If you're looking for that early morning or late afternoon pick-me-up, that coffee or soda you rely on may not give you the boost you need.
A new study shows that people who drink a lot of caffeine ultimately develop a tolerance to its ability to increase alertness. That means if you need more get-up-and-go, then you need to drink more caffeine than you normally do.
Study results also suggest that if you regularly consume caffeine and give it up for a while, you'll start to experience withdrawal symptoms. In that case, you'll need to drink the amount you regularly drink in order to feel normal again.
While we may be worried that our daily intake of caffeine won't give us the jolt we crave after all, some experts warn against rushing to judgment.
"I don't think a conclusion can be drawn based on the results of one study," said Keri Gans, a nutritionist and spokesperson for the American Dietetic Association.
"I think it's too soon to call it a myth," she added.
Still, the possibility that one of the most widely held food beliefs may indeed be untrue may have some people wondering about whether some other things we've heard about the food we eat are fact or fiction.
Greasy Foods Cause Acne
At the first appearance of a pimple, many people are quick to blame the food they ate recently, especially if it's greasy and fattening.
Nutrition experts say that's not true.
"The myth probably came about because there's grease in certain foods and oily skin causes acne, so someone just kind of made the connection," said Karen Ansel, also a spokesperson for the American Dietetic Association.
In fact, they say there's no link at all between any specific food and acne.
"There's really no research that's found a connection between diet and acne. It's not there," Gans said.
"The take home point is that acne is hereditary and hormonal. It's an internal thing you really can't control," said Heidi Skolnik, a New Jersey-based nutritionist and fitness instructor.
But there are some studies that do suggest a connection between high glycemic index foods and acne.
"High sugar foods can cause acne, because foods that have a high glycemic index increase insulin levels, and that makes your body produce androgens, which cause acne," said Ansel.
Dark Chocolate Is Good For the Heart
As it turns out, everyone's favorite comfort food does have health benefits -- but only the dark kind. Cocoa contains flavonoids, which can help lower blood pressure.
But that doesn't mean you should go out and indulge your sweet tooth by eating lots of dark chocolate. The bars of chocolate you see in the supermarket usually don't contain enough cocoa to be really heart-healthy.
"You've got to have something that has a substantial amount of cocoa in it, not your standard dark chocolate bars," said Ansel.
The kind that is good for you is extremely dark and can taste very bitter. There is a way you can get the benefits from it, though.
"You can take a little and add it to your coffee," said Ansel.
But if you've just got to have your dark chocolate fix, nutritionists say there's no reason you can't.
"The bottom line is eat everything mindfully and in moderation," said Stacey Nelson, the manager of clinical nutrition at Massachusetts General Hospital in Boston. "Leave out the marshmallow and caramel, which would only add sugar, calories and the potential for an expensive trip to the dentist," she added.
"If you want, eat a little square of dark chocolate a day," said Gans.
Fruit Juices Are Worse Than Soda
Many of us have heard that fruit juices have more calories than an equal amount of soda.
That's true, according to nutritionists.
"Apple juice has 14 calories per ounce. Soda has 11 calories per ounce," said Ansel.
But unlike soda, pure fruit juices have lots of other nutrients.
"Juice naturally provides folate, potassium and vitamin C. It's a very nutrient-rich food," said Skolnik. "An 8-ounce serving is going to provide almost 50 percent of your vitamin C for the day," she added.
While they say there's really no comparison between the benefits you can get from juice versus the complete lack of nutrients you get from soda, fruit juice does have its nutritional drawbacks.
"The calories can start to add up," said Gans.
"If you want nutrients, whole fruit is way better than juice. The sugar in juice enters your body very quickly," said Ansel.
Still, there's no reason you can't enjoy a glass of orange juice with your breakfast.
"Be mindful of portion size. You don't need to have 24 ounces of juice. Six to eight ounces Is a great way to get in your nutrients," said Skolnik.
Others suggested a novel way to satisfy your fruit juice craving throughout the day.
"If you want a sweet, fruit drink, add sparkling water," Ansel suggested.
Warm Milk Makes You Sleepy
The nutrition experts we talked to say this age-old suggestion is indeed a myth. If you're tossing and turning and looking for something to help you fall asleep, milk won't help you.
"This rumor came about because milk contains tryptophan, an amino acid that helps make serotonin, which is a natural sleep aid," said Ansel.
"But the little bit of tryptophan in milk isn't really going to do it," said Gans.
She added that it could be that another property of warm milk that helps make you sleepy.
"What people experience could be the soothing effect. Once you're soothed, you can sleep better."
"There is no real data to support its effectiveness as a sleep aid, but it's still the most popular placebo out there," said Nelson.
Instead of milk, try something like oatmeal or graham crackers.
"You want something low in protein and high in complex carbohydrates," Ansel said.
Carbohydrates Are Your Enemy
Even though the Atkins Diet craze has died down, people still consider carbohydrates to be bad for your health and even worse for your diet.
According to nutrition experts, that's a total myth.
"There is no evidence that a carb calorie is more fattening than a protein or fat calorie," said Nelson.
"Carbs do not make a person fat. Eating more calories than what you need is what causes a person to gain weight," said Gans.
In fact, our bodies need carbohydrates. Nutritionist Stacey Nelson recommended 45 to 65 percent of your total caloric intake be carbohydrates.
"Carbs are the most efficient fuel source for the body. It's where we get our energy from," she said.
The key is to eat the right kind and the right amount of carbohydrates.
"Great carbs are those that are high in fiber -- the whole grains," said Gans.
Carbohydrates that are high in fiber help you stay full longer because they take longer to digest. They also take longer to chew, which also makes you full faster.
If you can't bring yourself to eat whole grain bread or whole grain pasta all the time, you should at least try to incorporate them into your diet some of the time.
"Make it your goal to make half your carbohydrates whole grains," said Ansel.
Above all else, nutritionists stress that carbohydrates are a vital part of a balanced diet.
"As with everything, eating in moderation is key," Ansel added.