When the second atomic bomb fell on Nagasaki in
1945, Dr
Akizuki and 20 others were caring for 70 tuberculosis
patients in a hospital only 1.4 kilometres away from the epicentre of impact. Despite
usual expectations, Dr Akizuki and the others did not have their health
destroyed by acute radiation poisoning. He then considered that their
consumption of miso soup, with wakame seaweed, every day was the cause of this.
Subsequent research on mice found that miso eaten before, but not during or
after, irradiation protected against tissue damage and improved survival. The
length of fermentation time, from 3 days to 180 days, also had an association
with the efficacy of miso against radiation damage, with longer fermentation
increasing the effects.
This review also discussed a protective effect against
certain cancers such as breast cancer. In a human cohort study
involving 21, 852 women, it was found that consumption of miso soup and
isoflavones was associated with a reduced risk of breast cancer, but not other
soy foods. These findings did not change after adjusting for reproductive or
family history, smoking or other dietary factors. Compared with the lowest
quartile of soy isoflavone intake, women in the highest quartile had a 54% reduced
risk of breast cancer, with a stronger association in post-menopausal women.
The review also mentioned an epidemiologic study
where the risk of colon cancer was reduced by soybean consumption. A study on
mice was then discussed, where mice fed miso had a decreased number of abberant
crypt foci (ACFs) after carcinogen exposure. In another that followed, mice
administered 180 day fermented miso and the same carcinogen also saw a
significantly lowered number of ACFs, from an average of 87 to an average of 65
ACFs. Mice in the 3-4 and 120 day fermented miso groups had averages of 85 and
83 ACFs respectively, only a few less than the controls.
Additionally, in light of studies showing an
inhibition of lung cancer by soy isoflavones, research on rats once again found
a reduced number of tumours in rats given miso. Another epidemiological study
on humans found that miso soup consumption in women without a history of liver
disease is associated with a reduced risk of dying from liver cancer. Despite a
high salt content, miso may even lower the risk of stomach cancer too! This may
be because of other minerals and compounds present, or salt on its own being
harmless in terms of cancer as opposed to the foods that first come to mind
upon hearing the words “high salt”.
On top of these health benefits, compounds found in
miso soup may be an effective alternative to conventional treatments for osteoporosis.
In an animal study, 96 rats with their ovaries removed received either
oestrogen replacement therapy, anti-osteoporosis pharmaceuticals of genistein,
a phytochemical found in fermented soy products such as miso, for 12 weeks. The
genistein turned out to be the most effective, beating all other treatments in
improving bone mineral density, bone mineral content and breaking strength, but
does this hold up in human studies? A 2007 study on 389 postmenopausal
women with osteopenia compared the use of 54mg of genistein daily to a placebo,
alongside calcium and vitamin D supplementation. After two years, there was no
change in endometrial thickness in comparison to the placebo group. However,
bone mineral density increased in the femoral neck and lumbar spine, by
0.035g/cm2 and 0.049g/cm2 respectively, while in the control groups, bone
mineral density declined by 0.037g/cm2 and 0.053g/cm2 respectively. These
findings show that women do not have to choose between reproductive cancers and
osteoporosis, as natural treatments including genistein often have targeted
effects.
In conclusion, miso and other fermented soy products
can have many health benefits unlike their unfermented or processed cousins.
Miso can be taken as a drink, as a base in a light soup or a condiment in other
recipes.
No comments:
Post a Comment