Health benefits of soy isoflavones

1. Soy
Isoflavones
Heli J. Roy, PhD,
MBA, RD
Shanna Lundy, BS
Beth Kalicki, BS
Pennington Biomedical Research Center
Division of Education
Phillip Brantley, PhD, Director
Steven Heymsfield, MD,
Executive Director
www.pbrc.edu PBRC 2012
Publication # 18

2. Introduction
Soy is a low cost source of protein that has been
consumed in Asian nations for many centuries
Regular intake of this food is thought to be partially
responsible for the lower rates of heart disease, stroke,
and cancer observed in Eastern populations.
PBRC 2012

3. Isoflavones are members of the large flavonoid family of
plant compounds which are, in turn, members of the
larger group of plant constituents known as polyphenols
The principal isoflavones in soy are genistein, daidzein,
and their metabolites
PBRC 2012
DaidzeinGenistein
Introduction

4. Edamame or Soy beans:
Soy beans are the least processed form of soy protein. They are
available in most grocery stores and can be purchased in fresh, frozen,
or roasted forms.
Tofu:
Tofu, or bean curd, is made my curdling soymilk with a coagulant. Tofu
can be used in a variety of recipes to partially replace either meat or
dairy products. Because calcium sulfate is often used as the curdling
agent, tofu is also a good source of calcium.
Soymilk:
Soymilk is a high-quality source of soy protein that’s available in a
variety of forms, including chocolate.
PBRC 2012
Good sources of Soy…

5. Sources…
Isoflavone compounds, such as genistein and daidzein,
are found in a number of plants, but soybeans and soy
products like tofu and textured vegetable protein are the
primary food sources.
PBRC 2012

6. PBRC 2012
Food ServingSoy protein
(g)
Isoflavone
content (mg)
Kcal
Soy Burger 1 patty 8 7 100
Soy nuts 1 oz 12 38 150
Soy Milk 1 c 8 24 100
Texturized Vegetable
Protein (TVP)
¼ c 14 27 50
Tofu 3 oz 9 33 45
Soy Protein Bar1 bar 6 10-15 180
Soy Breakfast Patty2 patties 16 4 160
Soy Flour ¼ c 12 33 90
Soy Beans, Boiled½ c 7 47 190
Tempeh ½ c 18 36 200
Soy Nut Butter2 Tbs. 8 0 160

7. There are many proposed mechanisms for the
therapeutic effect of isoflavones
The mechanisms include:
 binding to estrogen receptors
 inhibition of production of reactive oxygen species
 induction of DNA strand breakage resulting in apoptosis or cell
death
 inhibition of angiogenesis
 inhibition of thrombin formation and platelet activation
 And increased LDL receptor activity
PBRC 2012
Mechanisms of Action..

8. Health Effects of Soy
PBRC 2012

9. Relative to physiologic estrogens, isoflavones appear to be a
weaker form according to both in vitro and in vivo assays
Because of this, its believed that isoflavones can compete at
estrogen receptor sites, blocking the stronger version naturally
produced by the body from exerting its full effect
Since high blood levels of estrogen are an established risk factor
for breast cancer, weaker forms of estrogen may provide
protection against this disease
PBRC 2012
Estrogenic and Antiestrogenic Activity

10. The prevailing hypothesis has been that isoflavones exert
antiestrogenic effects when placed in a high-estrogen
environment, such as exists in premenopausal women, and
estrogenic effects when in a low-estrogen environment, such
as exists in postmenopausal women
There has been some support to this hypothesis, however
definite conclusions regarding whether soy or isoflavones are
necessarily antiestrogenic in premenopausal women is still
currently a topic of much debate
PBRC 2012
Estrogenic and Antiestrogenic Activity

11. Interest in the relationship between soy intake and cancer risk
was due, in large part, to the relatively low breast cancer
mortality rates in Asian countries where soy foods are
commonly consumed.
In Japan, the breast cancer mortality rate is about ¼ that of
the United States.
PBRC 2012
Breast Cancer

12. Of the multitude of studies conducted outside the US on women,
most find that there are decreases in breast cancer risk with
consumption of soy products in premenopausal, but not
postmenopausal women
The only case-controlled study conducted thus far in the United
States to examine this possible relationship found that tofu
consumption was protective in both premenopausal and
postmenopausal Asian women
The downfall of this study was that it only included one particular
group of women- whether or not this would be indicative of other
women remains unseen
PBRC 2012
Breast Cancer

13. Overall, the epidemiologic data are inconclusive
There is little epidemiologic support for the notion that
soy intake is associated with a decreased risk of
postmenopausal breast cancer
However, there is some data suggestive of decreased
risk of premenopausal breast cancer with increased soy
intakes
PBRC 2012
Breast Cancer

14. There is speculation that the intake of soyfoods may be a
factor contributing to the low prostate cancer mortality rate in
Japan
Although the data in support of this hypothesis is intriguing,
it is also limiting
Genistein has shown to inhibit the growth of both androgen-
dependent and androgen-independent prostate cancer cells
in vitro
PBRC 2012
Prostate Cancer

15. How genistein or isoflavones could reduce prostate
cancer risk ?
Even though the precise role of estrogen in prostate cancer is
not well defined, the potential estrogenic effects of isoflavones
may be protective because estrogens have been used
successfully as a form of hormone therapy for metastatic
prostate cancer
PBRC 2012
Other Mechanisms

16. Human data available remains limited for use in evaluating
the soy-prostate cancer hypothesis
Of potential relevance to the effects of isoflavones on
prostate cancer risk is the finding that isoflavones appear in
the prostatic fluid, and that concentrations are highest in men
from soy food-consuming countries
Furthermore, relative to plasma concentrations, isoflavones
are concentrated several-fold in the prostatic fluid
PBRC 2012
Prostate Cancer

