Ignite Creation Date:
2024-05-05 @ 9:36 AM
Last Modification Date:
2024-10-26 @ 9:01 AM
Study NCT ID:
NCT00000538
Status:
COMPLETED
Last Update Posted:
2024-02-22
First Post:
1999-10-27
Brief Title:
Dietary Effects on Lipoproteins and Thrombogenic Activity
Sponsor:
University of North Carolina Chapel Hill
Organization:
University of North Carolina Chapel Hill
Study Overview
Official Title:
None
Status:
COMPLETED
Status Verified Date:
2014-08
Last Known Status:
None
Delayed Posting:
No
If Stopped, Why?:
Not Stopped
Has Expanded Access:
False
If Expanded Access, NCT#:
N/A
Has Expanded Access, NCT# Status:
N/A
Acronym:
DELTA
Brief Summary:
To evaluate the effects of carefully controlled diets on lipoproteins and clotting factors in different demographic groups
Detailed Description:
BACKGROUND
A solid foundation of epidemiologic clinical and laboratory evidence underlies the current dietary recommendations for population-based prevention of coronary heart disease Average blood cholesterol levels will decline with the consumption of less saturated fat and cholesterol than has been traditional in the United States It is not clear however whether reductions in total fat intake are necessary as well More research also is needed to define how best to provide a national food supply whose composition will enhance efforts to reduce coronary heart disease risk Fatty acid investigations are especially critical because this is an area in which the food industry has greater latitude in reformulating products according to current scientific evidence dietary recommendations and customer demand Stearic acid for example may be suitable as a replacement for hard fatty acids because it has relatively little effect on total blood cholesterol levels but it may be rendered less suitable for this purpose if it accelerates the tendency of blood to clot Similarly hydrogenated vegetable oils are used as substitutes for saturated animal fats but they contain trans-fatty acids that may raise low-density lipoprotein levels as do saturated fatty acids In general the mechanisms by which diet influences the eventual development of atherosclerosis through alterations in lipid and lipoprotein levels and metabolism and through other factors such as hemostasis still are not fully understood
Human clinical nutrition studies when feasible are among the best research approaches for addressing the links between diet and atherosclerosis Moreover because of their great relevance to everyday life their findings are quickly publicized Often however such studies do not yield consistent or reproducible results The resulting transmission of mixed messages to the scientific and lay communities seriously undermines both the credibility of nutrition research and the publics confidence in the possibility of obtaining reliable and practical advice on how to modify diet Oat bran with its rise and fall in the scientific and popular press as well as in the marketplace is a good example of this phenomenon
The lack of consistency among designs of clinical nutrition studies seeking to answer the same scientific question for example the influence of dietary fiber on serum cholesterol levels means that their results cannot be readily compared Some study designs are flawed lacking adequate hypotheses and control groups In addition compliance in dietary studies is frequently less than ideal Studies that allow participants to select and prepare their own food even when adhering to an experimental diet frequently do not provide reliable results Only in tightly controlled clinical settings in which the participants receive all food from the experimental kitchen and are known to consume it can the influence of poor compliance be minimized
A further complication is that the actual composition of study diets may not be as intended due to natural variations in food sources and the vagaries of food composition databases Such discrepancies can be sufficient to alter the results of the study and lead to false conclusions yet research budgets seldom allow for the high cost of food composition analyses
The typical small size of clinical nutrition studies has far-reaching effects Because these studies are expensive and require great commitments of labor and space it generally is very difficult for a single investigator funded by a traditional research grant to enroll feed and study more than 20 to 25 participants at one time This imposes constraints on duration design and statistical power consequently many human nutrition studies lack sufficient power to detect biologically meaningful differences between groups or treatments To avoid outside sources of variability that would further reduce study power investigators usually make efforts to assemble a homogeneous study population and minimize the number of factors that might impinge on the experimental design thus studies are most often conducted in young Caucasian males with average or even low plasma cholesterol levels Not much is known therefore about how response to diet is affected by sex age race co-morbid conditions such as obesity lipoprotein phenotype and other factors that would make the results more generalizable to the population at large Furthermore the mechanisms underlying the so-called hypo-responder phenomenon wherein individuals are presumed to be insensitive to the effects of diet on plasma lipid levels cannot be elucidated unless individuals with a wide range of response are studied in adequate numbers
The Arteriosclerosis Hypertension and Lipid Metabolism Advisory Committee recommended the development of the initiative at their February 1991 meeting The National Heart Lung and Blood Advisory Council approved the concept at its September 1991 meeting
DESIGN NARRATIVE
The first protocol conducted in 1993-1994 compared the effects of three diets varying in total fat 37 percent 30 percent and 26 percent and saturated fat 16 percent 9 percent and 5 percent on plasma lipoprotein and thrombogenic activity in 103 normal adults Subjects consumed the three diets for eight weeks each Ten meals per week were consumed on-site and all other food was packed for take-home use
The second protocol conducted in 1994-1995 examined lipoprotein levels and hemostatic parameters in 86 subjects having low high density lipoprotein levels andor high triglyceride levels andor high insulin levels and consuming for seven weeks each one of three diets a typical American diet a high monounsaturated fat diet or a high carbohydrate diet
DELTA also expended considerable effort in the field of food composition analysis Menus were analyzed chemically to verify their composition and to ensure that the nutrient content did not differ significantly among field centers and diet periods Food composition analysis research was conducted at Virginia Polytechnic and State University in consortium with the University of North Carolina
