I work mainly with weight loss, and many of the products
contain soy of some form. The most-asked
question I hear concerns the safely of soy.
The clients have heard that soy contains estrogen and can cause a whole
host of problems. A quick Google search
pulls up everything from the health effects to the dangers of soy. It is difficult to get a clear answer to the
question on health. Much of what one
finds is anecdotal, under-researched (meaning only one or two studies), or are
studies funded by organizations that are financially biased. So what is the truth? Are soy products safe for us to consume?
What we do know is that many of the studies that are
available do not show that soy product consumption causes ill health. Animal studies on soy protein isolate have
shown that it reduces tumor incidence and growth (NCI, n.d.). It is important, though, to note that humans
and rodents metabolize soy products differently. However, epidemiological and clinical human studies
have been promising.
A big concern is whether or not soy products will cause or
promote cancer. Actually, studies show
that the consumption of soy products may actually reduce the risk of breast,
colon, and prostrate cancer (pcrm, n.d.).
A study run on men has shown that soy protein isolate may increase
estrogen excretion and increase the 2:16 OH-E1 ratio, which is associated with
lower prostrate cancer risk (Hamilton-Reeves, et al., 2007). Also, epidemiological studies have shown that
women who ate more soy had less breast cancer (McCullough, 2012). I am still looking for studies that show that
soy products cause cancer.
When it comes to breast cancer specifically, it is generally
better to block estrogen receptors so the estrogen will not stimulate breast
tumor growth. Isoflavones from soy may
act like estrogen; however, they also block more potent natural estrogens from
binding to the estrogen receptor, stop the formation of estrogen in fat tissue,
and have anti-oxidant and anti-inflammatory properties (McCullough, 2012). These are all good things when it comes to
preventing cancer.
Another big concern about soy products is their effects on
the thyroid. While soy products appear
to have no adverse effects on the thyroid, isoflavones may take up some iodine
that is used to make thyroid hormone (pcrm, n.d.). This means that people consuming soy may need
more iodine. Iodine is found in many
plant foods and in iodized salt. The
best thing is to be sure to check up on your thyroid’s health every few years.
In short, soy is an excellent source of protein, it contains
several phytochemicals, and it may help protect against hormone-dependent
cancers (ACS, 2012). Some studies
suggest that the cancer-preventing properties (particularly breast) are better
when soy products are consumed from childhood.
However, other studies show benefits for all ages and both sexes. The take away is if you choose soy products,
then continue to do so. For best
results, choose to enjoy organic. I will
discuss why in another post.
ACS (2012) American Cancer
Society Guidelines on Nutrition and Physical Activity for Cancer
Prevention. Retrieved on July 25, 2014,
from http://www.cancer.org/acs/groups/cid/documents/webcontent/002577-pdf.pdf
Hamilton-Reeves, Jill M.; Rebelo, Salome A.; Thomas,
William; Slaton, Joel W.; Kurzer, Mindy S. (2007) Soy Protein Isolate Increases Urinary
Estrogens and the Ratio of 2:16alpha-Hydroxyesterone in Men at High Risk of
Prostate Cancer. The Journal of Nutrition 137(10): 2258-2263. http://jn.nutrition.org/content/137/10/2258.long
McCullough, Marji (2012)
The Bottom Line on Soy and Breast Cancer Risk. Retrieved on July 24, 2012, from http://www.cancer.org/cancer/news/expertvoices/post/2012/08/02/the-bottom-line-on-soy-and-breast-cancer-risk.aspx
NCI (n.d.) Soy Protein Isolate. Retrieved on July 24, 2014, from http://www.cancer.gov/drugdictionary?cdrid=42493
PCRM (n.d.) Soy and
Your Health. Retrieved on July 24, 2014,
from http://www.pcrm.org/health/health-topics/soy-and-your-health
