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Biomedical subjects

C W Kendall

Publications and source records attributed to C W Kendall.

At least 19 recordsLinked to original sources
PubMed2000

Effect of soy protein foods on low-density lipoprotein oxidation and ex vivo sex hormone receptor activity--a controlled crossover trial.

Plant-derived estrogen analogs (phytoestrogens) may confer significant health advantages including cholesterol reduction, antioxidant activity, and possibly a reduced cancer risk. However, the concern has also been raised that phytoestrogens may be endocrine disrupters and major health hazards. We therefore assessed the effects of soy foods as a rich source of isoflavonoid phytoestrogens on LDL oxidation and sex hormone receptor activity. Thirty-one hyperlipidemic subjects underwent two 1-month low-fat metabolic diets in a randomized crossover study. The major differences between the test and control diets were an increase in soy protein foods (33 g/d soy protein) providing 86 mg isoflavones/2,000 kcal/d and a doubling of the soluble fiber intake. Fasting blood samples were obtained at the start and at weeks 2 and 4, with 24-hour urine collections at the end of each phase. Soy foods increased urinary isoflavone excretion on the test diet versus the control (3.8+/-0.7 v 0.0+/-0.0 mg/d, P < .001). The test diet decreased both oxidized LDL measured as conjugated dienes in the LDL fraction (56+/-3 v 63+/-3 micromol/L, P < .001) and the ratio of conjugated dienes to LDL cholesterol (15.0+/-1.0 v 15.7+/-0.9, P = .032), even in subjects already using vitamin E supplements (400 to 800 mg/d). No significant difference was detected in ex vivo sex hormone activity between urine samples from the test and control periods. In conclusion, consumption of high-isoflavone foods was associated with reduced levels of circulating oxidized LDL even in subjects taking vitamin E, with no evidence of increased urinary estrogenic activity. Soy consumption may reduce cardiovascular disease risk without increasing the risk for hormone-dependent cancers.

Adult↗
PubMed2000

The effect on serum lipids and oxidized low-density lipoprotein of supplementing self-selected low-fat diets with soluble-fiber, soy, and vegetable protein foods.

An increased intake of soluble fiber and soy protein may improve the blood lipid profile. To assess any additional benefit on serum lipids of providing soy protein and soluble-fiber foods to hyperlipidemic subjects already consuming low-fat, low-cholesterol therapeutic diets, 20 hyperlipidemic men and postmenopausal women completed 8-week test and control dietary treatments in a randomized crossover design as part of an ad libitum National Cholesterol Education Program (NCEP) step 2 therapeutic diet (<7% saturated fat and <200 mg/d cholesterol). During the test phase, foods high in soy, other vegetable proteins, and soluble fiber were provided. During the control phase, low-fat dairy and low-soluble-fiber foods were provided. Fasting blood lipid and apolipoprotein levels were measured at 4 and 8 weeks of each phase. On the test diet, 12 +/- 2 g/d soy protein was selected from the foods chosen. Direct comparison of test and control treatments indicated an elevated high-density lipoprotein (HDL) cholesterol concentration on the test diet (6.4% +/- 2.4%, P = .013) and a significantly reduced total to HDL cholesterol ratio (-5.9% +/- 2.3%, P = .020). The proportion of conjugated dienes in the low-density lipoprotein (LDL) cholesterol fraction was significantly reduced (8.5% +/- 3.3%, P = .020) as a marker of oxidized LDL. A combination of acceptable amounts of soy, vegetable protein, and soluble-fiber foods as part of a conventional low-fat, low-cholesterol therapeutic diet is effective in further reducing serum lipid risk factors for cardiovascular disease.

Adult↗
PubMed2000

Dietary fibre, lente carbohydrates and the insulin-resistant diseases.

