Inhibitory effect of yoghurt and soya yoghurt containing bifidobacteria on the proliferation of Ehrlich ascites tumour cells in vitro and in vivo in a mouse tumour model

The effect of yoghurt and soya yoghurt containing Bifidobacterium lactis Bb-12 or B. longum Bb-46 on Ehrlich ascites tumour cell proliferation was investigated in vitro and in vivo. Tumour cells were incubated with B. lactis Bb-12 or B. longum Bb-46 cultivated in de Mann Rogosa Sharpe (MRS) broth medium, or with their centrifuged supernatant fractions or sediments, for 2h at 37 degreesC. Treatment resulted in the inhibition of tumour cell proliferation by 8542 (SD 0.78) and 8510 (SD 1.28) % by intact micro-organisms, 7761 (SD 0.29) and 7143 (SD 1.75) % by their supernatant fractions, but only 4.00 (SD 0.19) and 9.09 (So 1.24) % by the two sedimented bacteria, respectively. The incubation of tumour cells with yoghurt and soya yoghurt containing Bb-12 for 2h resulted in 8301 (SD 0.11) and 8823 (SD 0.06) % inhibition, respectively, while it was 8382 (SD 0.24) and 8636 (SD 0.06) %, respectively for the same products containing Bb-46. Corresponding values for plain yoghurt and soya milk (without bifidobacteria) were 3281 (SD 0.14) and 5.55 (SD 0.12) %, respectively. The differences between yoghurt or soya yoghurt containing Bb-12 or Bb-46 and plain yoghurt, soya milk or control treatments were statistically significant (n 3; P<0.05). Female Swiss albino mice were injected intraperitoneally with the same tumour cells. The lifespan of mice fed diets supplemented with yoghurt or soya yoghurt containing Bb-12 or Bb-46 was prolonged by 16, 23, 34 and 39 %, respectively compared with that of the positive control group (n 6; P< 0.05). The lifespan of groups fed plain yoghurt or soya milk was prolonged by 15 and 8 %, respectively. Prolongation of lifespan was positively correlated with faeces bifidobacterial count in the groups fed yoghurt or soya yoghurt containing bifidobacteria (r 0917; P<0.05).