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Research from the Dairy Research Institute

Study Finds Increased Consumption of Dairy Foods and Protein During Weight Loss Helps Preserve Muscle While Losing Fat

New research indicates that diet- and exercise-induced weight loss with higher protein and increased dairy product intakes improves weight loss quality by promoting more favorable body composition changes in overweight and obese women. The study, co-funded by the Dairy Research Institute™, Dairy Farmers of Canada and the Canadian Institutes of Health Research, was conducted by McMaster University, Ontario, Canada, and is now available online on the Journal of Nutrition website.

Researchers sought to determine how daily exercise and a reduced-calorie diet varying in total protein and dairy foods affected the composition (i.e., muscle and fat) of weight lost.
Press Release

Josse AR, Atkinson SA, Tarnopolsky MA, Phillips SM. Increased consumption of dairy foods and protein during diet- and exercise-induced weight loss promotes fat mass loss and lean mass gain in overweight and obese premenopausal women. J Nutr. [Epub ahead of print]. 2011 July 20.
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Research from the Dairy Research Institute

Supplemental Whey Protein Helps Preserve Muscle in Older Women on a Calorie-restricted Diet

Obese older women with decreased muscle mass and strength are at an increased risk of physical disability. A higher protein, calorie-restricted diet supplemented with whey protein showed a greater maintenance of muscle relative to weight loss compared with a diet higher in carbohydrates and lower in protein in a six-month, double-blind, randomized clinical trial in 26 overweight or obese older women (average age 65 years). The higher vs. lower protein group also showed a trend toward greater weight loss (8 vs. 4 percent body weight).

Meal plans were designed to decrease daily energy intake by approximately 500 calories/day, with a goal of 10 percent weight loss over six months. Participants were randomly assigned to receive a protein supplement (50 grams/day of whey protein isolate) or a carbohydrate supplement (50 g/day maltodextrin). The higher-protein diet provided approximately 30 percent of calories from protein, 40 percent of calories from carbohydrate and 30 percent of calories from fat; the higher-carbohydrate diet provided approximately 18 percent of calories from protein, 52 percent of calories from carbohydrate and 30 percent of calories from fat. Dual-energy x-ray absorptiometry (DXA) and magnetic resonance imaging (MRI) were used to measure muscle and fat changes during the intervention.

There were no differences in strength, balance or physical performance between the protein and carbohydrate groups. However, when data from groups were combined, strength decreased, but balance and physical performance improved from baseline for all subjects. The authors said in order to see a significant effect on physical function, some aspects of the study design may have needed to change, such as having a bigger sample size, providing more whey protein, inducing a greater weight change, using more sensitive performance measures or investigating a population with compromised physical function.

The authors said the improved maintenance of muscle seen in this population indicates that a higher-protein intake can be important during weight loss. This whey protein supplementation study adds to the published literature on the benefits of a higher-protein diet on body composition during weight loss. The study also provides excellent preliminary data for future clinical trials to determine the most beneficial combination of a higher protein diet, weight loss and exercise to improve body composition and physical function in older women.

Mojtahedi MC, Thorpe MP, Karampinos DC, et al. The effects of a higher protein intake during energy restriction on changes in body composition and physical function in older women. J Gerontol A Biol Sci Med Sci. [Epub ahead of print]. 2011 July 27.
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Clinical Trial Shows for the First Time That Milk Protein Lowers Blood Pressure in Those With Prehypertension and Stage 1 Hypertension

Emerging data indicates a potential favorable effect of dietary protein on blood pressure. A clinical trial recently published in Circulation is the first to show that milk protein lowers blood pressure in prehypertensive and stage 1 hypertensive individuals. It also is the first randomized, controlled trial that directly compares the effect of vegetable protein (soy), dairy protein (milk) and carbohydrate on blood pressure. This randomized, double-blind crossover trial among 352 adults (≥22 years) with prehypertension or stage 1 hypertension (120-159 mm Hg/80-95 mm Hg) found that supplementation with 40 g/day of soy protein or milk protein significantly reduced systolic blood pressure by a similar amount (-2.3 mm Hg vs. -2.0 mm Hg, respectively) when compared with a complex carbohydrate control. The authors said a blood pressure reduction of this magnitude is of public health importance.

Participants were assigned to receive one of three supplements (40 g of soy protein, milk protein or carbohydrate powder mixed with juice or water, taken twice a day) in addition to their usual diet in random order for eight weeks each, with three weeks between treatments. Energy intake remained consistent throughout the study period. Average intake of nutrients, other than carbohydrate and protein, was similar among participants, including sodium, potassium and calcium, which are known to influence blood pressure.

