The results of this study show that when instant oats are consumed daily in place of another staple food (rice, steamed bread, noodles, etc.) compared to wheat noodles as replacement for another staple food, there is a significant increase in dietary fiber intake and significant decreases in waist circumference, TC and LDL-C in Chinese adults with moderate hypercholesterolemia. During the intervention period there was a 6.2% decrease in TC for the oat group compared to a 2.3% decrease in the control group. There was also an 8.4% decrease in LDL-C for the oat group compared to a 3.5% decrease in the control group.
The oat group consumed 100 grams of instant oats per day which provided ~3.6 grams of soluble fiber. Oat products containing β-glucan soluble fiber decrease TC and LDL-C by altering bile acid metabolism and increasing bile acid excretion
]. The reductions in TC and LDL-C observed in this study are similar to previous reports in free living individuals. Van Horn et al.
] reported a 5.2% reduction in TC in healthy adults consuming 60g/day of either oat bran or oatmeal for 6weeks as part of a low fat diet. Karmally and colleagues
] provided 3g/day of β-glucan from ready-to-eat (RTE) oat cereal for 6weeks to adults with mild to moderate hypercholesterolemia and observed reductions of 4.5% in TC and 5.3% in LDL-C. In a recent trial a 5.4% reduction in TC along with an 8.7% decrease in LDL-C was reported following consumption of 3g/day of β-glucan from ready-to-eat (RTE) oat cereal for 12 weeks in overweight or obese adults
]. A 2007 cochrane review reported results of a meta-analysis based on 8 randomized clinical trials that used oats as a wholegrain intervention. A significant effect of oat consumption to lower both TC (P=.0005) and LDL-C concentrations (P=.0008) was observed. The mean percentage reduction in LDL-C from baseline (95% confidence interval) was 4.9% (7.6% to 2.4%)
The prevalence of dyslipidemia in Chinese adults has been reported to be 2.9% for hypercholesterolemia (serum TC ≥5.18 mmol/L) and 11.9% for hypertriglyceridemia (serum TG ≥1.70 mmol/L) based on a nationally representative sample of subjects
]. However, certain subgroups of the population have a higher reported prevalence of hypercholesterolemia. The prevalence is higher in adults over 60 years of age and has been reported to be 20.2% in males and 38.7% in females in this age group
]. The prevalence of dyslipidemia has also been reported to be higher for urban (21%) compared to rural (17.7%) Chinese adults
].The reduction in LDL-C observed in this study is of the magnitude to reduce risk of CHD since every 1% reduction in LDL-C is associated with a decreased risk for CHD of 1% to 3%
A dietary pattern characterized by a high intake of vegetables, fruit and soy is one protective lifestyle factor associated with a marked decreased risk of coronary heart disease, cerebrovascular disease, and overall CVD mortality in Chinese men and women
].The traditional Chinese diet included a high intake of vegetables and coarse grains, which are the main sources of total and insoluble dietary fiber in the Chinese population
]. However significant dietary changes have occurred in recent years which may be contributing to the prevalence of hypercholesterolemia within the population. The national average daily intake of cereals decreased from 510g/day in 1982 to 402g/day in 2002. The amount of coarse grains decreased from 104g/day to 24g/day in the same time period
]. Average intake of total dietary fiber decreased from 22.6g/day in 1989 to 18.1g/day in 2006 and insoluble dietary fiber intake decreased from 15.1g/day in 1989 to 11.9g/day in 2006
]. The 2007 Chinese food based dietary guidelines (FBDGs) issued by the Chinese Nutrition Society include a recommendation to include an appropriate amount of coarse grains. The proposed guidelines recommend a coarse grain intake, including whole grains, of no less than 50 grams per day for adults
]. In this study the oat group had a significant increase in dietary fiber intake (7.1 grams/day) compared to the control group (1.4grams/day, p<0.001) during the treatment period. Intake of course grains was not calculated in this study.
The control group had a significant decrease in HDL-C concentration compared to the oat group during the intervention period (p=0.017). Dietary factors that impact HDL-C concentration include total fat and trans
fat intakes along with the ratio of dietary saturated to unsaturated fat. The decrease in HDL-C in this study is puzzling since there were no significant changes in energy or total, saturated, mono- or poly-unsaturated fat intakes during the intervention period. There also was no significant change in ApoA-1 observed during the treatment period in this study. ApoA-1 concentration is also influenced by the ratio of polyunsaturated to saturated fat
Waist circumference decreased 1.27 cm in the oat group compared to a 0.85 cm increase in the control group (p=0.002). Abdominal obesity is strongly associated with metabolic disturbances such as hypertriglyceridemia and insulin resistance
]. Consumption of whole grains has been associated with smaller waist circumference in population studies
]. Maki et al
] reported a ~1.5cm reduction in waist circumference in overweight adults consuming 3g/day of β-glucan for 12weeks from RTE oat cereal. The clinical implications of a reduction in waist circumference without simultaneous changes in BMI or weight should be investigated.
There was no significant effect of oat consumption on blood pressure at the end of the 6 week treatment period in this study. Previous studies have reported mixed results of the effect of oats, β-glucan or whole grains on blood pressure. Keenan et al
] reported reduced systolic and diastolic blood pressure in a pilot trial with oats. Whole-grain diets reduced blood pressure in mildly hypercholelsterolemic men and women
]. Other investigators reported no effect on blood pressure after consumption of foods containing oat β-glucan
] and RTE oat cereal
]. One confounding factor in this study is that slightly more than 50% of the total subjects were using medications including antihypertensive medication during the intervention.
One limitation of this study is exercise/activity levels were not reported however the subjects were instructed not to make any changes to their habitual diet or other lifestyle factors during the intervention. Another limitation is that antihypertensive medications were allowed during the trial and therefore the impact of the oat intervention on blood pressure was confounded. As the soluble fiber content of the diet before and after intervention could not be calculated, it is not possible to determine if there were changes to soluble dietary fiber intake over the course of the study.