Gene A. Spiller

Nuts and plasma lipids : An almond-based diet lowers LDL-C while preserving HDL-C

OBJECTIVE To compare lipid-altering effects of an almond-based diet with an olive oil-based diet, against a cheese and butter-based control diet. METHODS Forty-five free-living hyperlipidemic men (n = 12) and women (n = 33) with a mean plasma total cholesterol (TC) of 251 +/- 30 mg/dL followed one of three diets; almond-based, olive oil-based, or dairy-based for 4 weeks. Total fat in each diet was matched, and the study-provided sources of fat comprised the major portion of fat intake. RESULTS Reductions in TC and low-density lipoprotein-cholesterol (LDL-C) between the three groups were significantly different from the almond group (both p < 0.001). Within group analysis revealed that the almond-based diet induced significant reductions in TC (p < 0.05), LDL-C (p < 0.001), and the TC:HDL ratio (p < 0.001), while HDL-C levels were preserved. TC and HDL-C in the control diet were significantly increased from baseline (both p < 0.05), while the olive oil-based diet resulted in no significant changes over the study period. Weight did not change significantly. CONCLUSION Results suggest that the more favorable lipid-altering effects induced by the almond group may be due to interactive or additive effects of the numerous bioactive constituents found in almonds.

The Effect of a Plant-Based Diet on Plasma Lipids in Hypercholesterolemic Adults: A Randomized Trial

