The lure of many of those dietary supplements is the promise of a protein boost, one that many people do not really need.
Labeling for BSN Core Series Syntha-6 is ambiguous and could lead males to consume as many as eight scoops (four two-scoop servings) per day. That would deliver up to 176 grams of protein in the powder alone, plus another 33 grams when mixed with four 8-ounce glasses of nonfat milk. When you add those 209 grams from the protein drinks to the average 82 grams most adults already get from their daily diet, according to federal data, a 150-pound nonathlete would consume 291 grams of protein, or about five times the amount needed. An athlete could get nearly double.
Only one of the products we tested, Six Star Muscle Professional Strength Whey Protein, specifies a maximum intake, warning that consumers should not exceed six servings in a 24-hour period. Others use vague language that could encourage a high level of consumption. For instance, labeling on BSN Lean Dessert and BSN Core Series Syntha-6 suggests an intake of one to four servings daily but then concludes, "or as needed to satisfy protein or body shaping/muscle building requirements."
Shao, the industry trade-group official, says there is no such thing as consuming too much protein, as long as you're getting other nutrients in your diet as well.
Not so, says Kathleen Laquale, a licensed nutritionist and certified athletic trainer. "The body can only break down 5 to 9 grams of protein per hour, and any excess that is not burned for energy is converted to fat or excreted, so it's a ridiculous waste to be recommending so much more than you really need," she says.
Roberta Anding, a clinical dietitian and director of sports nutrition at Baylor College of Medicine, agrees. And, she says, "If you ask the average consumer how much protein they need they have no clue."
Anding says protein drinks might help vegans or some seniors. The American Dietetic Association says proteins could help athletes after strength and endurance training, although it says they haven't been shown to improve athletic performance and should be used conservatively.
The products can be costly. For example, we paid $45 for a 2-pound jar of MuscleTech Nitro-Tech Hardcore powder; it yields servings for about five days if you follow directions for maximum results.
Consuming excess protein through supplements can cause health problems. "Often I see clients who are getting plenty of protein in their diets and then drinking three protein shakes on top of that," says Erin Palinski, a registered dietitian and certified personal trainer who has seen the ill effects. "Cutting back is one of the first pieces of advice I give them."
Among those she helped is Scott Baker, 24, of Hamburg, N.J., who found that when he was chugging down protein shakes to boost his total protein intake to more than 300 grams daily, he suffered from bouts of diarrhea. That's a side effect of too much protein, Palinski says. "When I began cutting down my use of shakes and trying to get most of my protein from whole foods instead," Baker says, "those symptoms went away completely and I also began seeing better results from my workouts at the gym."
Although protein is needed for bone development, excessive protein intake over the long term might also cause calcium to be excreted from bones, increasing the risk of osteoporosis. And for diabetics or others with kidney problems, it can lead to further complications. "There are a lot of people these days who are undiagnosed pre-diabetics who may not be aware their kidneys aren't fully functional and they definitely should not be loading up on protein," says Nancy Clark, an author and certified specialist in sports dietetics.