Low protein diet suppresses tumor metastasis and increases survival in rats

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Low protein diet in rats increases immunity against tumors and

activates natural killer cells (one of the cells of the immune system)

Cell Immunol. 2004 Sep-Oct;231(1-2):96-102. Epub 2005 Jan 20. Related

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Immunopotentiation of NKT cells by low-protein diet and the

suppressive effect on tumor metastasis.

Li C, Bai X, Wang S, Tomiyama-Miyaji C, Nagura T, Kawamura T, Abo T.

Department of Immunology, Niigata University School of Medicine,

Niigata 951-8510, Japan.

Mice were fed with a 5% low-protein diet for two weeks, at which

point tumor inoculation was conducted. Following this inoculation,

the 5% low-protein diet was continued. On the other hand, control

mice were fed with a normal diet (25% protein) and such diet was

continued after tumor inoculation. In comparison with control mice,

mice fed with the 5% low-protein diet showed a prominent prolongation

of survival rate when injected with both EL4 and 3LL tumors.

Interestingly, CD1d(-/-) mice, which primarily lack natural killer T

(NKT) cells, did not show the prolongation of survival rate even when

they received a 5% low-protein diet. The most striking phenomenon

seen in tumor-bearing mice fed with the 5% low-protein diet was the

suppression of tumor metastasis to the liver and lung. Such

suppression was not seen in CD1d(-/-) mice who were fed with a 5% low-

protein diet. Phenotypic study revealed that the proportion of NKT

cells after tumor inoculation decreased in the mice fed with a normal

diet. However, such decrease did not occur in mice fed with the 5%

low-protein diet. Reflecting the activation of NKT cells by feeding,

tumor cytotoxicity and cytokine production were also augmented by the

5% low-protein diet. These results suggest that a low-protein diet

has the potential to augment the innate immunity against tumors,

especially mediated by the activation of NKT cells.

PMID: 15919374 [PubMed - indexed for MEDLINE]