Coronary heart disease, CHD, has been predicted to persist as the major cause of high mortality rate for the coming decades. In line with this, the development of ischemic heart disease was attributed to the increasing level of low-density lipoprotein or LDL blood cholesterol. According to the National Cholesterol Education Program or NCNEP adult treatment panel, less than or equal to 5.17 millimole per liter (200 milligram per deciliter) is the ideal blood cholesterol level for individuals of age higher than 20 years while higher than 6.21 millimole per liter or 240 milligram per deciliter is risky. In connection to this, about twenty nine percent of adults older than 20 years in the United States have 6.21 millimoles per liter blood cholesterol. Meanwhile, researches have shown that consumption of dietary soluble fibers lowers blood cholesterol level as epidemiologic studies revealed that the CHD development can be alleviated by means of dietary fiber consumption. In fact, more than thirty researches that were submitted to the Food and Drug Administration of the United States by the Federation of American Societies for Experimental Biology Report validated the efficacy of soluble fiber consumption on blood cholesterol reduction. Clinical studies showed that soluble fibers from selected gums, psyllium, oat bran, pectin, and oats generally caused six percent to nineteen percent serum cholesterol reduction. Since the low cholesterol and low saturated fat diet has been employed in hypercholesterolemia medical therapy, this study aimed for the assessment of commercially available whole grain oat cereal, as employed with the step-one diet of the American Heart Association (AHA), in the reduction of blood cholesterol level.
This study has enlisted fifty-seven participants from previous researches advocated by the Heart Disease Prevention Clinic. While forty-six of these participants have joined the intervention phase, only forty-three persevere and endured until the end. The participants have ages in between twenty-seven and sixty-eight years with 50th to 90th percentile range of cholesterol level based on age and gender adjustments. In the recruitment of participants, individuals with higher than 3.39 millimole per liter of triglycerides, a body weight thirty percent higher than ideal, has major surgery and myocardial infarction history, gastrointestinal illness, unstable angina or heart failure was excluded form the enlistment. Also, those who were presently in taking up drugs for medication such as lipid-lowering agents, thiazides, antibiotics, estrogens, corticosteriods, and progesterones were excluded. In line with this, those who were taking ß-adregenic blockers needed to maintain the dosage of such drug during the duration of the study for them to become eligible. Finally, twenty-one men and twenty-two women were successfully made into the phases of this study.
The phases of the intervention plan were four-week washed out stage, two-week baseline, and four-week treatment part. Throughout the intervention phases, the participants were required to maintain weight while consuming about ready-to-eat cereals twice daily within four weeks. In connection to this, all participants were mandated to abide with the AHA step-one diet design during the duration of the study. Meanwhile, physiological data such as weight, nutrient data, and lipid profiles of the participants were determined from zero to four-week baseline. Moreover, the nutrient data based on four-day food records were evaluated by the National Coordinating Center.
In the intervention plan, pairing of participants was done based on gender and entry cholesterol data, whereas in each pair one was assigned to “Country Cornflakes” while the other has undergone the “Cheerios” diet. The former was the control cereal while the latter was the source of whole grain oat. Both of these cereal types were produced through cereal processing equipment and each were pre-packed into 42.5 grams upon distribution to the participant. This was done in order to hide the identity of the commercial cereals used in this study. In connection to this, the researchers also ensured which cereal type was assigned to whom and the participants’ adherence to the consumption design by personal interviews and visitation. Meanwhile, the participants’ clinical assessment, as approved by the Centers for Disease Control and Prevention, was done after twelve-hour and twenty-four fasts from food and alcoholic drinks respectively. In every visit, blood pressure, lipid profile, pulse, and body weight were accurately measured. In relation to this, participants have undergone clinical screening such as urinalysis, blood count, electrocardiogram, and physical examination.
The lipid content of the blood collected through sodium-potassium ethylenediamine tetraacetic was analyzed in the University of Minnesota’s laboratory for Lipid Research Core. The high-density lipoprotein or HDL cholesterol, total cholesterol, and triglycerides were determined. Also, very-low density lipoprotein or VLDL and LDL were precipitated; Friedewald formula was utilized for LDL calculation. Lastly, the cholesterol data of the participants before undergoing the treatment was statistically compared with their respective cholesterol data analyzed after the intervention phases by means of t-tests and analyses of covariance.
