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United States Department of Agriculture

Agricultural Research Service

Completed Studies
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Whey Protein and Blood Pressure

 

Main Study Questions

 

Does the consumption of whey protein, in overweight and obese adult humans fed at weight maintenance; result in reduced systolic and diastolic blood pressure?

 

Motivation for Research

 

Several lines of evidence suggest that consumption of dairy foods, and specifically whey protein, may reduce blood pressure.  This proposed study is designed investigate the effect of whey protein compared to another protein source.

 

Since blood pressure is a recognized risk factor for cardiovascular disease, if there is clear evidence that whey protein reduces blood pressure, dietary recommendations may be made regarding whey protein intake.  However, dietary recommendations to consume whey protein as a means to improve health status must be science-based.  Results from this study will provide a scientific basis for dietary recommendations regarding whey protein intake.

 

 

 

 

 

 

 

 

 

 

 


Lipid Study

 

Main Study Questions

1. Do naturally occurring trans fatty acids raise LDL cholesterol in when compared to trans fatty acids from partially hydrogenated vegetable oils?

2.  Do naturally occurring trans fatty acids raise LDL cholesterol compared to a control diet?

3.  Do trans fatty acids from partially hydrogenated vegetable oil raise LDL cholesterol compared to a low trans fatty acid diet?

Motivation for Research

There are two primary sources of dietary trans fatty acids in the food supply: 1) those from partially hydrogenated vegetable oils and 2) those found naturally in ruminant products (e.g., dairy, beef, lamb).

Since dietary trans fatty acids have been linked to cardiovascular disease, recent food labeling regulations have required that the trans fatty acid content of certain foods be listed on the Nutrition Facts panel. 

It is unclear if all isomers of trans fatty acids have the same effect on risk factors for cardiovascular disease.  Results from animal studies suggest that some naturally occurring trans fatty acids may actually lower cholesterol and decrease plaque buildup in arteries. 

The aim of this study is to determine if the different trans fatty acid isomers have different effects on markers for heart disease. The U.S. Department of Agriculture (USDA) wants to learn about how different types of fat in your diet can change your cholesterol level.

The study was completed in September 2009.

 

 

 

 

 

 

 


Pistachio Study

 

Main Study Questions

The objective of this study is to measure the energy value of pistachios in the human diet and study molecular mechanisms that may help explain the beneficial health effects of pistachios.

Motivation for Research

The aim of this study is to determine the energy value of pistachios in the human diet and to probe mechanisms by which pistachios impart health benefits. The metabolizable energy value of pistachio nuts will be calculated based on the chemical composition and energy content of the consumed diet and excreta. In addition to determining the energy value of pistachios, we will evaluate the effects of pistachio-rich diets on plasma phytonutrient levels and on gene expression changes to determine what protective mechanisms are activated by pistachio consumption.

The study ran from the beginning of October through December 2009. 

 

 

 

 

 

 

 


Almond Study

 

Main Study Questions

The objective of this study is to measure the energy value of almonds in the human diet and study molecular mechanisms that may help explain the beneficial health effects of almonds.

Motivation for Research

The aim of this study is to determine the energy value of almonds in the human diet and to probe mechanisms by which almonds impart health benefits. The metabolizable energy value of the almonds will be calculated based on the chemical composition and energy content of the consumed diet and excreta. In addition to determining the energy value of almonds, we will evaluate the effects of almond-rich diets on plasma phytonutrient levels and on gene expression changes to determine what protective mechanisms are activated by almond consumption.

The study ran from mid-March 2010 until the end of May 2010.

 


Garlic 2010 Study

 

 

Main Study Question

Does ingestion of garlic result in gene expression changes consistent with decreased risk of cancer?

Motivation for Research 

There is a significant body of epidemiological evidence linking intake of certain vegetables with decreased risk of several cancers. Consumption of garlic (Allium sativum L.) has been associated with prevention of breast, colorectal, lung, liver, and stomach cancers. The epidemiological evidence for the cancer preventive properties of garlic has been supported by cell and animal studies, but there is a significant need to conduct human studies that investigate the efficacy of garlic for cancer prevention. In particular, we propose to investigate whether garlic consumption causes gene expression changes that reflect protection against DNA damage, oxidative stress, or inflammation, all of which are associated with cancer risk.

