vitamin C

Vitamin C is an essential nutrient that is needed by many of our bodily systems. A recent study sought to determine if adults who consumed more vitamin C had stronger bones and a reduced risk of osteoporosis.

Many older adults suffer from osteoporosis. This disease affects almost 10 million Americans and is more common in women. Osteoporosis is a chronic condition that is characterized by decreased bone density, resulting in fragile bones that are more likely to fracture or break.

Bone density is regulated by the balance between bone loss and the creation of new bones. Both bone loss and bone growth continue throughout life, but at older ages, the rate of bone loss increases while bone growth does not.

Vitamin C: an important nutrient for bone proteins and bone growth

Vitamin C, also known as ascorbic acid, is a nutrient that is needed by the body to produce both bone protein and the cells that generate new bone. It is therefore possible that consuming more vitamin C could increase bone density and strength, decreasing the risk of bone fractures.

Previous studies have sought to determine if there is a relationship between vitamin C consumption and bone density, but the results of the studies were inconsistent. A group of researchers in Iran recently reviewed all of these previous studies and used statistical methods to combine their results. The results of their analysis were recently published in the British Journal of Nutrition.

The researchers sought to identify all published studies from around the world that had compared vitamin C intake and bone density, a risk of fracture, or osteoporosis. They only included studies on dietary vitamin C. They did not include any studies that included vitamin C supplements. Bone density was measured by a specialized X-ray technique.

More vitamin C is associated with higher bone density

The researchers identified four studies that compared vitamin C consumption and bone density,  including a total of 3,529 individuals. The combined results from all four studies showed that the study participants who had consumed more vitamin C had, on average, higher bone density in both the neck and spine.

More vitamin C is associated with less risk of hip fracture in men and older adults

The researchers found five studies that compared vitamin C consumption and hip fractures. These studies included 10,810 individuals. Overall, consuming more vitamin C was not associated with a lower risk of hip fracture. However, the researchers found different results when they divided up the studies based on age and gender. Men who consumed more vitamin C were 53% less likely to suffer from hip fractures than men who consumed less vitamin C. There was no effect of vitamin C consumption on hip fractures in women. Furthermore, among the study participants who were at least 70 years of age, those who consumed more vitamin C were 28% less likely to suffer from hip fractures.

More vitamin C is associated with decreased risk of osteoporosis

The researchers found three published studies that compared vitamin C consumption and the risk of developing osteoporosis. These studies included 3,378 people, with 1,301 cases of osteoporosis among them. The results showed that people who consumed more vitamin C were, on average, 33% less likely to have osteoporosis than people who consumed less vitamin C.

Observational study design limits the conclusions

All of the studies included in the analysis were strictly observational; they only compared past dietary history with current health status. Therefore, the researchers could only identify an association between vitamin C consumption and osteoporosis, and could not confirm that vitamin C itself actually decreases the risk of developing the disease.

Other nutrients could also contribute to bone health

The studies also did not attempt to account for other factors that could accompany vitamin C consumption and potentially alter their results. For example, some of the best sources of dietary vitamin C are fruits and vegetables. However, these foods also contain many other important vitamins and antioxidants. If high vitamin C consumption was actually due to eating more fruits and vegetables, then improved bone health may have actually been due to other nutrients.

Overall, the analysis does show that people who consume more dietary vitamin C are at decreased risk of developing osteoporosis and suffering from osteoporosis-related bone fractures. This was especially true for men and those over the age of 70 years. However, additional studies are needed to confirm that vitamin C itself actually protects against osteoporosis.

Written by Bryan Hughes, PhD

References:

(1) Malmir, H., Shab-Bidar, S. & Djafarian, K. Vitamin C intake in relation to bone mineral density and risk of hip fracture and osteoporosis: a systematic review and meta-analysis of observational studies. British Journal of Nutrition 119, 847-858 (2018)
(2) Golob, A. L. & Laya, M. B. Osteoporosis: Screening, Prevention, and Management. Medical Clinics of North America 99, 587-606 (2015)

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