Published by JAMA Pediatrics, the report looked at more than 96,000 men and women with a follow-up of over 22 years. The researchers, from Brigham and Women's Hospital and Harvard University, asked individuals to recall their milk consumption as a teenager. In the follow-up, men reported 490 hip fractures while women reported 1,226.
The results suggested that for men, each additional glass of milk per day as a teenager was associated with a 9% higher risk of hip fractures, with the association partially influenced by height. No association between teenage milk consumption and hip fractures in women was identified.
In regards to the differences between the two genders, the researchers cited the possibility of "an increase in bone mass with an adverse effect of greater height," the authors wrote. "Women are at higher risk for osteoporosis than men, hence the benefit of greater bone mass balanced the increased risk related to height."
Cheese intake, however, was not associated with a risk of hip fracture in either men or women.
"Dietary Guidelines for Americans, 2010 recommends the consumption of three cups of milk or equivalent dairy foods per day to promote maximal bone mass in adolescents," the researchers concluded. "In this investigation, higher milk consumption at this age did not translate into a lower risk of hip fracture for older adults, and a positive association was observed among men."
Connie Weaver, a nutrition scientist from Purdue University, expressed concerns regarding the the report.
"A main tenet of [the researchers] is that milk consumption in teens may have led to an increase in height as an adult. Height has been identified as a risk factor for osteoporosis," Weaver, who was not involved in the study, said in a statement. "It is not clear why this would be true in men but not women, and especially given that men experience about one-fourth the hip fractures that women do."
The investigators could have tested the contribution of other dietary protein sources (eggs, meat) to height and subsequent fracture risk to help confirm the impact of dietary protein more generally."