Results and Discussion
The participants in this study were equally divided into two groups; the control group received cornflakes food supply while the treatment group was fed on whole grain oat. Both groups have 51.6 years as average age of the participants. Although the baseline body weight of the treatment group was five kilogram lower as compared with that of the control group, the difference did not make statistics significance. As such, there was no significant difference on the body mass index or BMI, and the baseline and post-intervention phase blood pressure among the two groups. Further, personal interviews on the participants revealed that their smoking and alcohol drinking habits as well as regular exercise in either group was maintained throughout the study. Luckily, complete blood count and blood chemistry of the participants did not change significantly during the study period.
In terms of fat consumption, the total intake of the treatment group was decreased non-significantly from 56.7 grams to 51.8 grams. Moreover, the average diet changes were 11.2 milligrams per deciliter and +4.1 milligrams per deciliter for the treatment group and the control group respectively. Similarly, among the two groups, there was no significant difference on the key nutrients before and after the duration of intervention phases. Except for soluble fiber, there were no other significant changes with respect to diet composition among the two groups. Meanwhile, whole-grain oat group incurred 3.8% and 5.4% changes on total cholesterol and LDL cholesterol respectively. As compare with the control group, the treatment group had a decreased of 4.4% in total cholesterol and 4.9% LDL cholesterol. Although, there was no significant difference in HDL cholesterol between the two groups, they had a 0.20 millimole per liter LDL cholesterol difference.
The exact mechanism of the cholesterol reduction was still unclear. It was theorized that the viscosity of soluble fibers lessen the rate of chime transfer in the upper gastrointestinal tract that causes low absorption rates, less blood nutrients, and changes in hormonal responses to delimited nutrients. In their hamsters study, Gallaher, Hassel, and Lee associated the reduction of plasma and liver cholesterol to the increase in the viscosity of the intestinal contents. However, viscosity was deemed only as a crucial requirement for the reduction of serum cholesterol. In this connection, it was proposed that soluble fibers hinder bile activity lessening the absorption rate. This process obstructs enterohepatic circulation leading to fast conversion rate of cholesterol to bile acids. In addition, other compound constituent of the fibers may also promote this process. For instance, tocotrienol in rice bran, oats, and barley inhibits cholesterol synthesis. Furthermore, the soluble fiber fermentation produces chain fatty acids which in turn hinder cholesterol biosynthesis.
Changes in Serum Cholesterol and Sterol Metabolites after Intake of Products Enriched with an Oat Bran Concentrate within a Controlled Diet
The United States Food and Drug Administration or FDA, in 1997, approved the notion concerning soluble fiber consumption and coronary heart disease or CHD risk reduction. The serum cholesterol or S-cholesterol reduction was ascribed to the soluble fiber, (1-3),(1-4) ?-D-glucan or simply ?-glucan present in oats and whole oat flour. Based on clinical claims, the consumption of three grams of ?-glucan per day results to S-cholesterol lowering and CHD risk reduction. Meanwhile, the S-cholesterol lowering mechanism was theorized to depend largely on increased bile acid activity due to viscous ?-glucan which in turn induces cholesterol and bile acid biosyntheses. The rate of cholesterol and bile acid biosyntheses can be traced on through the ratio of lathosterol to cholesterol and the presence of 7-?-hydroxy-4-cholesten-3-one, respectively. Thus, this study aimed to assess the S-lowering of oat bran concentrate or OBC food products incorporated in the low-saturated fat and low-cholesterol diet of hypercholesterolaemic patients. Also, the OBC effect on bile acid and cholesterol biosyntheses were examined.
