Effect of soluble and insoluble fiber diets on serum prostate specific antigen in men.
OBJECTIVE
We assess whether high fiber diets influence serum prostate specific antigen (PSA) related to effects on serum sex hormone levels and fecal steroid excretion.


METHODS
A randomized crossover controlled trial was performed on 14 healthy men with hyperlipidemia on 2 metabolic diets 4 months in duration with each containing foods high in soluble or insoluble fiber and approximately 25 to 30 gm. dietary fiber per 1,000 kilocalories. Serum PSA, free testosterone and estradiol, and fecal bile acid and neutral sterol excretion were evaluated.


RESULTS
Mean serum PSA was lower with the soluble than the insoluble fiber diet (0.07+/-0.03 ng./ml., p = 0.035). No treatment difference was seen in free testosterone or estradiol, although the latter decreased significantly with the insoluble fiber diet (9+/-3 pmol./l., p = 0.004). After 16 weeks total fecal bile acid output was greater with the soluble (341+/-56 mg. daily) compared to the insoluble (203+/-35, p = 0.001) fiber diet but no differences were seen in fecal neutral sterol elimination. The treatment difference in fecal lithocholic acid output related to the difference in serum PSA (r = 0.57, p = 0.035).


CONCLUSIONS
A small but statistically significantly lower serum PSA was seen in healthy men consuming soluble fiber, which was not related to changes in serum sex hormones but was related to the increased lithocholic acid output as a possible marker of increased fecal steroid elimination. The effect of soluble fiber on prostatic disease may warrant further investigation.
Tariq
N
N
Clinical Nutrition and Risk Factor Modification Center, Division of Urology, St. Michael's Hospital, Toronto, Ontario, Canada.
Jenkins
D J
DJ
Vidgen
E
E
Fleshner
N
N
Kendall
C W
CW
Story
J A
JA
Singer
W
W
D'Costa
M
M
Struthers
N
N
D000328:Adult; D018592:Cross-Over Studies; D004043:Dietary Fiber / Q000494:pharmacology*; D004958:Estradiol / Q000097:blood; D005243:Feces / Q000737:chemistry; D006801:Humans; D008297:Male; D008875:Middle Aged; D017430:Prostate-Specific Antigen / Q000097:blood*; D013739:Testosterone / Q000097:blood
D004043:Dietary Fiber; D013739:Testosterone; D004958:Estradiol; D017430:Prostate-Specific Antigen