If you experienced an emotional reaction when reading this word, you are in the majority. Few individual words contain such power—an almost visceral synergy of fear, unpredictability, loss, and injustice—as cancer. Some studies suggest that cancer is the most dreaded disease in the U.S.1 and perhaps among the most frightening words in the entire English language.
Cancer has this scary reputation for good reasons:
- Cancer can happen to anyone and occur at any age.
- Although treatments have improved remarkably, a cancer diagnosis still often feels like a death sentence.
- Even cancer treatments provoke fear, being associated with side effects such as physical wasting and hair loss.
- And perhaps the most disturbing feature of all is the perception that cancer is out of our control, a biological boogeyman that lurks inside our cells and organs waiting to strike.
If you share this latter perception, however, recent cancer developments may give you cause to reconsider. The past decade of research suggests that cancer risk is far more under our control than is commonly believed. As an illustration, see how you answer the following question:
Which statement is the most accurate scientific summary of cancer risk2?
- A. Cancer risk is about 90 percent genetic and 10 percent environmental.
- B. Cancer risk is about 50 percent genetic and 50 percent environmental.
- C. Cancer risk is about 10 percent genetic and 90 percent environmental.
Surprisingly—possibly to many scientists and non-scientists alike—the best answer is C. Genes and genetic mutations alone explain as little as 5 to 10 percent of cancer risk for most people (there are, of course, rare cancers that are highly determined by genetic factors).
The figure below lists a few of the more than a dozen cancers that are strongly affected by environmental factors. Importantly, “environment” includes internal factors such as chronic stress, health behaviors such as sleep, smoking, nutrition, and exercise, and external factors such as excess sun exposure and air pollution.
Some of the many cancers linked to lifestyle
Source: Thomas Rutledge
Following the mapping of the human genome in the 1990s, scientists hoped that they would identify genes responsible for the majority of cancers; if so, they could potentially be targeted by new medicines and gene therapies. This quest, however, largely proved to be in vain. Instead, subsequent research revealed that most incidences of cancer were best explained by environmental factors acting on genes instead of the gene acting independently. The result has been a paradigm shift in understanding cancer risk and the role of prevention.2
To understand how our behaviors, stressors, and other environmental factors either increase or decrease cancer risk, we need to appreciate the critical role of the epigenome and how the epigenome functions as a mediator between our environment and our genes. Your body contains more than 20,000+ genes located inside the DNA of your cells. These genes serve as a kind of biological hardware or human blueprint to create and operate your body.
Further, genes work their engineering magic by producing proteins—lots and lots of proteins. Your 20k genes, for instance, are capable of producing >200,000 different proteins, each performing different functions (your body’s vast family of proteins is called your “proteome”3). When you’re fighting a cold, eating an ice cream cone, or training for a marathon, these behaviors interact with your epigenome to trigger different patterns of gene activation (e.g., some genes are turned off and others turned on) and protein production to facilitate your immune system, aid digestion, or enable adaptions to your training program.
If you’re wondering how your genes decide what proteins to make during the above scenarios, they don’t. That’s the critical job of your epigenome.4 Surrounding your genes are layers of cells called the epigenome that translate environmental signals from your body and behaviors into biochemical code to activate and deactivate certain genes.
This means that different environmental signals to your epigenome can result in wildly different responses from your genes. Some environmental signals, for example, will cause your epigenome to activate your genes in ways that raise cancer risk acutely or chronically, while other signals will result in gene changes that lower risk (see below figure for examples).
Source: Thomas Rutledge
As a practical example, imagine that the environment, epigenome, and genes were represented as a person’s lifestyle, ATM machine, and bank account, respectively. Depending on the person’s lifestyle (environment), they interact with their ATM machine (epigenome) to either mostly make deposits (e.g., good health habits) or mostly make withdrawals (e.g., poor health habits) into their bank account (gene function).
While there may be no immediate consequences to poor health habits or chronic stressors, over time these withdrawals may reach a point where the person’s “bank account” becomes overdrawn and their cancer risk exceeds their body’s defenses. If this example seems abstract or trivial, be aware that your sleep, meditation, exercise, and nutrition habits each modify the expression of 1,000s of your genes.5 Does this still sound trivial?
Cancer may be the second leading of cause of death in the U.S., but no disease inspires more fear or avoidance. Recent cancer research, however, shows that we possess considerable leverage for reducing our individual cancer risk. By appreciating the dynamic link between behavior, the epigenome, and gene function, your goals for healthy living may assume a new level of importance and be driven by a new sense of urgency.