[falsestprophet]

Dairy can be problematic for most people. Lactose tolerance is the exception outside of Europe [1] and west-central Africa [2].

  [1] http://www.medbio.info/Horn/Time%201-2/Lactase%20map.gif
  [2] http://upload.wikimedia.org/wikipedia/commons/9/9a/LacIntol-World2.png

[tallanvor]

Yogurt, especially with probiotics usually isn't a problem as it contains very little lactose.