N05045: Are diets rich in vitamin A detrimental to bone health?

Study Duration: February 2003 to February 2004

Contractor: University of Sheffield

There is controversy as to whether an excess of dietary vitamin A is detrimental to bone health. Numerous studies suggest that vitamin A toxicity is associated with increased bone resorption and hypercalcaemia. However, this relationship between habitual vitamin A intake and bone health is uncertain.

The National Diet and Nutrition Survey of Adults aged 65 years and over (1998) shows that women in this age group have an average intake of vitamin A from food and supplements that is 179% of the recommended nutrient intake. Approximately a quarter of these women had vitamin A intakes of 100 micrograms per day and 8% of these women exceed 2000 micrograms per day of retinol equivalents. In light of the emerging evidence it is not clear whether this should be a matter of concern.

This project addresses the relationship between serum indices of vitamin A status and risk of fracture in Great Britain.

The study will take the form of a nested case control based on the placebo arm of a prospective study carried out by the Medical Research Council investigating the effect of a bisphosphonate on the risk of fracture. Indices of vitamin A status as well as vitamin D and parathyroid hormone will be determined in serum samples collected at baseline. Vitamin A status will be evaluated as a predictor of fracture after accounting for potential confounders.

The objective of this study was to determine whether serum retinol, retinyl palmitate and β-carotene predicted the incidence of hip and other fractures in a large prospective study of British women over the age of 75 years (n = 2606). During the 4-year follow-up period there were 312 incident osteoporotic fractures and 92 incident hip fractures; three control per case were used.

Serum retinol, retinyl palmitate and carotene were assessed in a baseline blood sample, and used as univariate predictors of incident osteoporotic and hip fracture. baseline BMD at the total hip, age, vitamin D status, weight, height, smoking and alkaline phosphatise were considered as covariates in a multivariate model.

Women with high vitamin A status were not significantly more likely to have a fracture, and in fact, high vitamin A status was associated with a reduction in fracture risk of up to 26% for supplement users and 15% reduction in high compared to low consumers. Increased serum retinol also predicted benefit rather than harm in terms of BMD. In multivariate analysis, only age, total hip BMD and weight were significantly associated with fracture risk. In conclusion, this study found no relationship between skeletal harm and higher dietary vitamin A intake.

Barker ME, McCloskey E, Saha S, Gossiel F, Charlesworth D, Powers HJ, Blumsohn A (2005). Serum retinoids and β-carotene as predictors of hip and other fractures in elderly women. Journal of bone and mineral research, 20(6); 913-919

*The final report is available from the Agency’s Information Centre.
To obtain a copy, please contact the Enquiry Desk, Information Services, Food Standards Agency (tel: 020 7276 8181/8182 or email: infocentre@foodstandards.gsi.gov.uk)

eatwell.gov.uk/healthydiet/nutritionessentials/vitaminsandminerals/vitamina

eatwell.gov.uk/asksam/healthissues/foodmed

eatwell.gov.uk/asksam/healthydiet/vitandminq