Several epidemiological studies link consumption of fibre-rich foods to a reduced risk of type 2 diabetes and CHD. The 'fibre hypothesis' suggested that this was a direct effect of fibre. However, fibre-rich foods contain different types of fibre as well as other potentially beneficial compounds, and many foods naturally high in fibre have low glycaemic and insulinaemic indices, possibly due to food form. The question therefore emerges as to the effect of isolated fibre per se on insulin sensitivity, lipids and other risk factors associated with the metabolic syndrome. Many beneficial effects are seen with pharmacological doses of isolated viscous soluble fibre, including improved insulin sensitivity, decreased LDL-cholesterol levels and decreased clotting factors. Similar effects are seen with low glycaemic-index foods. In contrast, insoluble non-viscous cereal fibre is not seen to act directly on risk factors when taken in refined foods such as in milled flour. Since cereal fibre, the major type of fibre in western diets, does not directly act on the risk factors for the metabolic syndrome, the question remains as to possible mechanisms. Until now, fibre and the nature and processing of the starch and particle size have been seen as the main determinants of the metabolic response to starchy foods. However, fibre-rich foods also have an increased protein-to-carbohydrate ratio. Hence we suggest that the protective effect of fibre may also be due to increased vegetable protein content, which may act directly to reduce clotting factors and oxidized LDL-cholesterol levels.

Adult↗
PubMed2000

Effect of soy-based breakfast cereal on blood lipids and oxidized low-density lipoprotein.

Consumption of soy protein may reduce the risk of cardiovascular disease both through reduction in serum lipids and by the antioxidant properties of protein-associated soy isoflavones. However, the effect that processing required for the manufacture of breakfast cereals may have on the lipid lowering and antioxidant activities of soy has not been studied. We have therefore assessed the health benefits of soy incorporation into breakfast cereals. Twenty-five hyperlipidemic men and women took soy (providing 36 g/d soy protein and 168 mg/d isoflavones) and control breakfast cereals, each for 3 weeks in a randomized crossover study with a 2-week washout period between treatments. Fasting blood samples were obtained pretreatment and at weeks 2 and 3 of each treatment. No significant difference was seen in serum lipids between treatments at week 3 apart from a 3.8% +/- 1.5% higher apolipoprotein A-1 level on control versus soy (P = .021). However, oxidized low-density lipoprotein (LDL) was reduced on the test compared with the control both as total dienes in LDL and as the ratio of conjugated dienes to cholesterol in the LDL fraction by 9.2% +/- 4.3% (P = .042) and 8.7% +/- 4.2% (P = .050), respectively. High isoflavone intakes in soy breakfast cereals may decrease the risk of cardiovascular disease by reducing oxidized LDL, while having no significant effect on the absolute concentration of LDL cholesterol.

Adult↗
PubMed2000

Viscous and nonviscous fibres, nonabsorbable and low glycaemic index carbohydrates, blood lipids and coronary heart disease.

Viscous fibres such as guar, glucomannans, pectins, oat betaglucan and psyllium continue to be seen as hypocholesterolaemic. Nevertheless, in large cohort studies, ironically it is the insoluble cereal fibre that has been demonstrated to relate negatively to cardiovascular disease and diabetes, despite an absence of effect on fasting lipids or postprandial glycaemia. In general, resistant or nonabsorbable starch is lipid neutral, whereas some nonabsorbable sugars or oligosaccharides may raise serum cholesterol, possibly through providing more acetate after colonic fermentation by colonic microflora. On the other hand, fructo-oligosaccharides appear to reduce serum triglycerides for reasons that are not entirely clear. Of possibly greater recent interest have been the carbohydrates that are not so much resistant to absorption, but rather are slowly absorbed. They possess some of the features of dietary fibre in providing a substrate for colonic bacterial fermentation. In the small intestine, however, they form lente or sustained release carbohydrate. In the form of low glycaemic index foods, lente carbohydrate consumption has been shown to relate to improved blood lipid profiles in hyperlipidaemic individuals and improved glycaemic control in diabetes. In larger cohort studies, low glycaemic index foods or low glycaemic load diets have been associated with higher HDL-cholesterol levels and reduced incidence of diabetes and cardiovascular disease.

Blood Glucose↗
PubMed2000

Effect of soluble and insoluble fiber diets on serum prostate specific antigen in men.

