Bone Health

 
Introduction
Our bony skeleton serves to provide our bodies with mechanical rigidity and stiffness and enables movement on land. The second function is that bone provides the body with a reservoir of the essential minerals: calcium and phosphorus. 
 
Bone is composed of about 35-40% calcium, 50-58% phosphate and 2-8% carbonate with the total amount of calcium in the skeleton being about 1.1-1.5kg.
 
A brief review of the nutrients which have specific bone health benefits are outlined below. They have been divided into those where there is substantial evidence of benefit and those where benefits have less proof.
 
Nutrients with substantial evidence of benefit:
  • Calcium
  • Vitamin D

Nutrients with some evidence of benefit:

  • Magnesium
  • Vitamin K
  • Vitamin C
  • Boron
 

Nutrients with Substantial Evidence of Benefit

 
CALCIUM
The role of calcium in bone health and maintenance of bone mass, and hence prevention of osteoporosis has been extensively researched and major findings can be summarised as follows: 
  • Increasing calcium intake to 1300mg/day during childhood through to 18 years of age increases peak bone mass which is reached in the late 20’s by upto 5%. Higher peak bone mass increases the time period before age related bone mass loss becomes clinically relevant.  
  • High intakes of calcium, for example 800-1600mg/day (100-200% RDA) slows down rate of bone loss in pre-menopausal women. 
  • High calcium intake in the post-menopausal years 1200-1600mg/day can reduce rate of bone loss and subsequent risk of fracture by 30%.
 
Most women over 50 years of age in the UK have significantly lower intakes of calcium than is recommended above, and therefore either modification of diet or supplementation should be considered.
 
VITAMIN D
Vitamin D can be obtained from the diet or can be synthesised in the body when exposed to sunlight. There is increasing recognition that populations who live in countries with lower sunlight hours have significantly lower vitamin D status.
 
Vitamin D status has now been strongly linked with bone health. Several large scale clinical trials have now demonstrated that increasing vitamin D intake can:
 
  • Reduce bone mass loss
  • Reduce risk of fracture by between 26% and 50%
  • Increase absorption and bioavailability of calcium
 
It is now considered by many authorities that vitamin D may be just as important in maintaining bone health as calcium.
 
It should be noted that these impressive results are seen with supplementation levels of a minimum of 20ug per day which is 400% of the RDA.
 

Nutrients With Some Evidence of Benefit

 
MAGNESIUM
Bone tissue contains about 50% of the body’s supply of magnesium and as such when bone is renewed or ‘remodelled’ magnesium must be available.
 
Studies have now shown that when dietary intake of magnesium is deficient, bone turnover is reduced and this may result in increased risk of accelerated bone loss and fracture.
 
VITAMIN K
Vitamin K is required to form the bone proteins and support the cells which remodel bone tissue. There is some credible scientific evidence that shows that vitamin deficiency is related to increased rate of bone loss, and that supplementation of vitamin K reduces the rate of bone loss in post-menopausal women.   
 
VITAMIN C
Vitamin C is required as a precursor to collagen which is used in the bone remodelling process and also to convert vitamin D in the body to its´ active forms.
 
BORON
Increasing boron intake has been found to result in reduced excretion of calcium and magnesium and hence may help to reduce the rate of bone loss.