Myth #2: Drink more milk
You heard it from your parents, from your TV, and from our buddy Leon the Professional: Milk is good for your bones and your teeth, so you should drink at least a glass a day. Maybe two. Especially as a kid. On the surface, this makes sense. Milk contains a lot of calcium. Calcium is what they make bones and teeth out of. Ergo, bones and teeth are made of milk. Pour me a glass!
According to Dr. Willett, though, it’s "not such an emergency." A grip of studies during the '90s looked at comparative medical outcomes in countries where people drink a lot of milk (like Denmark and the USA) and countries where people hardly drink any milk at all (like Japan and Singapore). Turns out, there’s not a whole lot of difference in frequency of broken bones, age of osteoporosis onset, or dental problems. If drinking a lot of milk was so important, we’d see more bone and tooth problems in the countries with less moo juice.
Why don’t we see that difference? Because calcium is in all kinds of stuff. Oranges, green beans, sunflower seeds, broccoli, almonds, squash, clams, and rockfish are just a few of the dozens of foods with a powerful calcium content. Hell, Tums have more calcium than your body needs.
The takeaway: Eat cheese because that shit is delicious, not because you’re afraid you’ll break a hip if you don’t.
Myth #3: Fat is bad
This one is rooted in the fitness craze in the '70s and '80s that accompanied jogging, jazzercising, and Jane Fonda's Workout. Again, it made sense if you only gave it a little thought. Everyone wants to be thinner, and fat is the opposite of thin. So if we want to be thin, why would we put fat into our bodies?
But fat is one of three kinds of food substances our bodies need. Eating a diet with no fat is like running your car with no oil. Sure, you have plenty of gas and transmission fluid, but overall it’s a bad idea. Dr. Willett, and a few thousand other knowledgeable professionals, report that you shouldn’t avoid fats, but learn the differences between kinds of fat and eat accordingly. Roughly, these fall into three groups: good fats from plants and fish that you should eat plenty of; bad fats from animals (plus palm and coconut plants) that should represent no more than 10% of your daily caloric intake; and super-duper bad trans fats from industrial processes that you should not only avoid, but bury at a crossroads at midnight with a stake through their hearts.
There’s one piece of good news here. Back in the worst days of the fat scare, people ate butter substitutes made from trans fats and thought they were doing themselves a favor. According to Dr. Willett, "most butter substitutes are free of trans fats after we became aware of the problem in the early 2000s." So, we’ve got that going for us.
Myth #4: Low-carb is good
Low-carb, slow-carb, Atkins, Paleo, or Keto. Whatever you choose to call it, low-carb diets are a massive business, and for two good reasons: 1) people who follow low-carb diets tend to experience rapid weight loss in the early months of the diet, which is not only encouraging, it’s usually pretty good for them, and 2) they generally don't ask you to stop eating meat. Losing weight is good. Bacon is delicious. So what's the problem?
"No diet advice is complete if you only tell people what not to eat," says Dr. Willett. Breakfasts, lunches, and dinners consisting entirely of bacon and sawed-off chunks off cheese the size of a car battery is a staple of most low-carb diets, but your dietary approach needs to be far more complicated when you're looking at the bigger picture.
But complicated nutrition programs don’t sell books, and you can’t make a Dr. Phil-esque comment that sums it up succinctly. So low-carb programs sell big and folks keep on being skinny right up to their first heart attack.
Myth #5: Diet soda makes you thin
"Oh, for the love of..." you're saying. "Diet soda has zero calories. How can it not make you thin?"
That's what the makers of diet sodas have been banking on (and taking to the bank) for decades. Like all the other myths on this list, it passes the sniff test initially because its surface thesis is sound: If you drink sodas with lots of sugar and calories, you're going to put on more weight than if you drink sodas with zero calories.
But that's not necessarily true, and despite a lot of research over the years on the matter, science isn't entirely sure why yet. Some hypothesize that diet sodas contain a mess of chemicals that mess up your metabolism, make you crave sugar, or instruct your body to store fat. Other experts conjecture that it’s a correlation-not-causation thing -- that only people who are already overweight drink diet sodas. Psychologists have speculated that some people might use consumption of diet drinks as tacit permission to super-size their value meal.
Yeah, it’s all super-complicated and nobody's really sure what the hell is going on. Meanwhile, Dr. Willett recommends just setting the policy of never drinking calories. Water and tea are fine for most meals. Especially water. Drink more water.