PURPOSE: We assess whether high fiber diets influence serum prostate specific antigen (PSA) related to effects on serum sex hormone levels and fecal steroid excretion. MATERIALS AND METHODS: A randomized crossover controlled trial was performed on 14 healthy men with hyperlipidemia on 2 metabolic diets 4 months in duration with each containing foods high in soluble or insoluble fiber and approximately 25 to 30 gm. dietary fiber per 1,000 kilocalories. Serum PSA, free testosterone and estradiol, and fecal bile acid and neutral sterol excretion were evaluated. RESULTS: Mean serum PSA was lower with the soluble than the insoluble fiber diet (0.07+/-0.03 ng./ml., p = 0.035). No treatment difference was seen in free testosterone or estradiol, although the latter decreased significantly with the insoluble fiber diet (9+/-3 pmol./l., p = 0.004). After 16 weeks total fecal bile acid output was greater with the soluble (341+/-56 mg. daily) compared to the insoluble (203+/-35, p = 0.001) fiber diet but no differences were seen in fecal neutral sterol elimination. The treatment difference in fecal lithocholic acid output related to the difference in serum PSA (r = 0.57, p = 0.035). CONCLUSIONS: A small but statistically significantly lower serum PSA was seen in healthy men consuming soluble fiber, which was not related to changes in serum sex hormones but was related to the increased lithocholic acid output as a possible marker of increased fecal steroid elimination. The effect of soluble fiber on prostatic disease may warrant further investigation.

Adult↗
PubMed1999

Colonic bacterial activity and serum lipid risk factors for cardiovascular disease.

Antibiotics are being proposed for the treatment of cardiovascular disease. In the past, antibiotics were advocated for the control of hypercholesterolemia. We have therefore investigated the relation between colonic bacterial activity and serum lipids. In a four-phase randomized crossover study, we fed a different starch supplement during each 2-week phase to 24 healthy subjects. In two phases, supplements containing resistant starches were fed that reach the colon and are largely fermented by colonic bacteria. Fecal starch recovery therefore reflects the metabolic activity of colonic microflora. The control treatments were conventional starches. Blood lipid levels were obtained at the start and 4-day fecal collections at the end of each phase. Resistant starch supplements increased fecal starch excretion by 3.8 +/- 1.2 g/d more than conventional starches (P = .006). Mean starch excretion was related positively to pretreatment serum high-density lipoprotein (HDL) cholesterol (r = -.57, P = .003) and negatively to low-density lipoprotein (LDL) cholesterol (r = -.57, P = .004), apolipoprotein B:AI (r = -.56, P = .005), and fecal output of fusobacteria (r = -.73, P = .003) and bacteroides (r = -.72, P = .003). The ratio of fusobacteria to total anaerobes was also related to pretreatment LDL cholesterol (r = .56, P = .037). Differences in starch excretion between healthy subjects, as a measure of bacterial activity, accounted for 32% of the variation in pretreatment LDL cholesterol. The activity of colonic microflora therefore appears to influence serum lipid levels. Alterations of bacterial number and activity may provide an additional strategy to control serum lipid risk factors for cardiovascular disease.

Adult↗
PubMed1999

Combined effect of vegetable protein (soy) and soluble fiber added to a standard cholesterol-lowering diet.

Dietary treatment of hyperlipidemia focuses on reducing saturated fat and dietary cholesterol. Other aspects of diet are not emphasized at present, despite growing evidence that a number of plant components decrease serum cholesterol. We therefore determined whether a combination of two plant components, vegetable protein and soluble fiber, further reduce serum lipids when incorporated into the currently advocated low-saturated-fat diet. Thirty-one hyperlipidemic men and women ate two 1-month low-fat (<7% of total energy from saturated fat), low-cholesterol (<80 mg cholesterol/d) metabolic diets in a randomized crossover study. The major differences between test and control diets were an increased amount of vegetable protein (93% v 23% of total protein), of which 33 g/d was soy, and a doubling of soluble fiber. Fasting blood samples were obtained at the start and end of each phase. On the last 3 days of each phase, fecal collections were obtained. Compared with the low-fat control diet, the test diet decreased total cholesterol (6.2% +/- 1.2%, P < .001), low-density lipoprotein (LDL) cholesterol (6.7% +/- 1.7%, P < .001), apolipoprotein B (8.2% +/- 1.2%, P < .001), and the ratios of LDL to high-density lipoprotein (HDL) cholesterol (6.3% +/- 2.0%, P = .004) and apolipoprotein B to A-I (5.4% +/- 1.5%, P = .001). A combination of vegetable protein and soluble fiber significantly improved the lipid-lowering effect of a low-saturated-fat diet. The results support expanding the current dietary advice to include increased vegetable protein and soluble fiber intake so that the gap in effectiveness between a good diet and drug therapy is reduced.