Context People can achieve recommended fat intake while consuming high or low amounts of vegetables, fruits, legumes, and whole grains. Contribution This 4-week randomized trial compared 2 diets with different vegetable, fruit, legume, and whole-grain content but identical total fat, saturated fat, protein, carbohydrate, and cholesterol content. The 59 adults who consumed high amounts of vegetables, fruits, legumes, and whole grains had greater improvements in total and low-density lipoprotein cholesterol levels than the 61 adults who ate low amounts of these foods. Implications At least over the short term, greater improvements in low-density lipoprotein and total cholesterol are an additional benefit of diets high in vegetables, fruits, legumes, and whole grains. The Editors It is well established that elevated low-density lipoprotein (LDL) cholesterol concentrations are a risk factor for cardiovascular diseases and that dietary modification is considered a first approach to their treatment and control (1, 2). For several decades, dietary modification for lipid management traditionally focused on avoiding saturated fat and cholesterol (3-5). Previous examples of dietary interventions targeting LDL cholesterol level often reported only modest lipid improvements, leading some to consider diet a relatively ineffective therapy (6). However, recent developments have suggested that the traditional focus of lipid management may have been overly simplistic and that diets might be more effective if more attention was focused on including certain foods or factors rather than just avoiding saturated fat and cholesterol. Effective refinements of dietary strategies for lipid management could decrease the gap in effectiveness between dietary approaches and drug therapy. Several dietary factors or foods, including soy protein, soy isoflavones, plant sterols, soluble fiber, oats, nuts, and garlic, have established or potential lipid benefits (7-13). Each is derived from plant food sources, and it is inclusion of these factors, rather than avoidance, that is reported to confer benefits. However, given that most plant foods contain low or negligible amounts of saturated fat and that all plant foods are devoid of cholesterol, it follows that a plant-based diet is inherently low in saturated fat and cholesterol. Therefore, it is difficult to distinguish between plasma lipid benefits derived from the actual plant-based dietary components and those derived from avoidance of saturated fat and cholesterol. Several studies have been designed to test the effects on plasma lipids of diets with identical saturated fat and cholesterol intake but varied amounts of 1 or 2 additional dietary components (14-16). Data are more limited on dietary approaches that hold saturated fat and cholesterol intake constant while modifying multiple other dietary components simultaneously (17). Modifying multiple dietary components simultaneously (for example, increasing intake of vegetables, fruits, and low-fat dairy) while holding sodium intake constant has been shown to effectively lower elevated blood pressure in the Dietary Approaches to Stop Hypertension trials (DASH I and II) (18, 19). Testing a parallel approach to refining dietary intervention for lipid management is warranted. In 2000, the American Heart Association (AHA) reported revised dietary guidelines that substantially modified its 1993 and 1996 guidelines (2, 4, 5). All 3 versions of the guidelines recommended keeping saturated fat intake at less than 10% of energy and cholesterol intake below 300 mg/d. A notable modification of the 2000 guidelines was to emphasize foods and overall eating patterns, including increased intakes of vegetables and whole grains (in general, a plant-based diet). It was our hypothesis that a plant-based diet consistent with the revised AHA 2000 guidelines would increase the LDL cholesterol-lowering benefits of the previous AHA Step I guidelines. We theorized that this improvement would be independent of the plant-based diets saturated fat and cholesterol content. Therefore, we designed 2 diets that had identical levels of total fat (30% of energy), saturated fat (10% of energy), and cholesterol (<300 mg/d) but differed substantially in content of nutrient- and phytochemical-dense plant-based foods. The purpose of the study was to determine whether LDL cholesterol-lowering benefits among adults with moderately elevated cholesterol levels would be greater under weight-stable conditions with a plant-based low-fat diet than with a more typical, convenience-oriented low-fat diet that was identical in intake of total fat, saturated fat, and cholesterol. Methods Participants Participants were recruited from the local community, primarily through newspaper advertisements, letters to previous study participants, and flyers sent to university employees. Men and women were invited to enroll if they were 30 to 65 years of age with fasting plasma LDL cholesterol levels of 3.3 to 4.8 mmol/L (130 to 190 mg/dL), fasting plasma triglyceride levels less than 2.83 mmol/L (< 250 mg/dL), body mass index between 19 and 31 kg/m2, and a current diet estimated to derive at least 10% of energy from saturated fat. Pregnant women, persons who smoked, persons with prevalent heart disease or diabetes, or persons who had been using lipid-lowering or blood pressure-lowering medications within the past month (all determined through self-report) were excluded. During the recruitment phase, 1096 individuals were screened by telephone interview and 345 who met the initial inclusion criteria were considered eligible for cholesterol testing. Of these 345 persons, 188 who were found to have eligible concentrations of LDL cholesterol and triglycerides attended an orientation meeting. Fifty-one persons decided not to participate (primarily because of the time commitment), and an additional 12 potential participants were excluded after a 3-day food record showed that their estimated average intake of saturated fat was already less than 10% of energy. One hundred twenty-five participants were randomly assigned to 1 of the 2 diet groups. The Stanford University Human Subjects Committee reviewed and approved the investigation, all participants signed an informed consent form before enrollment, and the study was performed according to Declaration of Helsinki guidelines (20). Design The trial used a parallel design. We randomly assigned participants in blocks of 20 by selecting, without replacement, from a set of indistinguishable envelopes containing 10 assignments to each of the 2 diet groups. Randomization of the envelopes was done by hand, without a computer algorithm. No stratification criteria were used. Each participant was provided with meals, snacks, and beverages on an outpatient basis for 28 days, as described later. Diets Both study diets were designed to provide 30% of energy from total fat, 10% of energy from saturated fat, and approximately 100 mg of cholesterol per 1000 kcal per day. During the menu-designing stage of the study, the nutrient composition of the diets was determined by using the database of Food Processor software, version 7.0 (ESHA Research, Salem, Oregon). Menus were designed by using commonly available foods from local markets. The Low-Fat diet was designed to include many reduced-fat prepared-food items (for example, reduced-fat cheeses, low-fat frozen lasagna, and low-fat and sugar-rich snack foods). In contrast, the Low-Fat Plus diet was designed to include considerably more vegetables, legumes, whole grains, and fruits. Butter, cheese, and eggs were added to the daily menus for the Low-Fat Plus diet, increasing the saturated fat and cholesterol content to match the Low-Fat diet. A 7-day menu cycle was designed for each of the 2 study diets; therefore, each menu was repeated 4 times during the 28 days. The diets included breakfast, lunch, dinner, beverages, and snacks for each day. Each weekday, the participants ate either lunch or dinner at the dining facility of the Stanford General Clinical Research Center. After their on-site meal, they were given coolers that contained meals and snacks to be consumed off-site. On Fridays, participants received weekend meals to be consumed off-site. Appendix Table 1 and Appendix Table 2 list the daily menus. One free-choice evening meal was allowed each weekend. For this meal, participants were given guidelines for choosing low-fat meals consistent with their diet assignments and were required to keep a record of foods consumed. These records were analyzed for nutritional content and were used to determine the impact of the free-choice meals on the overall study diets. Adherence was measured by using daily log sheets kept by participants that tracked incomplete consumption of study foods or consumption of any nonstudy foods. The 28 daily food logs for each participant were examined for deviations from the diets. The energy contribution of each deviation was determined and then totaled for the entire 28-day protocol period. Each of the 14 daily menus (7-day cycle 2 diets) was analyzed chemically for nutrient content before the study and then again during the study (Covance Laboratories, Madison, Wisconsin). The chemical analyses performed before the study confirmed that the average composition of the daily menus provided 30% of energy from total fat, 10% of energy from saturated fat, and approximately 100 mg of cholesterol per 1000 kcal per day. When the 2 diets were first designed, we attempted to match their mono- and polyunsaturated fat content. However, the database used in the design phase was missing values for these nutrients for approximately 20% of the foods. In addition, many of the specific products purchased locally for the study provided incomplete information for the content of these unsaturated fats. The first round of chemical analyses of the diets, performed before enrollment began, indicated a modest discrepancy b

