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Colorectal Cancer Prevention (PDQ®): Prevention - Health Professional Information [NCI] - Overview

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Harms

There are no known harms from dietary modification, including reduction of fatty acids or meats and an increase in the intake of fiber, fruits, and vegetables.

Study Design: Cohort and RCTs.
Internal Validity: Good.
Consistency: Good.
External Validity: Good.

Calcium supplementation

Benefits

The evidence is inadequate to determine whether calcium supplementation reduces the risk of CRC.

Study Design: Pooled and individual prospective cohort studies, meta-analysis of three RCTs with adenoma recurrence as an outcome, and one large individual RCT in women with CRC as an outcome.
Internal Validity: Good.
Consistency: Poor; the RCT with CRC as an outcome [32] found no reduction in CRC incidence, while prospective cohort studies found a reduction in CRC incidence between high and low calcium groups; three RCTs found a reduction in adenoma recurrence with calcium supplementation.[33]
External Validity: N/A.

Harms

The evidence is fair that elemental calcium without vitamin D as a supplement in the level of 1,000 to 1,200 mg/day increases the risk of myocardial infarction. Based on fair evidence, calcium supplementation with vitamin D at doses less than 1,000 has few harms.

Magnitude of Effect: In a meta-analysis of RCTs of calcium alone, the risk of myocardial infarction was increased from 4.8% to 5.8% (HR = 1.31; 95% CI, 1.02–1.67).

Study Design: Pooled and individual prospective cohort studies plus RCTs.
Internal Validity: Good.
Consistency: Poor (one meta-analysis of 11 RCTs for calcium alone found increased myocardial infarction; no other individual studies found this).[34]
External Validity: Good.

Statins

Benefits

Based on solid evidence, statins do not reduce the incidence or mortality from CRC.

Study Design: Meta-analyses of RCTs.[35,36,37]
Internal Validity: Good.
Consistency: Good.
External Validity: N/A.

Harms

Based on solid evidence, the harms of statins are small.

Study Design: Observational studies,[38] multiple RCTs, and a review.[39]
Internal Validity: Good.
Consistency: Good.
External Validity: Good.

References:

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WebMD Public Information from the National Cancer Institute

Last Updated: September 04, 2014
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.
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