In the not-too-distant past, smoking was considered healthy–and doctors even recommended it to their patients. Fortunately, researches had the intellectual honesty to tell us about the dangers of cigarette smoking. In a similar way, nutrition recommendations often change do 180s. 
Things that used to be considered good are turning out to either do nothing or possibly cause harm. And things we thought were harmful are turning out to be either neutral or possibly even good for us. Here are the results of just a few very recent—and completely contrarian—research.
- Vitamin C may be doing more harm than good. Back in the 1970s, two-time Nobel prize winner Linus Pauling started touting the benefits of Vitamin C, and that led to a whole generation of people loading up on the stuff whenever we feel a cold coming on. And who’s going to argue with a guy with Pauling’s credentials? But you might want to give that a second thought—especially if you’re a man. Research over the past few decades has been unable to identify any concrete health benefits of taking megadoses of vitamin C. Even worse, a new study from Sweden just found that men who take vitamin C every day have twice the risk of developing kidney stones as men who don’t take any.
- Margarine may be worse than butter. Nutritionists have been beating up on the saturated fat in butter for years, telling us that vegetable fats—the kind margarine is made of—are healthier. Or at least less unhealthy. But in another case of conventional wisdom turned on its head, butter may have been the lesser of the two evils. Scientists reviewing research data from the 1960s and 70s found that people who switched from butter to margarine died sooner than those who stuck with butter.
- Diet drinks may not have the desired effect. With all the attention being paid to obesity and diabetes, a lot of people have switched to diet drinks, believing that they’re a healthier choice. Turns out they’re not—especially for women. While drinking sweetened beverages definitely helps pack on the pounds, diet drinks may increase your diabetes risk. Women who drank about 12 ounces of diet drinks per week had a 33% higher risk of developing the disease. Those who drank 20 ounces per week had a 66% higher risk. Other studies have noted a connection between diet drink consumption and increased risk of depression. Coffee, however, may offset that risk.
