"But I encourage everybody to go speak with a nutritionist before self prescribing multiple vitamins," she said.
Politi stressed that although some vitamin supplements might be good, more isn't always better.
"For example, iron fortification is something controversial. We want to prevent anemia… but adding iron to everything in our food supply might not be good," Politi said.
While iron can function as an antioxidant and help protect cells from cancer risk, Politi said "Iron in excess has been shown to promote oxidation instead of preventing it."
Politi also takes issue with the common practice of fortifying food -- fortified cereals, fortified health bars, even fortified water.
"I'm not particularly fond of food being enriched with a lot of vitamins -- you really don't know how much you're getting," said Politi. "The FDA allows a 20 percent margin of error."
Instead of spending extra money on new-fangled fortified health food, Politi just recommends one daily multivitamin and a varied diet with plenty of fruits and vegetables.
Yet even when patients stick to the basic meals, many nutritionists find their patients have been playing timing games with their food: No breakfast ever, no dinner after 8 p.m., no snacking at all.
Mayo Clinic dietician Jennifer Nelson said one of the most popular nutrition myths she hears is that skipping breakfast saves calories.
"Studies have shown that breakfast skipping is associated with a higher body mass index compared to those who eat breakfast," Nelson wrote in an e-mail to Abcnews.com. "If you eat a healthy breakfast, the overall quality of the diet improves, and breakfast can help regulate appetite."
Nelson said the same goes for the myth that snaking is bad. "Actually, snacking on healthy foods can actually improve the overall nutritional quality of a person's diet - and help control appetite," she wrote.
Often patients trying to lose weight may fall short not so much on what they eat, but what they drink. Politi said she frequently sees patients who fall into the trap of consuming a lot of sports drinks at the gym.
"My fitness colleagues tell me that sport drinks are only needed when you exercise for over an hour and most people really don't exercise that long," said Politi. "Especially if you're trying to control your weight, it's better to drink water. The [sports] drink is some extra calories you don't need."
Amid all the confusing marketing and government recommendations, Aronne suggested the public just go back to eating your vegetables.
"This is what your mother has been telling you," said Aronne. "If you eat your vegetables first and get the good nutrition that you need, then you can feel satisfied."