The best replacement for lactose is casein.

The best alternatives to lactose are rated as following:
★★★★★  casein
★★★★★  sucrose
★★★★  lactase
★★★★  dairy
★★★  glucose
★★★  lactate
★★  fructose
★★  gluten intolerance
★★  lactic acid
★★  iptg
★★  lactulose
★  dairy intolerance
★  milk sugar
★  galactose
★  dextrose
★  milk allergy
★  maltose
★  milk protein allergy
  dairy allergy
  milk protein
  lactaid
  gluten
  dairy free
  maltodextrin
  onpg

Your alternative for lactose is not listed? Suggest!
Speaking about lactose, one probably shouldn't forget about benedict's test.

Other search terms related to lactose and their ratings are:
★★★★★ benedict's test
★★★★ benedict's reagent
★ milk
You have in mind a companion for lactose and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of lactose in all years. Click on graph for more.
lactose
casein
sucrose