Chung-Ja Jackson

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.

Soy Consumption and Phytoestrogens: Effect on Serum Prostate Specific Antigen When Blood Lipids and Oxidized Low-Density Lipoprotein are Reduced in Hyperlipidemic Men

PURPOSE Herbal remedies high in phytoestrogens have been shown to reduce serum prostate specific antigen (PSA) and have been proposed as a treatment for prostate cancer. Soy proteins used to lower serum cholesterol are rich sources of phytoestrogens. Therefore, we assessed the effect of soy consumption on serum PSA in men who had participated in cholesterol lowering studies. MATERIALS AND METHODS For 3 to 4 weeks 46 healthy middle-aged men with a range of starting PSA values took soy (mean 44 gm. soy protein daily, 116 mg. isoflavones daily) or control foods, and a subgroup of men took a lower level of soy supplements for 3 months. PSA was measured at the start and end of each treatment. RESULTS Soy had no significant effect on serum total or free PSA, independent of PSA starting value or isoflavone intake. The lack of effect on PSA was seen, although soy intake was sufficient to reduce low-density lipoprotein cholesterol (5.8 +/- 2.2%, p = 0.012), the estimated coronary heart disease risk (6.1 +/- 2.8% for 10 years, p = 0.032) and the serum concentration of oxidized low-density lipoprotein measured as conjugated dienes (9.5 +/- 3.4%, p = 0.008) in the 3 to 4-week study. In addition, the lack of effect of soy on PSA persisted for the 3 months of the extended study. CONCLUSIONS At levels of soy intake which reduce low-density lipoprotein cholesterol any potential benefits of soy consumption on prostate cancer are likely to occur for reasons other than alterations in hormone activity.

Equol status and blood lipid profile in hyperlipidemia after consumption of diets containing soy foods

BACKGROUND Recent analyses have challenged the effectiveness of soy foods as part of a cardiovascular risk reduction diet. OBJECTIVE The objective of the study was to show whether equol status determines the effectiveness of soy foods to lower LDL cholesterol and to raise HDL cholesterol. DESIGN Eighty-five hypercholesterolemic men and postmenopausal women (42 men, 43 women) participated in 1 of 3 studies that represented a range of soy interventions and that followed the same general protocol at a Canadian university hospital research center. Soy foods were provided for 1 mo at doses of 30-52 g/d for the 3 studies as follows: 1) soy foods with either high-normal (73 mg/d) or low (10 mg/d) isoflavones, 2) soy foods with or without a prebiotic to enhance colonic fermentation (10 g polyfructans/d), or 3) soy foods with a low-carbohydrate diet (26% carbohydrate). Studies 1 and 2 were randomized controlled crossover trials, and study 3 was a parallel study. RESULTS The separation of the group into equol producers (n = 30) and nonproducers (n = 55) showed similar reductions from baseline in LDL cholesterol (-9.3 ± 2.5% and -11.1 ± 1.6%, respectively; P = 0.834), with preservation of HDL cholesterol and apolipoprotein A-I only in equol producers compared with reductions in nonproducers (HDL cholesterol: +0.9 ± 2.7% compared with -4.3 ± 1.1%, P = 0.006; apolipoprotein A-I: -1.0 ± 1.1% compared with -4.7 ± 1.0%; P = 0.011). The amount of urinary equol excreted did not relate to the changes in blood lipids. CONCLUSIONS Soy foods reduced serum LDL cholesterol equally in both equol producers and nonproducers. However, in equol producers, ~35% of our study population, soy consumption had the added cardiovascular benefit of maintaining higher HDL-cholesterol concentrations than those seen in equol nonproducers. This trial was registered at clinicaltrials.gov as NCT00877825 (study 1), NCT00516594 (study 2), and NCT00256516 (study 3).

Supplemental Barley Protein and Casein Similarly Affect Serum Lipids in Hypercholesterolemic Women and Men

High-protein diets have been advocated for weight loss and the treatment of diabetes. Yet animal protein sources are often high in saturated fat and cholesterol. Vegetable protein sources, by contrast, are low in saturated fat and without associated cholesterol. We have therefore assessed the effect on serum lipids of raising the protein intake by 5% using a cereal protein, barley protein, as part of a standard therapeutic diet. Twenty-three hypercholesterolemic men and postmenopausal women completed a randomized crossover study comparing a bread enriched with either barley protein or calcium caseinate [30 g protein, 8374 kJ (2000 kcal)] taken separately as two 1-mo treatment phases with a minimum 2-wk washout. Body weight and diet history were collected weekly during each treatment. Fasting blood samples were obtained at wk 0, 2, and 4. Palatability, satiety, and compliance were similar for both the barley protein- and casein-enriched breads, with no differences between the treatments in effects on serum LDL cholesterol or C-reactive protein, measures of oxidative stress, or blood pressure. Nevertheless, because no adverse effects were observed on cardiovascular risk factors, barley protein remains an additional option for raising the protein content of the diet.

Morphological and Ginsenoside Differences among North American Ginseng Leaves

Leaf characteristics of mature 2, 3 and 4-year-old North American ginseng (Panax quinquefolius L.) leaves on fruiting and non-fruiting (NF) plants were studied. Leaflets of the 2-year-old plants had the lowest fresh and dry weight, area, volume and internal gas volume. Inflorescence removal in 3-year-old plants did not affect leaf characteristics or ginsenoside concentration but in 4-yearold plants it increased leaf fresh (38.6%) and dry (43.9%) weight, leaf area (29.1%), specific leaf mass (11.4%), leaf volume (43.1%), and leaf thickness (12.1%), and decreased leaf water content (6.2%). Cultivated ginseng, although an understorey plant, had the specific leaf mass, 35.6 g m-2 (range, 36 to 39 g m-2) and a chlorophyll a/b ratio of 2.40 to 2.61, both suggesting the ability to perform like a sunny habitat plant. Also, specific leaf mass of 35.6 g m-2 is similar to that reported for perennial plants, 36.8 g m-2, rather than that for annuals, 30.9 g m-2.