Research Roundup: Yogurt, Vitamin K, Blood Pressure and More
In this edition, we cover new research on yogurt and its beneficial associations with bone health in older adults and on body composition/metabolic health, measuring the amount of different forms of vitamin K in dairy foods, the role of dairy foods in diets that support healthy blood pressure and more.
Frequency of yogurt consumption is associated with better bone health and physical function, especially in older women
A study of more than 4,000 older (>60 years) Irish adults showed eating yogurt daily was associated with a 31 percent decreased risk of low bone density (osteopenia) in women, a 39 percent lower risk of osteoporosis in women and a 52 percent lower risk of osteoporosis in men. Women who ate yogurt more frequently vs. no yogurt also had significantly higher hip and femoral neck bone mineral density and scored higher on assessment of ability to perform activities of daily living. No significant difference in measures of bone mineral density (with one exception) or performance of activities of daily living was seen in men. Frequency of milk and cheese consumption was not linked to bone mineral density, and for milk, measures of physical function were higher for those who consumed no milk.
Individual dairy foods are linked to distinct effects on health
Foods have complex physical structures and nutrient content that may influence health in ways that cannot be predicted by looking at the nutrition label. That was the premise of an expert panel workshop that evaluated the differential health effects of dairy foods (i.e., milk, yogurt and cheese), and found 1) Current evidence indicates consuming dairy foods is not associated with an increased risk of cardiovascular disease or Type 2 diabetes – and fermented dairy foods such as cheese and yogurt, generally are associated with slightly lower risk of these chronic diseases; 2) Results of intervention studies indicate that the effect of dairy foods (i.e. milk, yogurt and cheese) on body weight, cardiometabolic disease risk and bone health may be different than that of single dairy components (i.e. calcium, protein, saturated fat); 3) Different dairy foods seem to be linked to distinctive health effects and markers of disease risk.
The vitamin K content of dairy foods may be higher than previously thought
Vitamin K is an essential, fat-soluble vitamin that is crucial for blood clotting, bone metabolism, cell cycle regulation and cardiovascular health and is measured and commonly included in nutrient content databases. While vitamin K1 is plant-based, vitamin K2 (menaquinones or MK), on the other hand, is limited to animal and fermented foods and has not been analyzed in U.S. foods and as a result, has not been included in consumption surveys. Researchers at the USDA Human Nutrition Research Center on Aging at Tufts University quantified vitamins K1 and K2 in milk, yogurt, Greek yogurt, cream and cheeses. Although historically, dairy foods have not been considered a rich dietary source of vitamin K because of low vitamin K1 levels, results from this study showed that dairy foods available in the U.S., especially whole milk dairy foods, could contribute vitamin K2 to the US diet.
Supplemental dietary protein may help build muscle during resistance training
A systematic review and meta-analysis of 49 randomized, controlled trials found that dietary protein supplementation enhanced gains in fat-free mass (including muscle) and strength when paired with regular resistance exercise training in healthy adults. Sources of protein included whey protein, casein, soy, milk, yogurt and others. However, the researchers found that eating more than 1.6 grams of total protein per kilogram of body weight each day provided no further gains in fat-free mass. Subgroup analyses found that protein supplementation was more effective at improving fat-free mass in young (<45 years) vs. older (>45 years) participants and was more effective at improving fat-free mass in trained vs. untrained people. This meta-analysis provides important new findings and includes more than double the number of studies and participants as the largest meta-analysis published on this topic to date.
Eating yogurt is associated with benefits to body composition and metabolic health in a study of Canadian adults
A cross sectional analysis found men and women who ate one or more servings of yogurt per day had lower BMI, waist circumference, and percent body fat and fat mass, along with a better glycemic profile (i.e., fasting insulin and C-peptide), compared with those who didn’t eat yogurt. After accounting for diet quality, these observations remained for men and only the glycemic factors were seen in women. These findings were maintained after six years of follow up. The authors speculate that yogurt’s unique structure and composition – including protein, bioactive peptides and live bacterial cultures – may have contributed to the metabolic benefits seen in this study. Still, randomized controlled trials are needed to confirm these findings.
Consumption of dairy foods/nutrients included in evidence-based guidelines for managing high blood pressure
Trained evidence analysts evaluated and rated a total of 70 research studies to provide the most current evidence-based recommendations to support Registered Dietitian Nutritionists (RDNs) and other health professionals involved in the dietary management of high blood pressure in adults. The Evidence Analysis Library guidelines for the nutrition therapy and management of high blood pressure in adults (18+ years) states there is strong evidence to recommend 1) medical nutrition therapy by an RDN 2) adoption of the Dietary Approaches to Stop Hypertension eating pattern 3) calcium supplementation 4) physical activity as part of a healthy lifestyle 5) reduction in dietary sodium and 6) reduction of alcohol consumption in heavy drinkers. There was fair evidence to recommend increasing consumption of potassium and calcium from foods, such as dairy foods, as well as supplementing with potassium and magnesium to help lower blood pressure.
Dairy consumption is not associated with mortality in certain populations
The relationship between dairy consumption and mortality in non-Western countries with lower relative dairy consumption has not been well studied. A prospective study among more than 42,000 Iranian adults found that eating an average of 2.4 servings of dairy foods (milk, yogurt or cheese) a day vs. only one-half serving per day, was associated with a 28 percent lower risk of dying from cardiovascular disease and a 19 percent lower risk of dying from any cause, particularly if the participant was not obese. Eating whole-milk dairy foods was not associated with greater mortality, and neither total dairy nor individual dairy foods were associated with overall deaths from cancer.