Dietary fiber in human nutrition

In recent years there has been a reawakening of interest in the effect of plant fibers on human nutrition. This has been spurred by the epidemiological work of Burkitt, Painter, Walker, and Trowell and by some laboratory and clinical studies performed by Eastwood, Kritchevsky, and other investigators. “Fiber” is the collective term used to identify the various polysaccharides and lignin fractions of foods that are not hydrolyzed by the enzymes of the digestive system (but that are, or might be, hydrolyzed by intestinal microorganisms). To some investigators, “fiber” means all these polymers plus the other components of the cell wall (cutins, minerals, etc.) intimately involved in the fiber function. The combination of epidemiological studies and laboratory research has lead to various hypotheses that have linked “low fiber diets” in Western countries to various chronic diseases. Some of the diseases mentioned are major chronic afflictions of the developed nations (e.g., colon cancer and CHD), and the poss...

Role of water-soluble dietary fiber in the management of elevated plasma cholesterol in healthy subjects.

Guidelines for the use of water-soluble dietary fibers (WSDF) in the dietary management of elevated plasma cholesterol are not well-established. Consequently, 4 studies were conducted to explore the plasma lipid-lowering effects of a variety of WSDF. Studies were randomized, double-blind, placebo-controlled trials involving healthy men and women (plasma cholesterol greater than 5.17 mmol/liter; greater than 200 mg/dl). Study duration ranged from 4 to 12 weeks. The WSDF acacia gum yields a low viscosity, palatable beverage when mixed in water. However, despite its WSDF classification, acacia gum consumed for 4 weeks as the sole WSDF source (15 g of WSDF/day) or primary source in a WSDF mixture (17.2 g of WSDF/day; 56% derived from acacia gum) did not produce a significant lipid-lowering effect versus placebo. When 15 g of WSDF/day consisting of psyllium hust, pectin, and guar and locust bean gums (medium viscosity) was consumed for 4 weeks, significant reductions in cholesterol resulted (total cholesterol 8.3%, low-density lipoprotein cholesterol 12.4%; p less than 0.001) that were comparable to changes achieved with 10 g of WSDF/day from high-viscosity guar gum. The magnitude of the lipid-lowering effect was related to intake of WSDF ranging from 5 to 15 g/day (low-density lipoprotein cholesterol +0.8% [placebo], -5.6% [5 g/day], -6.8% [10 g/day], -14.9% [15 g/day]; p less than 0.01 for trend). The effects of WSDF on plasma lipids were similar for men and women. A diet rich in selected WSDF may be a useful adjunct to the dietary management of elevated plasma cholesterol.

A Diet High in Whole and Unrefined Foods Favorably Alters Lipids, Antioxidant Defenses, and Colon Function

Objective: Diets rich in whole and unrefined foods, like whole grains, dark green and yellow/orange-fleshed vegetables and fruits, legumes, nuts and seeds, contain high concentrations of antioxidant phenolics, fibers and numerous other phytochemicals that may be protective against chronic diseases. This study compared the effects of a phytochemical-rich diet versus a refined-food diet on lipoproteins, antioxidant defenses and colon function. Methods: Twelve hyperlipidemic women followed two diets for four weeks starting with a refined-food diet. Subjects then directly crossed over to the phytochemical-rich diet. Duplicate, fasting serum lipids and single, fasting antioxidant enzymes were measured at the end of the four-week refined-food diet period (baseline) and again at the end of the phytochemical-rich diet period. Results: Total energy and total fat intake were similar during both diet periods, but there was a decrease in saturated fat (SFA) of 61% in the phytochemical-rich diet group. Dietary fiber, vitamin E, vitamin C and carotene intakes were 160%, 145%, 160% and 500% more, respectively, than during the refined-food diet period. The phytochemical-rich diet induced a drop of 13% in total cholesterol (TC) (p < 0.05) and 16% (p < 0.001) in low density lipoprotein-cholesterol (LDL-C). Erythrocyte superoxide dismutase decreased 69% (p < 0.01) and glutathione peroxidase dropped 35% (p < 0.01). Colon function was improved on the phytochemical-rich diet Conclusions: A diet abundant in phytochemically-rich foods beneficially affected lipoproteins, decreased need for oxidative defense mechanisms and improved colon function

