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Whole Grain Oat Cereal Lowers Serum Lipids
Abstract
: This study examined a ready-to-eat breakfast cereal, Cheerios(R), made of whole grain oats, containing 8 grams of oat bran per oz., for its cholesterol-lowering effect. This was a randomized, double-blind study, with forty-three subjects (21 men and 22 women) who had mild to moderate hypercholesterolemia (mean baseline value 5.94+/-0.65 mmol/L [230.8 +/- 25.3 mg/dL]). Subjects followed medical nutrition therapy and ate either 3 oz. of Country Cornflakes(R), with essentially no bran or germ or Cheerios(R) for 4 weeks. Compared with the control, those consuming oat cereal achieved a 4.4% reduction in total cholesterol and a 4.9% reduction in low-density lipoprotein cholesterol compared with baseline.
... As most of the included studies did not report the mean difference for lipid profile variables, we calculated the value as post-intervention mean value minus baseline mean value. Furthermore, as most of the included studies (n = 15) [42][43][44][45][46][47][48][49][50][51][52][53][54][55][56] did not report the standard deviation of mean difference of the lipid profile outcomes (TC, HDL, LDL, and TG), the following equation (1) was used to estimate the standard deviation of mean difference [57]: ...
... Nine parallel-arm/oat studies were included in the analysis for TC, HDL, LDL and TG [45,47,[51][52][53][54][55][56]61], seven crossover/oat studies were included in the analysis for TC, HDL, LDL and TG [42,43,46,50,[66][67][68], nine parallel-arm/isolated β-glucan studies were included in the analysis for TC, HDL and LDL [48,[58][59][60][62][63][64]76,77], eight parallel-arm/isolated βglucan studies were included in the analysis for TG [48,[58][59][60]63,64,76,77], three crossover/isolated β-glucan studies were included in the analysis for TC, HDL and LDL [44,49,65], and two crossover/isolated β-glucan studies were included in the analysis for TG [44,49]. ...
... Almost half of the included studies did not mention or report precisely the information regarding the method used for the lipid profile assessment [46,49,63,67,[53][54][55][56]58,[60][61][62]. Of the remaining studies, 14 of them reported having used enzymatic methods of analysis [42,43,64,68,76,77,44,45,47,48,[50][51][52]59] and two studies reported a combination of enzymatic and colorimetric methods [65,66]. ...
Background & aims
It is well known that dietary fiber positively impacts the microbiome and health as a whole. However, the health effects of β-glucan, a dietary fiber extracted from oats, have been questioned when administered alone or incorporated into other foods. The purpose of this systematic review and meta-analysis was to evaluate the impact of oats or β-glucan supplements on the lipid profile.
Methods
Randomized controlled trials with parallel-arm or crossover blinded interventions at least two weeks in duration, for hyperlipidemic or non-hyperlipidemic men and women ≥18 years of age were selected. Only single (participants blinded) or double-blinded studies that compared oat or isolated β-glucan with a placebo/control group were considered for this review. The databases EMBASE, PubMed, Web of science and CINHAL were searched, from the earliest indexed year available online to the end of January 2022. Random-effects models were used to combine the estimated effects extracted from individual studies, and data were summarized as standardized mean difference (SMD) and 95% confidence interval (95%CI).
Results
A total of 811 articles were screened for eligibility, and relevant data were extracted from 28 studies, totaling 1494 subjects. Oat interventions TC (−0.61, 95%CI: −0.84;-0.39, p < 0.00001, and −0.70, 95%CI: −1.07;-0.34, p = 0.0002, respectively) and LDL (−0.51, 95%CI: −0.71;-0.31, p < 0.00001, and −0.38, 95%CI: −0.60;-0.15, p = 0.001, respectively). Moreover, isolated β-glucan interventions from parallel-arm studies decreased TC (−0.73, 95%CI: −1.01;-0.45, p < 0.00001), LDL (−0.58, 95%CI: −0.85;-0.32, p < 0.0001) and triglycerides (−0.30, 95%CI: −0.49;-0.12, p = 0.001). HDL was not altered by either oat or isolated β-glucan (p > 0.05).
