Researchers
to Men With Prostate Cancer: Avoid Whole Milk
Enjoying a tall glass of cold,
whole milk on a regular basis is a no-go for men with prostate cancer, advise
the authors of a new observational study.
“Men with non-metastatic
prostate cancer who choose to drink milk should select non-fat or low-fat
options,” conclude the authors, led by June Chan, ScD, a professor of
epidemiology and biostatistics and of urology, University of California, San
Francisco.
They found that whole milk
consumption after a prostate cancer diagnosis was tied to an increased risk for
recurrence, particularly among overweight men.
However, an expert not involved
in the study disagrees with the authors’ conclusion about milk, citing
insufficient evidence.
Men
with prostate cancer who choose to drink milk should select non-fat or low-fat
options.Chan et al.
The new study was published online November
6 in The
Prostate.
This was a prospective study
among 1334 men with nonmetastatic disease participating in the Cancer of the
Prostate Strategic Research Endeavor (CaPSURE). Participating men answered a
food questionnaire in 2004-2005 (a median of 2 years after their diagnosis).
They were followed until 2016 for post-treatment recurrence.
The median follow-up was 8 years.
During that time, there were 137 recurrence events, which included biochemical
recurrence, metastases, and prostate cancer-related deaths.
Dr Chan and colleagues found that
men who were regular milk drinkers (>4 servings a week) had about an 80%
increased risk for recurrence compared with infrequent milk drinkers (0 to 3
servings a month; hazard ratio [HR], 1.73; P= .04).
When the researchers looked at
the men according to different body mass indexes (BMIs), they found that those
who were very overweight and obese had a much greater risk and that the risk
disappeared among normal-weight men.
Among the big men (BMI > 27
kg/m2),
regular whole milk consumption was associated with a 3-fold higher risk for
recurrence when compared with infrequent consumption (HR, 2.96; P <
.001).
On the other hand, no tie between
milk-drinking frequency and recurrence risk was seen in men with BMI below this
cut-point.
Notably, the authors say that the
statistically significant interaction between whole milk consumption and BMI
may be due to chance.
Medscape
Medical News asked Dr Chan if her team’s recommendation for men
with prostate cancer to avoid whole milk was perhaps a bit over-restrictive,
given the uncertainty about the findings.
“The recommendation that men
try to switch to non- or low-fat milk is not solely based on our data or this
one study, but was intended to be a broader public health recommendations to
consume low-fat dairy products, to minimize saturated fat intake for general
health,” explained Dr Chan.
This is in line with recommendations for
the prevention of heart disease, which remains the main cause of death in
the United States, including for men diagnosed with prostate cancer, she
pointed out.
However, a prostate cancer expert
had a different take on the study’s conclusion.
“I don’t think based upon
these data we should tell men to avoid whole milk,” said Stephen
Freedland, MD, co-director, Cancer Genetics and Prevention Program, Samuel
Oschin Comprehensive Cancer Institute at Cedars-Sinai Medical Center in Los
Angeles, California.
“I am hesitant to translate
observational studies into direct patient advice,” he told Medscape
Medical News.
Dr Freedland explained that “perhaps to avoid whole milk, men will drink
more orange juice, which is high in sugar, which some studies suggest is bad
for prostate cancer.”
People often consume milk with
other foods, he also pointed out: “Perhaps this was related to men eating
sugary cereal with their milk and was unrelated to milk intake. Perhaps it is
the milk. The point is, we don’t know.”
Finally, Dr Freedland offered a
summary caution: “When we make suggestions to patients, there can often be
unintended consequences.”
For the past several decades,
academics have studied dairy products in relation to the development of
prostate cancer. The results have not been consistent, say both the study
authors and Dr Freedland.
However, Dr Chan and colleagues
add that the data “generally suggest that dairy products are associated
with an increased risk of being diagnosed with prostate cancer.”
Less studied has been the
relationship between dairy, including milk, and prostate cancer recurrence.
There have only been a few studies on the subject.
Previously, Dr Chan and
colleagues were the first to report, from the Health Professionals Follow-up
Study, that the frequent milk
consumers had a twofold increased
risk for dying of prostate cancer and a 51% increase in the relative risk for
recurrence compared with infrequent consumers (Cancer Epidemiol Biomarkers Prev. 2012;21:428-436).
Also, Swedish researchers
recently reported, in a study of men with localized prostate cancer, an
elevated risk for disease-specific mortality among men who drank a lot of
milk (3 or more servings a day) compared with men who drank less than 1 serving
a day (Int
J Cancer. 2017;140:2060-2069).
Other Dairy Foods
In the current study, Dr Chan and
colleagues also observed that even though whole milk was associated with an
increased risk for prostate cancer recurrence, no such increase was seen with
other dairy foods, including butter and ice cream, which are made from whole
milk.
Dr Chan commented on this
surprise about dairy foods: “They may not be consumed in the same volume
or frequency for us to detect an association at the individual level.”
The authors are not sure what
physiologic mechanisms may underlie any tie between whole milk consumption and
prostate cancer recurrence among overweight men.
“It is possible that
overweight and obese men have greater increases in systemic inflammation and
insulin resistance when consuming a high saturated fat diet compared to normal
weight men, thereby promoting prostate cancer progression,” they write.
Dr Freedland believes in summarizing
the data with patients: “I will tell them, ‘Some studies suggest high
whole milk intake may be bad for prostate cancer, but others say it is not.’
Let the patient make the decision.”
The study
was funded by the US Department of Defense Cancer Research Program, National
Institutes of Health and the Helen Diller Family Comprehensive Cancer Center at
UCSF. The authors and Dr Freedland have disclosed no relevant
financial relationships.
