Does coffee cause pancreatic cancer? Do B vitamins lower the risk of stroke? Do fruits and veggies prevent colon cancer? These are a few of the hunches about diet and disease from the last 40 years that haven't stood the test of time.
In my latest issue of Nutrition Action, there was a great article on Unexpected surprising findings from the last 40 years. I found all 9 findings incredibly exciting to read and I thought I'd share a few of them with you.
I'll start with one of my favorite topics: SLEEP!!!
Too little sleep can lead to too much fat
Thirty or 40 years ago, who would have suspected that too little sleep could show up on your bathroom scale? Today, we sleep less and weigh more..and the two may be related.
The average American now sleeps one or tow hours less per night than he or she did 40 or 50 years ago. In 1960, an estimated 16% of young adults slept fewer than seven hours a night. Today it's 37%.
"We now have lots of studies on sleep and obesity," explains Kristen Knutson, assistant professor of medicine at the University of Chicago.
"And most find that short sleepers are more likely to be obese than longer sleepers."
A "short sleeper," she notes, is "someone who typically sleeps fewer than six hours a night." But the link is stronger if you look at just five-hour-a-nighters.
For example, in a study that tracked more than 68,000 women, those who slept fewer than five hours a night were 32% more likely to gain roughly 30 pounds over the next 16 years than those who slept for at least seven hours a night.
To find out how sleep deprivation might alter fat deposits, Knutson and her colleagues enrolled volunteers who slept overnight in a laboratory. When they were allowed to sleep for just four hours a night for one or two nights, the researchers saw more ghrelin (A hormone that increases appetite) and less leptin (a hormone that tamps down appetite). than when the volunteers were allowed to sleep for nine hours.
"We also asked each person, 'Are you hungry"' during the day," notes Knutson.
"after two days of shorts sleep, people were hungrier than after the long sleep."
And the more ghrelin and leptin changed, the more hunger changed. "That confirmed our suspicions that these hormones are having a strong effect on appetite," she adds.
IN a month long study, volunteers averaged 1,090 calories a day from snacks when they were allowed to sleep for 5 1/2 hours a night, but only 870 calories a day from snacks when they could sleep for 8 1/2 hours (The participants, who couldn't leave the lab during the study, were allowed to eat as much as they wanted).
They got their extra calories mostly from high-carb snacks like pretzels, chips, crackers, popcorn, snack bars, muffins, cookies, pudding, ic crea and candy.
And they snacked more after 7 pm.
"The less people are allowed to sleep, the more they snack, and it's not just because they're awake fro more hours," says Knutson.
Why would lack of sleep lead to less leptin and more ghrelin?
"Sleep restriction is associated with increased sympathetic nerve activity-the flight-or-fight response," explains Knutson. That stress response "could explain why sleep affects not just leptin secrition but glucose metabolism and insulin resistance."
And insulin resistance-which means that the body's insulin does a lousy job of lowering blood sugar levels-raises the risk of heart disease and diabetes.
Sure enough, "In a recent meta-analysis, short sleepers were more likely to develop diabetes than normal sleepers," says Knutson. Short sleepers are also more likely to end up with high blood pressure.
What's the next step? "To see if extending sleep will make good things happen," she says. "Does it benefit insulin resistance, blood pressure, inflammatory markers, and appetite hormones?"
Time will tell.