Heme and chlorophyll intake and risk of colorectal cancer in the Netherlands cohort study.
BACKGROUND
The evidence for red meat as a determinant of colorectal cancer remains equivocal, which might be explained by differences in heme content. Heme is the pro-oxidant, iron-containing porphyrin pigment of meat and its content depends on the type of meat. Chlorophyll from green vegetables might modify this association.


METHODS
The Netherlands Cohort Study was initiated in 1986 when a self-administered questionnaire on risk factors for cancer was completed by 120,852 subjects ages 55 to 69 years. After 9.3 years of follow-up through the Cancer Registry, 1,535 incident colorectal cancer cases (869 men and 666 women) were available. Nineteen of the 150 items in the validated dietary questionnaire related to consumption of specific types of fresh and processed meat. Heme iron content was calculated as a type-specific percentage of the total iron content and chlorophyll content of vegetables was derived from the literature.


RESULTS
Multivariate rate ratios for quintiles of heme iron intake and colon cancer were 1.00, 0.98, 1.04, 1.13, and 1.29 (P(trend) = 0.10) among men and 1.00, 1.31, 1.44, 1.18, and 1.20 (P(trend) = 0.56) among women, respectively. No consistent associations were observed for rectal cancer. Rate ratios for colon cancer increased across successive quintiles of the ratio of heme/chlorophyll among men only (1.00, 1.08, 1.01, 1.32, and 1.43; P(trend) = 0.01). No associations were observed between fresh meat and colorectal cancer.


CONCLUSIONS
Our data suggest an elevated risk of colon cancer in men with increasing intake of heme iron and decreasing intake of chlorophyll. Further research is needed to confirm these results.
Balder
Helena F
HF
Department Food and Chemical Risk Analysis, TNO Quality of Life, Zeist, the Netherlands. balder@voeding.tno.nl
Vogel
Johande
J
Jansen
Margje C J F
MC
Weijenberg
Matty P
MP
van den Brandt
Piet A
PA
Westenbrink
Susanne
S
van der Meer
Roelof
R
Goldbohm
R Alexandra
RA
D000368:Aged; D002734:Chlorophyll; D015331:Cohort Studies; D015179:Colorectal Neoplasms / Q000453:epidemiology*; D005247:Feeding Behavior; D005260:Female; D006418:Heme / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008460:Meat / Q000009:adverse effects*; D008875:Middle Aged; D009426:Netherlands / Q000453:epidemiology; D011446:Prospective Studies; D012004:Rectal Neoplasms / Q000453:epidemiology*; D012306:Risk; D014675:Vegetables / Q000009:adverse effects*
D002734:Chlorophyll; D006418:Heme