Vitamin D is an essential, fat-soluble vitamin that acts as a steroid hormone and plays a central role in many components of our skeletal and extraskeletal health. Vitamin D is naturally present in some fish, mushrooms, and eggs; in select fortified foods such as milk products; and also in the form of dietary supplements and pharmaceuticals. It is also synthesized in the skin from 7-dehydrocholesterol when exposed to ultraviolet B (UVB) rays from sunlight.1
- Vitamin D is important for calcium homeostasis, bone mineralization, and promoting immune and cardiovascular function1
- Vitamin K is important in blood coagulation, and plays a central role in decreasing calcium accumulation in the smooth muscles of vascular walls2
- Vitamins D and K have a synergistic relationship since vitamin D positively impacts the production of vitamin K-dependent bone proteins to induce bone formation and reduce vascular calcification3
Common micronutrient shortfalls
According to nationally representative data, vitamins D and K represent common, significant nutrient gaps for the majority of Americans ≥ 2 years of age.9
Proposed synergy between vitamins D and K: bone
and cardiovascular health3
• Animal and human studies have demonstrated that vitamin D helps
stimulate the production of vitamin K-dependent proteins, OC and MGP,
which support bone mineralization and decrease vascular calcification.
• Long-term supplementation of vitamin D can lead to increased
production of vitamin K-dependent proteins. If the increased demand
is not adequately supported through diet or supplementation, the
proteins can remain uncarboxylated, which can lead to increased
vascular calcification and lower BMD.
• Excess supplemental calcium intake without the support of vitamins D
and K can lead to increased calcium deposits in the vascular tissue
instead of the bones.
A randomized controlled trial involving 78 post-menopausal women aged 60-plus was conducted to assess the effects of vitamins D and K on BMD and undercarboxylated OC (UcOC) over a six-month period; 45 women completed the study.
The vitamin K group (n=40) received 15 mg of K2 TID after every meal,
400 IU calcitriol once daily, and 315 mg calcium carbonate BID. The
control group (n=38) received 400 IU calcitriol once daily and 315 mg calcium carbonate BID.
Results: There was a statistically significant (P=0.049) increase in lumbar spine (L3) BMD in the vitamin K group compared to the control group. In addition, compared to baseline, the vitamin K group significantly decreased UcOC concentration (P≤0.01). Osteocalcin also non-significantly increased in the vitamin K group. Some observational and animal studies also support these findings.3
There were some limitations to the study, which included the small number of participants, high dropout rate, and the absence of a separate comparator group that did not receive any supplementation.
In a study with 42 patients with chronic kidney disease (CKD) stages 3-5 (non-dialyzed), the researchers assessed the effect of vitamin K2 substitution on the progression of atherosclerosis and calcification for
nine months. The vitamins K+D group received 90 mcg of K2 with
10 mcg (400 IU) of vitamin D3. The vitamin D alone group received
400 IU of vitamin D3.
The common carotid intima-media thickness (CCA-IMT), coronary artery calcification score (CACS), uncarboxylated MGP, and osteocalcin levels were measured. They found the thickness of the CCA-IMT along with CACS were significantly lower in the vitamins K+D group compared to the vitamin D
only group. The uncarboxylated MGP and OC levels also significantly decreased in the K+D group.
Additional health benefits
Researchers are also studying the impact of joint supplementation of vitamins D and K on glucose metabolism and inflammation. These studies have found beneficial effects on markers of oxidative stress, upregulation of insulin receptor genes, and enhancement of β-cell proliferation.3