5.1 Summary of Key Findings
• Daily intake of 12 oz. of low-fat yogurt or soy pudding did not lead to any changes in weight, BMI, waist circumference, or blood pressure in lean and obese women.
• Daily consumption of 12 oz. of low-fat yogurt increased carbohydrate intake by ~15% in lean and obese women. Soy pudding consumption increased carbohydrate intake in lean women only by ~15%. Low-fat yogurt consumption also significantly decreased protein and cholesterol intake in obese women.
• Daily low-fat yogurt consumption increased vitamin D and calcium intake in lean and obese women. Daily consumption of fortified soy pudding also increased vitamin D intake in lean and obese women and calcium intake in lean women. However, vitamin D intake in lean and obese women in both groups still fell well below the RDA.
• Daily low-fat yogurt consumption increased intake of dairy products by ~1 serving/day in lean and obese women. However, intake still fell below the recommended 3 servings/day. • Daily low-fat yogurt and soy pudding consumption decreased vitamin C intake in lean
women. Fruit intake also decreased in the LY and OY groups. Vegetable intake decreased in the LY and LS groups.
• Co-consumption of low-fat yogurt with a high-calorie, high-fat meal resulted in no significant changes in MDA, SH, or AGEs in the postprandial period, suggesting the low- fat yogurt may attenuate the postprandial response in obese women. However, 9-week daily consumption of low-fat yogurt did not further attenuate this response. Likewise, daily yogurt intake did not alter baseline levels of MDA, SH, or AGEs in obese women. • Co-consumption of soy pudding with a high-calorie, high-fat meal did not attenuate the
significantly decreased compared to week 2 at 2, 3, and 4 h postprandially. Conversely, 9-week daily intake of soy pudding increased baseline levels of MDA in obese women.
In summary, addition of low-fat yogurt to the diet of lean and obese women increased the intake of calcium and vitamin D, two nutrients which are not consumed in adequate amounts by many women [1]. Low-fat yogurt also increased dairy intake by ~1 serving/day in lean and obese women. Though the recommendations for vitamin D and dairy intake were still not met as a result of this intervention, low-fat yogurt could be added to the diet in concert with other dairy products and foods containing vitamin D to help meet recommendations. However, nutritional counseling should be provided to participants to avoid reductions in fruit and vegetable
consumption as a result of the increased dairy intake.
Furthermore, the addition of low-fat yogurt to the diet did not alter BMI, waist circumference, or blood pressure, parameters that are of particular importance to obese women. Co-consumption of low-fat yogurt and a high-calorie, high-fat meal led to suppression of postprandial increases in MDA and AGEs and depletions in SH in obese women at both the initial and final study visits. Sustained intake of soy pudding resulted in small reductions in postprandial MDA from week 2 to week 11; however daily soy pudding intake increased baseline MDA, suggesting that total exposure to MDA was likely unchanged. Conversely, sustained low-fat yogurt consumption showed no effect on chronic levels of oxidative stress in obese women; fasting MDA, SH, and AGEs were unaffected by daily intake. Therefore, addition of low-fat yogurt to the diet of obese women could be employed as a strategy to increase vitamin D, calcium, and dairy intake without any unfavorable changes in body composition, blood pressure, and postprandial or chronic levels of oxidative stress.
5.2 Future Directions
Previous epidemiological and intervention studies support an association between adequate dairy, calcium, and vitamin D intake and numerous favorable health outcomes. In addition, dairy intake decreases oxidative stress in overweight and obese individuals [2, 3]. However, much remains unknown regarding this association. For example, the impact of consumption of
individual dairy products on oxidative stress has not been elucidated. Furthermore, though dairy products contain calcium, vitamin D, protein, whey, casein, numerous bioactive peptides, and probiotics, the effects of these components, alone and in tandem, are unknown. Furthermore, the mechanisms responsible for observed reductions in oxidative stress are not well understood.
Future studies should examine the impact of other types of low-fat yogurt on postprandial and chronic oxidative stress, particularly those products lower in carbohydrates and higher in
probiotics. In the present study, fruit and vegetable intake decreased in some of the study groups as a result of the intervention. Moreover, the addition of low-fat yogurt to the diet raised dairy intake by ~1 serving per day and increased vitamin D intake; however, neither of these increases were sufficient to reach recommendations. Therefore, intervention studies should also be
conducted to examine the impacts of low-fat yogurt intake as a part of a diet rich in fruits and vegetables. Studies should also incorporate the consumption of low-fat yogurt with other dairy products and/or foods rich in vitamin D. Finally, future studies should include more
comprehensive measurements of oxidative stress, including not only the markers used in this study but also the examination of urinary isoprostanes and 8-deoxyguanosine, as well as endogenous antioxidant enzyme activity.
5.3 References
[1] Ross, A. C., The 2011 report on dietary reference intakes for calcium and vitamin D. Public
Health Nutr 2011, 14, 938-939.
[2] Stancliffe, R. A., Thorpe, T., Zemel, M. B., Dairy attentuates oxidative and inflammatory stress in metabolic syndrome. Am J Clin Nutr 2011, 94, 422-430.
[3] Zemel, M. B., Sun, X., Sobhani, T., Wilson, B., Effects of dairy compared with soy on oxidative and inflammatory stress in overweight and obese subjects. Am J Clin Nutr 2009, 91, 16-22.