It helps with normal bowel function and it adds bulk to foods to make you feel fuller. However, there is evidence of another essential benefit that fiber may have is that it can improve your heart health.
Although there are several forms of fiber, they can be classified into two major groups: soluble fiber and insoluble fiber. While both are good for the body, only one group has been shown to be beneficial in lowering your cholesterol.
Soluble fiber can be dissolved in water and forms a gel-like consistency in the digestive tract. On the other hand, insoluble fiber cannot be dissolved in water, so it passes through the digestive tract relatively unchanged. When it comes to your heart health, it appears that only soluble fiber is beneficial in lowering your cholesterol.
Soluble fiber lowers cholesterol by binding to it in the small intestine. Once inside the small intestine, the fiber attaches to the cholesterol particles, preventing them from entering your bloodstream and traveling to other parts of the body. Soluble fiber appears to be only effective against your LDL cholesterol, so if you also need to lower your triglycerides, or boost your HDL, soluble fiber may not be able to help you with this since the effect can range from very slight to no benefit at all.
Additionally, you should not solely rely on fiber to lower your cholesterol, since the effect is only slight.
In studies to date, LDL cholesterol can decrease by at most 18 percent by consuming roughly 30 grams of soluble fiber daily. The other type of fiber, insoluble fiber, is also in many healthy foods. While this type of fiber also appears to have many health benefits, it does not lower cholesterol levels. A variety of foods contain soluble fiber. By consuming the recommended amounts of fruits, vegetables, whole grains, and legumes in the Food Pyramid, you should be able to obtain the recommended amount of soluble fiber each day.
Preparing for the holidays? Dietary fiber is a good carbohydrate, also known as roughage, found in plant foods not supplements. There are two kinds , soluble or insoluble, and both are really good for us. Sources of soluble fiber include oatmeal, beans, lentils, and many fruits. Insoluble fiber helps keep our stools soft and regular, always a good thing!
Sources of insoluble fiber include whole grains, beans, lentils, and most vegetables. Both soluble and insoluble fiber make us feel full, which helps us to eat less. But fiber does so, so much more. In a recent research study published in The Lancet , investigators pooled the results from studies looking at health effects of dietary fiber.
They excluded any studies about fiber supplements — this was all about fiber from food. They ended up with data from over 4, people, and found a very strong relationship between higher dietary fiber intake and better health outcomes.
Basically, intake of at least 25 grams of food fiber a day is associated with a lower weight, blood pressure, blood sugars, cholesterol, as well as lower risk of developing or dying from diabetes, heart disease, strokes, and breast or colon cancer. Study results were extremely consistent, and the dose-response curve was very linear, meaning the more fiber, the better the outcomes. Unfortunately, most of us are consuming fewer than 20 grams of fiber per day.
I know many people who shy away from the carbs in whole grains, beans, and fruit, thus missing out on all that healthy fiber. Increasing soluble fiber can make only a small contribution to dietary therapy to lower cholesterol. Abstract Background: The effects of dietary soluble fibers on blood cholesterol are uncertain. Publication types Meta-Analysis.
The number of male and female subjects does not equal the total number of subjects because some studies did not specify the sex of the subjects. Meta-analysis included 67 trials; however, studies did not necessarily report measurements of all 4 lipid changes total cholesterol, LDL cholesterol, HDL cholesterol, and triacylglycerol. The meta-analyses included subjects men, women, sex not specified whose average age was 50 y.
The average dose of 9. During the high-fiber intervention, subjects consumed an average of kJ more energy than during the control period. Both groups receiving the high- and low-soluble-fiber interventions lost weight, 0. Soluble fiber intake did not significantly affect triacylglycerol concentrations: 0. Net change in blood lipids in subjects consuming diets high in soluble fiber compared with low-fiber diets 1.
P, parallel study; X, crossover study; T, treated; C, control. Average daily dose of soluble fiber: oat products, 5. Net change expressed as the value during the high-fiber diet minus that during the control low fiber period.
