Abstracts
Cholesterol 1
Cholesterol 1
The higher your cholesterol levels, the more protection you can get from soy protein.
The study found the starting cholesterol levels had more than twice as much impact on the amount of reduction as all other causes combined. Mildly high cholesterol (200 to 255 mg per deciliter) was lowered an average of 4.4% (not statistically significant), while severe high cholesterol (more than 335 mg per deciliter) was lowered an average of 19.6% (significant).
Anderson, J.W. et al: Meta-analysis of the effects of soy protein intake on serum lipids. New England Journal of Medicine vol. 333: 276-282, 1995.
Cholesterol 2
Cholesterol 2
Evaluated the effects of consuming a soy protein isolate beverage powder (60 g/d for 28 d) vs. a casein.
A dramatic rise in plasma isoflavone concentrations was observed after supplementation in the soy protein group, the levels reaching 907 +/- 245 nmol/L for genistein (a 110-fold increase) and 498 +/- 102 nmol/L for daidzein (a 150-fold increase) as measured by isotope dilution gas chromatography - mass spectrometry.
These concentrations are higher than previously reported for the plasma of Japanese subjects consuming a traditional diet (276 nmol/L and 107 nmol/L, respectively).
Although soy protein supplementation to a typical Western diet can increase plasma concentrations of isoflavones, this may not necessarily be sufficient to counter heart disease risk factors such as high plasma cholesterol and platelet aggregation.
Gooderham, MH et al: A soy protein isolate rich in genistein and daidzein and its effects on plasma isoflavone concentrations, platelet aggregation, blood lipids and fatty acid composition of plasma phospholipid in normal men. J Nutr 1996 Aug;126(8):2000-6.
Sports bars
Sports bars
The ingredients used were isolated soy protein, texturized soy flour, milk solids, cocoa powder, toasted oat, nuts, almonds, authorized flavors, preservatives and antioxidants.
Two varieties of soy-based candy bars were developed for sportsmen who need a higher protein intake. Both were covered with chocolate. Controls were carried out in the optimized products and the results indicate a very good sensory and microbiological quality.
The average nutritional composition of both varieties is: 12,4% proteins, 9% lipids and 58,7% carbohydrates, and the caloric value is 375,2 kcal/100 g.
A shelf-life packed in an aluminium foil was: 30 days for the nut candy, and at least for 60 days for the almond candy bar.
[Development of soy-based protein candy bars for athletes] [Desarrollo de confites proteicos a base de soya para deportistas.] Arch Latinoam Nutr 1993 Sep;43(3):241-7.
Cardiovascular Disease & Soy Supps.
Cardiovascular disease and menopausal symptoms
According to this study, soy supplementation may decrease the risk of cardiovascular disease and menopausal symptoms. In this trial, perimenopausal women were supplemented with either soy protein containing phytoestrogens, with one or two doses; or a placebo diet containing complex carbohydrates. Those women who were supplemented with the soy diets had a significant decline in LDL cholesterol levels, 7%, compared with the placebo diet. The severity of hypoestrogenic symptoms among the soy diet group was reduced. Soy supplements may therefore reduce the risk of cardiovascular disease and may alleviate menopausal symptoms.
Washburn S, Burke GL, Morgan T, Anthony M: Effect of soy protein supplementation on serum lipoproteins, blood pressure, and menopausal symptoms in perimenopausal women. Menopause 1999 Spring; 6(1): 7-13
Postprandial Lipemia
Postprandial lipemia
Soy protein isolate (SPI) may exhibit beneficial effects in the postprandial remnant lipoprotein response. According to this study, soy protein isolate and casein supplements were given to normolipidemic men. Eleven males were given either a soy protein isolate or a casein dietary supplement for three weeks. The results indicate that SPI supplements had a better effect than casein supplements on the postprandial remnant lipoprotein response.
Shige H, Ishikawa T, Higashi K, Yamashita T, Tomiyasu K, Yoshida H, Hosoai H, Ito T, Nakajima K, Ayaori M, Yonemura A, Suzukawa M, Nakamura H: Effects of soy protein isolate (SPI) and casein on the postprandial lipemia in normolipidemic men. J Nutr Sci Vitaminol (Tokyo) 1998 Feb; 44(1):113-27
Hot Flashes
Hot flashes
Soy protein may substantially reduce the frequency of hot flashes among women. In a clinical trial of 104 postmenopausal women, patients took either isolated soy protein or placebo daily. After 12 weeks, patients taking soy had a 45% reduction in their daily hot flashes versus a 30% reduction in the placebo group. Fourteen patients withdrew from the study due to gastrointestinal side effects. Soy protein may reduce the incidence of hot flashes among postmenopausal women.