The study ran from the end of July through August 2010.

 

 


Anthocyanin Study

 

Main Study Question

Is absorption efficiency of anthocyanins from strawberries and blackberries affected by gastric pH? 

Motivation for Research 

Consumers are increasing consumption of anthocyanin-rich foods, especially berries, as a strategy to prevent chronic diseases including cancer, heart disease and diminished brain function.  In order for anthocyanins to reach internal tissues and provide purported protection, they must be absorbed from the gastrointestinal tract.  This research is aimed at identifying the site of anthocyanin absorption in humans and the degree to which pH influences transfer of anthocyanins from the GI tract to the bloodstream.  An understanding of these factors will lead to strategies for enhancing efficiency of absorption of anthocyanins.

The study ran from the end of July to mid- October 2010.


Cranberry Study

 

Main Study Question

The objective of this study is to determine the influence of cranberry juice on risk factors for cardiovascular disease (CVD).

Motivation for Research 

Previous studies have shown that consumption of a low calorie cranberry beverage imparts a favorable impact on HDL cholesterol, LDL oxidation, and cell adhesion molecules in men. However, these studies were not well controlled.  Thus, it is important to confirm these effects in a blinded, placebo-controlled feeding study.        

The study ran from the end of September to end of November 2010.


Whole Grain Acute Study

 

Main Study Question

The objectives of this study were the following:  1) to determine the acute effect of whole grain barley on risk factors of cardiovascular disease compared to a diet low in whole grain, and 2) to compare the effects of whole grain barley to those of whole grain oats to determine if the response to these two grains is similar. 

Motivation for Research

Increasing whole grain intake is associated with decreased risk of biomarkers of cardiovascular disease and diabetes.  Whole grains contain bioactive components that may contribute to reduced risk of cardiovascular disease, and there may be significant differences among whole grain sources with respect to ability to alter biomarkers of cardiovascular disease.  Research has focused on the effect of whole grains on lipoprotein changes (particularly LDL cholesterol concentration).  Whole grains can also alter glucose and lipid response after a meal.  Emerging evidence suggests that glucose and lipid response after a meal alters endothelial function (proper reactivity of blood vessels) and contributes to insulin resistance.  This acute study is designed to determine if whole grain barley improves lipid metabolism and endothelial function after a meal.  Further, we will determine if acute consumption of whole grain barley verses acute consumption of whole grain oats results in differential response with respect to biomarkers of cardiovascular disease risk.  

The study ran from mid-February to end of April 2011.


Blackberry Study

 

Main Study Question

The objective of this study is to investigate whether blackberry consumption causes biomarker and gene expression changes that reflect protection against DNA damage, oxidative stress, or inflammation, all of which are associated with cancer risk.

Motivation for Research

There is a significant body of epidemiological evidence linking intake of certain fruits and vegetables with decreased risk of several cancers. Consumption of berries or foods high in anthocyanins has been associated with prevention of breast, colorectal, esophageal, skin, lung, and liver cancers. The epidemiological evidence for the cancer preventive properties of berries has been supported by cell and animal studies, but there is a significant need to conduct human studies that investigate the efficacy of berries for cancer prevention. In particular, we propose to investigate whether blackberry consumption causes biomarker and gene expression changes that reflect protection against DNA damage, oxidative stress, or inflammation, all of which are associated with cancer risk.

The study ran from mid-March to early May 2011.


Whole Grain Daily Intake Study

 

Main Study Question

The objectives of this study were the following:  1) to determine the effect of daily consumption of whole grain barley for six weeks on risk factors of cardiovascular disease compared to a diet low in whole grains, and 2) to compare the effects of daily consumption of whole grain barley to those of whole grain oats for six weeks to determine if the response to these two grains is different. 

