Prostate Cancer and Low-Fat Diets: 4 Studies

Coincidentally, Tara over at the New York Times' Well Blog just posted this:
Low-Fat Diet May Cut Prostate Cancer Risk, NYTs Well Blog, May 16 2008.

It's based on this study:
Effect of Low-Fat Diet on Development of Prostate Cancer and Akt Phosphorylation in the Hi-Myc Transgenic Mouse Model, Cancer Research, April 2008

Where mice were fed:

• High-fat diet (HF: 42% of calories from fat)
  
• Low-fat diet (LF: 12% of calories from fat)

Findings:

"The number of mice that developed invasive adenocarcinoma at 7 months was 27% less in the LF diet group (12/28) compared with the HF diet group (23/33, P < 0.05)."

Fat used was corn oil. (By the way, 13% of the fat in corn oil is saturated.) The diets had the same number of calories, and the same amount of protein (19.9%). What the low-fat fed mice didn't eat in fat, they made up for with cornstarch. Thus, the mice with reduced prostate cancer growth were eating a high-carbohydrate diet (68%).

I say coincidentally because the men in the study in my post from yesterday - the ones whose prostate cancer regressed - were also eating a low-fat (11.2% of calories from fat), high-carbohydrate diet.
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So, do low-fat, high-carb diets slow prostate cancer growth?

I sure don't know. But here's another mouse study that supports this notion:
Effect of Isocaloric Low-Fat Diet on Prostate Cancer Xenograft Progression to Androgen Independence, Cancer Research, 2004

Where mice were fed (same as above):

• High-fat diet (HF: 42% of calories from fat)
  
• Low-fat diet (LF: 12% of calories from fat)

Findings:

"Reduced dietary fat intake delayed conversion from androgen-sensitive to -insensitive prostate cancer and significantly prolonged survival."

I found the following interesting, that prostate tumors eventually become insensitive to androgen, such that androgen deprivation therapies eventually become ineffective:

"Prostate cancer growth is initially highly dependent on androgens, and androgen suppression leads to significant reduction in tumor burden in most patients. However, androgen insensitive (AI) disease inevitably develops resulting in tumor regrowth, metastasis, and eventual mortality."

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Another:
Effect of Isocaloric Low-fat Diet on Human LAPC-4 Prostate Cancer Xenografts in Severe Combined Immunodeficient Mice and the Insulin-like Growth Factor Axis, Clinical Cancer Research, 2003

Where mice were fed (same as above):

• High-fat diet (HF: 42% of calories from fat)
  
• Low-fat diet (LF: 12% of calories from fat)

Findings:

"[After 16 weeks] Although caloric intakes and mouse weights were equal between groups, the LF mice had significantly slower tumor growth rates and lower serum prostate-specific antigen [PSA] levels compared with the HF mice."

Keep this following point in mind, and remember that the LF mice were eating a high-carb diet: "LF mice had significantly lower levels of serum insulin." I have a post coming up on it.
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One more, an older one:
Decreased Growth of Established Human Prostate LNCaP Tumors in Nude Mice Fed a Low-Fat Diet, Journal of the National Cancer Institute, 1995

Where mice were fed:

• 40.5% of calories from fat
  
• 30.8% of calories from fat
  
• 21.2% of calories from fat
  
• 11.6% of calories from fat
  
• 2.3% of calories from fat

Fat used was corn oil. Calories were made up with sucrose, a carbohydrate.

Findings:

"Mice fed a high-fat diet (e.g., 40.5 kcal% fat) exhibit increased growth of LNCaP tumors when compared with mice consuming lower fat diets (2.3-21.2 kcal% fat)."

"Serum PSA levels were highest in the 40.5-kcal% fat group and lowest in the 2.3-kcal% fat group."

I like this finding:

"The slower tumor growth associated with a low-fat diet occurred even after the formation of measurable tumors when the diets were changed from 40.5-kcal% fat to 2.3-21.2 kcal% fat."