Soft Drink Consumption Related to Weak Bones in Teenage Girls

FOR IMMEDIATE RELEASE - Wednesday, September 6, 2001 2001-09-02-PH

Soft Drink Consumption Related to Weak Bones in Teenage Girls

In a just-published article in Nutrition Research, University of
Saskatchewan researchers have found that girls in their early teens who
often drink soft drinks instead of milk face a life-long increased risk for
fractures and osteoporosis.

In the most comprehensive study ever done on soft drinks and bone mass, the
researchers looked at the bone mineral content and diet of 59 boys and 53
girls during the two years in early adolescence when bone mass build-up
peaks (ages 13 to 15 for boys and 11.5 to 13.5 for girls).

They found that teenagers who drink soft drinks and other-low nutrient
beverages, such as punch or sugary drinks made from powder, drink less milk.

With girls, the reduced calcium intake led to weaker bones. Though boys
drink more low-nutrient beverages than girls, they still maintain a higher
calcium intake and a higher activity level, each of which provides
protection against an otherwise poor beverage choice.

"We can't tell from our analysis what the ideal amount of milk versus soft
drinks is," said Susan Whiting, a U of S professor of nutrition and
dietetics. "The Canada Food Guide recommends four glasses of milk per day
for adolescents so as this is replaced by soft drinks, the risk for
fractures and osteoporosis goes up."

Despite the relatively small size of the group studied, the results are
clear and statistically significant, she said.

Her advice for teens: Don't have sugary beverages at mealtime. Choose milk
or water to go with meals instead. She stressed that milk provides not just
calcium but other nutrients that are important for bone such as riboflavin
and vitamins A and D.

"Everyone loses bone mass as they age so building up bone mineral content
when you're young delays the onset of osteoporosis," she said.

She noted there's a two-year window during early adolescence when roughly 25
per cent of total bone mass is accumulated so it's critical that young teens
get the minerals necessary for bone growth.

"People who don't build up their bones have two strikes against them -- they
aren't putting on bone when they need to, and their dietary habits likely
aren't going to change to improve that," Whiting said.

Funded by Health Canada, the study was part of the Saskatchewan Pediatric
Bone Mineral Accrual Study, a project that began 10 years ago to study the
effects of diet and physical activity on the growth and strength of bones.

Besides Whiting, the researchers on the soft drink study were undergraduate
student Adrienne Healey, recent nutrition graduate Sheryl Psiuk, kinesiology
professor Robert Mirwald, kinesiology professor Kent Kowalski, and
kinesiology professor emeritus Donald Bailey. Healey is the recipient of a
Canadian Institutes of Health Research summer student award.

The link between soft drinks and weak bones made the news last year after
Harvard Medical School professor Grace Wyshak released a study linking cola
consumption to an increased risk of fractures, particularly among girls who
are physically active. Wyshak suggested that chemicals found in cola impair
calcium absorption, but did not measure the calcium intake of her subjects.

The U of S study, which examined overall diet and milk consumption as well
as consumption of colas, other soft drinks and low-nutrient drinks,
indicates that the problem is not consumption of soft drinks, but the drop
in milk consumption that goes with it.

While this study does not absolutely rule out the possibility that chemicals
found in soft drinks damage bones, it seems unlikely because all the
low-nutrient drinks had the same effect on bones, whether they were colas or
sugary drinks made from powder, Whiting said.

The team now hopes to study whether it is possible to build up bone mass
during early adulthood.

"How much bone mass you put on in your 20s is a controversial issue," said
Whiting. "We hope to be one of the few groups studying this."

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Susan Whiting
Professor of Nutrition and Dietetics
College of Pharmacy and Nutrition
University of Saskatchewan
Tel: (306) 966-5837
Fax: (306) 966-6377
susan.whiting@usask.ca

Kathryn Warden
Research Communications Officer
University of Saskatchewan
Tel: (306) 966-2506
Fax: (306) 966-2411
kathryn.warden@usask.ca

Backgrounder

- In the U.S., daily consumption of carbonated beverages by adolescent boys
and girls has increased by 74 per cent and 65 per cent respectively,
according to data from the U.S. Continuing Survey of Food Intake of
Individuals (CSFII) conducted since the late 1970s through to the mid-1990s.

- The same trend is apparent in Canada. In 1999, the average Canadian drank
87.5 litres of milk (down from 95.4 litres in 1990), and nearly 117 litres
of soft drinks (up from less than 100 litres in 1990).

- A study by Grace Wyshak of the Harvard Medical School published in June
2000 studied fracture incidence and cola intake in adolescents. In that
study, 460 ninth and 10th grade girls completed a questionnaire reporting
physical activity, carbonated beverage consumption and bone fractures.
Wyshak found a correlation between soft drink consumption and bone
fractures, particularly among active girls. She then speculated that the
chemicals in the carbonated beverages retard bone growth.

U of S Findings:
From "Relationship between carbonated and other low nutrient dense beverages
and bone mineral content of adolescents" by Whiting, Healey, Psiuk, Mirwald,
Kowalski, and Bailey (Nutrition Research, Volume 21/8, pp. 1107-1115)

Methodology:
- The study looked at the bone mineral content and diet of 59 boys and 53
girls over the two years when their bone mass build-up peaked.
- The eating habits of subjects were assessed based on their reported diet.
All participants received an initial 20-minute training session on food
portion sizes. Life-size pictures of food and beverage portion sizes were
present when the subjects reported their food and beverage intake.
- Bone measurements were obtained using dual X-ray absorptiometry (DXA)
scans of the whole body, spine, and hip. In DXA scans, low dose X-rays of
two different energies are used to distinguish between bone and soft tissue,
giving a very accurate measurement of bone density.

Conclusions:
- Milk consumption decreased as consumption of low-nutrient beverages --
such as soft drinks, Kool-Aid, or fruit drinks with less than 50 per cent
real juice -- increased. This provides support for the theory that
low-nutrient beverages affect bone mass by replacing milk in the diet.
- These results do not support the theory that carbonated beverages contain
sufficient amounts of bone-retarding chemicals (such as phosphorus,
fructose, or caffeine) to adversely affect bone health.
- Adolescent girls, but not boys, have reduced bone buildup when
low-nutrient beverages replace milk. Although boys drink more low-nutrient
beverages than girls, boys have a higher calcium intake as well as a higher
activity level, each of which provides protection against an otherwise poor
beverage choice.
- Low-nutrient beverages in general, not just carbonated or cola beverages,
are a concern for adolescent bone health.

University Communications, University of Saskatchewan (306) 966-6607