By Denise Foley
From Completely You

An estimated 27 million people in the U.S. are going to work when the rest of us are going to bed. That's about one-quarter of the U.S. workforce. But working the graveyard shift appears to edge you closer to the graveyard.

A just-published Harvard study found that irregular sleep patterns disrupt your body clock, which sets the stage for diabetes. Add this to studies that found that women working the night shift are at higher risk for breast cancer, and you have a clearer picture of the dark side of working at night.

The Link Between Lack of Sleep and Diabetes

At Harvard, neuroscientist Orfeu Buxton and his colleagues had 21 healthy volunteers spend almost six weeks living in a lab where their diet, activity, sleep and light conditions were strictly controlled. For three of the weeks, they were only allowed about 5.5 hours of sleep every 24 hours at varying times of the day or night to mimic jet lag, a rotating work shift or a simple 24/7 lifestyle.

What happened sure looked like diabetes. "After three weeks of circadian disruptions and sleep restriction, the subjects' blood sugar went much higher and stayed higher for three to four hours after they ate a standardized meal," says Buxton. In three volunteers, blood sugar reached levels so high they could have been diagnosed with prediabetes.

In addition, the participants' metabolic rate -- how efficiently they burned calories for energy -- slowed by 8 percent. Their meals were controlled so they didn't gain weight, but a metabolic slowdown like that would, over a year, produce a 10-12 pound weight gain, says Buxton.

Insulin, a hormone produced by the pancreas, helps the body scoop up glucose (sugar) from the blood and use it as fuel. But when you work the night shift, it can disrupt this process, causing blood sugar increases that could eventually lead to diabetes. The good news is that the volunteers' bodies returned to normal after they got enough sleep at the right time for nine nights.

But that's not good news for people who work rotating shifts who never get enough sleep at the right times. There's no way to know when the damage from a perpetually disrupted body clock becomes permanent, says Buxton.

What to Do If You Work the Night Shift

Here are a few ways to keep your blood sugar -- not to mention your energy and your digestive tract -- healthy:

1. Be extra-careful to eat healthfully. "People who are sleep-restricted prefer more food and inappropriate food, like high-carb potatoey-ricey things, sugar and fat, which are more likely to go directly to fat," says Buxton. So be sure to do the following to ensure you're not one of them:

Maintain a normal eating pattern (three meals a day and two snacks, with breakfast when you wake up, no matter what time it is).

Stick to foods that are less likely to raise your blood sugar. Protein (e.g., nuts, poultry, and low-fat dairy) gives you a steady stream of energy, while chocolate doughnuts from the vending machine give you a quick burst followed by a rapid letdown.

Avoid excessive caffeine. Since caffeine can stay in your system for up to seven hours, have it once at the beginning of your shift but not close to quitting (and sleep) time. Stick to water the rest of the time.

Have a carb snack, like whole-grain bread and jam, before your head hits the pillow. Carbs will help you sleep.

2. Fit in some exercise. Night shift workers are also likely to be too tired to exercise once they leave work. Plus, they have a tough time sleeping when it's light out and the rest of the world is awake. If you can't exercise after work, says Buxton, try doing it during breaks while you're on the job, when you have the energy.

3. Make it easier to sleep. When you go home at night -- err, in the morning -- make sure you have room-darkening shades and a white noise machine so it seems like night in your bedroom. Your body clock is regulated by light exposure. You need total darkness to produce the sleep-inducing hormone melatonin.