Scientists zero in on a serious, yet little-known risk factor for breast cancer

Early in my career as a scientist at the National Cancer Institute (NCI), and for my Ph.D. dissertation research, I researched the strongest risk factors for breast cancer:

  • Hitting puberty at an early age
  • Going through menopause at a late age
  • Having no or late pregnancies (over age 30)
  • Having fewer pregnancies overall
  • Not breastfeeding
  • Taking birth control pills
  • Post-menopausal hormone therapy

Granted, most older women can’t do much about most of those risk factors. But a recent study has uncovered a powerful way that women can reduce their risk and protect themselves against advanced breast cancer. And it’s linked to something as simple as avoiding exposure to light at nighttime.

Let’s jump right in…

Nighttime light exposure changes circadian rhythm

Our bodies rely on exposure to natural sunlight for many things (as discussed this week). For one, it triggers the skin’s production of vitamin D—the all-important vitamin that protects you against almost every chronic disease on the planet.

In addition, exposure to sunlight during the day triggers the pineal gland in your brain to start producing serotonin—the “feel-good” neurotransmitter. (The pineal gland is also called the vestigial “third eye” because it shares embryological development with the two eyes. In ancient Ayurvedic medicine, the pineal gland is the site of one of the bioenergetic chakras.)

Then, when darkness descends, your body starts to convert the circulating serotonin into melatonin, which helps you sleep.

However, exposure to light at nighttime suppresses natural melatonin production and disrupts your sleep. And—it also seems to disrupt your hormonal balance, too.

Which brings us right back to the new study about nighttime light exposure and breast cancer…

Exposure to outdoor light at night increases breast cancer risk

For the new study, researchers looked at data on nearly 190,000 women with an average age of 62 years who had participated in the NIH-AARP Diet and Health Study. They determined the occurrence of breast cancer using national cancer registry data. And they determined the amount of outdoor, nighttime light exposure by using satellite imagery data.

During 16 years of follow-up, more than 12,000 women developed breast cancer.

The researchers found that the women in the group with the most exposure to nighttime light had up to an 18 percent higher risk of developing breast cancer than the women with the least nighttime light exposure. The effect was even greater for those women with estrogen-receptor positive breast cancers.

This finding supports the idea that nighttime light exposure suppresses melatonin production and thereby influences a woman’s estrogen hormone balance. And remember, science shows that higher estrogen levels over a woman’s lifetime is THE key factor that increases her risk of developing breast cancer.

I should also mention that women with the least nighttime light exposure (and lower breast cancer risk) were also less likely to be childless and less likely to have had her first child after the age of 30. (Again, being childless and/or having your first child after age 30 are strong breast cancer risk factors associated with higher estrogen.

Of course, this isn’t the first study to find a connection between nighttime light exposure and breast cancer. In fact, some previous studies had already found that women who work long periods on night shifts have a much higher chance of developing breast cancer compared to the general population.

These results were published in the International Journal of Cancer—which often seems to publish solid science that’s outside the realm of typical, run-of-the-mill, cancer research topics.

In fact, 30 years ago, when working with Richard Stevens and Nobel laureate Baruch Blumberg, we found clear evidence of the association between excess iron and cancer. But the mainstream wasn’t interested.

Not only were they not interested in the latest findings of a Nobel Prize winner, some were downright hostile. In fact, Dr. Clement Yip and a couple other clowns at the Centers for Disease Control and Prevention (CDC) even publicly claimed it was “irresponsible” to publish our genuine scientific results. (Of course, they were busy pushing dangerous iron supplements on the public.)

Eventually, we got our results published in the International Journal of Cancer—the same journal in which this new study was published—and also in the grand-daddy of them all, the New England Journal of Medicine.

In the end, this study on nighttime light exposure definitely offers some new insight into what contributes to breast cancer in postmenopausal women.

So, if you’re a woman (or a man), make sure to spend 15 to 20 minutes in the sun each day (preferably in the morning) and limit nighttime exposure to light. This simple lifestyle modification can help you boost your nighttime melatonin production and thereby lower breast cancer risk.

Of course, there are dozens of other safe, natural alternatives for preventing, detecting, AND treating cancer. And I’ve outlined them all in detail in my groundbreaking online learning tool, my Authentic Anti-Cancer Protocol. To learn more about it, or to enroll today, click here now!


“Outdoor light at night and postmenopausal breast cancer risk in the NIH‐AARP diet and health study.” Int. J. Cancer, 6/20/20.