Effects of plant-based diets high in raw or roasted almonds, or roasted almond butter on serum lipoproteins in humans

Objective: To compare the lipid-altering effect of roasted salted almonds and roasted almond butter with that of raw almonds, as part of a plant-based diet. Methods: Thirty-eight free-living, hypercholesterolemic men (n = 12) and women (n = 26) with a mean total serum cholesterol (TC) of 245 + 29 mg/dL (mean + SD) followed a heart-healthy diet including 100g of one of three forms of almonds: roasted salted almonds, roasted almond butter or raw almonds for four weeks. Measurements of serum TC, triglycerides (TG), selected lipoproteins and blood pressure were taken at baseline and after four weeks. Results: All three forms of almonds in the context of a heart-healthy diet significantly lowered low-density lipoprotein-cholesterol (LDL) from baseline to the completion of the study. Both raw and roasted almonds significantly lowered TC, whereas the decrease by almond butter (in a smaller cohort) did not reach statistical significance. High-density lipoprotein-cholesterol (HDL) did not significantly change with raw or roasted almonds but slightly increased with almond butter. At the end of the study, blood pressure did not change significantly from baseline values for any of the groups. Conclusion: These results suggest that unblanched almonds—whether raw, dry roasted, or in roasted butter form—can play an effective role in cholesterol-lowering, plant-based diets.

Effects of a Very Low-Fat, Vegan Diet in Subjects with Rheumatoid Arthritis

OBJECTIVE To demonstrate the effects of a very low-fat, vegan diet on patients with rheumatoid arthritis (RA). DESIGN Single-blind dietary intervention study. SUBJECTS AND STUDY INTERVENTIONS: This study evaluated the influence of a 4-week, very low-fat (approximately 10%), vegan diet on 24 free-living subjects with RA, average age, 56 +/- 11 years old. OUTCOME MEASUREMENTS Prestudy and poststudy assessment of RA symptomatology was performed by a rheumatologist blind to the study design. Biochemical measures and 4-day diet data were also collected. Subjects met weekly for diet instruction, compliance monitoring, and progress assessments. RESULTS There were significant (p < 0.001) decreases in fat (69%), protein (24%), and energy (22%), and a significant increase in carbohydrate (55%) intake. All measures of RA symptomatology decreased significantly (p < 0.05), except for duration of morning stiffness (p > 0.05). Weight also decreased significantly (p < 0.001). At 4 weeks, C-reactive protein decreased 16% (ns, p > 0.05), RA factor decreased 10% (ns, p > 0.05), while erythrocyte sedimentation rate was unchanged (p > 0.05). CONCLUSION This study showed that patients with moderate-to-severe RA, who switch to a very low-fat, vegan diet can experience significant reductions in RA symptoms.

The effect of acacia gum and a water-soluble dietary fiber mixture on blood lipids in humans.

Water-soluble dietary fibers (WSDF) are generally thought to lower cholesterol. This study compared the cholesterol-lowering effects of a medium viscosity WSDF mixture (psyllium, pectin, guar gum and locust bean gum) with an equal amount of WSDF from acacia gum, which has a lower viscosity. Hypercholesterolemic males (n = 13) and females (n = 16) were randomly assigned to one of two WSDF treatments provided in a low-calorie powder form for mixing into beverages (< 4 kcal/serving). Subjects were instructed to mix powders into their usual beverages and to consume them three times daily (5 g WSDF/serving) for 4 weeks while consuming their typical fat-modified diets. Exercise and body weights were also held constant. The WSDF mixture yielded a 10% decrease in plasma total cholesterol (from 251 +/- 20 to 225 +/- 19 mg/dL; p < 0.01), and a 14% reduction in low-density lipoprotein cholesterol (from 167 +/- 14 to 144 +/- 14 mg/dL; p < 0.001). No significant changes in plasma high-density lipoprotein cholesterol, very-low-density lipoprotein cholesterol or triglycerides were observed. In contrast, the acacia gum-treated group showed no change in any plasma lipid parameters. The WSDF treatments did not produce significant changes in mean dietary intakes within or between treatment groups. These data support previous findings that a diet rich in select WSDF can be a useful cholesterol-lowering adjunct to a fat-modified diet, but that caution should be exercised in ascribing cholesterol-lowering efficacy to dietary fibers based solely on their WSDF classification. Finally, WSDF viscosity is a potential cholesterol-lowering factor to be explored further.

