Extract supplements and vitamins from this medical document. Return a JSON array or null.

Each entry:
- type: "vitamin", "mineral", "herbal", "other"
- value: (empty)
- summary: supplement name + dosage, e.g. "Vitamin D3 2000 IU"
- timestamp: "YYYY-MM-DD" if start date mentioned
- data: {"supplement": "...", "dosage": "...", "frequency": "..."}

Document:
{{MARKDOWN}}