Bee pollen, creatinine, conjugated linoleic acid (CLA), green tea powder, guarana, vitamin C, protein powder—these are just a few of the extras found in so-called healthy smoothies available at smoothie shops, gyms, and supermarkets. You’ll often see some kind of claim attached to these extras—more energy, muscle builder, immune system booster, burn fat faster, to name a few.
The problem isn’t just that these claims have little, if any, good evidence behind them, some of the ingredients can be harmful if consumed in excess. For example, guarana naturally contains caffeine. Up to 400 mg of caffeine—the amount in two to four 8-ounce cups of coffee—per day can be part of a healthy diet for most adults, but chances are you won’t know how much caffeine guarana adds to your smoothie, and you may easily exceed
600 mg, the amount the Food and Drug Administration says is too much in a day.
What about extra vitamins and minerals? You can skip those too. “The vast majority of people can meet their nutrient needs with food alone. But high doses of some vitamins and minerals can have negative effects and when you start adding them to foods, you risk overdoing it,” says Keating. For example, Naked Plus with Vitamin C smoothie packs 1,270 percent of your daily vitamin C needs in one 15-ounce serving. According to the National Institutes of Health, too much vitamin C can cause abdominal cramps, diarrhea, nausea, and other intestinal problems.