The study was active through August 31 1999 under grant U01-HL-49644
A solid foundation of epidemiologic clinical and laboratory evidence underlies the current dietary recommendations for population-based prevention of coronary heart disease Average blood cholesterol levels will decline with the consumption of less saturated fat and cholesterol than has been traditional in the United States It is not clear however whether reductions in total fat intake are necessary as well More research also is needed to define how best to provide a national food supply whose composition will enhance efforts to reduce coronary heart disease risk Fatty acid investigations are especially critical because this is an area in which the food industry has greater latitude in reformulating products according to current scientific evidence dietary recommendations and customer demand Stearic acid for example may be suitable as a replacement for hard fatty acids because it has relatively little effect on total blood cholesterol levels but it may be rendered less suitable for this purpose if it accelerates the tendency of blood to clot Similarly hydrogenated vegetable oils are used as substitutes for saturated animal fats but they contain trans-fatty acids that may raise low-density lipoprotein levels as do saturated fatty acids In general the mechanisms by which diet influences the eventual development of atherosclerosis through alterations in lipid and lipoprotein levels and metabolism and through other factors such as hemostasis still are not fully understood
Human clinical nutrition studies when feasible are among the best research approaches for addressing the links between diet and atherosclerosis Moreover because of their great relevance to everyday life their findings are quickly publicized Often however such studies do not yield consistent or reproducible results The resulting transmission of mixed messages to the scientific and lay communities seriously undermines both the credibility of nutrition research and the publics confidence in the possibility of obtaining reliable and practical advice on how to modify diet Oat bran with its rise and fall in the scientific and popular press as well as in the marketplace is a good example of this phenomenon
The lack of consistency among designs of clinical nutrition studies seeking to answer the same scientific question for example the influence of dietary fiber on serum cholesterol levels means that their results cannot be readily compared Some study designs are flawed lacking adequate hypotheses and control groups In addition compliance in dietary studies is frequently less than ideal Studies that allow participants to select and prepare their own food even when adhering to an experimental diet frequently do not provide reliable results Only in tightly controlled clinical settings in which the participants receive all food from the experimental kitchen and are known to consume it can the influence of poor compliance be minimized
A further complication is that the actual composition of study diets may not be as intended due to natural variations in food sources and the vagaries of food composition databases Such discrepancies can be sufficient to alter the results of the study and lead to false conclusions yet research budgets seldom allow for the high cost of food composition analyses
The typical small size of clinical nutrition studies has far-reaching effects Because these studies are expensive and require great commitments of labor and space it generally is very difficult for a single investigator funded by a traditional research grant to enroll feed and study more than 20 to 25 participants at one time This imposes constraints on duration design and statistical power consequently many human nutrition studies lack sufficient power to detect biologically meaningful differences between groups or treatments To avoid outside sources of variability that would further reduce study power investigators usually make efforts to assemble a homogeneous study population and minimize the number of factors that might impinge on the experimental design thus studies are most often conducted in young Caucasian males with average or even low plasma cholesterol levels Not much is known therefore about how response to diet is affected by sex age race co-morbid conditions such as obesity lipoprotein phenotype and other factors that would make the results more generalizable to the population at large Furthermore the mechanisms underlying the so-called hypo-responder phenomenon wherein individuals are presumed to be insensitive to the effects of diet on plasma lipid levels cannot be elucidated unless individuals with a wide range of response are studied in adequate numbers
The Arteriosclerosis Hypertension and Lipid Metabolism Advisory Committee recommended the development of the initiative at their February 1991 meeting The National Heart Lung and Blood Advisory Council approved the concept at its September 1991 meeting
DESIGN NARRATIVE
The first protocol conducted in 1993-1994 compared the effects of three diets varying in total fat 37 percent 30 percent and 26 percent and saturated fat 16 percent 9 percent and 5 percent on plasma lipoprotein and thrombogenic activity in 103 normal adults Subjects consumed the three diets for eight weeks each Ten meals per week were consumed on-site and all other food was packed for take-home use
The second protocol conducted in 1994-1995 examined lipoprotein levels and hemostatic parameters in 86 subjects having low high density lipoprotein levels andor high triglyceride levels andor high insulin levels and consuming for seven weeks each one of three diets a typical American diet a high monounsaturated fat diet or a high carbohydrate diet
DELTA also expended considerable effort in the field of food composition analysis Menus were analyzed chemically to verify their composition and to ensure that the nutrient content did not differ significantly among field centers and diet periods Food composition analysis research was conducted at Virginia Polytechnic and State University in consortium with the University of North Carolina
The study was active through August 31 1999 under grant U01-HL-49644
Study Oversight
Has Oversight DMC:
Is a FDA Regulated Drug?:
Is a FDA Regulated Device?:
Is an Unapproved Device?:
Is a PPSD?:
Is a US Export?:
Is an FDA AA801 Violation?:
Secondary IDs
| Secondary ID | Type | Domain | Link |
|---|---|---|---|
| U01HL049644 | NIH | None | httpsreporternihgovquickSearchU01HL049644 |