A Look at the Protective Power of Vitamins D3 and K2
Ah, that summer sun—how we all look forward to it, at the beach, poolside, park, patio, or just walking down the street on a midsummer day. Our mood lifts. Our bodies feel stronger. In essence, we feel more vital. But alas, autumn and winter are not far behind, and bring with them shorter days, longer nights, and for many, a slump in mood that seems abetted by darkness, as well as seasonal colds and flus as we shiver through winter’s wind and snow or rain. Why can’t it be eternal summer? Or if it can’t, are there ways we can mimic summer’s blessings by supporting our body nutritionally?Supplemental vitamin D is one such tool that helps us to combat winter’s challenges. Most of life on earth is dependent on the sun for energy, warmth and often, vitamin D.1 For humans, vitamin D3 (cholecalciferol) is literally light transformed. During exposure to sunlight, a molecule in our skin called 7-dehydrocholesterol absorbs ultraviolet B radiation, which is the initial reaction in the process of several steps which are necessary for conversion to the active form of vitamin D3. Vitamin D3 is then metabolized in the liver into 25-hydroxyvitamin D (the form we measure) and in the kidneys to 1,25-dihydroxyvitamin D (the biologically active form).
Receptors for vitamin D are widely expressed throughout the body, being found in over 36 different cell types.2 In 2012, a remarkable feat of sequencing revealed that the human genome itself literally has thousands of binding sites for vitamin D, reaffirming how fundamental this vitamin is for the body.3 And yet, there is widespread vitamin D deficiency—as many as a billion people worldwide are deficient in vitamin D, according to a 2017 review.4 Vitamin D deficiency has been linked to numerous health issues: autoimmune disease, allergies, certain cancers, depression, multiple sclerosis, inflammatory bowel disease, rheumatoid arthritis, type 2 diabetes, and cardiovascular disease, to name a few.5,6,7,8,9,10,11,12,13 Vitamin D3 is also the precursor to a class of D3-related hormones that have numerous functions in the body beyond balancing levels of calcium.
Vitamin D synthesis is influenced by season, time of day, latitude, altitude, as well as less well known factors of air pollution, skin pigmentation, aging, and whether or not you use sunscreen.14 One of the most dramatic factors is latitude, and in the shorter days of winter, the skin makes very little vitamin D at above 37 degrees north or below 37 degrees south of the equator.15 As the 37th parallel defines the southern borders of Utah, Colorado, and Kansas, and the northern borders of Arizona, New Mexico, and Oklahoma, this represents a large population of the US. Anyone living to the north of this line, including major cities such as San Francisco, Chicago, New York, St. Louis, Denver, Boston, and Seattle, are at an increased risk of winter vitamin D deficiency. Even people living in regions with abundant sunlight year-round often do not get enough sun exposure to ensure vitamin D adequacy, as winter simply adds to the burden of long hours in offices, commutes by train, subway or car, and evenings spent indoors.
Vitamin D supplementation is not only important for reversing or preventing deficiency, but also for healthy immune system function and mood.16,17 Adequate levels of vitamin D are necessary for the innate immune system, our body’s first defenders, to function normally, preventing infection by bacterial, fungal, and viral invaders.18 Lower vitamin D levels are associated with larger tonsil size and recurrent tonsillopharyngitis in children,19 as well as increased incidence of upper respiratory infection (URTI) and community acquired pneumonia in adults.20,21 Vitamin D supplementation also may help prevent URTI in children with asthma.22Vitamin D deficiency has been found in many studies to be associated with depression, which a recent systematic review and meta-analysis of observational studies and randomized controlled trials also reaffirmed.23 Supplementation of vitamin D was associated with an improvement in vitamin D levels as well as depression scale scores in patients with seasonal affective disorder, while those in the light therapy group only had improvements in their vitamin D levels.24 Although larger meta-analysis have failed to show an impact of vitamin D supplementation on mood in a broad population, improvements have been seen in smaller studies with an overweight or obese population,25 patients with major depressive disorder,26 and women with seasonal depressive symptoms.27
In addition to its importance for mood and immune function, vitamin D is important for maintaining healthy bones. Without it, the body can’t absorb the calcium it ingests, and may borrow calcium from bones, increasing the risk of osteoporosis and fractures.28 It is important to note, however, that vitamin D should not be supplemented alone. Scientific studies, especially focusing on bone health and vascular calcification, find that supplementing with vitamin K at the same time is important.29,30,31 Vitamin K is important for arterial health and assists vitamin D in accomplishing many of its activities in the body.32 Vitamin K helps direct calcium deposition to the bone matrix, by activating osteocalcin. Vitamin K deficiency may be associated with soft tissue calcification and lower bone mineral density.33Certain forms of vitamin K are more active in the body than others. Menaquinone-7, or MK-7, is a highly bioactive form of vitamin K2.34 MK-7 also has been shown to have a longer half-life than vitamin K1, resulting in more stable serum levels. Similarly, for vitamin D, vitamin D3 has been shown to be up to 3 times more effective than vitamin D2 (calciferol) at raising the body’s serum 25-hydroxyvitamin D levels.35 Absorption of both vitamin D and K also can be dramatically improved when they are provided in a nanoemulsified format.
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