National population guidelines have identified several lifestyle modifications important for the prevention and treatment of high blood pressure, including being physically active, maintaining a healthy weight, moderating alcohol consumption, reducing sodium intake, increasing potassium intake and consuming a diet rich in fruits, vegetables and low-fat dairy products. A recent systematic review by Ralston, et al., summarized in the April issue of Dairy Research Insights found that consumption of low-fat dairy foods was associated with reduced risk of elevated blood pressure. The Dairy Research Institute™ is committed to furthering research on the benefits of dairy foods and their components on blood pressure.

He J, Wofford MR, Reynolds K, et al. Effect of dietary protein supplementation on blood pressure: a randomized, controlled trial. Circulation. 2011;124(5):589-595.
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Breakfast Drink Containing Milk Protein Shown to be Better Than Soy Protein Drink for Reducing Weight and Visceral Fat in Obese Japanese Adults

Consumption of a milk protein breakfast replacement drink reduced visceral fat by approximately 15 percent over 20 weeks —demonstrating an important reason to include milk protein at breakfast. A randomized, double-blind, controlled trial compared the effectiveness of a drink containing soy protein with one containing milk protein on changes in visceral fat and other parameters among 48 obese Japanese adults (20-75 years) when consumed as a breakfast replacement for 20 weeks. Over the trial period, visceral fat and subcutaneous fat areas were significantly reduced in the milk protein group, while, contrary to the study hypothesis, those in the soy protein group did not change. While waist circumference was reduced in both the milk protein and soy protein groups, “body weight and body mass index were significantly reduced only in the milk protein group,” reported the authors. Visceral, or intra-abdominal fat, refers to the fat that surrounds the internal organs. Those with visceral fat are more susceptible to heart disease, stroke, diabetes and hypertension. Subcutaneous fat is body fat that is close to the skin’s surface and is considered less dangerous, and easier to lose, than visceral fat.

The soy protein drink contained 12 grams of soy protein, 9.25 g of milk protein (needed to dissolve the soy protein) and a wide range of other nutrients, while the milk protein drink (control) contained 21.9 g and contained more calcium, phosphorus and potassium. Each protein formula was dissolved in a cup of water and was consumed as breakfast. Participants were otherwise encouraged to follow their usual diet with the exception of the breakfast drink.

This study underscores the benefit of including milk protein at breakfast. In addition, the authors said a promising next step would be to identify and isolate the effective components in milk protein. This research could help develop a functional food designed to help reduce visceral fat even more effectively and potentially improve metabolic health.

Takahira M, Noda K, Fukushima M, et al. Randomized, double-blind, controlled, comparative trial of formula food containing soy protein vs. milk protein in visceral fat obesity. Circ J. [Epub ahead of print]. 2011 July 16.
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Higher Intake of Dietary Protein, Including Dairy Protein, Protects Bone in Postmenopausal Women During Weight Loss

Calorie restriction has been associated with bone loss, particularly in older adults. A new study shows that a higher-protein diet (24 percent of total calories) containing recommended* amounts of calcium and vitamin D decreases loss of bone in postmenopausal women during weight loss. This one-year, randomized, controlled trial examined the role of higher protein (24 percent of calories) compared with typical protein (18 percent of calories) during caloric restriction on bone mineral density in 47 postmenopausal women (50-70 years) who had controlled and recommended intakes of calcium and vitamin D. Compared with the typical protein diet, the higher-protein diet that included protein from dairy foods, lean meat, fish and a whey protein supplement significantly slowed loss of bone mineral density at the forearm, lumbar spine and total hip, and slowed loss of trabecular volumetric bone mineral density and bone mineral content of the leg (tibia).“This is the first study to examine the effect of one year of calorie restriction on bone and to demonstrate that dietary protein alone, with calcium and vitamin D at recommended intakes, will attenuate bone loss during calorie restriction,” the authors said.

Participants received a customized 500- to 600- calorie deficit diet plan and participated in group and individual counseling sessions throughout the one-year intervention. They were stabilized to a calcium intake of 1,200 milligrams/day from food and supplements beginning one month prior to the study and throughout the intervention. They also received 400 IU vitamin D₃ from a daily multivitamin.

Although all participants lost bone during weight loss, the higher-protein group lost significantly less at certain sites. This study adds to an emerging body of science indicating that dietary protein may favorably affect bone. It reinforces the idea that dairy foods, as important contributors of protein, calcium and vitamin D to the diet, can be part of effective weight-loss plans.

*Refers to 1997 calcium and vitamin D intake recommendations. These recommendations were updated in December 2010 after this study was accepted for publication.

