Girls take note: Corn fiber can strengthen bones

Many older women suffer hip fractures, from which they may never fully recover. Thin and brittle bones can put them at risk for such breaks. And that risk may trace all of the way back to childhood. That’s when much of a woman’s bone is built up. Not surprisingly, girls are often told to consume plenty of milk and other sources of bone-building calcium. Now a study finds that teens and women could boost the value of that calcium even more by also eating foods rich in soluble corn fiber.

“You build about half of your adult bone mass in adolescence,” says Connie Weaver. She heads nutrition science at Purdue University in West Lafayette, Ind. Once women hit menopause (typically between 45 and 52 years of age), their bones can rapidly lose mass (thin), she notes. So Weaver’s team led two new studies to look at the role soluble corn fiber might play in limiting that. Many processed foods already contain this fiber. These include protein bars, cereals and frozen desserts. It’s added to boost the fiber content of these foods.

For their study in 11- to 14-year-old girls, the researchers included the fiber in muffins and fruit drinks. The trial was divided into three parts. At some point, each of the 28 girls cycled through every 4-week phase. During those phases, the girls got drinks and muffins that provided either 0, 10 grams or 20 grams of extra corn fiber per day. The girls were free to exercise or eat anything else throughout the trial.

The researchers also fed the girls calcium along with their breakfasts and injected some of this mineral directly into their blood. The calcium in blood is completely absorbed by the body. But calcium in the diet is only partly absorbed as it passes through the gut. What isn’t taken up will be excreted in urine. By comparing the amounts of calcium in urine and blood, the researchers were able to calculate how much of this bone-building mineral each girl had absorbed in each phase of the trial.

This was a double blind study. That means that until the experiment ended, nobody — neither the participants nor the researchers — knew which phase of the trial a patient was in (and what fiber dose a girl was getting).

The researchers compared calcium absorption from the fiber-rich diets to the four-week phase when they got no bonus fiber. This showed that the girls absorbed around 13 percent more calcium during the bonus 10 and 20-grams-per-day phases. Moreover, their stool samples showed this was happening because gut microbes were breaking down this fiber into short-chain fatty acids. Those fatty acids are known to aid calcium uptake.

The findings appear in the July Journal of Nutrition.

Older women also benefit from this fiber

For the second trial, Weaver’s team recruited 14 post-menopausal women into a 50-day-long double-blind study. As with the girls, these women got calcium injections and foods with an extra 0, 10 or 20 grams of soluble corn fiber. And these participants, too, got similar benefits from the fiber. This research appeared online July 17 in the American Journal of Clinical Nutrition.

With an extra 10 grams of the fiber each day, the women lost 4.8 percent less calcium, as measured in their urine. Since that calcium comes from bone, this indicated the women were slowly losing bone mass with their regular diet. When the women got an extra 20 grams of corn fiber daily, they preserved even more of their bone — 7 percent more than when they were on their regular diet.

Weaver hopes the study will make women more aware of bone health. “Your choices —exercise and what you eat — matter for bones,” she says.

Jeri Nieves studies bone health at Columbia University in New York City. She says the new studies were well conducted. But although soluble corn fiber appears to be safe, she would not yet recommend people start adding high quantities of it to their diets. For that, we would need more studies.

She also would like to see studies try to confirm bone benefits, such as improvements in bone strength or density, from long-term consumption of this fiber.