Aged↗
PubMed1999

Effect of wheat bran on serum lipids: influence of particle size and wheat protein.

OBJECTIVE: Wheat fiber appears to protect from cardiovascular disease despite its lack of consistent effect on serum lipids. We therefore wished to determine whether reported inconsistencies in the effect of wheat bran resulted from differences in particle size or its high gluten content. METHODS: Two studies were conducted. In one-month metabolic diets, 24 hyperlipidemic subjects consumed breads providing an additional 19 g/d dietary fiber as medium or ultra-fine wheat bran and extra protein (10% of energy as wheat gluten). In two-week ad libitum diets, 24 predominantly normolipidemic subjects consumed breakfast cereals providing an additional 19 g/d of dietary fiber as coarse or a mixture of ultra-fine and coarse wheat bran with no change in gluten intake. Both studies followed a randomized crossover design with control periods when subjects ate low-fiber breads and cereals respectively with no added gluten. Fasting blood lipids were measured on day zero and at the end of each phase. RESULTS: Wheat bran had no effect on total, LDL or HDL cholesterol irrespective of particle size or level of gluten in the diet. However, consumption of increased gluten in the metabolic study was associated with a 13+/-4% reduction in serum triglycerides (p = 0.005) which was not seen in the normal-gluten ad libitum study. CONCLUSIONS: The protective effect of wheat fiber in cardiovascular disease cannot be explained by an effect of wheat bran in reducing serum cholesterol although in hyperlipidemic subjects displacement of carbohydrate by gluten on the high-fiber phases was associated with lower serum triglycerides.

Adult↗
PubMed1999

Health aspects of partially defatted flaxseed, including effects on serum lipids, oxidative measures, and ex vivo androgen and progestin activity: a controlled crossover trial.

BACKGROUND: Currently there is considerable interest in the potential health benefits of oil seeds, such as soy and flaxseed, especially in relation to cardiovascular disease and cancer. OBJECTIVE: We therefore evaluated health aspects of partially defatted flaxseed in relation to serum lipids, indicators of oxidative stress, and ex vivo sex hormone activities. DESIGN: Twenty-nine hyperlipidemic subjects (22 men and 7 postmenopausal women) completed two 3-wk treatment periods in a randomized, crossover trial. Subjects were given muffins that contributed approximately 20 g fiber/d from either flaxseed (approximately 50 g partially defatted flaxseed/d) or wheat bran (control) while they consumed self-selected National Cholesterol Education Program Step II diets. Both muffins had similar macronutrient profiles. Treatment phases were separated by > or = 2 wk. RESULTS: Partially defatted flaxseed reduced total cholesterol (4.6+/-1.2%; P = 0.001), LDL cholesterol (7.6+/-1.8%; P < 0.001), apolipoprotein B (5.4+/-1.4%; P = 0.001), and apolipoprotein A-I (5.8+/-1.9%; P = 0.005), but had no effect on serum lipoprotein ratios at week 3 compared with the control. There were no significant effects on serum HDL cholesterol, serum protein carbonyl content, or ex vivo androgen or progestin activity after either treatment. Unexpectedly, serum protein thiol groups were significantly lower (10.8+/-3.6%; P = 0.007) at week 3 after the flaxseed treatment than after the control, suggesting increased oxidation. CONCLUSIONS: These data indicate that partially defatted flaxseed is effective in lowering LDL cholesterol. No effects on lipoprotein ratios, ex vivo serum androgen or progestin activity, or protein carbonyl content were observed. The significance of increased oxidation of protein thiol groups with flaxseed consumption requires further investigation.

