June 2014 Issue

The Lowdown on Dairy — A Review on Dairy’s Value in Disease Prevention
By Constance Brown-Riggs, MSEd, RD, CDE, CDN
Today’s Dietitian
Vol. 16 No. 6 P. 30

Decades of research support dairy products’ role in a healthful diet. The 2010 Dietary Guidelines for Americans recommend consuming three daily servings of low-fat and fat-free milk and milk products, such as yogurt and cheese, to help close the gap on three of the four nutrients of public health concern: calcium, potassium, and vitamin D.1 In addition, the Academy of Nutrition and Dietetics, the American Heart Association (AHA), and the DASH diet program all make the same recommendation.

This article will discuss recent evidence of dairy’s health benefits and its value in disease prevention and provide strategies to help clients and patients close the nutrient intake gap and overcome barriers to including dairy in their diets.

Nutrients of Concern
Milk, yogurt, cheese, and other dairy products provide calcium, potassium, and vitamin D to the diet. According to the Dietary Guidelines evidence rating, moderate evidence shows that milk and milk product intake is linked to improved bone health, especially in children and adolescents.1 Moderate evidence also shows that milk and milk product intake is associated with a reduced risk of cardiovascular disease and type 2 diabetes and lower blood pressure in adults.1 The Dietary Guidelines specifically call for an increased intake of low-fat and fat-free milk and milk products as a vehicle to close the nutrient intake gap for calcium, potassium, and vitamin D.

Some experts argue that there’s insufficient evidence to support the recommendation of three servings of dairy per day. In a review of the 2010 Dietary Guidelines, Harvard School of Public Health researchers found little, if any, evidence that eating dairy prevents osteoporosis or fractures and considerable evidence that high dairy intake is associated with an increased risk of fatal prostate and ovarian cancers. According to these researchers, Americans don’t need as much calcium as the Dietary Guidelines recommend. In fact, they suggest limiting dairy to one or two servings per day or taking a calcium and vitamin D supplement instead.2

“Based on the evidence I’ve seen, there’s no need to acquire dairy products in general or on MyPlate,” says Susan Levin, MS, RD, director of nutrition education for the Physicians Committee for Responsible Medicine in Washington, D.C., who believes a plant-based diet is a healthier way to meet calcium, potassium, and vitamin D requirements. However, this may be easier said than done for many people.

“Assuming the Recommended Dietary Allowance of 1,000 to 1,500 mg of calcium per day is correct, it’s difficult, if not impossible, to get that much calcium in the diet without dairy products,” says Densie Webb, PhD, RD, an industry consultant in Austin, Texas. “Even products fortified with calcium typically provide only about 100 mg per serving.”

The Adequate Intake for potassium for adults is 4,700 mg/day. However, in the United States, the consumption of fruits and vegetables, which are high in potassium, is lower than recommended. As a result, dietary intake of potassium is low and, as mentioned, is one of the nutrients of concern in the Dietary Guidelines. “It’s nearly impossible to meet the potassium recommendations without that third serving of dairy,” says Keith-Thomas Ayoob, EdD, RD, FAND, an associate clinical professor in the department of pediatrics at Albert Einstein College of Medicine in the Bronx, New York.

Despite the disagreement over the Dietary Guidelines’ dairy recommendations, the preponderance of evidence continues to support the benefit of dairy as part of a healthful diet and its value in disease prevention and other chronic conditions.

Acne
For example, the association between diet and acne has been around for centuries. During the late 1800s and early 1900s, diet commonly was used as an adjunct treatment for acne. However, during the 1960s, most experts in the dermatology community believed there were no specific foods that played a role in acne prevention and treatment. In recent years, though, there has been a renewed interest in the diet and acne connection.3

In 2006 and 2008, Adebamowo and colleagues used a prospective cohort method to examine the association between milk product consumption and acne among 6,094 teenage girls and 4,273 teenage boys. Study results showed skim milk drinkers had fewer self-reported acne breakouts, but there were no significant associations between acne breakouts and total, whole, and low-fat milk consumption.4

“These studies suggest a correlation, not a cause-and-effect relationship,” says Karen Kafer, RD, vice president of health partnerships for the National Dairy Council. “More research is needed to confirm whether specific foods and/or dietary constituents have a direct effect on acne.” To date there are no randomized controlled trials investigating the relationship between frequent dairy or milk consumption and acne incidence.3