The recruitment of the respondents for this study was done through newspaper advertisement. Twenty-seven individuals were examined but only sixteen has passed the screening and participated in the study. The participants should have ages of 35-70 years and 50-70 years for men and women respectively. In addition, all participants should have less than six millimoles per liter S-cholesterol level. On the other hand, individuals with less than four millimoles per liter S-triacylglycerol or TG, hyperlipedaemia, less than 30 kilogram per meter square body mass index or BMI, and with cases diabetes mellitus, liver disease, thyroid problems or kidney trouble and those under hormonal therapy or cholesterol medication were excluded. Hence, the final participants were composed of seven women and nine men with average age of 57 years, 25.4 kilogram per meter square BMI, and 7.47 millimoles per liter S-cholesterol level.
This study was a single-blind and randomized cross-over that lasted for two by three weeks with 2.5 weeks washout period. As such, the experimental group was supplemented with OBC of about 2.7 grams per day ?-glucan in their diet while the control group was told to maintain their typical diet. In relation to this, laboratory test such as fasting blood sampling and body weight recording were performed. The results of every clinical test were only revealed to the participants after the completion of the study.
The American Heart Association recommended diet was utilized as computations of every participant’s daily food requirements and menu planning were facilitated by MATS computer program. Strict compliance with the diet was imposed through regular checking as amounts of sweet foods and drinks were regulated. For instance, maximum of 375 grams of wine or 660 milliliter of beer were only allowed per week. Additionally, participants were given copies of the foods they ate for the first week and told to stick to such as much as possible.
Fasting blood sampling was done every morning as the blood samples were analyzed in terms of low density lipoprotein or LDL cholesterol, TG, and high density lipoprotein of HDL cholesterol, and S-cholesterol. Further, serum lathosterol and 7-?-hydroxy-4-cholesten-3-one levels were determined through gas chromatography. Meanwhile, statistical treatments were done by means of MS Excel and SYSTAT package. Pearson’s correlation and t-test were employed for correlational analysis and paired comparison respectively.
Results and Discussion
As compared with the control group, the experimental group has incurred six percent S-cholesterol reduction based on five-gram ?-glucan daily diet. In fact, a significant correlation S-cholesterol baseline level and total S-cholesterol changes during diet period were observed. In addition, changes on the serum metabolites which reflected bile acid secretion and cholesterol biosynthesis were noted. Moreover, the solubility of ?-glucan in OBC was calculated and found only as 50%. Weight losses which denoted S-cholesterol reduction also were observed. Meanwhile, due to the delimited fat intake, HDL-cholesterol reduction was noted as TG level was decreases in some participants only. Correlational changes on lathosterol and S-cholesterol implied cholesterol biosynthesis after oat diet. This observation was attributed to increase in bile acid production that was mediated by ?-glucan which in turn caused reduction in bile acid reabsorption. This process triggered bile acid synthesis through cholesterol from plasma pool by means of LDL-receptor. Yet, no significant change on serum lathosterol and 7-?-hydroxy-4-cholesten-3-one levels observed on participants.
High-Fiber Oat Cereal Compared with Wheat Cereal Consumption Favorably Alters LDL-Cholesterol Subclass and Particle Numbers in Middle-Aged and Older Men
High in fiber diet, in parallel with low-fat intake and other dietary factors, has been associated with the reduction of cardiovascular disease or CVD risk. Based on the meta-analyses of a number of studies, ?-glucan soluble fibers in oat products lessened serum cholesterol and low-density lipoprotein or LDL-cholesterol. It was inferred then that the capability of soluble fibers for CVD risk reduction is in concurrence with its capacity in modifying lipoproteins and serum lipids. In a number of cases, individuals with normal profile of serum lipids developed CVD. Thus, a closer examination on blood lipids attributes may provide insights on the possible CVD risk development and modify the efficacy of intervention for the prevention of such risk. However, no research has been conducted with respect to the effects of cereal and soluble fibers on lipoprotein subclasses, and particle size and number. Also, none has reported on lipoprotein and lipid changes brought either by carbohydrate, and cereal or oat diet. Hence, this study aimed to determine cereal or oat diet on plasma lipid indexes such as LDL particle number, and lipoprotein subclasses and particle diameter.