Conclusion
Overall, this review showed that both oat and isolated β-glucan interventions improved lipid profiles. Furthermore, the ingestion of oats or isolated β-glucan supplements are effective tools to combat dyslipidemia and should be considered in cardiovascular disease prevention.
... In total, 32 studies met the criteria for inclusion (Table 6). Of 26 intervention studies (from 27 papers) 17 were parallel [6,8,9,11,18,[24][25][26][27][28][29][30][31][32][33][34][35] and 9 were crossover design [7,10,19,20,[36][37][38][39][40][41]. Six prospective cohort studies were selected for inclusion [42][43][44][45][46][47]. ...
... Twelve parallel studies examined the effects of whole grain oats [6,8,[25][26][27][29][30][31][32][33][34][35]. Four oat studies tested a ready-to-eat breakfast cereal that meets the criteria for classification as whole grain [8,25,27,30]. ...
... Twelve parallel studies examined the effects of whole grain oats [6,8,[25][26][27][29][30][31][32][33][34][35]. Four oat studies tested a ready-to-eat breakfast cereal that meets the criteria for classification as whole grain [8,25,27,30]. Five parallel studies investigated the effects of a mix of whole grain foods [9,11,18,24,28]. ...
A systematic review was undertaken to evaluate the evidence for a health claim about whole grain (WG) products and coronary heart disease (CHD). Studies were excluded if the American Association of Cereal Chemists International WG definition was not met or if foods with less than 51% WG ingredients were classified as WG. Seventeen of 26 clinical trials reported sufficient information to be included in the meta‐ analysis. Overall, pooled analyses suggested that WG products have total and LDL cholesterol‐lowering effects. No effect remained when trials that tested single grains high in β‐glucan fibre, such as oats, and poor quality studies were removed from the analysis. The cohort studies were too heterogeneous to calculate pooled risk estimates. Four of 6 cohort studies reported at least one improved CHD outcome in individuals who consumed more WG products. Two of the positive studies were poor quality; the remaining 2 were separate analyses of the same cohort. Health Canada concluded that the evidence to date was not sufficient to support a health claim about WG products in general and CHD. The effect of β‐glucan fibre cannot be generalized to other grains, including wheat, the main grain consumed in Canada. Health Canada has already accepted health claims about oat and barley products and cholesterol‐lowering.
... Much of the debate resides in regards to cardio-protection offered from these types of grain fibres, in part due to disparity between consistent observational evidence (20) and, on the contrary, inconsistent RCT data on major CVD risk factors including lipids (21) , making this topic a highly controversial issue in nutrition. Although certain assumptions prevail that non-gelling insoluble cereal fibres may not be metabolically inactive, several novel mechanisms supporting the cardiometabolic relevance of insoluble fibre have also emerged (22)(23)(24) . ...
... Characteristics of included studies are summarised in Table 1 (10,24, . The majority of the studies (45 %) were set in North America (twenty-seven in the USA, twelve in Canada and one in Mexico), 33 % of the studies were conducted in Europe (ten in Finland, seven in the UK, three in Netherlands, three in Sweden, one each in Italy, Greece, Slovenia and Norway and one each across Spain and Netherlands and UK and Germany), 11 % of the studies were conducted in Asia (three in Japan, three in Iran and one each in China, Thailand, Taiwan and Pakistan), 7 % in Australia, 2 % in New Zealand, and 2 % in South America (one in Brazil and one in Venezuela). ...
