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Secret shopper: Should I take vitamin D with K2?Secret shopper: Should I take vitamin D with K2?

Vitamins D and K2 are both involved in calcium metabolism, and some clinical research shows synergistic effects of combined vitamin D and K2 supplementation.

2 Min Read
Secret shopper: Should I take vitamin D with K2?

Multifunctional vitamin D is a perennially popular supplement, especially for immune support, women’s health and bone health. More recently, vitamin K2 has been gaining traction, with more consumers inquiring about its benefits, particularly when paired with vitamin D. Curious how natural products retailers are handling these questions in the aisles, we tasked our secret shopper with finding out.  

Secret Shopper: Should I be taking vitamin D with K2? 

Retailer: Both are great for bones, and since it’s tough to get enough vitamin D from diet or sunlight, most people can benefit from a vitamin D supplement. Similar story with vitamin K: It’s found in some foods, but it can be hard to get enough. 

Secret Shopper: But beyond both being necessary nutrients, do they somehow work synergistically?  

Retailer: I’m not exactly sure how it all works inside the body. I just know that both are beneficial for bone health. 

How did this retailer do?

andrea-wong-crn-andrea-wong-crn-portrait.jpg.jpgOur expert educator: Andrea Wong, Ph.D., senior vice president of scientific and regulatory affairs at the Council for Responsible Nutrition

Overall, the retailer did well, although they talked about “vitamin K” rather than vitamin K2 specifically, as the shopper asked. Since vitamin K encompasses a group of compounds—including phylloquinone, or vitamin K1, and menaquinones, or vitamin K2—it’s important to distinguish between them. While they share some common benefits, they also have distinct roles in the body.

Related:Secret shopper: How do consumers know if their fish oil is fresh?

The retailer made good points about it being difficult to get enough of these nutrients from food. Few foods naturally contain vitamin D, so most of what we get in the diet is from fortified foods such as milk or cereals. In the U.S., vitamin D is considered a nutrient of public health concern because of low intakes. Vitamin K2 is present in some meats, eggs, cheeses and fermented foods like sauerkraut and natto (fermented soybeans).

Since there is no formal recommendation for vitamin K2 intake, the prevalence of inadequacy or deficiency hasn’t been established.

I’m not surprised that the retailer knew that vitamin D is beneficial for bone health since this role is well established. In fact, the U.S. Food and Drug Administration has authorized a health claim for the relationship between calcium and vitamin D and osteoporosis risk. Vitamin D helps with calcium absorption while vitamin K2 helps calcium bind to bones. Vitamins D and K2 are both involved in calcium metabolism, and some clinical research shows synergistic effects of combined vitamin D and K2 supplementation for bone mineral density.

Beyond bone health, retailers can also mention that vitamin D has many other roles in the body, and that a growing body of research supports its functions in immune, oral and muscle health. Also, vitamin K2 helps prevent calcium deposits from forming in artery walls, thereby keeping the arteries from stiffening.

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