These powder- or capsule-form health supplements are a roughly $1-billion business and a growing health-food trend. Made from ingredients like alfalfa, barley, wheat, and algae, as well as fruits, vegetables, herbs, and probiotics, the supplements may provide a healthy boost of vitamins and nutrients. (The products aren’t FDA-approved, so health claims aren’t verified.) But among the 16 popular products tested, five did not pass muster, including products like All-Day Energy Greens, InnerLight Super Greens, and The Ultimate Meal, according to ConsumerLab.com, an independent food research company that examines health and nutrition products. One supplement, Vibrant Health’s “Green Vibrance” product, contained roughly 24 micrograms of the carcinogen arsenic per .4-ounce serving, which far exceeds the 10-mcg-per-34-ounce safety limit established by the Environmental Protection Agency. Another powder supplement, Ultimate Life’s “The Ultimate Meal”, contained more than double the allowable amount of aerobic bacteria, which can cause inflammation and infections, research shows. “Greens and whole foods powders and pills can provide a range of vitamins and natural antioxidants,” said Tod Cooperman, MD, president of ConsumerLab.com. But because these products include ingredients like kelp, spirulina, and many other unusual plants and herbs, contamination is a problem, Dr. Cooperman adds. If you’re interested in these supplements and searching for some ConsumerLab-approved options, you could opt for a powder like Green Max Powder from Swanson or Juice Plus+ Garden Blend capsules. Study after study has indicated actual fruits and vegetables are healthier than supplements. But Dr. Cooperman says these powder and capsule products may offer some health benefits if you have problems swallowing 4 cups of fruits and vegetables a day, as the Centers for Disease Control and Prevention recommends. More from Prevention: The 3 Supplements You Don’t Know About (But May Need) and The Supplements That Keep You Young