Many workout supplements and black market drugs don't contain what the labels say - they might have harmful stuff mixed in or be labeled completely wrong.

The study looked at brain health supplements and found most were mislabeled or adulterated - 83% had hidden ingredients. This proves supplements often contain things not listed on the label, supporting the claim about supplement contamination and mislabeling.

The study looked at sports supplements and found that 12-58% of them contained hidden banned substances like steroids or stimulants that weren't listed on the label - this proves the claim that sports supplements often have contaminated or mislabeled ingredients.