Resistant starch lowers colon cancer risk?

[Guest guest]

A recent study with rats found that adding dietary resistant starch

(RS) in the form of high amylase maize starch reduced DNA damage

induced by high casein (25%) or high red meat (25%) diets:

" Resistant Starch Prevents Colonic DNA Damage Induced by High Dietary

Cooked Red Meat or Casein in Rats "

http://www.landesbioscience.com/journals/cbt/article/toden5-3.pdf

I ran across the link to this study in a blog article about RS:

http://fanaticcook.blogspot.com/2008/01/resistant-starch-may-reduce-risk-of.html

This blog also has links to a couple of similar studies.

The study report did not discuss how the casein protein was produced,

but I am guessing it was obtained in the form of protein powder. Most

likely the protein powder was produced in a way that would denature

the casein and oxidize substantial amounts of associated lipoprotein.

So, I expect that the increased DNA damage in this study induced by

the casein increase is more reflective of pasteurized/processed dairy

and not representative of raw dairy.

The study report said that the red meat used was round rump beef

cooked on a hot plate until browned at 150C (300F) and then dried at

45C for 48 hours and milled to provide a product containing 68.5%

protein and 22.3% fat. They did not indicate if any kind of

preservative was used. I'm not sure why this meat would cause a

significant increase in DNA damage. The authors speculate that:

" The mechanism of dietary protein-induced colonic DNA damage

in the absence of RS may be related to undigested protein reaching

the colon. Increased intake of dietary protein would be expected to

lower its ileal digestibility and greater entry of protein into the

large bowel would result in its enhanced fermentation by the

microflora, yielding end products such as phenol, cresol, indoles,

amines and ammonia. "

It is interesting that in both the high casein and high red meat diet,

the dietary RS substantially reduced the DNA damage. However, I have

no idea how similar the digestion and microflora in rats is to that in

humans. If they are significantly dissimilar then this study may not

tell us much.

I'd be curious what would happen if refined sugar was used in place of

the RS or if increased omega-6 fat was tested instead of increased

protein.