Sukumar D, Ambia-Sobhan H, Zurfluh R, et al. Areal and volumetric bone mineral density and geometry at two levels of protein intake during caloric restriction: a randomized, controlled trial. J Bone Miner Res. 2011;26(6):1339-1348.
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New Research Explores the Effect of Milk-derived Dietary Proteins on Blood Lipids After a Meal

A high concentration of fat in the blood after a meal (postprandial lipemia) is associated with cardiovascular disease risk and progression. A previous study demonstrated that whey protein reduced postprandial lipemia in those with type 2 diabetes. Based on this previous work, researchers in Denmark investigated the effect of consuming whey protein and/or its subfractions on postprandial lipemia (triglycerides) in nondiabetic obese individuals. Results showed no differences in blood triglyceride concentration between whey treatments, but all treatments beneficially suppressed the concentration of free fatty acids in the blood after the meal – a secondary endpoint of the study.

Three subfractions of whey (whey hydrolysate, alpha-lactalbumin and caseinoglycomacropeptide) and intact whey protein isolate (control) were compared for their effect on postprandial lipemia (triglycerides) when given as a milkshake with a high-fat test meal. Secondarily, the researchers compared the effects of the whey treatments on blood concentration of free fatty acids and on glucose metabolism. Using a crossover design, 11 obese non-diabetic adults were given each of the four milkshakes in random order.

Although all whey treatments suppressed free fatty acids, whey hydrolysate suppressed them the least. Because this study examines the effect at only a single meal, long-term studies among subjects on ordinary diets are needed to further define whey protein’s benefits in terms of lipid metabolism.

Holmer-Jensen J, Hartvigsen ML, Mortensen LS, et al. Acute differential effects of milk-derived dietary proteins on postprandial lipaemia in obese non-diabetic subjects. Eur J Clin Nutr. [Epub ahead of print]. 2011 July 27.
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Higher Intake of Dairy-specific Saturated Fats Associated with Significantly Lower Levels of Inflammatory and Oxidative Stress in Overweight Teens

Research on individual saturated fatty acids continues to demonstrate unique beneficial effects of fatty acids in dairy fat. The authors of a new study concluded, “Dairy-specific saturated fats; i.e., 15:0 and 17:0 fatty acids, may contribute to the potential health benefits of dairy products, especially for overweight adolescents.”

Chronically high levels of inflammatory and oxidative stress markers have been observed in adults and children with excess body fat, and in adults with cardiovascular disease. Although intake of saturated fat may also contribute to inflammation and other cardiovascular risk factors, research has shown that not all saturated fats have the same physiological effects. In fact, elevated levels of two saturated fatty acids — pentadecanoic acid (15:0) and heptadecanoic acid (17:0), found primarily in dairy products — have been linked to lower insulin resistance syndrome, triglycerides and risk of heart attack among adults. Researchers used data from 305 adolescents (average age 15 years) in Minnesota who were enrolled in a larger prospective study to determine whether 15:0 and 17:0 saturated fatty acids in serum phospholipids (an objective measure of dairy intake) were related to six biomarkers of inflammation and oxidative stress, and whether these associations differed between overweight and normal weight teens.

Results showed that higher levels of dairy fatty acids incorporated in serum phospholipids were associated with significantly lower concentrations of three of the inflammatory biomarkers only in overweight adolescents — while all adolescents showed a significantly lower level of a different inflammatory marker. These relationships did not change after adjustment for factors that might influence fatty acid metabolism or contribute to the beneficial effects of dairy foods (i.e., dietary intake of calcium, vitamin D, protein, total flavonoids and omega-3 fatty acids).

Future studies are needed to discover specifically how dairy fatty acids, body fatness and inflammation/oxidative stress influence one another.

Wang H, Steffen LM, Vessby B, et al. Obesity modifies the relations between serum markers of dairy fats and inflammation and oxidative stress among adolescents. Obesity. [Epub ahead of print]. 2011 July 21.
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Cochrane Review Concludes That Reducing Intake or Changing the Type of Fat Consumed May Reduce Risk for Heart Disease but Not Mortality

“There were no clear effects of dietary fat changes on total mortality or cardiovascular mortality,” concludes a recent Cochrane systematic review of randomized controlled trials assessing the effect of reducing or modifying intake of dietary fats on mortality, cardiovascular events (e.g., nonfatal heart attack, angina, stroke, heart failure) and cancer diagnoses. Although the authors did find a reduction in cardiovascular events with dietary fat manipulation (a reduction in total fat and a change in the composition of fat), reducing total fat to 30 percent of calories or increasing amounts of poly- or mono-unsaturated fats alone in the diet had no effect on incidence of heart attacks, stroke, cancer or diabetes. The review also found no clear health benefits of reducing the amount of total fat consumed when replacing it with carbohydrate foods.