17. Speculation about the potential benefits of isoflavones
was in part fueled by the similarity in chemical structure
between the soybean isoflavones and the synthetic
isoflavone, 7-isopropoxyisoflavone, which was shown to
increase bone mass in postmenopausal women
PBRC 2012
Soy and Bone Health

18. Two human studies that examined the effects of soy
consumption on bone mineral loss in postmenopausal
women have been reported thus far.
In both studies, soy was associated with favorable
effects on bone density or content; however, the results
are still considered preliminary.
PBRC 2012
Soy and Bone Health

19. Although the effects of soy and isoflavones on bone
health constitutes and exciting area of research, no firm
conclusions can be reached at this time.
With the large number of studies currently underway in
this area; however, a better understanding should be on
its way soon.
PBRC 2012
Soy & Bone Health

20. Dietary soy protein has been shown to have several beneficial effects on
cardiovascular health.
Best-documented effect is on plasma lipid and lipoprotein concentrations,
with reductions of ~10% in LDL cholesterol, and small increases in HDL
cholesterol.
Dietary soy protein improves flow-mediated arterial dilation.
Soy isoflavone extract improves systemic arterial compliance, an
indicator of atherosclerosis extent.
PBRC 2012
Soy & Cardiovascular Health: An Overview

21. Plasma lipids and lipoproteins
Effects of dietary soy protein in human subjects has
shown reductions in LDL cholesterol of ~13%, reductions
in plasma triglycerides of ~10%, and increases in HDL
cholesterol of around 2%
These beneficial effects of soy protein on plasma
lipoproteins culminated recently in the U.S. Food and
Drug Administration’s approval of the health claim that:
“25 g of soy protein a day, as part of a diet low in saturated fat
and cholesterol, may reduce the risk of heart disease”
PBRC 2012
Soy & Cardiovascular Health

22. Interest is increasing in the role of LDL particle oxidation on
both atherogenesis and vascular function
In healthy subjects receiving supplementation, soy treatment
significantly prolonged LDL oxidation by ~20 minutes
Based on the findings that estradiol fatty esters were
incorporated into LDL, Helisten et al. described that because
soy isoflavones are incorporated into LDL particles, it results
in much greater oxidation resistance
PBRC 2012
Soy & Cardiovascular Health:
LDL Oxidation

23. Endothelium-mediated vasodilation
Two approaches are used to evaluate endothelium-mediated vasodilation:
One determines the response of arteries to the perfusion of
acetylcholine.
The other is flow-mediated dilation whereby flow is restricted.
When genistein was infused it resulted in increased brachial artery dilation
of both men and women comparable to the effect of estradiol.
PBRC 2012
Soy & Cardiovascular Health:
Arterial Function

24. Arterial Compliance
Unlike endothelial-mediated vasodilation (primarily nitric oxide
dependent), arterial compliance relates to the constriction and
dilation of arteries associated with systole and diastole.
In humans, supplementation with soy protein or the
administration of isoflavone extracts seems to improve
arterial compliance.
PBRC 2012
Soy & Cardiovascular Health:
Arterial Function
Systole diastole

25. Currently, there is considerable literature establishing that
substitution of animal protein (usually casein) with soy protein
results in reduced amounts of atherosclerosis resulting from
diets with added cholesterol.
Current research is focusing primarily on identifying what
components of soy protein provide this atherosclerosis
protection.
PBRC 2012
Soy & Cardiovascular Health:
Atherosclerosis

26. Intact soy protein provides more cardiovascular benefits than
does alcohol-washed soy protein.
The addition of soy isoflavone extracts to diets containing animal
protein or alcohol-washed soy protein does not provide plasma
lipid concentration benefits.
Lastly, soy isoflavone extracts given to human subjects do not
result in cardiovascular benefits except for improvements in
systemic arterial compliance .
PBRC 2012
Soy & Cardiovascular Health
Atherosclerosis: Conclusions

27. Dietary soy intake seems to be promising in the areas of
cardiovascular, cancer (especially prostate), and bone
health.
In time, soy’s roles and possibly emerging ones will be
better understood.
PBRC 2012
Conclusions…

28. References…
http://www.fwhc.org/health/soy.htm
http://www.cancer.org/Search/index?QueryText=soy&x=0&y=0
http://www.aicr.org/foods-that-fight-
cancer/foodsthatfightcancer_soy.html?
gclid=COuO9IOCmrICFcFgTAodUFsAxA
http://jn.nutrition.org/content/132/3/566S.long
http://www.fda.gov/food/labelingnutrition/labelclaims/healthclaim
smeetingsignificantscientificagreementssa/default.htm
PBRC 2012

29. About Our Company…
The Pennington Biomedical Research Center is a world-renowned nutrition research center.
 
Mission:
To promote healthier lives through research and education in nutrition and preventive medicine.
 
The Pennington Center has several research areas, including:
 
Clinical Obesity Research
Experimental Obesity
Functional Foods
Health and Performance Enhancement
Nutrition and Chronic Diseases
Nutrition and the Brain
Dementia, Alzheimer’s and healthy aging
Diet, exercise, weight loss and weight loss maintenance
 
The research fostered in these areas can have a profound impact on healthy living and on the prevention of common
chronic diseases, such as heart disease, cancer, diabetes, hypertension and osteoporosis.
 
The Division of Education provides education and information to the scientific community and the public about research
findings, training programs and research areas, and coordinates educational events for the public on various health issues.
 
We invite people of all ages and backgrounds to participate in the exciting research studies being conducted at the
Pennington  Center in Baton Rouge, Louisiana. If you would like to take part, visit the clinical trials web page at
www.pbrc.edu or call [phone].
PBRC 2012