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Recently I was at a dinner party, and when the guests discovered I was a nutritionist, they began peppering me with questions (happens all the time). One asked, what is the #1 thing we can do to improve health, and I answered SLEEP, without delay. As we settled on the topic of sleep, they were astounded when I told them to get 8 hours. It occurred to me that most adults are confused about how much sleep they really need.

We’ve been told that our ancestors would “rise and fall with the sun,” heading for bed when the sun set and getting up at sunrise. Somewhere the tide shifted, and we began to believe we didn’t need as much sleep, maybe only five to six hours. Sleeping too much and prioritizing rest was considered lazy in our always busy, 24 hours on-the-go society. By some estimates, Americans sleep two to three hours less today than they did before the industrial revolution. Most people are shocked when I tell them they need eight to nine hours of sleep ideally.

But recent studies are showing that our ancestors may not have slept a full 12 hours. In fact, we’re learning their sleep duration may have ranged from five to seven hours, and that they’d hit the sack about three or four hours after sunset.

What does this mean for us humans living in the modern world?

How Much Sleep Do You Really Need?

We only have theories about why we need sleep, but scientists believe that we need periods of uninterrupted dormancy for repair, detoxification, and rejuvenation. We also know that after sleep, we tend to retain information and perform better on memory tasks. And, let’s face it, restful sleep improves one’s mood and outlook, am I right? Quality sleep is the number one lifestyle habit that can absolutely improve your health, hormone balance, and weight loss goals. Many studies suggest that lack of sleep, independent of other factors like physical activity, is associated with obesity and chronic disease.

A new study is challenging our beliefs about how long our ancestors may have slept. Researchers at UCLA studied three hunter-gatherer tribes and their sleep habits. They found that the tribes slept about 6.5 hours per night. They’d stay awake past sunset with only the glow of the fire as their light source, and they were often up an hour before dawn.

But they’re not staying up and watching TV and reading their iPads, exposing them to artificial light that can alter cortisol levels and circadian rhythms. Experts agree that exposure to artificial light interferes with sleep and biological sleep rhythms that affect not only sleep quality but overall health. Insomnia affects up to 30 percent of Americans, but less than 2 percent of hunter-gatherers. So even if we’re finding our ancestors slept less than we originally thought, they were getting better quality sleep than we.

Also interesting is that recent research points to the idea that humans used to sleep in two four-hour chunks, with a period of wakefulness in the middle of the night. This is called biphasic sleeping. People would wake up around 2 or 3am and do light chores, have sex, or read by candlelight before falling asleep again.

But back to the original question: How much sleep do we need? Well, another question to ask would be for what? Do you simply want to feel rested and energetic throughout the day? Are you looking to lose weight? Enhance athletic performance? The short answer is however many hours of sleep leaves you feeling good: you don’t have to drag yourself out of bed in the morning, your energy is good during the day, you have the energy to meet your goals, and you naturally become tired at night. For most people this is somewhere between six and eight hours. The National Sleep Foundation’s updated recs released early in 2015 state that adults need seven to nine hours. I fully support this recommendation.

So why do our hunter-gatherer and ancestral tribes need less sleep than we do? Well, researchers point out that the hunter-gatherer societies were found to have a sleep period — meaning the time they were actually in bed — of roughly seven to eight and a half hours, which is consistent with our current recommendations. I would also posit that because they are not exposed to artificial lights, excessive sugar and caffeine, and the frenetic stressors of city living, their circadian rhythms allow them to sleep deeply and restfully for the hours they are actually asleep.

Bottom line: the amount of sleep that leaves you feeling refreshed and alert is what’s right for you. I work with so many people addressing hormone imbalance and other health conditions, and these folks typically need more sleep– up to nine hours if they can get it– while they’re healing and recovering. For the rest of us, the seven to nine hours stands.

Trouble falling or staying asleep?




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