Cardiovascular calcification and bone: a comparison of the effects of dietary and serum antioxidants
<p>Severe cardiovascular (CV) calcification can manifest as fully formed bone and is regularly found with osteoporosis; both have been shown to be associated with oxidative stress. Studies of the effect of antioxidants on CV calcification are few, but show that deficiency can induce both CV calcification and bone loss, while in conditions of oxidative stress such as renal failure, diabetes and smoking or in osteoporosis and fracture, antioxidants can reduce CV calcification and improve bone. The benefit of antioxidants in healthy adults is less clear and some may be detrimental. Higher intake of <em>α</em>-tocopherol (105.5mg/d vs 76.4mg/d) and β-cryptoxanthin may increase risk of CV calcification while high intake of retinol (≥3000mcg/d) may increase hip fracture risk, although possibly only with vitamin D intake ≤440IU/d; the carotenoids lycopene and β-carotene, however, appear beneficial in bone. Vitamin C shows little effect on CV calcification, although longer term supplementation may improve bone mineral density where calcium intake is >500mg/d. Potential reasons for this include a U-shaped dose/response curve for the fat-soluble antioxidants vitamins A and E (with peak bone mass achieved with retinol intake of 600–840 mcg/d), a failure to measure baseline concentrations so that the response cannot be stratified by requirement, the need to be replete in calcium and vitamin D and supplementation of the wrong isomer of vitamin E. Finally, although little studied, tocotrienols, tocopherols (with the exception of α-tocopherol), resveratrol, epigallocatechin gallate, quercetin, α-lipoic acid and N-acetylcysteine may be effective in both the CV system and bone. </p>