Isoflavone Supplements Do Not Affect Thyroid Function in Iodine-Replete Postmenopausal Women

Despite the safety review conducted by the U.S. Food and Drug Administration in the process of awarding a health claim for the cholesterol-lowering properties of soy protein, concerns about the possible goitrogenic effects of soybean isoflavones persist. Concerns are based primarily on in vitro research, animal studies, and older reports of goiter in infants fed soy formula not fortified with iodine. In a randomized, double blind, placebo-controlled study, we investigated the effect on thyroid function of a daily supplement containing 90 mg (aglycone weight) of total isoflavones/day versus placebo in 38 postmenopausal women, 64-83 years old, not on hormone replacement therapy. Serum thyroid-stimulating hormone (TSH), thyroxine (T4), and triiodothyronine (T3) were measured at baseline and after 90 and 180 days. In the supplement group, at baseline and 6 months, TSH (micro U/ml), T4 (nM), and T3 (nM) levels (mean +/- SE) were 3.00 +/- 0.44, 149.00 +/- 5.04, and 1.53 +/- 0.13, respectively, and 3.49 +/- 0.52, 154.52 +/- 2.09, and 1.78 +/- 0.12, respectively. In the control group, levels at baseline and at 6 months were 3.35 +/- 0.51, 145.39 +/- 6.69, and 1.55 +/- 0.18, respectively, and 3.63 +/- 0.57, 153.77 +/- 6.64, and 1.75 +/- 0.10, respectively. Intragroup differences for all three measures were statistically indistinguishable at 6 months, and levels were similar between the isoflavone supplement and placebo groups at each measurement. These results indicate that in this group of healthy iodine-replete subjects, soy isoflavones do not adversely affect thyroid function.

Effect of tartaric acid and dietary fibre from sun-dried raisins on colonic function and on bile acid and volatile fatty acid excretion in healthy adults.

Sun-dried raisins are a source of dietary fibre and tartaric acid. The effects of tartaric acid on colon function have not been the focus of extensive research. The purpose of the present study was to evaluate the effects of dietary fibre and tartaric acid from sun-dried raisins on colon function and on faecal bile acid and short-chain fatty acid (SCFA) excretion in healthy adults. Thirteen healthy subjects were fed 120 g sun-dried raisins/d or 5 g cream of tartar (equivalent to the tartaric acid in 120 g sun-dried raisins)/d for 9 weeks, divided into 3-week cycles. The experimental diets were fed in a crossover design after an initial control period. Faeces were collected for the last 4 d of each cycle for analysis of SCFA and bile acids. Intestinal transit time decreased from 42 h on the baseline diet to 31 h on cream of tartar (P<0.1) and to 28 h on sun-dried raisins (P<0.05). Faeces were softer on both sun-dried raisins and cream of tartar, but sun-dried raisins increased faecal wet weight (P<0.05), while cream of tartar did not. Sun-dried raisins caused significant reductions from baseline values in total bile acid concentration (from 1.42 (SD 1.03) to 1.09 (SD 0.76) mg/g, P<0.05), whereas cream of tartar did not (1.40 (SD 1.06) mg/g). Sun-dried raisins also significantly reduced the lithocholic (LC):deoxylithocholic acid (DC) ratio (from 1.63 (SD 0.85) to 1.09 (SD 0.50), P<0.02), whereas cream of tartar reduced the ratio, but to a lesser extent (1.29 (SD 0.79), NS). Both faecal bile acids and the LC:DC ratio are indicators of reduced risk for colon cancer. Sun-dried raisins increased total SCFA excretion (from 5.6 (SD 3.4) to 7.6 (SD 3.0) g/4 d, P<0.05), which remained unchanged with cream of tartar (5.6 (SD 3.0) g/4 d). Both sun-dried raisins and cream of tartar appear to be good stool softeners and to shorten intestinal transit time, although the fibre in sun-dried raisins has the added benefit of increasing faecal weight. Both sun-dried raisins and cream of tartar modulate the composition of faecal bile acids and SCFA in a way that has potential health benefits.