Research...
General Reference
Wikipedia: Lactose Intolerance
This article is rated "start class" in the category of food and drink, but has been given a "B-class" rating in the area of Medicine. Explore the "talk" tab and give special attention to suggested "ideal sources" provided there (yellow box)
Consumer Medical Resources
WebMD | MayoClinic.com | Healthline | Sharecare
Periodical Databases
AltHealthWatch | Consumer Health Complete | Health Source | Medline
The Open Web
For each site you find ask yourself:
Is this a personal blog? a forum?
Who sponsored/authored this site and what professional credentials do they lend to the site?
Is the site selling some product or idea? Does this effect the message (expected bias)?