Motivation for Research

Increasing whole grain intake is associated with decreased risk of biomarkers of cardiovascular disease and diabetes.  Whole grains contain bioactive components that may contribute to reduced risk of cardiovascular disease, and there may be significant differences among whole grain sources with respect to ability to alter biomarkers of cardiovascular disease.  Research has focused on the effect of whole grains on lipoprotein changes (particularly LDL cholesterol concentration).  Whole grains can also alter postprandial glucose and lipid response, and changes in postprandial lipemia is thought to be particularly important since much of the time blood contains fat from the previous meal.  Emerging evidence suggests that postprandial lipemia alters endothelial function (proper reactivity of blood vessels) and contributes to insulin resistance.  This study is designed to determine if daily intake for 6 weeks of whole grain barley improves markers of cardiovascular disease in the fasted and postprandial states.  Further, we will determine if daily consumption of whole grain barley vs. daily consumption of whole grain oats results in differential response with respect to biomarkers of cardiovascular disease risk. 

The study ran from mid-January to end of July 2011.


Grape Juice Study

 

Main Study Questions

The objective of this study is to learn about the absorption and metabolism of grape polyphenols by the human body that may help explain the beneficial health effects of grapes.

Motivation for Research

The aim of this study is to learn about the absorption and metabolism of grape polyphenols by the human body. Polyphenols are healthful compounds found throughout the fruits and vegetables in our diets.  Polyphenols seem to help reduce risk of many diseases, and appear to be effective in preventing and reversing memory loss.

The study ran from mid-September to mid-October 2011.


AGE Study

 

Main Study Question

To conduct a controlled dietary intervention trial of high versus low dietary intake of advanced glycation end products (AGEs).

Motivation for Research

Advanced glycation end products (AGEs), bioactive molecules formed by the non-enzymatic glycation of proteins, are emerging as a possible dietary risk factor for many key adverse health outcomes related to obesity and to aging.  When food is heated to high temperatures, the characteristic “browning” generates AGEs.  The Western diet is rich in AGEs that are formed when food is processed at high temperatures, for example, fried chicken, french fries, hamburgers, hot dogs, sausages, potato chips, pretzels, heated milk products, and processed cheeses.

Although AGEs have been implicated in various chronic diseases, the possible adverse effects of dietary AGEs have not been well characterized in humans.  This study will investigate the effects of a high and low AGE diet on risk factors of cardiovascular disease, within the context of a controlled diet.

This study ran from early October to mid-November 2011.


Plant Sterol Study

 

Main Study Question

The objective of this study is to determine how individual genetic profiles influence the effect of plant sterols (natural plant compounds) on cholesterol and fat metabolism.

 

Motivation for Research

Numerous studies have shown that consumption of plant sterols and stanols can effectively reduce LDL-cholesterol. However, growing research has shown that not all individuals respond equally to doses of plant sterols and stanols. This study will examine the genetic basis for differing responses to plant stanol consumption. The long-term goal is to predetermine who will, and will not, respond to plant sterols as functional food ingredients.

The study ran from mid-November to mid-February 2012.

 

 

 

 


Avocado Study

 

Main Study Questions

The objective of this study is to determine the effect of daily avocado consumption on vascular health, including endothelial function and blood pressure.

Motivation for Research

Ongoing research is being conducted to assess the effect of avocado consumption on blood lipids and lipoproteins; however, cardiovascular disease is a disease with multiple etiologies reaching beyond those associated with changes in lipids and lipoproteins. The effects of avocado consumption on endothelial function and blood pressure are unknown. Additional research with avocados is needed to determine the effects of this fruit on vascular health beyond cholesterol.

The study ran from early June to mid-July 2012.


Pomegranate Juice Study

 

Main Study Questions

The objective of this study is to determine if consumption of pomegranate juice, a polyphenol-rich juice, can ameliorate the endothelial dysfunction resulting from consumption of a high fat meal.    

Motivation for Research

Cardiovascular disease remains a major killer in the United States and throughout the world. Many mechanisms contribute to risk for cardiovascular disease, including the responsiveness of blood vessels to perturbations.  Diet has been shown to influence blood vessel responsiveness. The aim of this study is to investigate the ability of polyphenol-rich fruit juice (pomegranate juice) to improve blood vessel reactivity after a high fat meal. 

The study ran from early December 2012 to mid-January 2013.


Metabolic Flexibility Study

 

Main Study Questions

The objective of this study is to develop a new metabolic flexibility biomarker, which has application in the study of changes in diet and exercise on fuel management in humans.

