Every two weeks, I call my 99-year-old grandmother in Taiwan on Skype. And every time she repeats the same message before we sign off: “Eat well, sleep well, don’t work too hard.” This is exactly what she used to say to me when I was a child growing up in Taipei. Now, fifty years later and halfway around the world, she repeats the same advice to me as if I were still a little girl.
As much as I respected her, for most of my adult life I considered my grandma’s words a well-intentioned old wives’ tale. I am a woman of science, after all - a molecular epidemiologist who has devoted her life to cutting-edge cancer research. I believe in data, not proverbs.
Of course, it turns out that Grandma was right. I am now aware of abundant data suggesting that eating and sleeping well boost our immune function, minimize harmful inflammatory conditions and regulate hormonal metabolism, thereby lowering our risk for cancer.
Epidemiological studies suggest that consuming whole grains (containing fiber and vitamins), fruits and vegetables (antioxidants, fiber, and specific compounds such as sulforaphane in cruciferous vegetables), tomatoes (lycopene), allium vegetables such as garlic and chives, tofu (isoflavones) and fish (the omega-3-containing varieties) reduces the risk of cancer. Research also suggests that eating foods high in certain chemicals, such as heterocyclic amines found in some grilled foods, increases the risk of cancer.
Although we are still learning about the specific biological mechanisms underlying these epidemiologic findings, ongoing studies, including those at the Stanford Cancer Institute and the affiliated Cancer Prevention Institute of California (CPIC), are revealing the molecular relationships between dietary components and cancer risk.
The value of getting to sleep early (before 11 p.m.) and sleeping well long escaped the attention of scientists. I first became interested in sleep as a risk factor for cancer when epidemiologic studies began to show that rotating-shift workers have a higher risk of endocrine-related malignancies, including breast and prostate cancers.
Over the last seven years, my research group has investigated the association of circadian rhythms, including sleep duration, serum melatonin, and 9 circadian core genes, with prostate cancer risk. During the same period, laboratory studies have shown a link between circadian rhythms and inflammation. The numbers of different immune cells (e.g., “T-cells” or natural killer cells) have been shown to peak during different parts of the sleep/wake cycle. We have found evidence that several risk factors that appear to be related to inflammation - including gallstones, obesity, and diet - are risk factors for cancers of the prostate, gallbladder and liver.
While I and other researchers continue our quest to understand the molecular steps involved in carcinogenesis and design the most effective interventions and medicines for cancer prevention, it is clear that we can behave better to reduce our cancer risk - even without knowing the detailed biological pathways - through a sensible lifestyle. My 99-year-old grandmother, who loves broccoli but doesn’t know anything about DNA methylation, is living proof. And her habits reveal a lot: She rises each day at 5 a.m. and is asleep at 11 p.m.; she eats three small meals daily, at exactly the same time; and she has a cup of coffee (containing phenols) every day at 3 p.m. My grandma believes that having healthy habits improves life, and I now have the data suggesting that they decrease cancer risk and improve life expectancy, as well.
Before I ever studied the role of circadian rhythms in cancer, my grandmother knew that sleeping well was good for her health. So I'm looking forward to my next conversation with my grandma. Perhaps if I listen well, I'll find another pearl of wisdom that leads to my next research project.
Ann Hsing, PhD, MPH, is director of research for the Cancer Prevention Institute of California (CPIC). Part of the Stanford Cancer Institute, the CPIC conducts population-based research to prevent cancer and reduce its burden where it cannot yet be prevented.