BOSTON (CBS) – That protein powder in your morning smoothie may not be as healthy as you think.

A new study by the Clean Label Project found that several protein powders contain toxins that are harmful to your health.

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High levels of heavy metals, BPA, pesticides and other toxins associated with cancer were found in the 134 protein powder products, from 52 brands, tested by the Clean Label Project.

It screened animal-based, plant-based and whey protein powders for over 130 toxins.

More than half of the protein powders tested had detectable levels of BPA, or Bisphenol-A, an industrial chemical used in manufacturing plastic items.

Studies have linked BPA to cancer. The chemical, which is also found in some plastic items, is also linked to infertility.

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And according to the study, organic powders aren’t necessarily better, or safer.

The organic powders tested in the study had, on average, more than twice the heavy metals, such as arsenic, lead and cadmium, than non-organic powders.

A whopping 75 percent of plant-based powders tested positive for lead.

The study rated these products among the worst protein powders:

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  • Garden of Life Organic Plant Formula Chocolate Raw Organic Protein
  • Orgain Organic Meal Creamy Chocolate Fudge
  • Vega Vanilla Protein and Greens
  • Ancient Nutrition Vanilla Bone Broth Protein
  • Quest Vanilla Milkshake Protein Powder

The study rated these products among the best protein powders:

  • Ancient Nutrition Cinnamon Apple Bone Broth Protein
  • Biochem Vanilla 100% Whey Protein
  • Jarrow Formulas Chocolate Whey Protein
  • Naked Nutrition Naked Whey
  • Pure Protein Vanilla Cream 100% Whey