Although compelling evidence from observational studies supports a positive association between consumption of cereal fiber and cardiovascular disease (CVD) risk reduction, randomized clinical trials (RCT)s often target viscous fiber type as the prospective contributor to lipid lowering to reduce CVD risk. The objective of our study is to compare the lipids lowering effects of viscous dietary fiber to non-viscous, cereal-type fiber in clinical studies. RCTs that evaluated the effect of viscous dietary fiber compared to non-viscous, cereal fiber on LDL cholesterol and alternative lipid markers, with duration of ≥ 3 weeks, in adults with or without hypercholesterolemia were included. Medline, EMBASE, CINAHL, and the Cochrane Central Register were searched through October 19, 2021. Data was extracted and assessed by 2 independent reviewers. The generic inverse variance method with random effects model was utilized to pool the data which were expressed as mean differences (MD)s with 95% confidence intervals (CI). Eighty-nine trials met eligibility criteria (n = 4755). Mean differences for the effect of viscous dietary fiber compared to non-viscous cereal fiber were: LDL cholesterol (MD = –0.26 mmol/L; 95% CI: –0.30, -0.22 mmol/L; P < 0.01), non-HDL cholesterol (MD = –0.33 mmol/L; 95% CI: –0.39, -0.28 mmol/L; P < 0.01), and Apo-B (MD = –0.04 g/L; 95% CI: –0.06, -0.03 g/L; P < 0.01). Viscous dietary fiber reduces LDL cholesterol and alternative lipid markers relative to the fiber from cereal sources, hence may be a preferred type of fiber-based dietary intervention targeting cardiovascular disease risk reduction.
... Therefore β-glucans increase exclusion of bile acids (Marlett 1997;Ellegard and Anderson 2007) and this in turn activates cholesterol 7α-hydroxylase and up-regulates low-density lipoprotein receptor (LDLR) and thus increase the transport of LDL into hepatocytes and the conversion of cholesterol into bile acids (Nilsson et al. 2007). It has been reported that every 1% reduction in LDL is associated with a decreased risk for CHD of 1% to 3% (Reynolds, 2000). In addition, oat β-glucans have also been shown to be fermented by human fecal micro biota to produce short-chain fatty acids such as acetate, propionate and butyrate and after absorption into the portal vein both acetate and propionate inhibit hepatic cholesterol synthesis (Wright et al. 1990). ...
... It has been reported that every 1% reduction in LDL is associated with a decreased risk for CHD of 1% to 3% (Reynolds 2000). In addition, oat β-glucans have also been shown to be fermented by human fecal micro biota to produce short-chain fatty acids such as acetate, propionate and butyrate and after absorption into the portal vein both acetate and propionate inhibit hepatic cholesterol synthesis (Wright et al. 1990). ...
... where possible. This estimation was calculated in one of the following ways: 1) from the given amount of whole-grain foods in the diet (34), 2) from the reported total amount of whole grain added to the habitual diet (31,35,36), 3) from the amount of whole-grain present in the food multiplied by the reported serving size (37)(38)(39)(40)(41), 4) from the reported addition of whole grain per kilogram of body weight (42), or 5) from the reported addition of whole grain per energy (MJ) consumed. In 8 studies, it was not possible to quantify the amount of the whole grain provided (21,22,25,(43)(44)(45)(46)(47). ...
... Nine studies evaluated a mixed whole-grain diet [containing whole-grain products such as bread, crisp bread, rolls, muesli, ready-to-eat (RTE) cereals, pasta, rice, snack bar, crisps, muffin, and cookies] compared with a mixed refined-grain diet (containing the same products but produced of refined grain) (22,25,30,32,46,47), or the participants' habitual diet (21,23,34). Seven studies included only oat (eg, oatmeal, instant oats, RTE cereal or Cheerios cereal (General Mills), hot cereal, or oat incorporated into other foods) compared with a refinedgrain diet (other carbohydrate foods with the avoidance of oat, corn cereals, participants' habitual diet including wheat, cream of wheat, or nonoat RTE cereal, or low-fiber breakfast and snack foods) (36,37,39,41,50,51). In 7 studies, whole-grain wheat (bread, crackers, muffins, RTE cereal, bread rolls, rusks, and biscuits) were compared with refined-grain wheat (containing the same products but of refined wheat or other non-whole-grain Where data were not accessible, the mean or the range is presented. ...
Whole grains have received increased attention for their potential role in weight regulation. A high intake has been associated with smaller weight gain in prospective cohort studies, whereas the evidence from randomized controlled studies has been less consistent.
