low carb, high protein diets

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Low-carbohydrate, high-protein diets may reduce both tumor growth

rates and cancer risk

American Association for Cancer Research ^ | June 14, 2011 |

PHILADELPHIA - Eating a low-carbohydrate, high-protein diet may

reduce the risk of cancer and slow the growth of tumors already

present, according to a study published in Cancer Research, a journal

of the American Association for Cancer Research.

The study was conducted in mice, but the scientists involved agree

that the strong biological findings are definitive enough that an

effect in humans can be considered.

" This shows that something as simple as a change in diet can have an

impact on cancer risk, " said lead researcher Gerald Krystal, Ph.D., a

distinguished scientist at the British Columbia Cancer Research

Centre.

Cancer Research editor-in-chief Prendergast, Ph.D., CEO of the

Lankenau Institute for Medical Research, agreed. " Many cancer

patients are interested in making changes in areas that they can

control, and this study definitely lends credence to the idea that a

change in diet can be beneficial, " said Prendergast, who was not

involved with the study.

Krystal and his colleagues implanted various strains of mice with

human tumor cells or with mouse tumor cells and assigned them to one

of two diets. The first diet, a typical Western diet, contained about

55 percent carbohydrate, 23 percent protein and 22 percent fat. The

second, which is somewhat like a South Beach diet but higher in

protein, contained 15 percent carbohydrate, 58 percent protein and 26

percent fat. They found that the tumor cells grew consistently slower

on the second diet.

As well, mice genetically predisposed to breast cancer were put on

these two diets and almost half of them on the Western diet developed

breast cancer within their first year of life while none on the

low-carbohydrate, high-protein diet did. Interestingly, only one on

the Western diet reached a normal life span (approximately 2 years),

with 70 percent of them dying from cancer while only 30 percent of

those on the low-carbohydrate diet developed cancer and more than

half these mice reached or exceeded their normal life span.

Krystal and colleagues also tested the effect of an mTOR inhibitor,

which inhibits cell growth, and a COX-2 inhibitor, which reduces

inflammation, on tumor development, and found these agents had an

additive effect in the mice fed the low-carbohydrate, high-protein

diet.

When asked to speculate on the biological mechanism, Krystal said

that tumor cells, unlike normal cells, need significantly more

glucose to grow and thrive. Restricting carbohydrate intake can

significantly limit blood glucose and insulin, a hormone that has

been shown in many independent studies to promote tumor growth in

both humans and mice.

Furthermore, a low-carbohydrate, high-protein diet has the potential

to both boost the ability of the immune system to kill cancer cells

and prevent obesity, which leads to chronic inflammation and cancer.

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