite and weight.10
High-protein snacks also can help maintain normal blood glucose levels. In a study of 20 healthy males, who were given a variety of midmorning snacks, those given the snacks with the greatest protein-to-carbohydrate ratio, including plain yogurt and skim milk, had the lowest blood sugar levels.11 Researchers determined that the improvement in blood sugar was due to improved insulin action, rather than to increased concentrations of insulin.
In another study of overweight to moderately obese women, eating a high-protein snack bar containing 10.1 g of protein between breakfast and lunch resulted in lower blood glucose levels over a nine-hour period.12 Some research suggests it may not be the total protein that has an effect, but amino acids in proteins that improve glucose metabolism,13 though the specific amino acids that might be responsible for the improvement have yet to be identified.
Nonetheless, Harvey Anderson, PhD, a professor of nutritional sciences and physiology at the University of Toronto, says protein as a whole serves important functions in the body that go beyond amino acids, so getting enough is critical.
A high-protein diet also may help lower the risk of developing hypertension. A study published in the American Journal of Hypertension found that participants consuming the highest amount of protein (an average of 100 g per day) had a 40% lower risk of high blood pressure compared with those consuming the least.14 The researchers found that adults who consumed the most protein, whether from animal or plant sources, had significantly lower systolic blood pressure and diastolic blood pressure levels after four years of follow-up. Because high-protein snacks contribute to overall protein intake, based on the findings of this study, it would appear that high-protein snacks could aid in lowering blood pressure.
However, a recent study found that among people with type 2 diabetes, consuming an average of 20% of calories as protein increased the risk of experiencing higher daytime blood pressure.15
For athletes, protein powders and high-protein snacks are plentiful. But how necessary are they, and can they really improve performance? The International Society of Sports Nutrition recommends consuming high-quality protein, and singles out milk-derived whey protein isolate and casein, egg white powder, and soy protein isolate as proteins that provide essential amino acids that readily aid in muscle tissue synthesis.16
"Athletes should include protein at all meals and snacks, especially postworkout," says Amy Goodson, MS, RD, CSSD, LD, Texas Health Ben Hogan Sports Medicine sports dietitian and team dietitian for the Dallas Cowboys. Ideally, 20 g of high-quality protein should be consumed within 45 minutes after exercise to promote the recovery process, she says. Athletes demand a higher level of protein intake (1.2 to 1.4 g/kg for endurance athletes and 1.6 to 2 g/kg for strength athletes), and they have to work harder to obtain it, because of the larger quantities of high-protein foods they must consume, she adds. High-protein snacks, such as low-fat dairy foods or protein bars, are a good way to work more protein into the diet.
While dietary protein is important, Isabel Maples, RDN, a spokesperson for the Academy, says research suggests that the combination of physical activity (eg, resistance, interval, stretching, and endurance) and 20 g of whey protein may be particularly beneficial for weight loss, fat loss, increasing lean body mass, and improving insulin resistance.
Just as important as consuming high-quality protein is the time of day when it's consumed. The typical American dietary pattern is a consumption of about three times more protein at dinner than at breakfast.17 "Most Americans don't eat an adequate amount of protein in the morning, which may cause decreased performance, hunger, and poor eating habits throughout the day," Crandall says.
Several studies have suggested that this pattern may not be the most beneficial. Instead, evenly distributing protein intake throughout the day has been found to be optimal. A recent study showed that muscle protein synthesis was 25% higher over a 24-hour period when the same quantity of protein was evenly distributed across breakfast, lunch, and dinner.18 While it hasn't been studied, the same may be true of including protein-rich snacks in the diet. "There's increasing evidence that distribution of protein so that more is consumed at breakfast may be beneficial. The idea of 30% of daily protein intake at each meal is being promoted, with some protein snacks between meals," Anderson says.
Maintaining muscle mass is important for overall health, especially in older individuals. Research shows that proper protein distribution also may help prevent age-related sarcopenia, the loss of muscle mass with age, Maples says. To lower the risk, research suggests 25 g to 30 g of protein per meal in older people.19 Protein synthesis response is blunted in older adults when protein is less than 20 g per meal or snack, research suggests, so getting enough protein becomes even more important with age, she says.
While there's evidence of a protein threshold of 20 g to 30 g to trigger muscle protein synthesis, more research is needed. "It's premature to put it in the dietary guidelines. Randomized, controlled trials haven't been done," Anderson says. More research also is needed on the potential benefits of protein in weight loss, satiety, and blood glucose and blood pressure management. In the meantime, it makes good nutrition sense to recommend to clients and patients to snack on foods that provide a good supply of protein compared with fat and carbohydrate, both for possible appetite and blood sugar control.