A September 2010 study published in Nutrition examined the effect of the whey milk protein lactoferrin on acne. Participants were randomly assigned to consume fermented milk with 200 mg of lactoferrin daily or fermented milk alone (placebo group). The lactoferrin group showed significant improvements in acne, with significant decreases in inflammatory acne lesion counts and acne grade.4

Although most evidence suggests that total milk consumption is the most critical dairy component that promotes acne, there’s currently insufficient evidence to recommend milk restriction as a treatment for patients with acne.3

Allergy
Over the past decade, the incidence and prevalence of food allergy has increased substantially, leading the American Academy of Pediatrics (AAP) to reevaluate its previous recommendations. In 2000, the AAP recommended a delayed introduction of allergenic foods such as cow’s milk until age 1 as a means of preventing future allergy development.5

In 2008, after a literature review, the AAP’s Committee on Nutrition and Section on Allergy and Immunology determined there was no convincing evidence for delaying the introduction of cow’s milk or other highly allergenic foods—a consensus shared with the European Society for Pediatric Gastroenterology, Hepatology, and Nutrition Committee and the Section on Pediatrics of the European Academy of Allergology and Clinical Immunology.5

The new guidelines state that cow’s milk added to complementary foods in small amounts, such as baked goods, and other dairy products such as yogurt is safe to introduce as early as 4 to 6 months of age.5

New data are emerging that suggest the delayed introduction of allergenic foods may increase the risk of food allergies, and early introduction of highly allergenic foods actually may reduce the risk.5 “The theory behind early introduction is to gradually acclimate the body so that it’s less likely to be recognized as an allergen,” Ayoob says.

A July 2010 study published in the Journal of Allergy and Clinical Immunology suggests that immunoglobulin E–mediated cow’s milk allergy is less common than generally reported, and early exposure to cow’s milk protein via infant formula as a supplement to breast-feeding may promote tolerance. However, the amount of cow’s milk protein needed to prevent cow’s milk allergy wasn’t determined in the study.6

“There’s also some evidence for pregnant women to eat common allergens while pregnant so as to help the infant ward off allergens after birth, but this is in the hypothesis stage and more research is needed,” Ayoob says.

The new guidelines state that pregnant women shouldn’t avoid essential foods such as milk and eggs during pregnancy. Lactating women are advised to follow the same guidelines as pregnant women except for infants who manifest signs of allergic disease shortly after birth because treatment may, in some cases, involve dietary interventions during lactation.3

According to the AAP, current evidence supports the general notion that highly allergenic foods may be introduced earlier in the diet as complementary foods. However, whether the early introduction of highly allergenic foods proves to prevent food allergies remains unanswered. Intervention studies must be performed to support the data from observational studies.

Cancer
Milk and dairy products may have beneficial and adverse effects with regard to the risk of different cancers. In 2007, the World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR) published an authoritative review of existing evidence relating food, nutrition, and physical activity to cancer risk and concluded that milk probably has a protective effect against colorectal cancer, and that diets high in calcium are a probable cause of prostate cancer.7

In the WCRF/AICR Continuous Update Project’s October 2011 review of current scientific evidence, the panel concluded that the new evidence didn’t warrant a change in its initial judgment, as it was consistent with the 2007 evidence, showing that milk probably protects against colorectal cancer. In addition, the panel conducted a meta-analysis that found increased milk intake was associated with a decreased risk of colorectal cancer in eight of 10 new cohort studies. The meta-analysis also showed that increasing dietary calcium by 200 mg/day lowered risk of colorectal cancer by 6%. The panel added that any effect of milk consumption on reducing colorectal cancer risk may be explained at least in part by increased calcium.

Conversely, “The Harvard study provides some of the strongest research against dairy consumption and prostate cancer,” Levin says. In a February 1998 Harvard study of male health professionals, Giovannucci and colleagues found that men who drank two or more glasses of milk per day were almost twice as likely to develop advanced prostate cancer and metastatic prostate cancer than those who didn’t drink milk.8

After a 2011 review, the WCRF/AICR panel stated that there’s substantial and consistent evidence from both cohort and case-control studies that a dose-response relationship exists, and diets high in calcium are a probable cause of prostate cancer. The AICR advises consuming no more than 1,500 mg of calcium from diet and supplements daily.

