The purpose of this study is to define whether the acute consumption of low-fat milk protects against postprandial vascular endothelial dysfunction by reducing oxidative stress responses that limit nitric oxide bioavailability to the vascular endothelium. The investigators hypothesis is that the consumption of low-fat milk will improve postprandial vascular endothelial function in an oxidative stress-dependent manner that allows greater nitric oxide (NO) bioavailability. The objectives of this study are to 1) examine improvements in postprandial vascular endothelial function in response to low-fat milk ingestion, 2) define low-fat milk-mediated improvements in circulating biomarkers of redox status, and 3) define the mechanism by which low-fat milk improves NO bioavailability. Collectively, the successful completion of these studies is expected to define NO mediated activities of low-fat milk that protect against vascular endothelial dysfunction in individuals at high risk for developing CVD.

Cardiovascular disease (CVD) is the leading cause of death in the United States, accounting for ~830,000 deaths annually. Oxidative stress and inflammatory responses are fundamental mechanisms leading to vascular endothelial dysfunction because of their role in reducing nitric oxide (NO) bioavailability. Greater intakes of dairy foods have been associated with a lower incidence of CVD-related morbidity. Although the mechanisms by which dairy protects against CVD remain unclear, epidemiological and experimental evidence suggest that the concerted actions of bioactive milk-derived peptides and micronutrients may protect against hypertension and future CVD risk by improving vascular endothelial function. Therefore, the objective of this study is to define the mechanisms by which the acute consumption of low-fat milk protects against postprandial vascular endothelial dysfunction by reducing oxidative stress responses that limit NO bioavailability to the vascular endothelium. In this study, participants having the metabolic syndrome will ingest low-fat milk or rice milk on a single occasion. Then, vascular function and biomarkers of oxidative stress and NO metabolism will be monitored at 30 min intervals throughout a 180 min postprandial period. Collectively, these studies will help identify how postprandial vascular function is regulated in individuals at high-risk for CVD, and whether low-fat dairy consumption can be used as a strategy to better improve vascular function.

Inclusion Criteria:

• specific criteria of the metabolic syndrome (waist circumference (102-137 or 88-123 cm for men and women, respectively), fasting triglycerides 150-300 mg/dL, and fasting glucose (110-180 mg/dL)
• BMI: >30 kg/m2,
• non-dietary supplement users for >2-mo
• no use of any prescription or over-the-counter medications known to affect vasodilatory responses
• no known history of vascular disease
• nonsmokers
• resting blood pressure <140 mmHg
• not taking any medications that control hypertension

Exclusion Criteria:

• lactose-intolerant
• excessive alcohol consumption (>3 drinks/d or >10 drinks/wk)
• >7 h/wk of aerobic activity
• use of medications known to affect carbohydrate or lipid/lipoprotein metabolism
• regular use of any anti-inflammatory medications (e.g. aspirin, non-steroidal anti-inflammatory drugs) or over-the-counter aids (e.g. fish oils)
• women who are pregnant, lactating, and have initiated or changed birth control in the past 3-mo