A high protein moderate carbohydrate diet fed at discrete meals reduces early

Breast cancer is the most prevalent cancer in American women. Dietary factors

are thought to have a strong influence on breast cancer incidence. This study utilized a

meal-feeding protocol with female Sprague-Dawley rats to evaluate effects of two ratios

of carbohydrate:protein on promotion and early progression of breast tissue carcinomas.

Mammary tumors were induced by N-methyl-N-nitrosourea (MNU) at 52 d of age. Postinduction,

animals were assigned to consume either a low protein high carbohydrate diet

(LPHC; 15% and 60% of energy, respectively) or a high protein moderate carbohydrate

diet (HPMC; 35% and 40% of energy, respectively) for 10 wk. Animals were fed 3

meals/day to mimic human absorption and metabolism patterns. The rate of palpable

tumor incidence was reduced in HPMC relative to LPHC (12.9 ±1.4 %/wk vs. 18.2 ± 1.3

%/wk). At 3 wk, post-prandial serum insulin was larger in the LPHC relative to HPMC

(+136.4 ± 33.1 pmol/L vs. +38.1 ± 23.4 pmol/L), while at 10 wk there was a trend for

post-prandial IGF-I to be increased in HPMC (P = 0.055). There were no differences in

tumor latency, tumor surface area, or cumulative tumor mass between diet groups. The

present study provides evidence that reducing the dietary carbohydrate:protein ratio

attenuates the development of mammary tumors. These findings are consistent with

reduced post-prandial insulin release potentially diminishing the proliferative

environment required for breast cancer tumors to progress.

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