We assessed the effects of whole-grain compared with non-whole-grain foods on changes in body weight, percentage of body fat, and waist circumference by using a meta-analytic approach.
We conducted a systematic literature search in selected databases. Studies were included in the review if they were randomized controlled studies of whole-grain compared with a non-whole-grain control in adults. A total of 2516 articles were screened for eligibility, and relevant data were extracted from 26 studies. Weighted mean differences were calculated, and a metaregression analysis was performed by using the whole-grain dose (g/d).
Data from 2060 participants were included. Whole-grain intake did not show any effect on body weight (weighted difference: 0.06 kg; 95% CI: -0.09, 0.20 kg, P = 0.45), but a small effect on the percentage of body fat was seen (weighted difference: -0.48%; 95% CI: -0.95, -0.01; P = 0.04) compared with that for a control. An examination of the impact of daily whole-grain intake could predict differences between groups, but there was no significant association (β = -0.0013 kg × g/d; 95% CI: -0.011, 0.009 kg × g/d) .
Whole-grain consumption does not decrease body weight compared with control consumption, but a small beneficial effect on body fat may be present. The relatively short duration of intervention studies (≤16 wk) may explain the lack of difference in body weight and fat. Discrepancies between studies may be caused by differences in study design.
... Oats have demonstrated the ability to decrease both serum total cholesterol and LDL cholesterol levels in comparison to control groups [14][15][16][17] . Studies indicate that for every 1% decrease in LDL (low-density lipoprotein), the associated risk of coronary heart disease (CHD) is reduced by 1% to 3% [18] . Additionally, oat β-glucans undergo fermentation by human fecal microbiota, generating short-chain fatty acids like acetate, propionate, and butyrate. ...
... ¶ Agency funding is that from government, university or not-for-profit health agency sources. Subgroup and study, year (Reference) Turnbull & Leeds, 1987Hypercholesterolaemic Kestin et al., 1990Anderson et al.,1991Bremer et al., 1991Davidson et al., 1991Leadbetter et al., 1991Stewart et al., 1992Uusitupa et al., 1992Whyte et al., 1992Braaten et al., 1994Noakes et al., 1996Onning et al., 1999Lovegrove et al., 2000Reynolds et al., 2000Van Horn et al., 1991 Romero et al., (b), Johnston et al., 1998Van Horn et al., 2001Amundsen et al., 2003Berg et al., 2003Kerckhoffs et al., 2003Maki et al., 2003Biorklund et al., 2005Karmally et al., 2005Martensson et al., 2005Queenan et al., 2007Reyna-Villasmil et al., 2007Biorklund et al., 2008Liatis et al., 2009Maki et al., 2010Wolever et al., 2010Charlton et al., 2012Zhang et al., 2012Thongoun et al., 2013Momenizadeh et al., 2014 Subtotal Heterogeneity: 2 = 0. 03; 2 = 222. 02, df = 37 (P < 0. 00001); I 2 = 83 % Test for overall effect: Z = 5. 89 (P < 0. 00001) Unclassified Gold & Davidson, 1988Van Horn et al., 1988Swain et al., 1990Zhang et al., 1992Poulter et al., 1994Pick et al., 1996Gerhardt & Gallo, 1998Romero et al., (a), 1998Saltzman et al., 2001Davy et al., 2002Pins et al., 2002Robitaille et al., 2005Chen et al., 2006Naumann et al., 2006Beck et al., 2010Cugnet-Anceau et al., 2010Ibrugger et al., 2013Ma et al., 2013McGeoch et al., 2013 Heterogeneity: Mean difference (95% CI) (mmol/l) 2. 70 2. 10 1. 80 0. 70 1. ...