Adult↗
PubMed1999

Inulin, oligofructose and intestinal function.

Inulin and oligofructose have attracted much attention recently as nonabsorbable carbohydrates with prebiotic properties. When inulin and oligofructose were added to a controlled diet, significant increases were noted in colonic bifidobacterial populations, and it has been proposed that these changes promote both colonic and systemic health through modification of the intestinal microflora. Inulin and oligofructose are rapidly and completely fermented by the colonic microflora with the production of acetate and other short-chain fatty acids. As with lactulose, they may also result in the growth of the fecal biomass, and in doing so, entrap ammonia for bacterial protein synthesis or conversion to the ammonium ion. As with dietary fiber and other nonabsorbable carbohydrates, there is also interest in inulin and oligofructose from the standpoint of inhibition of colonic carcinogenesis, blood cholesterol reduction, immune stimulation and enhanced vitamin synthesis. In these areas, the influence of their molecular weight is also an issue, with the longer chain length providing a more sustained fermentation pattern. More human studies are now required, including studies on the long-term effects of inulin and oligofructose consumption on colonic health, in particular on markers of cancer risk such as reduction in colonic polyp recurrence.

Animals↗
PubMed1998

Modulation of androgen and progesterone receptors by phytochemicals in breast cancer cell lines.

We have used a tissue culture system based on breast carcinoma cell lines to investigate a large number of naturally occurring compounds and beverages for steroid hormone agonist and antagonist activity. The cell lines used, T-47D and BT-474, produce prostate specific antigen (PSA) upon stimulation with androgens, progestins, glucocorticoids and mineralocorticoids. This biomarker is secreted and can be measured in the tissue culture supernatant with very high sensitivity by an immunofluorometric procedure. Steroid hormone antagonist activity can be assessed with the same system by adding the candidate antagonist first and then stimulating the cells with a known agonist. By using this system we have identified three natural compounds, apigenin, naringenin and syringic acid which exhibited weak progestational activity and eleven other compounds which exhibited weak antiandrogenic/antiprogestational activity. Our study indicates that a significant number of natural compounds have the ability to bind to steroid hormone receptors and act as weak blockers. A fewer number of compounds not only bind to the receptors but they also mediate transcriptional activity, acting as agonists. The agonists and antagonists were active at levels around 10(-5) M, in accordance with previous reports for other phytochemicals. In comparison to synthetic and natural steroid hormones, the biological activity of these compounds is weaker by a factor of approximately 10(4)-fold.

Beverages↗
PubMed1998

Thermally oxidized dietary fat and colon carcinogenesis in rodents.

Thermally oxidized animal fat (beef tallow) was assessed for colon cancer-promoting and -initiating activity in F-344 rats and CF-1 mice with the use of the aberrant crypt focus (ACF) assay. In two promotion studies, extensively oxidized beef tallow (110 degrees C for 144-168 h, peroxide value approx 200 meq/kg, with > 80% loss of allylic and olefinic protons) had relatively little effect on the growth of ACF in F-344 rats. The multiplication constant for treatment/control of ACF size in aberrant crypts per ACF at 100 days was 1.07 (95% confidence interval = 1.01-1.14) and 0.98 (95% confidence interval = 0.91-1.06). ACF size was not affected by less extensively oxidized beef tallow or by a 10-fold reduction of dietary alpha-tocopherol during the growth of the ACF. In initiation studies, extensively oxidized beef tallow administered by gavage increased the number of animals with ACF and the number of ACF per colon (11 of 23 and 5 of 29 animals with ACF; 1.09 +/- 0.29 and 0.21 +/- 0.09 ACF/colon, respectively). Less severely oxidized beef tallow was without effect. Further studies with CF-1 mice confirmed that extensively oxidized beef tallow increased numbers of animals with ACF and average ACF per colon. The unsaturated aldehyde acrolein was without effect in the ACF assay. These data suggest that highly thermolyzed beef tallow contains an uncharacterized initiator or leads to conditions in which spontaneously initiated ACF are increased.