Men selected for this study were in between 25-35 years of age and have 50-75 kilogram per meter square body mass index. Individuals with CVD, diabetes, abnormal blood pressure, smoking habits, thyroid gland or eating disorders, and those who currently in any medication and with high amount consumption of fibers were excluded. At last, 36 men were successfully passed then clinical requirements that were divided into two groups. Then, weight and bodily measurements were gauged initially and periodically during the study. Nonetheless, the participants, under the instruction of dietitian, recorded their food preparations and sizes in four-day food intake. In connection to this, records of food intake were analyzed through Food Intake Analysis System or FIAS. Meanwhile, participants’ blood samples were taken before and after the twelve-week intervention. By means of nuclear magnetic resonance spectroscopy or NMR, the concentrations and particle size of blood lipids and lipoproteins were assessed. Further, the insulin-augmented frequently sampled intravenous-glucose-tolerance test or IVGTT was applied to participants.
For statistical treatments, Kolmogorov-Smirnov normality tests were employed prior to analysis of variance done through SPSS package. Also, analysis of covariance was performed for body weight changes and macronutrient intake. Nonetheless, t-tests were utilized to examine lipoprotein and lipid response differences.
Results and Discussion
Based on the results of this study, two large oat servings added to the regular diet of the participants, lowered small, dense LDL and LDL particle concentrations. In addition, in spite of the carbohydrate intake elevation and saturated-fat intake lowering, the concentration of triacylglycerol did not significantly increase for high-fiber oat group. In contrast, it was reported that triacylglcerol in blood increases along with the changes in lipoprotein and lipids in individuals who fed on wheat cereal with high carbohydrate intake and low-fat diet. Meanwhile, the association between triacylglycerol elevation and CVD risk development was linked on the changes in the composition of LDL and high-density lipoprotein or HDL cholesterol. In relation to this, the substitution of triacylglycerol by cholesterol esters in lipoproteins results to accumulation of triacylglycerols in HDL and LDL which in turn serve as reactant in hepatic triacylglycerol lipase. Then, the removal of triacylglycerol leads to particle size decreased and density increased. Hence, in this study, the decrease in plasma tiaclyglycerol resulted to increase in LDL particle size for oat group but not with wheat cereal group.
Analysis and Conclusion
From the abovementioned studies, it was statistically proven that supplementation of oat cereals to the controlled diet of hypercholesterolemia patients caused blood lipids and HDL reductions. Further, oat meal diet results to LDL-particle size decreased and particle number increased which is beneficial in the part of hypercholesterolemia patients. On the other hand, it was theorized that the viscosity of soluble fibers lessen the rate of chime transfer in the upper gastrointestinal tract that causes low absorption rates, less blood nutrients, and changes in hormonal responses to delimited nutrients (Reynolds, Quiter, and Hunninghake, 2000). This process obstructs enterohepatic circulation leading to fast conversion rate of cholesterol to bile acids (Reynolds, Quiter, and Hunninghake, 2000). Thus, the increase in bile acid production as mediated by ?-glucan caused reduction in bile acid reabsorption (Davy, Davy, Ho, Beske, Davrath, and Melby, 2002). This process triggered bile acid synthesis through cholesterol from plasma pool by means of LDL-receptor (Davy, Davy, Ho, Beske, Davrath, and Melby, 2002). As a consequence, the substitution of triacylglycerol by cholesterol esters in lipoproteins results to accumulation of triacylglycerols in HDL and LDL which in turn serve as reactant in hepatic triacylglycerol lipase. Then, the removal of triacylglycerol leads to particle size decreased and density increased (Davy, Davy, Ho, Beske, Davrath, and Melby, 2002). Nonetheless, other compound constituent of the fibers may also promote this process. For instance, tocotrienol in rice bran, oats, and barley inhibits cholesterol synthesis. Moreover, the soluble fiber fermentation produces chain fatty acids which in turn hinder cholesterol biosynthesis (Reynolds, Quiter, and Hunninghake, 2000). With these reasons, the research question “What is the effect of a diet high in dietary fiber and how does it decrease LDL – cholesterol and serum lipids?” was plausibly answered.