November 19, 2013
Milk consumption during adolescence is not associated with decreased risk for hip fracture later in life, according to results from a new study. In fact, high consumption of milk may actually up risk by increasing height.
The study was published online November 18 in JAMA Pediatrics.
“Greater milk consumption during childhood and adolescence contributes to peak bone mass and is therefore expected to help avoid osteoporosis and bone fractures in later life,” write Diane Feskanich, ScD, from the Channing Laboratory, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Harvard University, Boston, Massachusetts, and colleagues. “However, milk consumption during teenage years was not associated with a lower risk of hip fracture in older adults in our cohorts.”
In fact, the investigators found a significant increase in risk for hip fracture in men for each additional glass of milk consumed each day during teenage years. They say that positive association was mediated, at least in part, by increased height.
The researchers analyzed data from 2 prospective cohort studies that included 22 years of follow-up in more than 96,000 people: 61,578 white postmenopausal women from the Nurses’ Heath Study and 35,349 men aged 50 years and older from the Health Professionals Followup Study.
On entrance into each of those studies, the participants completed questionnaires that asked about medical history, lifestyle, and disease risk factors. During the study, participants also completed food frequency questionnaires, including how frequently and in what quantities they consumed milk (whole, low-fat, and skim) or cheese during their teenage years.
The baseline assessment also included information about participants’ attained height. After the initial assessment, participants updated their status every 2 years. The updates included information on any hip fractures that had occurred.
The investigators used Cox proportional hazards models to calculate relative risk for hip fracture from low-trauma events per glass of milk consumed daily on average during teenage years.
During the 22 years of follow-up, men reported 490 hip fractures and women reported 1226. Fractures in men occurred at a median age of 78 years; in women, the median age was 73 years.
“After controlling for known risk factors and current milk consumption, each additional glass of milk per day during teenage years was associated with a significant 9% higher risk of hip fracture in men ([relative risk (RR)] = 1.09; 95% [confidence interval (CI)], 1.01-1.17),” the researchers report. However, they note, “The association was attenuated when height was added to the model (RR = 1.06; 95% CI, 0.98-1.14).”
In contrast, they say, they saw no such association between teenage milk consumption and hip fracture in women (RR, 1.00 per glass per day; 95% CI, 0.95 – 1.05).
The authors concede that the results of the study are limited by potential recall bias regarding milk consumption. However, they note, “Although diet in the distant past may be poorly recalled, long-term recall of milk is better than for many other foods owing to the relative stability in the diet.”
Still, they say, additional research is needed to find out more about how early consumption of milk and attained height affect risk for adult hip fracture.
In an accompanying editorial, Connie M. Weaver, PhD, from the Department of Nutrition Science, Purdue University, West Lafayette, Indiana, notes that the current study runs counter to much of what is known about dietary intake and bone health. In fact, several studies have suggested that milk consumption during childhood and adolescence reduces fracture risk, and mechanistic data indicate that milk consumption increases bone strength.
“Practically speaking, does the study by Feskanich and colleagues offer a solution to osteoporosis? Without dairy, dietary quality is compromised.”
This research was supported by the National Institute on Aging and the National Cancer Institute. The authors have disclosed no relevant financial relationships. Dr. Weaver has reported that she has received funding from the Dairy Research Institute and Nestlé.
JAMA Pediatrics. Published online November 18, 2013. Article abstract, Editorial extract