While there are many options for high-protein snacking (see Table), Maples recommends choosing dairy foods. "Three out of four Americans don't get the recommended three servings per day of dairy," she says. "An extra glass of skim milk per day would cost maybe 20 cents and provide 8 g of high-quality protein, plus supply calcium and vitamin D."
— Densie Webb, PhD, RD, is a freelance writer, editor, and industry consultant based in Austin, Texas.
1. Sebastian RS, Wilkinson Enns C, Goldman JD. Snacking patterns of US adults: what we eat in America, NHANES 2007–2008. Food Surveys Research Group Dietary Data Brief No. 4. http://ars.usda.gov/SP2UserFiles/Place/80400530/pdf/DBrief/4_adult
_snacking_0708.pdf. Published June 2011.
2. Sebastian RS, Goldman JD, Wilkinson Enns C. Snacking patterns of US adolescents: what we eat in America, NHANES 2005–2006. Food Surveys Research Group Dietary Data Brief No 2. http://ars.usda.gov/SP2UserFiles/Place/80400530/pdf/DBrief/2_adolescents
_snacking_0506.pdf. Published September 2010.
3. Piernas C, Popkin BM. Trends in snacking among U.S. children. Health Aff (Millwood). 2010;29(3):398-404.
4. Kerver JM, Yang EJ, Obayashi S, Bianchi L, Song WO. Meal and snack patterns are associated with dietary intake of energy and nutrient in US adults. J Am Diet Assoc. 2006;106(1):46-53.
5. Navas-Carretero S, Abete I, Zulet MA, Martinez JA. Chronologically scheduled snacking with high-protein products within the habitual diet in type-2 diabetes patients leads to a fat mass loss: a longitudinal study. Nutr J. 2011;10:74.
6. Ortinau LC, Hoertel HA, Douglas SM, Leidy HJ. Effects of high-protein vs. high-fat snacks on appetite control, satiety, and eating initiation in healthy women. Nutr J. 2014;13:97.
7. Johnson GH, Anderson GH. Snacking definitions: impact on interpretation of the literature and dietary recommendations. Crit Rev Food Sci Nutr. 2010;50(9):848-871.
8. McCrory MA, Campbell WW. Effects of eating frequency, snacking and breakfast skipping on energy regulation: symposium overview. J Nutr. 2011;141(1):144-147.
9. Mattes R, Tan SY. Snacking and energy balance in humans. In: Ferruzzi M, Coulston AM, Boushey CJ, eds. Nutrition in the Prevention and Treatment of Disease. 3rd ed. Elsevier Inc; 2013:501-510.
10. Chapman CD, Benedict C, Brooks SJ, Schiöth HB. Lifestyle determinants of the drive to eat: a meta-analysis. Am J Clin Nutr. 2012;96(3):492-497.
11. El Khoury D, Brown P, Smith G, et al. Increasing the protein to carbohydrate ratio in yogurts consumed as a snack reduces post-consumption glycemia independent of insulin. Clin Nutr. 2014;33(1):29-38.
12. Williams G, Naokes M, Keogh J, Foster P, Clifton P. High protein high fibre snack bars reduce food intake and improve short-term glucose and insulin profiles compared with high fat snack bars. Asia Pac J Clin Nutr. 2006;15(4):443-450.
13. Monti LD, Casiraghi MC, Setola E, et al. L-arginine enriched biscuits improve endothelial function and glucose metabolism: a pilot study in healthy subjects and a cross-over study in subjects with impaired glucose tolerance and metabolic syndrome. Metabolism. 2013;62(2):255-264.
14. Buendia JR, Bradlee ML, Singer MR, Moore LL. Diets higher in protein predict lower high blood pressure risk in Framingham Offspring Study adults. Am J Hypertens. 2015;28(3):372-379.
15. Mattos CB, Viana LV, Paula TP, at al. Increased protein intake is associated with uncontrolled blood pressure by 24-hour ambulatory blood pressure monitoring in patients with type 2 diabetes [published online March 11, 2015]. J Am Coll Nutr. doi: 10.1080/07315724.2014.926155.
16. Campbell B, Kreider RB, Ziegenfuss T, et al. International Society of Sports Nutrition position stand: protein and exercise. J Int Soc Sports Nutr. 2007;4:8.
17. Fulgoni VL 3rd. Current protein intake in America: analysis of the National Health and Nutrition Examination Survey, 2003-2004. Am J Clin Nutr. 2008;87(5):1554S-1557S.
18. Mammerow MM, Mettler JA, English KL, et al. Dietary protein distribution positively influences 24-hour muscle protein synthesis in healthy adults. J Nutr. 2014;144(6):876-880.
19. Paddon-Jones D, Rasmussen BB. Dietary protein recommendations and the prevention of sarcopenia. Curr Opin Clin Nutr Metab Care. 2009;12(1):86-90.