A Guide To the Health Effects of Soy Products
Soy
has a bad reputation, as soybeans contain a substance that can
supposedly mimic human female hormones. Simultaneously, soy products are
the most widespread and affordable replacements for meat and dairy
produce, and people following a vegan and other dairy-free diets can
really benefit from this nutrient-rich source of protein. Furthermore,
soybeans might be even beneficial to people suffering from high
cholesterol, infertility and even menopause.
This
disparity created quite a lot of controversy surrounding soy, a
significant part of which is ungrounded. This article provides a full
review of both the nutritional value and the health effects of soy and
soy products, which will help you make up your mind on whether or not
consuming soy is right for you.
What is soy, exactly?
Soybeans
are a type of legumes native to East Asia, being a crucial domestic
crop throughout Asia for millennia. The first mentions of the soya bean,
an alternative name of the crop, are between 7000 and 6600 BC in China,
but it is very likely that they have been in widespread use even before
that.
Today,
soybeans are a staple food throughout Asia, where they are used to
prepare a wide variety of products, starting from soy milk and soy
sauce, to tofu and tempeh, which are meat alternatives, and even
consumed raw in the form of edamame beans, which are immature soybeans
commonly used as healthy snacks (pictured below).
Soy
is also a key ingredient in many protein supplements, vitamins and
processed foods. And finally, soybean meal is widely used to feed
livestock. This means that soy products are more than simply widespread,
they are quite challenging to avoid.
Nutritional Value
It
is important to start from mentioning that soy products are some of the
most cost-effective alternatives for both meat and dairy products. Soy
products come in a variety of textures and flavors, such as milks,
yogurts, cheeses, and meat substitutes, and they are usually widely
available on the market.
But
this is not the only reason why soy products are a great replacement
for animal-derived produce, as they are also extremely nutrient-dense
and provide a lot of protein, which is often lacking in meat- and
dairy-free diets. Soy is a complete protein source, meaning that it
contains all the essential amino acids the human body doesn’t produce.
Apart
from that, soy is a good source for healthy fats, especially omega-3
fats. Finally, it contains a type of phytoestrogens called isoflavones
that can also be beneficial to health. For your reference, the table
above illustrates the nutritional content of one type of soy, edamame
beans, but the overall nutritional value of other soy products will be
similar.
Apart
from being a great source of nutrients, however, soy can also be
beneficial for those suffering from certain conditions, but it can also
be possibly worse for others. A detailed review of the health effects of
soy follows below.
1. Decreasing Cholesterol Levels
There
is an extensive body of research suggesting that soy foods (but not soy
supplements) may help lower the levels of bad cholesterol (LDL) and
increase the levels of the good (HDL) cholesterol, especially among
individuals who have higher than normal cholesterol levels.
A review study suggested that consuming only 47 grams of soy daily was associated with
a 13% decrease in LDL cholesterol. This means that eating soy products
can help stop the progression of atherosclerosis, as bad cholesterol is
responsible for creating plaques in blood vessels,
whereas HDL cholesterol helps clear those up.
2. Helps Relieve Menopause Symptoms
During
menopause, women experience a range of uncomfortable symptoms (hot
flashes, sleep problems, urinary symptoms, etc.) brought about by the
shortage of female hormones called estrogens in the blood. Soy contains a
type of phytoestrogens called isoflavones that can mimic the effect of
human estrogens.
However,
soy foods contain quite low levels of isoflavones, so in order to see a
difference in symptoms, studies gave soy supplements to women and found
that they, in fact, can be converted into estradiol (a type of
estrogen) and partly compensate for the lack of estrogens observed in
menopausal women.
A review article found that taking 54 mg of soy isoflavone supplements during a period
of 3 months decreased hot flashes by over 20% and weakened all the
symptoms by over 25%.
3. Improves Fertility in Women
Women who have difficulty conceiving or are currently undergoing a fertility treatment may benefit from soy. In a study,
women who took 6g of soybean powder daily for a period of 6 months
experienced more ovulations and an overall normalization of their
menstrual cycles. On top of that, other studies suggest that soy
supplements help women undergoing in vitro fertilization (IVF) get
pregnant.
4. The Influence on Male Sex Hormones
Since
soy contains phytoestrogens, men are sometimes afraid to include soy in
their diet, claiming it may lower their testosterone levels. This is a
crucial issue, as many protein powders and supplements advertised to
promote muscle growth are soy-based, and if soy can affect the hormone
balance in men, it may render these supplements worthless or harmful.
However, a review of 15 studies
showed that it is completely safe for men to consume soy foods, protein
powders up to 70g per day, and even isoflavone supplements up to 240 mg
daily. In addition, there is even scientific evidence suggesting that
soy can potentially lower the risk of developing prostate cancer, so not
only is soy safe to eat in moderation, but it may even be beneficial
for men.
5. Decreases the Likelihood of Developing Breast Cancer
The
evidence about soy and breast cancer is very conflicting, as there is a
large and growing body of evidence from Asian studies suggesting that a
higher soy intake may decrease the likelihood of developing breast
cancer, whereas the Western studies did not find any link between breast
cancer and foods containing soy.
Scientists
believe that this might be due to the fact than in Asian countries,
people usually consume more fermented soy products compared to Western
countries, and it may be the case that fermented soy foods has more
cancer-fighting properties than regular ones.
6. The Effect On Thyroid Function
One of the most controversial findings regarding soy is that a test-tube study reported that goitrogens, compounds found in soy, may have a negative effect on the thyroid. Human studies
did not confirm this finding and suggested that individuals with an
enlarged thyroid do not have to avoid soy products as long as they’re
meeting their daily nutritional needs in iodine.
In summary,
consuming soy products in moderation is not only safe, but also very
beneficial to everyone, and especially for those who follow a meat- and
dairy-free diet. What’s more, consuming soy products may even be
beneficial at decreasing cholesterol levels, improving fertility,
relieving menopausal symptoms and lowering the risk of developing
certain cancers.