Vitamin K2 vs Vitamin D for Bone Health During Perimenopause
Vitamin K2 and vitamin D both support bone health during perimenopause but work differently. Learn which you need, how much, and why both often matter.
Bone Loss and Perimenopause
Bone density loss accelerates markedly during perimenopause and the years immediately following menopause. Estrogen plays a key protective role in bone maintenance, and as levels decline, the balance between bone formation and bone resorption shifts in favour of resorption. Women can lose up to 20% of their bone density in the five to seven years around menopause, significantly raising the risk of osteoporosis and fractures later in life. This makes bone-protective nutrition a genuine priority from perimenopause onwards, not something to address only after a fracture or osteoporosis diagnosis. Two nutrients that frequently come up in discussions of bone health are vitamin D and vitamin K2, each playing distinct roles in the process.
What Vitamin D Does for Bones
Vitamin D is essential for calcium absorption from the gut. Without adequate vitamin D, your body cannot absorb sufficient calcium from your diet regardless of how much you consume. Low vitamin D leads to poor calcium uptake, which forces the body to draw calcium from bones to maintain blood calcium levels. This accelerates bone loss. Vitamin D also plays roles in muscle function, immune regulation, and mood, all of which are relevant during perimenopause. Deficiency is extremely common in countries with limited sun exposure, and many women in the UK are deficient particularly through autumn and winter. The UK government recommends that all adults consider a vitamin D supplement of 10 micrograms (400 IU) daily through the winter months, though many experts recommend higher doses for those who are deficient.
What Vitamin K2 Does for Bones
Vitamin K2 plays a different role in bone health. It activates a protein called osteocalcin, which is produced by bone-building cells and is responsible for binding calcium into the bone matrix. Without adequate K2, osteocalcin remains in an inactive form and cannot perform this function effectively. K2 also activates another protein called Matrix Gla Protein (MGP), which prevents calcium from being deposited in soft tissues such as arteries. This is significant because calcium supplements without K2 have been associated in some studies with increased arterial calcification. K2 helps direct calcium into bones, where it is needed, and away from blood vessels, where it can be harmful. The most studied and bioavailable form of K2 is MK-7, found in fermented foods and supplements.
How Vitamin D and K2 Work Together
These two nutrients are often described as partners rather than alternatives. Vitamin D ensures calcium is absorbed from the gut and reaches the bloodstream. Vitamin K2 ensures that circulating calcium is directed into bones rather than deposited inappropriately in soft tissues. Without adequate K2, high vitamin D intake (which boosts calcium absorption) could theoretically increase the amount of calcium in circulation without ensuring it reaches the skeleton. This is one reason why some researchers and practitioners now recommend taking K2 alongside vitamin D when supplementing. The combined approach supports the complete pathway from dietary calcium absorption to deposition in bone.
Food Sources of Each
Vitamin D is produced by the skin on exposure to ultraviolet B sunlight. Dietary sources include oily fish (salmon, mackerel, sardines), eggs, and fortified foods such as some cereals and plant milks. However, it is difficult to get enough from diet alone, particularly in countries with limited sun, which is why supplementation is widely recommended. Vitamin K2 is found primarily in fermented foods. Natto, a Japanese fermented soybean product, is exceptionally rich in K2 as MK-7. Other fermented foods including hard cheeses, sauerkraut, and some dairy products contain smaller amounts. Animal liver and egg yolks provide some K2 but typically less than fermented sources. Many Western diets are low in K2, making supplementation a practical option for those not regularly eating fermented foods.
Supplement Dosing Considerations
For vitamin D, a common supplementation dose for adults in the UK is 1,000 to 2,000 IU daily, though deficient individuals may need higher doses under medical supervision. A blood test measuring 25-hydroxyvitamin D levels can confirm whether you are deficient and guide appropriate dosing. For vitamin K2 as MK-7, doses studied in bone health research typically range from 90 to 200 micrograms per day. K2 is fat-soluble and is best absorbed when taken with a meal containing fat. It is generally considered safe with no established tolerable upper limit for K2 from food, though very high supplemental doses have not been extensively studied long-term. Those taking anticoagulant medications such as warfarin should consult their GP before taking vitamin K supplements, as K affects clotting pathways.
Building a Bone Health Strategy
Neither vitamin D nor K2 should be viewed as a replacement for the two most powerful interventions for perimenopausal bone health, which are weight-bearing exercise and, where appropriate, HRT. Estrogen replacement is the most effective way to slow the accelerated bone loss of the perimenopausal transition. Resistance training and high-impact exercise provide the mechanical stimulus bones need. Adequate dietary calcium (around 700 to 1,200 mg daily from food sources) forms the foundation. Vitamin D ensures that calcium is absorbed, and K2 ensures it is used correctly. Together, these nutritional tools support a comprehensive approach to protecting bone density through the years of greatest risk.
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