Albertazzi P, Pansini F, Bonaccorsi G, Zanotti L, Forini E, De Aloysio D: The effect of dietary soy supplementation on hot flushes: Obstet Gynecol 1998 Jan; 91(1): 6-11
Strenuous Exercise
Strenuous Exercise
Supplementation with soy protein may reduce metabolic-hormonal stress experienced by female athletes who train strenuously, according to this randomized study conducted on 14 top female gymnasts from Romania. Subjects received either soy protein (1 g/kg body weight) or placebo twice daily during a four-month period, in which they trained strenuously 4-6 hours/day, six days a week. After four months, subjects who received soy exhibited increased levels of lean body mass, serum prolactin, and serum T4. The soy group also experienced decreases in serum alkaline phosphatases. Non-supplemented subjects exhibited an increased level of serum T4 and an increased level of urinary mucoproteins.
Stroescu V, Dragan J, Simionescu L, Stroescu OV: Hormonal and metabolic response in elite female gymnasts undergoing strenuous training and supplementation with SUPRO(R) Brand Isolated Soy Protein, J Sports Med Phys Fitness 2001 Mar;41(1):89-94
Microflora Production of Equol
Microflora Production of Equol
Consumption of fiber and soy do not alter the ability of colonic microflora to produce equol, a product of soy isoflavone conversion and measurement of intestinal microflora population. Subjects included 26 women ages 20 to 40 years, who received either short-term or long-term soy supplementation, during which they also supplemented with 0 g or 16 g dietary fiber. Among women who completed the study, fiber supplementation did not increase equol production during soy supplementation.
Lampe JW, et al: Wheat bran and soy protein feeding do not alter urinary excretion of the isoflavan equol in premenopausal women, J Nutr 2001 Mar;131(3):740-4
Chronic Pain & Soy
Chronic pain
Diets high in soy may help to reduce pain after nerve injury (neuropathic pain), according to this animal study conducted on Wistar rats in a Baltimore laboratory. Rats received soy-free or soy-containing diets for 28 days, and were then subjected to partial sciatic nerve ligation to produce chronic neuropathic sensory disorder (chronic pain). During recovery from this nerve injury, soy-supplemented rats exhibited a higher tolerance for pain than rats receiving a soy-free diet.
Shir Y, Sheth R, Campbell JN, Raja SN, Seltzer Z: Soy-containing diet suppresses chronic neuropathic sensory disorders in rats, Anesth Analg 2001 Apr;92(4):1029-34
Cardiovascular Risk in Type II Diabetes
Cardiovascular risk in type II diabetes
Type II diabetics may reduce their risk for cardiovascular disease by supplementing with soy and isoflavones, according to this randomized, double-blind study conducted on 20 type II diabetics. Subjects received either placebo or supplement (soy, isoflavones, and cotyledon fiber), separated by a three week wash-out period. After six weeks, patients treated with the soy-based supplement exhibited significantly lower levels of LDL cholesterol, triglycerides, apolipoprotein B, total cholesterol and homocysteine. HDL cholesterol levels were not affected.
Hermansen K, Sondergaard M, Hoie L, Carstensen M, Brock B: Beneficial effects of a soy-based dietary supplement on lipid levels and cardiovascular risk markers in type 2 diabetic subjects, Diabetes Care 2001 Feb;24(2):228-33
Oxidative Stress & Soy
Oxidative stress
Soy isoflavone supplementation may lower oxidative DNA damage in humans, according to this study. Soy tablets were given to six women and six men for three weeks. Blood samples were taken from the women, who took 50 mg isoflavones once a day, and from the men, who took 50 mg twice daily, once every week.
Isoflavone levels, measured by the levels of genistein and daidzein, peaked in women during the second week and kept increasing in men over the three weeks of the study. Using levels of 5-hydroxymethyl-2-deoxyuridine in DNA as a measure of oxidative stress, the researchers found that stress levels decreased by 47% in women over the three-week period, and men saw a 61% decrease at the end of three weeks. The decrease in oxidative DNA damage seen with soy isoflavone supplementation may be part of the mechanism responsible for the cancer-preventive effects seen with the dietary intake of soy.
Djuric Z, Chen G, Doerge DR, Heilbrun LK, Kucuk O: Effect of soy isoflavone supplementation on markers of oxidative stress in men and women, Cancer Lett 2001 Oct 22;172(1):1-6
Phytoestrogens' Effect on Development
Phytoestrogens' effect on development
Despite their high intake of phytoestrogens, infants fed soy-based formula do not appear to suffer different health or reproductive outcomes than infants fed cow milk-based formula, according to this study. A total of 811 young adults, who had been involved in a controlled feeding study conducted between 1965 and 1978 at the University of Iowa, self-reported their pubertal maturation, menstrual and reproductive history, height and usual weight, and current health in 1999. The two formula groups were then compared using the reports collected from the participants. No significant difference was found in the general health and reproductive health of the two groups, but it was found that women who were given soy-based formula had longer menstrual periods and greater discomfort with menstruation.