Bone Health
The benefits of dairy in bone health are well-known. The 2010 Dietary Guidelines, the Institute of Medicine, and the AAP all recognize the importance of dairy foods for bone health, especially in children and adolescents. However, recent evidence suggests not all dairy products are equally beneficial.

A February 2013 study published online in the Archives of Osteoporosis found that dairy intake, specifically milk and yogurt, is associated with higher bone mineral density in the hip but not in the spine. Researchers reviewed data collected from food-frequency questionnaires completed by 3,212 participants from the Framingham Offspring study. Participants’ dairy intake was compared with bone mineral density measurements, which revealed the benefits of milk and yogurt, while evidence suggested that cream may adversely influence bone mineral density.9 Choosing low-fat milk or yogurt over cream can increase intake of protein, calcium, and vitamin D, which contribute to normal bone maintenance.

Weight Control, Heart Disease, and Diabetes
In addition to its association with bone health, research shows that increased milk and yogurt intake is linked to better weight management, reduced hyperglycemia, and decreased hypertension, all risk factors for cardiovascular disease. In a June 2011 prospective study published in The New England Journal of Medicine, researchers examined three separate cohorts of more than 120,000 US women and men followed every four years. Evidence showed that yogurt, fruit, vegetable, and whole grain consumption was associated with less weight gain over time, with yogurt having the greatest impact. In the study, whole milk and cheese consumption was linked with weight gain over the two decades.10

Other research has found that maintaining a healthy weight and eating a nutrient-dense diet can help prevent type 2 diabetes. “Though research isn’t conclusive, some suggest that dairy products can help prevent the disease,” says Jill Weisenberger, MS, RDN, CDE, author of Diabetes Weight Loss — Week by Week.

An August 2013 meta-analysis published in the American Journal of Clinical Nutrition analyzed 17 studies with data from more than 370,000 men and women to determine the relationship between dairy intake and diabetes risk. Evidence suggests there’s a significant inverse association between the intake of dairy products, low-fat dairy products, and cheese and type 2 diabetes risk.11 “For nearly one extra daily glass [6.5 oz], milk drinkers had a 13% lower risk of type 2 diabetes,” Weisenberger says.

Moreover, the type of dairy may be beneficial for the prevention of type 2 diabetes. In a May 2014 study published in Diabetologia, researchers found that higher consumption of low-fat fermented dairy products, largely driven by yogurt intake, was associated with a decreased risk of type 2 diabetes.12

Over the past decade, researchers have investigated the effect of cow’s milk on the development of type 1 diabetes, particularly in individuals at high risk of the disease. To date, no specific dietary factor or nutrient in infancy has been shown to unequivocally play a role in the development of type 1 diabetes.13 More research is needed to confirm the contribution of early dietary factors in type 1 diabetes development.13

The AHA and the DASH diet program both recommend consuming fat-free and low-fat milk and milk products for optimal health. In a January 2013 study in Nutrition Research, researchers examined whether yogurt consumption was associated with better diet quality and metabolic profile among adults. Yogurt consumers compared with non–yogurt consumers had higher potassium intakes, lower levels of circulating triglycerides and glucose, and lower systolic blood pressure and insulin resistance.14

Counseling Clients and Patients
Many individuals miss out on the health benefits of dairy because of real or perceived lactose intolerance. According to the National Institutes of Health, an estimated 30 million to 50 million American adults are lactose intolerant. Some ethnic groups show high levels of intolerance, including about 95% of Asians, 60% to 80% of blacks and Ashkenazi Jews, and 50% to 80% of Hispanics. Yogurt can help individuals with lactose intolerance meet their dairy requirements and obtain calcium, potassium, and vitamin D. Due to the presence of lactase-producing yogurt cultures and because it contains less lactose per serving than milk on average, yogurt is a more easily digestible alternative to milk.10

According to Weisenberger, clients and patients can get three servings of dairy each day by doing the following:

• Eating 1 cup of low-fat yogurt or cottage cheese instead of a few handfuls of potato chips.

• Mixing fresh fruit with low-fat cottage cheese.

• Adding one glass of skim or low-fat milk to a meal instead of tea or a sugary soda.

• Drinking a hot or iced nonfat latté instead of a high-calorie coffee drink.