Oats are a rich source of β -glucan, a viscous, soluble fibre recognised for its cholesterol-lowering properties, and are associated with reduced risk of CVD. Our objective was to conduct a systematic review and meta-analysis of randomised-controlled trials (RCT) investigating the cholesterol-lowering potential of oat β -glucan on LDL-cholesterol, non-HDL-cholesterol and apoB for the risk reduction of CVD. MEDLINE, Embase, CINAHL and Cochrane CENTRAL were searched. We included RCT of ≥3 weeks of follow-up, assessing the effect of diets enriched with oat β -glucan compared with controlled diets on LDL-cholesterol, non-HDL-cholesterol or apoB. Two independent reviewers extracted data and assessed study quality and risk of bias. Data were pooled using the generic inverse-variance method with random effects models and expressed as mean differences with 95 % CI. Heterogeneity was assessed by the Cochran’s Q statistic and quantified by the I² -statistic. In total, fifty-eight trials ( n 3974) were included. A median dose of 3·5 g/d of oat β -glucan significantly lowered LDL-cholesterol (−0·19; 95 % CI −0·23, −0·14 mmol/l, P <0·00001), non-HDL-cholesterol (−0·20; 95 % CI −0·26, −0·15 mmol/l, P <0·00001) and apoB (−0·03; 95 % CI −0·05, −0·02 g/l, P <0·0001) compared with control interventions. There was evidence for considerable unexplained heterogeneity in the analysis of LDL-cholesterol ( I² =79 %) and non-HDL-cholesterol ( I² =99 %). Pooled analyses showed that oat β -glucan has a lowering effect on LDL-cholesterol, non-HDL-cholesterol and apoB. Inclusion of oat-containing foods may be a strategy for achieving targets in CVD reduction.
... The LDL-cholesterol value equated to a mean percentage reduction (95% confidence interval) from baseline of -4.9% (-7.6% to -2.4%). HDLcholesterol and triglyceride concentrations were measured in an additional six studies and the weighted treatment differences in the meta-analysis were not significant (p = 0.95 for HDL-cholesterol, p = 0.83 for triglyceride) (20)(21)(22)(23) . Anthropometric assessment including body weight, body mass index, body fat percentage, visceral fat, and waist circumference of subjects were not significantly different throughout the intervention periods. ...
Background:
Hypercholesterolemia is a strong risk factor in cardiovascular disease. Oat (Avena sativa L.) beta-glucan, the soluble fiber in oat, has been known to reduce blood cholesterol levels considerably. However, the effect of oat soluble fiber in the Thai population is unknown.
Objective:
To determine the effect of oat consumption on serum lipid profiles in Thai hypercholesterolemic adults.
Material and method:
The present study was a randomized, crossover design. Twenty-four hypercholesterolemic adults, male and female aged 30-60 years, were randomly assigned into two groups of twelve each. Group 1 consumed 70 g (3 g beta-glucan) of oatmeal daily through the first 4-week intervention, and then switched to 70 g rice porridge (control product) daily for the next 4-week intervention. Group 2 consumed rice porridge first and then oatmeal. Before and after each intervention period, lipid profiles including total cholesterol (TC), triglycerides (TG), high density lipoprotein cholesterol (HDL-C), and low density lipoprotein cholesterol (LDL-C) of all subjects were measured.
Results:
Following daily oat consumption, total cholesterol and LDL-cholesterol levels were significantly lower than baseline levels and lower than the levels observed with rice consumption. Oat consumption reduced total cholesterol by 5% and LDL-cholesterol by 10% from baseline levels. In addition, mean and percent changes were significantly different from the levels after consuming rice porridge (p < 0.05).
Conclusion:
Oatmeal reduced serum total cholesterol and LDL-cholesterol levels in hypercholesterolemic Thai adults. Hence, oat consumption is a reasonable recommendation for Thai individuals with hyperlipidemia.
... Three of the 8 oat-based studies selected in the Cochrane review were included in the FDA's evaluation of the oat-soluble fiber health claim, [11][12][13] and the remaining 5 studies were published after 1997. [14][15][16][17][18] The authors had concerns regarding the short duration of the studies and the small number of subjects in some studies. However, when all 8 oat studies were pooled in a meta-analysis, a significant effect of oat consumption to lower TC (P = .0005) ...
