Bone health is closely linked to the strength and flexibility of bone structures. However, bones are living tissues which are composed of, amongst other factors, cells which build up the stiff hydroxyapatite skeleton (osteoblasts), and cells which break this skeleton down (osteoclasts).
The building of bones is a complex process with many contributing factors in tightly regulated sequences. As we get older we are used to seeing that the skeleton deteriorates. Old people shrink in height; bones get more brittle and vertebra often change shape. In our minds this is a natural process; however, when people start breaking their ribs, their hips, wrists or get breakage in the vertebra, osteoporosis is often diagnosed.
Osteoporosis is thus a disease in which the density and quality of bone are reduced, leading to weakness of the skeleton and increased risk of fracture. Osteoporosis and associated fractures are painful, often requiring hospitalization and are a frequent cause of morbidity and mortality.
Osteoporosis is a global problem that is increasing in significance as the population of the world both grows and ages. Worldwide, lifetime risk for osteoporotic fractures in women is 30-50%, in men the risk is 15-30%. Three main types of osteoporosis fractures are wrist fracture, vertebral fracture and hip fracture.
Osteoporosis is often called the "silent disease" because the bone loss occurs without symptoms. In many cases, the first "symptom" is a broken bone. Patients with osteoporosis may not know that they have the disease until their bones become so weak that a sudden strain, bump, or fall causes a hip fracture or a vertebra to collapse. Collapsed vertebra may initially be felt or seen in the form of severe back pain, loss of height, or spinal deformities such as kyphosis, or severely stooped posture.
More than twenty years ago Hart postulated that vitamin K is important for bone health (1984). He found that circulating vitamin K1 concentrations in 16 patients with hip fractures were extremely low. This observation was later confirmed by others who correlated fracture risk with serum osteocalcin carboxylation or dietary vitamin K1. Most published papers have found an association between vitamin K status and bone mineral density (BMD). However, only a limited number of intervention studies have been published testing the effect of K1 on bone. A general trend is that K1 (in ranges between 250 μg up to 10 mg/day) alone improves osteocalcin carboxylation, but has little effect on BMD 13-15.
In combination with calcium and vitamin D, a moderate effect of vitamin K1 on BMD has been reported (35% less bone loss than with calcium and vitamin D alone) 13. In a large number of Japanese studies, K2 has been tested in high doses (45 mg/day) 16-18. With these doses vitamin K is not used as a nutritional supplement, but as a pharmaceutical drug. Obviously, the extremely high K2 intake resulted in maximal osteocalcin carboxylation. In a randomised placebo-controlled vitamin K2 intervention trial among 340 Caucasian postmenopausal women, it was demonstrated that K2 (45 mg/day during 3 years) had little effect on the BMD, but induced an increase of the BMC and showed that bone strength at the site of the femoral neck did not vary during the entire duration of K2 treatment, whereas in the placebo group there was a significant and consistent decline of bone strength 19. Re-examination of the DXA scans of previous vitamin K1 trials did not show such an effect for vitamin K1!
Calcium, Vitamin D and Vitamin K2 in relation to bone health
Calcium has for decades been the most obvious choice of dietary supplement for improving bone health. The large majority of calcium (99%) in our bodies is in our skeleton and some in teeth, only ca 1% is found in the circulation. We need calcium to keep up with the turnover of the skeleton. However, we also require that the body can optimise the use of calcium. Too much calcium also seems no good. Several studies show that supplementing with calcium is not enough for optimal bone health. Adding vitamin D and vitamin K significantly improved bone health. The scientific rationale and documentation is that vitamin D stimulates the synthesis of osteocalcin, while vitamin K2 is needed for the activation of osteocalcin. Only the vitamin K2 activated osteocalcin will bind calcium optimally. In this way both vitamin D and vitamin k2 work in synergies to make the body able to use calcium efficiently for improved bone health.