Joelle heard that vitamin k can strengthen her bones so she started taking megadoses of it daily. what negative effect could this have? get her banned from sports tournaments

You may have heard the saying "don't overdo it". This is an incredibly important phrase in terms of certain nutritional items. There is a reason why certain nutritional items give you a count of the percent of "What a Normal Human should consume in a day" or "Daily Value" (nutritional facts). A lot of times you should only consume that one hundred percent more or less, because that is the amount your body will tolerate and the max it makes use of; Vitamin C for example, you'd just urinate, if you have too much.

Vitamin K though is a bit nastier than Vitamin C. It is a fat soluble vitamin (is stored in fat for a long amount of time) in the DEKA group of vitamins (D, E, K, and A) While vital at normal levels for blood coagulation and calcium metabolism, Excessive consumption of excess of Vitamin K can lead to a condition called Hypervitaminosis or Vitamin (K) Toxicity. This can cause a break down especially in regards to blood coagulation, and you may begin to bleed... a lot. It doesn't help that instead of passing itself swiftly out of the body, it will instead stick to fat cells, for a great deal of time (makes it easier to reach toxic levels too)