We were unable to analyze guar studies separately because of the limited number of studies within the restricted dose range. The net change in total and LDL cholesterol is plotted against the mean daily dose of soluble fiber in Figure 1. The plot suggests a nonlinear dose response.
To test for nonlinearity, an exponential term for dose natural log of the amount of soluble fiber was used in the weighted least-squares regression models. Relation between dose of soluble fiber and mean lipid changes. For each study, the net change in total cholesterol and LDL cholesterol expressed as the change during the high-soluble-fiber period minus the change during the low-soluble-fiber period is plotted against the mean daily dose of soluble fiber.
All models were weighted by using the inverse of the variance of each effect size and forcing the intercept through zero. Individual studies with low variance in the meta-analysis are denoted with circles around the point estimates. There was no significant dose-response relation between soluble fiber and changes in HDL-cholesterol or triacylglycerol concentrations.
Soluble fiber from oat products, psyllium, pectin, and guar gum each significantly lowered total cholesterol Figure 2 , Table 2. These values were slightly higher when the meta-analysis was repeated for the practical dose range. Psyllium and guar gum lowered HDL cholesterol significantly but minimally Table 2.
None of the soluble fibers affected triacylglycerols. Type of soluble fiber was not a significant predictor of lipid changes after the initial lipid concentration was controlled for by linear regression.
Net change in total cholesterol. The net effect of consumption of different dietary fibers on total cholesterol concentrations for oat products, psyllium, pectin, and guar gum. Note that one guar study 85 did not include measures for total cholesterol. After dose of soluble fiber and initial lipid concentrations were controlled for, none of the following factors was a significant predictor of changes in blood lipids: type of study design, type of control, treatment length, background diet, type of subject, weight change, or changes in dietary intake of fat and cholesterol.
There were 13 oat, 6 psyllium, and 3 pectin studies with doses of soluble fiber ranging between 2. Most of the studies reported reductions in total cholesterol that were greater than predicted from changes in fatty acid or cholesterol intake. Thus, because the adjusted estimates were similar to the unadjusted estimates, the observed lipid changes cannot be attributed primarily to the substitution of dietary fats and cholesterol for dietary fiber within this subset of trials.
This analysis of 67 controlled clinical trials indicated that diets high in soluble fiber decrease total and LDL cholesterol. Dietary fiber had a small HDL-lowering effect at the borderline of statistical significance and did not affect triacylglycerol concentrations. There was substantial heterogeneity among individual studies, suggesting that effects of fiber are not uniform. Differences in the dose of soluble fiber accounted for some of the variability in study results.
We found significant nonlinearity at higher doses, which may have been due to diminished adherence or a biological maximum being reached at higher doses Our primary dose-response analyses were conducted by assuming a zero intercept. Analyses allowing a nonzero intercept produced a slightly smaller effect of fiber because the intercepts were negative. This suggests that cholesterol would decrease in the treatment group even if there was no added fiber in the high-fiber group.
This could result from nonlinearity of the relation between fiber intake and change in lipids or residual confounding by other important factors, such as body weight or dietary fat changes, for which we were unable to adequately control. For example, although we found that the changes in blood cholesterol could not be attributed to the substitution of fiber for dietary fats and cholesterol in most of the studies with available data, most of the published reports did not provide sufficient dietary data.
This lack of sufficient data limits our ability to conclusively rule out this possibility. We also cannot rule out chance as an explanation because the intercepts were not significantly different from zero. The mechanism by which fiber lowers blood cholesterol remains undefined. Evidence suggests that some soluble fibers bind bile acids or cholesterol during the intraluminal formation of micelles The resulting reduction in the cholesterol content of liver cells leads to an up-regulation of the LDL receptors and thus increased clearance of LDL cholesterol.