Cochrane Reviews are prepared by the Cochrane Collaboration, an international network of medical and public health professionals dedicated to systematically reviewing the effectiveness of health-care interventions. Focusing on disease outcomes (cardiovascular events and mortality) rather than on specific risk factors (e.g., blood pressure, cholesterol level) allowed the researchers to assess the net effect of changing dietary fat intake on all risk factors combined.

Research continues to show that all saturated fatty acids do not have the same effect on cardiovascular health. In fact, the 2010 Dietary Guidelines Advisory Committee (DGAC) suggested that future research should continue to “examine the role of dairy products in modulating lipid profiles, especially through intervention trials in which all types of dairy products, both low and high fat, are fed.” The authors of the DGAC added that “bioactive components that alter serum lipid levels may be contained in milk fat.”

Hooper L, Summerbell CD, Thompson R, et al. Reduced or modified dietary fat for preventing cardiovascular disease (Review). Cochrane Database Syst Rev. 2011;7:CD002137.
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Review Examines Research on Calcium and/or Vitamin D in Weight Regulation

A review by Australian researchers evaluating 22 randomized controlled trials (RCTs) published since 2000 concluded that current evidence “did not consistently support” the contention that calcium and vitamin D accelerate weight or fat loss during calorie restriction. However, studies that increased calcium or vitamin D specifically by increasing servings of dairy foods were excluded from the analysis. In addition, lack of consistent design among the studies examined may have limited the authors’ ability to draw firm conclusions. These include differences in subject characteristics, study execution and compliance, weak statistical power, weight/fat loss being a secondary rather than primary outcome of the analysis and differing baseline calcium intakes of participants.

An abundance of data over the last 10 years has addressed the potential role of calcium and vitamin D in body weight regulation. Overall, the authors said there is good evidence supporting various mechanisms whereby calcium can have an anti-obesity effect; these include stimulating fat oxidation, binding and excretion of fat and up-regulating heat production (thermogenesis). Though some studies favored the hypothesis that increased calcium and/or vitamin D accelerated weight and fat loss during energy restriction, they lacked statistical power.

A recent review of observational data by Dougkas, et al., summarized in the April issue of Dairy Research Insights, supports the role of dairy consumption in weight maintenance and that dietary calcium, especially from dairy products, is associated with a lower body fat and lower body mass index (BMI).

Soares MJ, Chan She Ping-Delfos W, Ghanbari MH. Calcium and vitamin D for obesity: a review of randomized controlled trials. Eur J Clin Nutr. [Epub ahead of print]. 2011 July 6.
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Dairy Foods, Sufficient Calories and Vigorous Physical Activity Are Key Influencers of Bone Mass and Height in Growing Youth

Higher levels of dairy servings, calcium and vitamin D intakes, energy intake, and vigorous physical activity (e.g., running, basketball, soccer, dance) were associated with higher levels of bone mineral content and greater height, after adjustment for age, race and sex, in a large group of black and white teens. Vigorous physical activity was only associated with height in girls. This large study among 660 adolescents (14-18 years) in Georgia investigated the potential inter-relationships between diet and physical activity on bone mineral content, and secondarily, on height, in order to guide interventions that will help youth develop a healthy body composition.

Previously published data from this population found that adolescents who engage in more vigorous physical activity consume more calories than those less physically active, but tend to have relatively low body fat, putting them at lower risk for cardiometabolic disease. It is possible that consuming more calories allows for greater consumption of bone- and growth-enhancing nutrients. This combined with the effect of vigorous activity may have favorable effects not only on risk for cardiometabolic disease, but also on bone health.

Dairy products with calcium and vitamin D provide building material for bone, while vigorous physical activity provides the mechanical stimulation needed to promote bone formation. These results indicate that interventions designed to help youth develop healthy bodies should focus on encouraging physical activity and eating sufficient food and nutrients rather than on negative messages of restricting calories, which may lead to reduced intake of nutrients critically needed for growth.

The results of this study confirm the guiding principles of the in-school nutrition and physical activity program, Fuel Up to Play 60 (FUTP 60), launched by National Dairy Council® and the National Football League®, in collaboration with United States Department of Agriculture. This interactive program, available in schools across the country, encourages youth to consume nutrient-rich foods (low-fat and fat-free dairy foods, fruits, vegetables and whole grains) and achieve at least 60 minutes of physical activity every day. FUTP 60 is designed to engage and empower youth to take action for their own health by implementing long-term, positive changes for themselves and their schools.

Gutin B, Stallmann-Jorgensen IS, Le AH, Johnson MH, Dong Y. Relations of diet and physical activity to bone mass and height in black and white adolescents. Pediatric Rep. 2011;3(2):e10
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