The effect of yogurt on the inhibition of colon
tumours induced by 1,2-dimethylhydrazine in BALB/c mice
has been studied, and the hypothesis examined
that yogurt induces a great reduction in the inflammatory
immune response and
inhibits tumour growth. Mice were assigned to five
experimental groups: a control
group fed with a conventional balanced diet, and four
other test groups that received
yogurt supplements for 2, 5, 7 or 10 consecutive days. At
the end of each feeding
period, mice were given subcutaneous injections of
1,2-dimethylhydrazine (20 mg/kg) once a week for 8 weeks.
After tumour induction,
yogurt was given again for 2,
5, 7 or 10 consecutive days each 10 d for 20 weeks. By
week 20, 70% of the animals
in the control group had developed colorectal tumours.
From week 8, there was a
considerable infiltration of mononuclear cells into
the lamina propria of the large
intestine. There was an increase in the number of
IgG-producing cells and a slight
increase in the IgA-secreting cells, and of CD8+
but not CD4+ T lymphocytes, a high
level of β-glucuronidase activity in the intestinal
fluid and leucocytosis with
neutrophilia in the blood. However, in the test groups
given yogurt tumour growth
was inhibited, the effect being more evident with 7 or
10 d treatment. The
inflammatory immune response as measured by the
characteristics we assessed was
also reduced, with an increase in the IgA-secreting cells
and in CD4+ T lymphocytes.
The blood count was similar to that of normal animals and
no colorectal tumours
were observed in week 20. We suggest that one of the
mechanisms by which yogurt
exerts antitumour activity is through its immunomodulator
activity, by reducing
the inflammatory immune response, which was markedly
increased when the carcinogen was administered.