Ten years have passed since the Food and Drug Administration (FDA) completed their review of the literature pertaining to the consumption of whole-oat sources of soluble fiber and a reduction in blood cholesterol concentrations. Since that time, data have continued to accumulate regarding oat-soluble fiber consumption, cholesterol, and other physiologic vectors related to cardiovascular health. The objective of this review was to compare the findings of more contemporary analyses of the oat and cholesterol-reduction literature to determine if newer information is consistent with the original conclusion reached by the FDA. A number of formal assessments have been conducted subsequent to the FDA review, and virtually all have reached the same conclusion, namely, consumption of oats and oat-based products significantly reduces total cholesterol and low-density lipoprotein cholesterol concentrations without adverse effects on high-density lipoprotein cholesterol or triglyceride concentrations. In addition, a number of new insights about the potential benefits of oats have emerged over the past 10 years. These more recent data indicate that including oats and oat-based products as part of a lifestyle management program may confer health benefits that extend beyond total cholesterol and low-density lipoprotein cholesterol reduction.
Overweight and obesity are major risk factors for development of non-communicable diseases, such as type-2 diabetes and cardiovascular disease, and increase the risk of early mortality. Diet and food consumption are among the most important factors in preventing and reversing overweight, obesity and their comorbidities. Whole grain has been associated with decreased risk of overweight and obesity in observational studies, but the results from interventions are inconsistent. This may be because very few interventions have been adequately designed for evaluation of the effects of whole grain on body weight management and these effects may differ between different whole grain sources. Rye is the cereal with the highest fiber content and has been suggested to be superior to wheat in inducing beneficial physiological effects with health implications, but large randomized controlled trials with well-characterized intervention foods are lacking. This thesis aimed to investigate the effects of rye-based cereals, compared with refined wheat-based cereals, on body weight loss and metabolic risk factors. Furthermore, the potential influence of subjective appetite and gut microbiota were investigated. High fiber rye-based cereal products were shown to induce greater reduction in body weight and body fat than corresponding refined wheat products after 6 and 12 weeks of intervention among overweight and obese men and women. No consistent effect of rye products on appetite response was found and the changes in body weight and body fat could not be linked to differences in subjective appetite or food intake. However, this may be due to methodological issues and warrants further research. Compared with refined wheat products, high fiber rye-based cereal products were shown to lower C-reactive protein, a marker of inflammation and a risk factor for cardiovascular disease, in two different populations. This effect was associated with reduction in abundance of certain bacteria in the gut that have previously been associated with decreased gut barrier integrity, suggesting that the effect of rye consumption on inflammation may, at least partly, be mediated through changes in gut microbiota composition and decreased gut permeability. In conclusion, the work included in this thesis suggests that replacing wheat-based cereals with high fiber rye-based cereals can aid the reduction of body weight and body fat, and reduce low-grade inflammation. These results can support the development of dietary guidelines and promote the development of healthier food products.
Fullt text: https://research.chalmers.se/en/publication/525267
Overweight and obesity are key features of the metabolic syndrome and closely linked to risk of developing chronic diseases. This chapter reviews evidence from both observational and dietary intervention studies to provide a comprehensive picture of the relationship between whole grains and body weight management. There is consensus among medical professionals that greater abdominal obesity predisposes individuals to greater cardiometabolic risk through a myriad of potential mechanisms, including dyslipidemia, increasing insulin resistance, greater inflammation and increasing blood pressure. Whole grains contribute considerably more dietary fibre than their refined-grain counterparts, which may contribute to suppression of hunger. This may ease adherence to a calorie-restricted diet. Evidence from randomized controlled intervention studies provide only limited evidence supporting a benefit of whole grain intake on body weight regulation. A relatively large number of randomized controlled whole grain intervention studies have been conducted to date, although only a few studies focus primarily on measures of body weight and composition.
Background
In previous meta-analyses of prospective observational studies, we investigated the association between food groups and risk of chronic disease.
Objective
The aim of the present network meta-analysis (NMA) was to assess the effects of these food groups on intermediate-disease markers across randomized intervention trials.
