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Late Night Snacks Could Increase Your Chance of Breast Cancer

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Late Night Snacks Could Increase Your Chance of Breast Cancer

Sep 15, 2023

A large-scale study shows a connection between the eating habits of women and the chance of developing breast cancer. More surprisingly, eating junk food late at night may increase your risk. Women’s health expert Kirtly Parker Jones, MD, explains what types of foods you should be eating—and when you should be eating them—to reduce your risk of breast cancer.

Episode Transcript

More research suggests that eating fruits and veggies decreases the risk of breast cancer. But it isn't only what you eat, but when you eat it.

Diet and Breast Cancer

The influences of risk in getting cancers and really any fatal disease are probably one-third genetic, one-third environmental, and one-third bad luck. Now, we all understand the bad luck part. You were in the wrong place at the wrong time. And we intuitively understand that some diseases run in families. The environmental part includes cancer risks from environmental risks, such as bad air quality, and working in chemically toxic environments, and there are behaviors such as smoking, excessive alcohol, bad diet, and no exercise. In fact, it turns out that many of the bad luck and genetic-environmental factors may actually affect other risks positively or negatively. It is, of course, complicated.

Much has been written about diet and the risk of cardiovascular disease and cancers. Fruits and veggies come up over and over as important factors that may increase or decrease the risk of some cancers. Most recently, researchers reviewed the extensive nutrition questionnaires from the Nurses' Health Studies 1 and 2.

Nurses' Health Studies: What the Research Means

Now, okay, Nurses' Health Studies 1 and 2, researchers used well-validated nutrition questionnaires to examine the association of diet with the risk of invasive breast cancer in over 180,000 women. They followed them with periodic examinations for about 24 years. These studies are some of the very best that we have about women and aging and health and disease. They looked at women who had less than two and a half servings of fruits and veggies daily. And potatoes and ketchup do not count as veggies in these studies. They compared those women with women who ate more than five and a half servings a day. That's about two cups.

There was an 11% reduction in breast cancer in the veggie-eating nurses, especially greens and yellow veggies. Now, this isn't a huge reduction. A 50% reduction would be huge and would be a very big deal. But given that fruits and veggies, not ketchup and fries, decrease the risk of heart disease and dementia, it seems like a pretty good idea.

The Link Between Meal Timing and Health

Now, it isn't just important what you eat, but when you eat it. A recent study looked at when people eat compared to when they go to sleep at night. To back up, we know that mice and rats who are fed all day long and eat right before they go to sleep time, get fat. This is compared to mice that were given the same amount of calories during their normal active period, which is at night. So they were eating at the wrong time of day. This has also been shown in people. People who eat before going to bed at night gain weight and develop more pre-diabetes.

Now, there is a lot of research on this and there are some randomized trials in humans. Some people were forbidden to eat in the four hours before bedtime, and some people were given food right before bed. Even when the food content was the same, eating right before bed messed with these research subjects' normal insulin and inflammation patterns. Now, this research shows that eating before bedtime isn't good for you.

Of course, we all know that the food choices we make right before bedtime aren't like the ones we made five hours earlier. I just can't see myself standing at the counter rubbing baby kale and cruciferous vegetables to make them more palatable than shredded cardboard. A spoon and a carton of ice cream or a box of cookies is much more likely to be on the just-before-bed menu. We also know that eating right before bedtime is bad for your gut and is more likely to cause reflux or heartburn.

The Importance of Circadian Rhythms

Now, there's evidence from Spain that long-term disruption of endogenous circadian rhythms. Mistimed eating and sleeping patterns are how the researchers phrased it. Eating just before sleeping is what I would call it. This increases the risk of breast cancer by 20%. In fact, not eating for three to four hours before your bedtime, whatever that is for you, and having prolonged periods of fasting before you eat again is good for you. By fasting, they mean at least 8 hours and preferably 12 hours. And this fasting period decreases your risk of cancer, diabetes, inflammation, and heart disease.

Breakfast means breaking your fast. Fasting doesn't count if you ate before bed, got up in the middle of the night for a cookie or a spoonful of butter, slept only six hours, and then ate in the morning.

So how can eating before sleeping increase your risk of breast cancer and, you guys, prostate cancer as well? Again, it might be the problem of food choices. High-fat choices for late-night snacking versus rubbed kale salad at dinner. High-fat foods increase the risk of breast cancer. It can be suppression of melatonin just before you go to bed. That bright light in the refrigerator on your eyes as you're seeking out something yummy. It can also be a rise in insulin, which is a risk for breast cancer or can be messing with your immune system by eating before bedtime.

Recommendations for a Healthy Eating Schedule

So intermittent fasting is a big fad in diets these days. We evolved without a refrigerator in a grocery store and often went hours or days without food. We're not recommending fasting for days, but eating dinner at 7 p.m., going to bed at 10:00, getting up at 6:00, and then eating breakfast at 7:00. Yielding about a 12-hour fast would be a pretty good idea. That is if you're a morning person. If you're a night person, eat at 8:00, go to bed at midnight, get up at 8:00, and don't eat in between. Be sure you're getting enough sleep, seven to nine hours for most people, and try to get sleep that is as non-interrupted as you can. Don't interrupt it with late-night or middle-of-the-night snacking.

And for your adolescents, if you can keep them on a decent food schedule, eat dinner at 6:00 to 7:00, and no late-night videos or screens with high-fat snacking, you'll be doing them a big favor.

And I extend gratitude to the 180,000 nurses who participated over the many years of the Nurses' Health Study. And thanks for joining us on The Scope.


updated: September 15, 2023
originally published: August 23, 2018