I don’t know, and I’m not sure anybody knows.
The biggest concern about inadequate calcium consumption is that your bones will be weak and brittle, leading to fractures.
Dr Harriet Hall at Science Based Medicine reviewed a NEJM article written by Drs Willets and Ludwig on the health effects of milk.
From Dr Hall:
I was surprised to learn that the US recommendations for milk consumption were based on small, flawed studies of calcium balance. Other countries recommend lower levels of calcium intake. The US recommends 1000-1200 mg for adults, the UK 700 mg, and the World Health Organization, 500 mg. Counterintuitively, countries with high milk and calcium intake actually have the highest rates of hip fracture. Clinical trials of calcium for fracture prevention are complicated, because of confounding factors like vitamin D, phosphorous, and adult height. High calcium intake during childhood and adolescence was thought to serve as a way to “bank” calcium, but studies have not supported that hypothesis. In fact, men’s risk of hip fracture increased by 9% for every additional glass of milk consumed during adolescence.
Steve Parker, M.D.