However, increased bile acid excretion may not be sufficient to account for the observed cholesterol reduction Other suggested mechanisms include inhibition of hepatic fatty acid synthesis by products of fermentation production of short-chain fatty acids such as acetate, butyrate, propionate ; changes in intestinal motility ; fibers with high viscosity causing slowed absorption of macronutrients, leading to increased insulin sensitivity ; and increased satiety, leading to lower overall energy intake Our data do not support previous findings that patients with hypercholesterolemia are more responsive to dietary fiber than are healthy individuals 14 , We did, however, find that initial LDL cholesterol was a moderately significant predictor of LDL-cholesterol changes, but the difference in responsiveness was small: 0.
Most of the available epidemiologic studies suggest that dietary fiber is inversely related to coronary artery disease 5 , — Earlier studies suggested that the effects of fiber may be larger than those shown in this meta-analysis.
However, methodologic problems including small sample sizes, incomplete dietary measures, and inadequate control of important confounders made it difficult to determine the effects of dietary fiber independently of other dietary components and, more specifically, the contribution of soluble compared with insoluble fiber.
The modest reductions in cholesterol expected from intakes of soluble fiber within practical ranges may exert only a small effect on the risk of heart disease. These findings are consistent with an earlier summary of the cholesterol-lowering effects of oat products Publication bias toward studies that showed positive results is always a potential issue in meta-analyses and could be operating in this study.
If this were true, then the small effect estimates associated with intake of dietary soluble fiber would be further attenuated, further highlighting the need for conservative public health claims. The major benefit from eating fiber-rich foods may be a change in dietary pattern, resulting in a diet that is lower in saturated and trans-unsaturated fats and cholesterol and higher in protective nutrients such as unsaturated fatty acids, minerals, folate, and antioxidant vitamins.
The treatment effect was divided by the average daily amount dose in grams of soluble fiber. A negative effect size indicates a reduction during the intervention phase. The primary endpoint is the change in total cholesterol, LDL cholesterol, HDL cholesterol, and triacylglycerol from the end of the dietary run-in period if applicable or the concentration before the intervention was initiated total cholesterol 1 to the end of the intervention period total cholesterol 2.
To derive a model for the variance of total cholesterol change, we first assumed the following variance component model of Rosner and Polk 1 , which includes day-to-day variability and subject-to-subject variability. Within-day variability is also included but it does not apply in our model because lipids were measured once per visit.
If we assume that both total cholesterol 1 and total cholesterol 2 are computed as the mean of k measurements, then the variance of each of these measures is given by. This quantifies the association between initial and subsequent cholesterol concentrations. The observed tracking correlation between the initial and follow-up total cholesterol equaled 0.
This value was corrected for within-person variation by using the following formula 5 and the variance components as calculated above. This model assumes that the variance components remain constant over time. The true mean for an individual is allowed to vary over time with a correlation P ts for measurements at time t and s. Thus, we estimated that the SD of the change in total cholesterol would be Q is used to assess homogeneity of study estimates of effect 7.
Rosner B , Polk BF. Predictive values of routine blood pressure measurements in screening for hypertension. Am J Epidemiol ; : — Google Scholar. The Lipid Research Clinics population studies data book.
Vol 1. The prevalence study. NIH publication no. Google Preview. Retest reliability of plasma cholesterol and triglyceride. A single cholesterol measurement underestimates the risk of coronary heart disease.
JAMA ; : — 6. Sample size estimation for clinical trials with longitudinal measures: applications to studies of blood pressure. J Epidemiol Biostat ; 2 : 65 — Clin Chem ; 31 : — 6.
Laird N , Mosteller F. Some statistical methods for combining experimental results. Facts about cardiovascular disease. Circulation ; 85 : A abstr. Serum cholesterol, lipoproteins, and risk of coronary artery disease. The Framingham Study. Ann Intern Med ; 74 : 1 — The effect of pravastatin on coronary events after myocardial infarction in patients with average cholesterol levels.
N Engl J Med ; : — 9. Reduction in cardiovascular events during pravastatin therapy: pooled analysis of clinical events of the Pravastatin Atherosclerosis Intervention Program. Circulation ; 92 : — Effects of changes in fat, fish, and fibre intakes on death and myocardial reinfarction.
Lancet ; 2 : — JAMA ; : —
0コメント