Acrolein↗
PubMed1998

Physiological effects of resistant starches on fecal bulk, short chain fatty acids, blood lipids and glycemic index.

OBJECTIVE: To assess the effects on fecal bulking, fecal short chain fatty acid (SCFA) production, blood lipids and glycemic indices of two different forms of resistant starch (RS2 and RS3) from a high-amylose cornstarch. METHODS: Twenty-four healthy subjects (12 men; 12 women) consumed four supplements taken for 2 weeks in random order separated by 2-week washout periods. The supplements were a low-fiber (control) and supplements providing an additional 30 g dietary fiber as wheat bran (high-fiber control) or the equivalent amount of resistant starch analyzed gravimetrically as dietary fiber from RS2 or RS3. Four-day fecal collections and 12-hour breath gas collections were obtained at the end of each period. Fasting blood was taken at the beginning and end of each period. Glycemic indices of supplements were also assessed. RESULTS: The wheat bran supplement increased fecal bulk 96+/-14 g/day compared with the low-fiber control (p<0.001) with the mean for both resistant starches also being greater (22+/-8 g/day) than the low-fiber control (p=0.013). On the resistant starch phases, the mean fecal butyrate:SCFA ratio, which has been suggested to have positive implications for colonic health, was significantly above the low-fiber control by 31+/-14% (p=0.035). Resistant starches did not alter serum lipids, urea or breath H2 or CH4. No significant differences in glycemic index were seen between the RS and control supplements. CONCLUSION: The potential physiological benefits of the resistant starches studied appear to relate to colonic health in terms of effects on fecal bulk and SCFA metabolism.

Adult↗
PubMed1997

Effect of a diet high in vegetables, fruit, and nuts on serum lipids.

We assessed the effect of a diet high in leafy and green vegetables, fruit, and nuts on serum lipid risk factors for cardiovascular disease. Ten healthy volunteers (seven men and three women aged 33 +/- 4 years [mean +/- SEM]; body mass index, 23 +/- 1 kg/m2) consumed their habitual diet (control diet, 29% +/- 2% fat calories) and a diet consisting largely of leafy and other low-calorie vegetables, fruit, and nuts (vegetable diet, 25% +/- 3% fat calories) for two 2-week periods in a randomized crossover design. After 2 weeks on the vegetable diet, lipid risk factors for cardiovascular disease were significantly reduced by comparison with the control diet (low-density lipoprotein [LDL] cholesterol, 33% +/- 4%, P < .001; ratio of total to high-density lipoprotein [HDL] cholesterol, 21% +/- 4%, P < .001; apolipoprotein [apo] B:A-I, 23% +/- 2%, P < .001; and lipoprotein (a) [Lp(a)], 24% +/- 9%, P = .031). The reduction in apo B was related to increased intakes of soluble fiber (r = .84, P = .003) and vegetable protein (r = -.65, P = .041). On the vegetable compared with the control diet, the reduction in total serum cholesterol was 34% to 49% greater than would be predicted by differences in dietary fat and cholesterol. A diet consisting largely of low-calorie vegetables and fruit and nuts markedly reduced lipid risk factors for cardiovascular disease. Several aspects of such diets, which may have been consumed early in human evolution, have implications for cardiovascular disease prevention.

Adult↗
PubMed1997

Metabolic effects of non-absorbable carbohydrates.

Food components which are incompletely absorbed in the small intestine or not absorbed at all but are delivered to the colon have been part of the diet throughout the course of human evolution. Our great ape cousins may derive 30% or more of their dietary calories from colonic uptake of short-chain fatty acids (SCFAs) generated in the colon. The metabolic effects of dietary carbohydrate entering the colon are many and include laxation, the growth of the fecal biomass, nitrogen entrapment and SCFA generation. These SCFAs in turn may nourish mucosal cells, spare glutamine utilization, enhance hepatic gluconeogenesis and lipogenesis and possibly influence renal handling of uric acid. The health implications are significant in terms of modifying risk factors for disease and disease prevention and justify interest in the metabolic effects of non-absorbable sugars such as lactulose.

Animals↗