Motivation for Research

The aim of this study is to examine the relationship between exercise intensity and duration on whole body fuel use and substrate supply over 24 hour periods of time. The unique aspect of this work is the long time frame of measurement (24 hours) while measuring the dynamics (2 minute interval) of energy expenditure and substrate utilization. The new biomarker involves the characterization of an individual’s metabolic flexibility utilizing room calorimeters rather than the current method, which is based on glucose clamp data.

The study ran from mid-December 2012 to late June 2013.


Walnut Study

 

Main Study Question

The objective of this study is to measure the energy value of walnuts in the human diet and study molecular mechanisms that may help explain the beneficial health effects of walnuts.

Motivation for Research

Previous studies have demonstrated that nut consumption imparts a variety of health benefits, including reduction of cardiovascular disease and improved satiety. The aim of this study is to determine the energy value of walnuts in the human diet and to probe mechanisms by which walnuts impart health benefits. The metabolizable energy value of walnuts will be calculated based on the chemical composition and energy content of the consumed diet and excreta. This will provide a better estimate of the energy value of walnuts than simply calculating energy value based on Atwater factors (4 kcal/g of carbohydrate, 4 kcal/g of protein, 9 kcal/g of fat). In addition to determining the energy value of walnuts, we will evaluate the effects of walnut-rich diets on plasma phytonutrient levels and on gene expression changes to determine what protective mechanisms are activated by walnut consumption.

The study ran from early May to end of June 2013.


Blackberry & Fat Oxidation Study

 

Main Study Question

How does consumption of blackberries affect the body’s fuel management?

Motivation for Research

The most recent statistics from the World Health Organization show that 1.5 billion adults are overweight, with 500 million of these adults being classified as obese. Worldwide, obesity has more than doubled in the last 30 years. The aim of this work is to seek dietary influences that can alter the body’s fuel management to reduce body fatness. Studies in animals have suggested that berry preparations or anthocyanin-rich berry extracts can reduce body fatness. Previous studies with tea catechins, which belong to the flavonoid class of chemicals as do anthocyanins, suggest that these compounds can alter fat oxidation, and this may be the mechanism by which body fatness is influenced by anthocyanin intake. However, well-controlled studies in humans are lacking.

The study ran from early July to end of September 2013.


Blackberry Microbiota Study

 

Main Study Questions

How does consumption of blackberries affect intestinal bacteria and is the effect different for obese and non-obese individuals?

Motivation for Research

There is an increasing appreciation for the importance of intestinal bacteria in impacting health. Intestinal bacteria can metabolize unabsorbed polyphenols (plant compounds) to produce smaller molecules which may impact health.  In addition, evidence suggests that this process may be affected by body fatness. This study aims to investigate absorption of blackberry polyphenols, their impact on intestinal bacteria, polyphenol metabolites formed by intestinal bacteria, and how these processes differ for obese and lean individuals. 

The study ran from mid-November 2013 to early April 2014.


Almond Processing Study

 

Main Study Question

The objective of this study is to measure the effect of processing (roasting, slicing, or grinding) on the energy value of almonds in the human diet and study molecular mechanisms that may help explain the beneficial health effects of almonds.

Motivation for Research

Previous studies have demonstrated that the measured energy value of almonds (dry roasted) is lower than predicted using the Atwater factors (4 kcal/g of carbohydrate, 4 kcal/g of protein, 9 kcal/g of fat). However, data are lacking on the effect of processing (roasting, slicing, or grinding) on nutrient bioavailability of almonds. The aim of this study is to determine the energy value of 4 different forms of almonds in the human diet: whole, natural almonds, roasted whole almonds, diced almonds, and almond butter. We will also probe mechanisms by which almonds impart health benefits. The metabolizable energy value of almonds and almond butter will be calculated based on the chemical composition and energy content of the consumed diet and excreta. This will provide a better estimate of the energy value than simply calculating energy value based on Atwater factors. In addition to determining the metabolizable energy, we will evaluate the effects of almond-rich diets on plasma phytonutrient levels and on gene expression changes to determine what protective mechanisms are activated by almond consumption.

The study ran from early March to end of July 2014.


Last Modified: 11/24/2014