Research suggests that for every 5 years a woman’s biological age is older than her chronological age, her risk of breast cancer increases by 15%.
While this sounds like a big increase, it’s important to remember that the average woman has a 12.5% risk of breast cancer, just because she is a woman. So, if a woman’s 12.5% risk increases by 15%, it means that a woman whose biological age is 5 years older than her chronological age has a 14.3% risk of developing breast cancer.
The study was published online on Feb. 22, 2019, by JNCI: Journal of the National Cancer Institute. Read the abstract of “Methylation-based biological age and breast cancer risk.”
Chronological age vs. biological age
Your chronological age is the number of years you’ve been alive. Your biological age is how old your body seems, based on a number of factors, including how your chromosomes have changed over time.
In this study, the researchers measured DNA methylation to calculate the women’s biological age.
DNA stands for deoxyribonucleic acid, a substance that is the main component of chromosomes. DNA methylation is a chemical change to DNA that is part of the normal aging process. DNA methylation that happens in abnormal patterns — meaning some DNA that should methylate doesn’t and DNA that should not methylate does — has been linked to cancer.
Scientists think that DNA methylation and biological age may be affected by exposure to things in the environment, such as sunlight, automobile exhaust, alcohol, and chemicals in food, plastics, and water.
In this study, the researchers estimated the women’s biological ages using three different measures called “epigenetic clocks.” Epigenetics is the study of changes that happen in a living thing caused by changes in how genes are expressed, rather than changes to the genes themselves. The epigenetic clocks measure methylation at specific locations in the DNA.
How this study was done
The researchers used blood samples from 2,764 women in the Sister Study to extract DNA and measure methylation using the three epigenetic clocks. They then estimated the women’s biological ages.
None of the women had been diagnosed with cancer when their blood samples were drawn.
The Sister Study, being conducted by the National Institute of Environmental Health Sciences (NIEHS), part of the National Institutes of Health (NIH), enrolled more than 50,000 women from the United States and Puerto Rico from 2003 to 2009. All the women in the study had a sister who had been diagnosed with breast cancer. Because the sisters have shared genes, environments, and experiences, the researchers hope to identify breast cancer risk factors, as well as ways to prevent the disease.
Of the 2,764 women in this study, 1,566 eventually were diagnosed with breast cancer. The diagnoses happened, on average, about 6 years after the blood samples were drawn.
The researchers then compared each woman’s chronological age to her estimated biological age.
The researchers found that women whose biological age was older than their chronological age had an increased risk of developing breast cancer. This increase in risk was statistically significant, which means that it was likely due to the difference in biological and chronological age rather than just because of chance.
"We found that if your biologic age is older than your chronologic age, your breast cancer risk is increased. The converse was also true. If your biologic age is younger than your chronologic age, you may have decreased risk of developing breast cancer," said corresponding author Jack Taylor, M.D., Ph.D., head of the NIEHS Molecular and Genetic Epidemiology Group. "However, we don't yet know how exposures and lifestyle factors may affect biologic age or whether this process can be reversed."
The researchers noted that using DNA methylation to measure biological age may help doctors better understand who is at risk for developing cancer and other age-related diseases.
What this means for you
DNA methylation testing isn’t routinely done, and the results can sometimes be hard for people who aren’t scientists to interpret.
Still, research suggests that certain nutrients, including folate, choline, vitamin B12, and vitamin B6, play a role in DNA methylation. So many researchers think that eating more of these nutrients can help keep the DNA methylation process normal. While all these nutrients are available as supplements, most dietitians believe that getting the nutrients from food is a better option.
Folate is a B vitamin found in dark green leafy vegetables, such as spinach or greens, as well as meat, seafood, dairy products, and other foods. Spinach, liver, asparagus, and brussels sprouts are some foods with the highest levels of folate. The NIH recommends that adult women and men consume 400 micrograms (mcg) of folate per day.
Choline is an essential nutrient found in meat, poultry, fish, dairy products, eggs, and cruciferous vegetables, such as broccoli. Choline is a source of the methyl groups that are needed for DNA methylation. The NIH recommends that adult women consume 425 milligrams (mg) and adult men consume 550 mg of choline per day.
Vitamin B12 is naturally found in animal products, including fish, meat, poultry, eggs, milk, and milk products. Beef liver and clams have some of the highest levels of vitamin B12. The NIH recommends that adult women and men consume 2.4 mcg of vitamin B12 per day.
Vitamin B6 is found in a variety of foods, including fish, beef liver and other organ meats, potatoes and other starchy vegetables, and non-citrus fruit. Chickpeas (garbanzo beans), tuna, and salmon have some of the highest levels of vitamin B6. The NIH recommends that adults consume between 1.3 mg and 1.7 mg of vitamin B6 per day.
It’s important to remember that while an older biological age compared to chronological age is linked to an increase in breast cancer risk, the absolute increase in risk is only about 2% — going from 12.5% to 14.3% for an average woman whose biological age is 5 years older than her chronological age.
It’s also important to know that DNA methylation is a complex biological process, and much more research is needed before we fully understand the process and how it might affect cancer risk.
Written by: Jamie DePolo, senior editor
Reviewed by: Brian Wojciechowski, M.D., medical adviser