The Adventist Health Study-2 has published results of their study on prostate cancer risk among various diet groups after 7.8 years of follow-up.
Vegans were shown to have a 34% lower risk of being diagnosed with prostate cancer than regular meat-eaters. The other diet groups were not found to be statistically different than regular meat-eaters. Here are the confidence intervals:
- Non-Veg: 1.00
- Semi-Veg: 1.18 (.91, 1.54)
- Pesco: 1.07 (.88, 1.31)
- Lacto-Ovo: .96 (.83, 1.12)
- Vegan: .66 (.50, .87)
The results were adjusted for age, race, family history, education, screening, caloric intake, and body mass index. There were 2,140 vegans in the study.
A similar trend was found when looking only at African American participants, but the results didn’t reach statistical significance.
Among those diagnosed with advanced prostate cancer (as distinct from all types of prostate cancer) vegans had a 30% reduced risk, but it wasn’t statistically significant.
The authors speculated on a number of mechanisms that could be responsible for the lower rates among vegans:
- Lower levels of insulin-like growth factor 1
- Lower insulin resistance
- Lower calcium intakes increasing the need for the conversion of vitamin D into its active form which might reduce prostate cancer
- Reduced inflammation due to higher antioxidant intakes
- Increased soy consumption which has been linked to lower prostate cancer risk (with a large number of possible mechanisms)
I have updated the prostate cancer section of the VeganHealth.org article, Cancer, Vegetarianism, and Diet.