Prostate cancer prevention diet

Previously, the EPIC consortium found an increased prostate cancer risk with the highest quartiles of dairy protein,³³ but no association with dietary fat (mostly using FFQs).^{32, 34} Data from the US Health Professionals study based on clinically detected cases found no association between calcium intake and localised prostate cancer (measured with FFQs) but a positive association with advanced disease.³⁵Conversely, calcium intake was related to an increased risk of localised disease with screen-detected cases in the US PLCO trial.³⁶

The evidence for a link between obesity and fatal prostate cancer⁴ is strengthening and energy intake might be on that causal pathway. An association between energy intake and advanced disease was shown in a meta-analysis for studies with disease stage with a combined odds ratio of 1.6 for advanced disease.³⁷ In this study, there was no overall relationship between energy intake and prostate cancer nor heterogeneity in the risk of disease by stage (P=0.07); the association with advanced disease was positive (23% increase) but did not reach conventional statistical significance (95% CI 1.00–1.51).

The finding of weak evidence of heterogeneity in the association of vitamin D with risk between clinically and screen-detected disease may merit further investigation. The precision of estimates of foods consumed irregularly, such as oily fish, a good source of vitamin D, may be lower in food diaries than in questionnaires. Vitamin D levels are also related to sunlight exposure, making serological assessments more comprehensive. In the ProtecT study, deficiency in vitamin D (circulating concentration <12 ng/ml) was associated with a greater risk of aggressive prostate cancer (higher grade or stage),³⁸ which would be more prevalent in clinically detected cases, but the recent meta-analysis does not support vitamin D supplementation, except for deficiency.⁶

There was no association of overall diet (assessed using FFQs) and screen-detected prostate cancer in the US PCPT trial nor in the Swedish study.^{39, 40} Food diary data from 133 prostate cancer cases also revealed no association with diet and prostate cancer, but a reduction with a Mediterranean-style diet rich in monounsaturated fatty acids and vegetables/fruits and low in red meats.⁴¹ A recent meta-analysis of adherence to a Mediterranean diet and overall cancer risk showed a 4% risk reduction for prostate cancer incidence.⁴²

The natural history of prostate cancer remains poorly understood, including the time points when dietary and environmental factors may influence disease development or progression.⁴³ This study measured dietary intake prior to diagnosis and found no major associations with prostate cancer risk, yet migrant studies and international variation in prostate cancer incidence suggest that dietary or other environmental components contribute to disease risk. More recent evidence highlights a role of dietary factors in disease progression, for example, fat intake may influence prostate cancer mortality.⁴⁴ Future studies will need to extend measurement of dietary intake across the life course, consider intermediary influences such as the insulin-like growth factor axis and examine the role of obesity, which increases the risk of aggressive prostate cancer, subsequent disease progression and mortality.⁴

Conclusions

In summary, this large study revealed no strong evidence that prostate cancer risk is associated with dietary intake measured prior to diagnosis in middle-aged and older men.

Acknowledgments

Footnotes

References