• Having an 8-oz cup of hot chocolate made with low-fat milk, cocoa powder, and sugar or a nonnutritive sweetener.

• Adding tomatoes, fresh basil, and black pepper to low-fat cottage cheese for a low-carb snack.

• Eating a reduced-fat cheese stick and a handful of raw veggies.

Emerging Research
A body of evidence is emerging that links milk and other dairy products to a reduced risk of heart disease, hypertension, obesity, and type 2 diabetes. Currently, there’s insufficient evidence to recommend milk restriction as a treatment for patients with acne. The AAP supports the early introduction of milk into the diet of infants as young as 4 months of age. Adequate calcium intake from diet and supplements is associated with a lower incidence of colorectal cancer. Conversely, too much calcium from diet and supplements is associated with an increased risk of prostate cancer.

Calcium is necessary for bone health, and the AICR recommends nonfat and low-fat dairy products such as milk, yogurt, and cheese as part of a balanced diet for bone health and cancer prevention.

— Constance Brown-Riggs, MSEd, RD, CDE, CDN, is the nutrition advisor for the Dannon One Yogurt Every Day Initiative; a past national spokesperson for the Academy of Nutrition and Dietetics, specializing in African American nutrition; and the author of The African American Guide to Living Well With Diabetes and Eating Soulfully and Healthfully With Diabetes.

 

References
1. US Department of Agriculture, US Department of Health and Human Services. Dietary Guidelines for Americans, 2010. 7th ed. Washington, DC: US Government Printing Office; 2010.

2. New US Dietary Guidelines: progress, not perfection. Harvard School of Public Health website. http://www.hsph.harvard.edu/nutritionsource/dietary-guidelines-2010

3. Burris J, Rietkerk W, Woolf K. Acne: the role of medical nutrition therapy. J Acad Nutr Diet. 2013;113(3):416-430.

4. Is there a link between acne and milk products? Summary of evidence. Dairy Nutrition website. http://www.dairynutrition.ca/scientific-evidence/roles-on-certain-health-conditions/is-there-a-link-between-acne-and-milk-products-summary-of-evidence. Accessed April 4, 2014.

5. Fleischer DM, Spergel JM, Assa’ad AH, Pongracic JA. Primary prevention of allergic disease through nutritional interventions. J Allergy Clin Immunol Pract. 2013;1(1):29-36.

6. Katz Y, Rajuan N, Goldberg MR, et al. Early exposure to cow’s milk protein is protective against IgE-mediated cow’s milk protein allergy. J Allergy Clin Immunol. 2010;126(1):77-82.

7. Calcium and cancer prevention: strengths and limits of the evidence. National Cancer Institute website. http://www.cancer.gov/cancertopics/factsheet/prevention/calcium. Accessed April 4, 2014.

8. Giovannucci E, Rimm EB, Wolk A, et al. Calcium and fructose intake in relation to risk of prostate cancer. Cancer Res. 1998;58(3):442-447.

9. Sahni S, Tucker KL, Kiel DP, Quach L, Casey VA, Hannan MT. Milk and yogurt consumption are linked with higher bone mineral density but not with hip fracture: the Framingham Offspring Study. Arch Osteoporos. 2013;8(1-2). doi: 10.1007/s11657-013-0119-2.

10. Mozaffarian D, Hao T, Rimm EB, Willet WC, Hu FB. Changes in diet and lifestyle and long-term weight gain in women and men. N Engl J Med. 2011;364:2392-2404.

11. Aune D, Norat T, Romundstad P, Vatten LJ. Dairy products and the risk of type 2 diabetes: a systematic review and dose-response meta-analysis of cohort studies. Am J Clin Nutr. 2013;98(4):1066-1083.

12. O’Connor LM, Lentjes MA, Luben RN, Khaw KT, Wareham NJ, Forouhi NG. Dietary dairy product intake and incident type 2 diabetes: a prospective study using dietary data from a 7-day food diary. Diabetologia. 2014;57(5):909-917.

13. Knip M, Virtanen SM, Akerblom HK. Infant feeding and the risk of type 1 diabetes. Am J Clin Nutr. 2010;91(5)1506S-1513S.

14. Wang H, Livingston KA, Fox CS, Meigs JB, Jacques PF. Yogurt consumption is associated with better diet quality and metabolic profile in American men and women. Nutr Res. 2013;33(1):18-26.

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