Design
Literature searches were performed until January 2018. The following inclusion criteria were defined a priori: 1) randomized trial (≥4 wk duration) comparing ≥2 of the following food groups: refined grains, whole grains, nuts, legumes, fruits and vegetables, eggs, dairy, fish, red meat, and sugar-sweetened beverages (SSBs); 2) LDL cholesterol and triacylglycerol (TG) were defined as primary outcomes; total cholesterol, HDL cholesterol, fasting glucose, glycated hemoglobin, homeostasis model assessment insulin resistance, systolic and diastolic blood pressure, and C-reactive protein were defined as secondary outcomes. For each outcome, a random NMA was performed, and for the ranking, the surface under the cumulative ranking curves (SUCRA) was determined.
Results
A total of 66 randomized trials (86 reports) comparing 10 food groups and enrolling 3595 participants was identified. Nuts were ranked as the best food group at reducing LDL cholesterol (SUCRA: 93%), followed by legumes (85%) and whole grains (70%). For reducing TG, fish (97%) was ranked best, followed by nuts (78%) and red meat (72%). However, these findings are limited by the low quality of the evidence. When combining all 10 outcomes, the highest SUCRA values were found for nuts (66%), legumes (62%), and whole grains (62%), whereas SSBs performed worst (29%).
Conclusion
The present NMA provides evidence that increased intake of nuts, legumes, and whole grains is more effective at improving metabolic health than other food groups. For the credibility of diet-disease relations, high-quality randomized trials focusing on well-established intermediate-disease markers could play an important role. This systematic review was registered at PROSPERO (www.crd.york.ac.uk/PROSPERO) as CRD42018086753.
Background:
There is evidence from observational studies that whole grains can have a beneficial effect on risk for cardiovascular disease (CVD). Earlier versions of this review found mainly short-term intervention studies. There are now longer-term randomised controlled trials (RCTs) available. This is an update and expansion of the original review conducted in 2007.
Objectives:
The aim of this systematic review was to assess the effect of whole grain foods or diets on total mortality, cardiovascular events, and cardiovascular risk factors (blood lipids, blood pressure) in healthy people or people who have established cardiovascular disease or related risk factors, using all eligible RCTs.
Search methods:
We searched CENTRAL (Issue 8, 2016) in the Cochrane Library, MEDLINE (1946 to 31 August 2016), Embase (1980 to week 35 2016), and CINAHL Plus (1937 to 31 August 2016) on 31 August 2016. We also searched ClinicalTrials.gov on 5 July 2017 and the World Health Organization International Clinical Trials Registry Platform (WHO ICTRP) on 6 July 2017. We checked reference lists of relevant articles and applied no language restrictions.
Selection criteria:
We selected RCTs assessing the effects of whole grain foods or diets containing whole grains compared to foods or diets with a similar composition, over a minimum of 12 weeks, on cardiovascular disease and related risk factors. Eligible for inclusion were healthy adults, those at increased risk of CVD, or those previously diagnosed with CVD.
Data collection and analysis:
Two review authors independently selected studies. Data were extracted and quality-checked by one review author and checked by a second review author. A second review author checked the analyses. We assessed treatment effect using mean difference in a fixed-effect model and heterogeneity using the I(2) statistic and the Chi(2) test of heterogeneity. We assessed the overall quality of evidence using GRADE with GRADEpro software.
Main results:
We included nine RCTs randomising a total of 1414 participants (age range 24 to 70; mean age 45 to 59, where reported) to whole grain versus lower whole grain or refined grain control groups. We found no studies that reported the effect of whole grain diets on total cardiovascular mortality or cardiovascular events (total myocardial infarction, unstable angina, coronary artery bypass graft surgery, percutaneous transluminal coronary angioplasty, total stroke). All included studies reported the effect of whole grain diets on risk factors for cardiovascular disease including blood lipids and blood pressure. All studies were in primary prevention populations and had an unclear or high risk of bias, and no studies had an intervention duration greater than 16 weeks.Overall, we found no difference between whole grain and control groups for total cholesterol (mean difference 0.07, 95% confidence interval -0.07 to 0.21; 6 studies (7 comparisons); 722 participants; low-quality evidence).Using GRADE, we assessed the overall quality of the available evidence on cholesterol as low. Four studies were funded by independent national and government funding bodies, while the remaining studies reported funding or partial funding by organisations with commercial interests in cereals.
