GETTING STARTED
Why Lifestyle Matters
Research shows that environmental factors such as
diet and exercise are heavy hitters in prostate cancer risk
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June 2020 | by Dr. Benny Gavi
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Modern life is busy, with multiple demands coming from every direction. The Silicon Valley glorifies
multi-tasking executives, but yet the more difficult task is balancing these demands with healthy
lifestyle habits that weigh heavily in cancer prevention.
It is well known in the medical research community that lifestyle plays an important role in cancer prevention, especially for prostate cancer. Yet, we don’t hear about it through mainstream media or our education system: there really is good reason to eat broccoli!
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The void in nutrition education hurts our collective health. But, who reads medical research papers regularly unless this is part of your job or academic training? The news of the day has been dramatic during the pandemic, unemployment, Black Lives Matter protests, and upcoming presidential election.
You may already know that prostate cancer is common, yet preventable. In the United States, the American Cancer Society estimates that 1 in 9 men are living with prostate cancer. It’s the 5th leading cause of cancer-related deaths worldwide. Although the mortality rate is alarming, the good news is we know how to address prostate cancer risk through simple lifestyle strategics.
Cancer is a
complex disease.
Healthy living is more important today than ever before
Research shows that environmental factors, such as diet and exercise, are heavy hitters in reducing prostate cancer risk. Studies of identical twins show that your genes account for less than 50% of your prostate cancer risk. Twins help us understand the heritability of a disease, a term denoting the magnitude of the genetic effect.
"Environmental and heritable factors in the causation of cancer—analyses of cohorts of twins from Sweden, Denmark, and Finland." Published in The New England Journal of Medicine (2000). In this study, Dr. Paul Lichtenstein looked at 89,576 twin individuals and found that 42% of prostate cancer risk could be attributed to genetics. Approximately 58% of a person's prostate cancer risk comes from environmental and lifestyle contributions.
"Familial risk and heritability of cancer among twins in Nordic Countries." Published in JAMA (2016). In this paper, Dr. Lorelei Mucci conducted a larger twin study that followed 203,691 twin individuals over 3 decades to quantify the impact of nature versus nurture in prostate cancer risk. The researchers found that 57% of risk is attributed to heritability, still leaving a 43% contribution from other influences such as environment, lifestyle factors, and preventative measures. Data for this study came from the Nordic Twin Study of Cancer, an international collaboration that evaluates the role of genetics and the environment in overall cancer risk.
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Where you live plays a role in prostate cancer risk and morbidity
Based on data from the World Health Organization, Dr. Ahmedin Jemal, a researcher for the American Cancer Society, found that the rate of prostate cancer is highest among countries with the most resources, such as the United States. The study found that developed countries are home to 72% of the prostate cancer cases globally. Yet, countries with more resources witnessed lower mortality rates from the disease.
“International variation in prostate cancer incidence and mortality rates” is available online. Published in European Urology (2012). An abstract of Dr. Jemal’s article is available online and the full article PDF is available for purchase. The same research team determined from their data that there were 213,700 new cases in North America compared with less than 20,000 cases in Southeast Asia. Compared with South-Central Asia, North America reported 50 times more prostate cancer cases.
Check out the Global Cancer Observatory's interactive web-based platform that presents global cancer statistics. The map below
illustrates the global variation in prostate cancer incidence rates. Image courtesy of GCO, a division of the World Health Organization.
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Risk is strongly correlated with where you live, not where you were born.
After Dr. Jemal’s article was published in European Urology, Dr. Laurence Kolonel and his research team at the University of Southern California and University of Hawaii looked at 215,000 people to determine the contribution of ethnicity on prostate cancer incidence. Cross-cultural studies of disease risk help to disentangle the influences of genes and the environment.
The abstract for Dr. Kolone's article "The multiethnic cohort study: exploring genes, lifestyle and cancer risk" is available online. Published in Nature Reviews Cancer (2004). There are options to rent, get cloud access, or buy the full article. The research team looked at men from Japan, a country with low rates of prostate cancer, who migrated to the United States, a country with one of the highest rates of prostate cancer. Four years after migrating, the Japanese men had a 700% increase in prostate cancer incidence.
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Does the increased rates of testing in the United States explain why we see higher rates of prostate cancer?
No - the same study conducted by
Dr. Kolonel found
that stomach cancer decreased by ~50%
in the same cohort of Japanese migrant men after immigrating to the
United States.
The rate of prostate cancer doubled in the U.S.
In 1999, Dr. Ann Hsing published in International Journal of Cancer a paper with a 20-year timeframe from 1973 to 1992 across fifteen countries. The dataset for the study was taken from the International Agency for Research on Cancer (IARC). Dr. Hsing's research team found marked increases in prostate cancer incidence in all fifteen countries, with rates doubling among U.S. whites, Canada, France, and Singapore.
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"International trends and patterns of prostate cancer incidence and mortality." Published in the International Journal of Cancer (1999). U.S. blacks and whites demonstrated the highest rate of prostate cancer over the course of 20 years. The U.S. rates of prostate cancer are 50 - 60 times higher than that of Asian countries.Take a close look at Figure 2 in the article, which illustrates that in all countries incidence of prostate cancer was extremely low for men younger than the age of 50, but then rose exponentially with advancing age and reached a maximum after age 80.
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American Cancer Society Guidelines
According to the American Cancer Society (ACS), cancer is the second leading cause of death in both men and women in the United States, behind only heart disease. People with cancer also often experience physical effects (from the cancer itself and from treatment), distress, and a lower quality of life. Quality of life can also be affected for family members, caregivers, and friends of people with cancer.
In June 2020, the ACS issued an updated "Guideline for Diet and Physical Activity for Cancer Prevention" which highlights the small lifestyle changes people can make. Click here to see the full article (including references), which is written for health care professionals. Here is a summary of the ACS recommendations:
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Swedish study of exercise & cancer prevention
Dr. Helene Rundqvist from the Karolinska Institute published a research article in 2013 examining the correlation of endurance exercise and prostate cancer progression to malignancy. They understood that physical activity is associated with reduced risk of several cancers, including aggressive prostate cancer. Also, long-term exercise is known to reduce serum levels of growth stimulating hormones. But yet, it was unknown if there are deterimental effects of acute exercise blood serum on tumor cell growth.
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"Effects of Acute Exercise on Prostate Cancer Cell Growth." Published under the terms of the Creative Commons Attribution License by PLOS ONE (2013). Dr. Rundqvist designed a study where 10 men performed 60 minutes of bicycle exercise, and blood samples were taken before (rest serum) and after exercise was completed (exercise serum). The prostate cancer cell line LNCaP was exposed to exercise or rest serum. What researchers found was astonishing: exercise serum from 9 out of 10 men had a growth inhibitory effect on LNCaP cells. Specifically, exercise serum had a 31% inhibition of prostate cancer cell growth. Even an hour of exercise had a beneficial effect on cancer cell growth.
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Clinical trials
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What is statistical significance?
Watch a 2-minute video in statistical versus clinical significance in medical trials, produced by BioMed Central (BMC), a part of Springer Nature and pioneer of open access publishing.
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