Well that entire response talks a lot but says little.
To sum it up, the FDA gives a basic overview of how they regulate supplements under DSHEA, acknowledges that the 5 supplements listed by Amy Shipley in the Washington Post are under investigation, reassures the Congressman that they are doing their job and generally give a runaround excuse about how supplements are regulated post-market.
The investigation here will center on whether the 5 supplements incuded a NDI (new ingredient not marketed commercially previous to the passing of DSHEA in 1994) and if so, whether:
1. That ingredient was submitted properly to the FDA for approval in the correct time frame by the manufacturer of said product.
2. Whether ingredient in question is actually DSHEA-compliant; that is, naturally present in the food chain without chemical alteration.
3. Whether said ingredient was commercially marketed or submitted for approval as a drug; or contains a mislabeled or misbranded drug.
If a company under investigation did not follow the rules regarding all this, then they may be in trouble.
I personally don't think our fair Congressman is going to be satisfied with a simple letter filled with what would likely sound to him excuses and placation.