Authors' conclusions:
There is insufficient evidence from RCTs of an effect of whole grain diets on cardiovascular outcomes or on major CVD risk factors such as blood lipids and blood pressure. Trials were at unclear or high risk of bias with small sample sizes and relatively short-term interventions, and the overall quality of the evidence was low. There is a need for well-designed, adequately powered RCTs with longer durations assessing cardiovascular events as well as cardiovascular risk factors.
Angie Jefferson reviews the role of oats and their constituent fibre beta-glucan in cholesterol reduction, and provides practical advice for supporting patients with dietary change
The lipid-lowering effect of a carob pulp preparation rich in insoluble dietary fiber and polyphenols was investigated in a noncomparative, open-label pilot study. Over 8 weeks, 47 volunteers with moderate hypercholesterolemia (total cholesterol 232-302 mg/dL) consumed 15 g of carob per day in three products (breakfast cereal, fruit muesli bar, powdered drink) as a supplement to their regular diet. After 4 weeks, reductions of 7.1% in mean total cholesterol and 10.6% in LDL cholesterol were noted; respective decreases after 6 weeks were 7.8% and 12.2% (all P<.001). HDL cholesterol and triglyceride levels remained unchanged. Overall compliance was good. Only 3 volunteers (6%) reported a sensation of fullness, which led to 2 of the 3 dropouts. The carob preparation may have value in the dietary treatment of hypercholesterolemia.
Background:
There is increasing evidence from observational studies that wholegrains can have a beneficial effect on risk factors for coronary heart disease (CHD).
Objectives:
The primary objective is to review the current evidence from randomised controlled trials (RCTs) that assess the relationship between the consumption of wholegrain foods and the effects on CHD mortality, morbidity and on risk factors for CHD, in participants previously diagnosed with CHD or with existing risk factors for CHD.
Search strategy:
We searched CENTRAL (Issue 4, 2005), MEDLINE (1966 to 2005), EMBASE (1980 to 2005), CINAHL (1982 to 2005), ProQuest Digital Dissertations (2004 to 2005). No language restrictions were applied.
Selection criteria:
We selected randomised controlled trials that assessed the effects of wholegrain foods or diets containing wholegrains, over a minimum of 4 weeks, on CHD and risk factors. Participants included were adults with existing CHD or who had at least one risk factor for CHD, such as abnormal lipids, raised blood pressure or being overweight.
Data collection and analysis:
Two of our research team independently assessed trial quality and extracted data. Authors of the included studies were contacted for additional information where this was appropriate.
Main results:
Ten trials met the inclusion criteria. None of the studies found reported the effect of wholegrain diets on CHD mortality or CHD events or morbidity. All 10 included studies reported the effect of wholegrain foods or diets on risk factors for CHD. Studies ranged in duration from 4 to 8 weeks. In eight of the included studies, the wholegrain component was oats. Seven of the eight studies reported lower total and low density lipoproteins (LDL) cholesterol with oatmeal foods than control foods. When the studies were combined in a meta-analysis lower total cholesterol (-0.20 mmol/L, 95% confidence interval (CI) -0.31 to -0.10, P = 0.0001 ) and LDL cholesterol (0.18 mmol/L, 95% CI -0.28 to -0.09, P < 0.0001) were found with oatmeal foods. However, there is a lack of studies on other wholegrains or wholegrain diets.
Authors' conclusions:
Despite the consistency of effects seen in trials of wholegrain oats, the positive findings should be interpreted cautiously. Many of the trials identified were short term, of poor quality and had insufficient power. Most of the trials were funded by companies with commercial interests in wholegrains. There is a need for well-designed, adequately powered, longer term randomised controlled studies in this area. In particular there is a need for randomised controlled trials on wholegrain foods and diets other than oats.
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