Strom BL, et al: Exposure to soy-based formula in infancy and endocrinological and reproductive outcomes in young adulthood, JAMA 2001 Aug 15;286(7):807-814
Natural Soy Lowers Blood Pressure in Postmenopausal Women
Michelle Bridenbaker, BS
Replacing traditional protein sources with dry roasted soy nuts can significantly reduce systolic and diastolic pressure in postmenopausal women with normal and moderately high blood pressure, according to a new study.[1]
Two recent meta-analyses[2,3] regarding the use of hormone replacement therapy (HRT) among postmenopausal women suggests that the medical regimen can increase the risk of thromboembolic events and may also be responsible for an increased incidence of breast and other cancers. These findings have prompted investigators to examine other areas of the world that have fewer cases of heart disease and cancer to determine whether specific factors could also influence outcomes among American women. In Japan, for example, the incidence of breast and cardiovascular disease in women is significantly lower than in the United States and may be attributable to high dietary intakes of soy.
This proposed association led researchers from Beth Israel Deaconess Medical Center in Boston, Massachusetts, to investigate whether the addition of natural, unprocessed soy into the diets of postmenopausal women would lower systolic (SBP) and diastolic blood pressures (DBP), subsequently reducing the risk of cardiovascular events.
Trial Design
They conducted a controlled crossover trial in which 60 hypertensive and normotensive postmenopausal women (menopausal for at least 1 year) who were not on HRT or statin therapy were randomized to either a therapeutic lifestyle change (TLC) diet with a daily intake of dry-roasted soy nuts (58 g [1/2 cup]; 25 mg soy protein, 101 mg aglycone isoflavones, and 150 mg of sodium) or the TLC diet without soy. After 8 weeks of following the assigned regimen, there was a 4-week "wash-out" period, and then patients were crossed over to the other arm of the study for another 8 weeks. The administered soy nuts were substituted in place of the protein sources these women normally consumed in their diet.
The TLC diet, introduced to each patient by a dietitian 4 weeks prior to randomization, called for the consumption of < 7% saturated fat, 30% to 35% total fat, < 300 mg of cholesterol, 2 fish servings per week, and 1200 mg of calcium via diet or supplement.
Blood pressure, lipid levels, 24-hour urine samples, and brachial artery studies were recorded before and after crossover. At baseline, hypertensive women (SBP >/= 140 mm Hg; n = 12) were significantly older and had significantly higher total cholesterol, low-density lipoprotein cholesterol (LDL-C), and body mass index compared with the normotensive group (SBP < 140 mm Hg; n = 48).
Results
Compared with the control diet, both hypertensive and normotensive women had significant reductions in both SBP and DBP during the course of adding soy to their diets (Table). In addition, these blood pressure reductions in hypertensive patients were accompanied by a significant decrease in LDL-C (11%, P = .05) -- a finding that was not noted among normotensive women.
These findings were bolstered by the fact that dietary intake and weight did not significantly change over the course of the study -- implying that many of the antihypertensive properties can be attributed to the soybeans and isoflavins.
Table. Control vs Soy: Blood Pressure Reductions in Hypertensive and Normotensive Women[1]
|
Population |
Control |
Soy Diet |
% Reduction |
P |
|
Hypertensives (n = 12) |
|
|
|
|
|
SBP (mm Hg) |
152 +/- 12 |
137 +/- 15 |
9.9 |
.003 |
|
DBP (mm Hg) |
88 +/- 7 |
82 +/- 8 |
6.8 |
.001 |
|
Normotensives (n = 48) |
|
|
|
|
|
SBP (mm Hg) |
116 +/- 10 |
110 +/- 11 |
5.2 |
< .001 |
|
DBP (mm Hg) |
69.8 +/-8 |
67 +/- 7 |
2.9 |
.03 |
Discussion
Soy has been targeted as a promoter of cardiovascular health in women because isoflavin, or phytoestrogen, is a plant-based estrogen that closely resembles the chemical structure of the human hormone, estrogen. Nevertheless, earlier studies with soy found minimal benefits from its consumption. Unlike older studies that utilized processed soy, the current study is unique in that it used a more natural form of soy, which could be responsible for the significant results.
According to investigators, data from this study are compelling because the results are "comparable to reductions seen with some antihypertensive medications." Of course, the small study population is a limitation, and the findings will have to be confirmed in further studies with larger cohorts and longer follow-up periods. Nevertheless, these preliminary findings indicate that adding unprocessed soy to a healthy diet may have potential as a preventive therapy for hypertension and hyperlipidemia in women. Lastly, soy therapy may also have the potential to provide relief from postmenopausal symptoms (eg, sleep disturbances, emotional lability, and hot flashes) without the associated risks of HRT. Investigators report that roughly half the women in the study reported symptom relief while using soy protein.
References
Welty F, Guida K, Lee K. Soy nuts lower systolic and diastolic blood pressure in hypertensive and normotensive menopausal women. Circulation. 2002;106:II-611. Abstract 3018.
Nelson HD, Humphrey LL, Nygren P, Teutsch SM, Allan JD. Postmenopausal hormone replacement therapy: scientific review. JAMA. 2002;288:872-881.
Humphrey LL, Chan BK, Sox HC. Postmenopausal hormone replacement therapy and the primary prevention of cardiovascular disease. Ann Intern Med. 2002;137:273-284.
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