Men with a higher intake of dairy, especially milk, face a significantly higher risk of prostate cancer compared to men with a lower intake, according to a new study by researchers at Loma Linda University Health . The study found no association between increased risk of prostate cancer and non-dairy calcium intake, suggesting that substances other than calcium play a role in the risk of dairy products for breast cancer. prostate.
Our findings add significant weight to other evidence linking dairy products, rather than non-dairy calcium, as a modifiable risk factor for prostate cancer. “
Gary Fraser, MBChB, PhD, Principal Investigator and Professor, School of Medicine and School of Public Health, Loma Linda University
The results of the study reveal that men who consumed about 430 grams of dairy a day (1 ¾ cup of milk) had a 25% higher risk of prostate cancer compared to men who consumed only 20, 2 grams of dairy a day (1/2 cup milk). per week). In addition, men who consumed about 430 grams of dairy per day faced an even greater increase in risk compared to men with zero dairy intake in their diet.
Fraser noted that the results had minimal variation when comparing milk intake in total fat versus reduced or fat-free milk; there were no major associations with cheese and yogurt.
Fraser and co-authors published the study “Dairy Foods, Calcium Intake, and Prostate Cancer Risk Incident in the Adventist Health Study-2,” today in the American Journal of Clinical Nutrition.
The study assessed the dietary intake of more than 28,000 American men with a wide range of exposure to dairy and calcium, all of whom were initially cancer-free. Dietary intake was estimated from food frequency questionnaires (FFQ) and repeated 24-hour reminders. A baseline questionnaire included demographics, family history of prostate cancer, physical activity, alcohol consumption, prostate cancer screening, and BMI.
The researchers then used cancer status records to track participants’ prostate cancer status for an average time of nearly eight years. At the end of the study period, state cancer registries reported 1,254 new cases of prostate cancer among participants during follow-up.
As part of his analysis, Fraser said that he and his co-authors separated the intake of non-lactic calcium (from nuts, seeds, crucifers and other green vegetables, legumes, fruits and fortified cereals) from the intake of dairy foods. They used a statistical model to focus on dairy food intake regardless of other factors such as non-dairy calcium intake, family history of prostate cancer, race, or age.
The nature of the large and diverse cohort placed the study authors in a solid position to assess these differences, Fraser said. “Because our study cohort showed great disparity and divergence in dairy intake and calcium levels, we could ask the question with unusual force.”
Fraser says an interesting factor to consider is that the results did not show a uniform increase in risk in men with an incremental dairy intake. In other words, increasing dairy intake in 50-gram increments did not produce the same increases in risk as portions grew larger and larger.
“Most of the continued increase in risk is done when you get to 150 grams, about two-thirds of a cup of milk a day,” Fraser said. “It’s almost as if some biological or biochemical pathway is saturated about two-thirds of a cup of milk a day.”
Previous studies may have lost the curvilinear effect or the uneven increase in risk between dairy consumption and prostate cancer if most of these participants already drank more than one cup of milk a day. However, the cohort of this study allowed researchers to compare a wide range of dairy consumption, including very low levels.
The data provided little evidence of an association between calcium intake and incident prostate cancer. “One interpretation is that dairy, or some closely associated unknown risk factor, is causally related to the risk of prostate cancer,” the study said.
Fraser said the possible reasons for these associations between prostate cancer and dairy milk could be the sex hormone content of dairy milk. Up to 75% of lactating dairy cows are pregnant and prostate cancer is a hormone-responsive cancer. In addition, previous reports have linked the intake of dairy and other animal proteins to higher blood levels of a hormone, insulin-like growth factor-1 (IGF-1), which is thought to promote certain cancers. including the prostate.
A previous Adventist Health Study-2 study on the effects of dairy on breast cancer risk in women reported similar results in both non-uniform risk with increased consumption levels and the magnitude of the risk, Fraser said. .
“The parallels between our breast cancer in the role of women a year ago and this male-related document are striking,” she said. “It seems possible that the same biological mechanisms work.” However, Fraser says this study does not yet conclusively indicate that milk causes prostate cancer.
As more research investigates how dairy consumption may increase the risk of prostate cancer, Fraser advises that cautious men with a family history of prostate cancer or other risk factors would be “cautious” about consuming even moderate levels of prostate cancer. Dairy milk as part of your diet until this is cleared up.
“If you think you’re at higher than average risk, consider alternatives to soy, oats, cashews and other non-dairy milks,” he said.
The study is part of the Adventist Health Study-2, a long-term health study that explores the links between lifestyle, diet, and illness among members of the Seventh-day Adventist Church. The Adventist health study is funded in part by the generosity of the Ardmore Institute of Health.
Source:
Adventist Center for Health Sciences at Loma Linda University
Magazine reference:
Orlich, MJ, et al. (2022) Dairy foods, calcium intake, and prostate cancer risk incident in Adventist health study-2. American Journal of Clinical Nutrition.