23 Aug Vitamins D and K Work as a Team
Is Vitamin D Harmful Without Vitamin K?
Getting adequate amounts of vitamin D and vitamin K is essential for your health.
But some sources claim that supplementing with vitamin D is harmful if you are low in vitamin K.
What Are Vitamins D and K?
Vitamin D and vitamin K are essential, fat-soluble nutrients.
They are generally most abundant in high-fat foods, and their absorption into the bloodstream is enhanced when they are consumed with fat.
Often called the “sunshine vitamin,” vitamin D is abundant in fatty fish and fish oil, but it’s also produced by your skin when it’s exposed to sunlight.
One of vitamin D’s primary functions is to promote calcium absorption and maintain adequate calcium levels in your blood. A vitamin D deficiency may cause bone loss.
Vitamin K is found in leafy greens, fermented legumes and vegetables, as well as in some fatty, animal-sourced foods, such as egg yolk, liver and cheese.
It’s necessary for blood clotting and promotes the accumulation of calcium in your bones and teeth.
SUMMARY: Vitamins D and K are fat-soluble nutrients that play an essential role in your body’s calcium metabolism.
Vitamins D and K Work as a Team
The Role of Vitamin D
Vitamin D is a nutrient your body needs for building and maintaining healthy bones. That’s because your body can only absorb calcium, the primary component of bone, when vitamin D is present. Vitamin D also regulates many other cellular functions in your body. Its anti-inflammatory, antioxidant and neuroprotective properties support immune health, muscle function and brain cell activity.
The amount of vitamin D your skin makes depends on many factors, including the time of day, season, latitude and your skin pigmentation. Depending on where you live and your lifestyle, vitamin D production might decrease or be completely absent during the winter months. Sunscreen, while important to prevent skin cancer, also can decrease vitamin D production.
Many older adults don’t get regular exposure to sunlight and have trouble absorbing vitamin D. If your doctor suspects you’re not getting enough vitamin D, a simple blood test can check the levels of this vitamin in your blood.
Taking a multivitamin with vitamin D may help improve bone health. The recommended daily amount of vitamin D is 400 international units (IU) for children up to age 12 months, 600 IU for people ages 1 to 70 years, and 800 IU for people over 70 years.
What the research says
Research on vitamin D use for specific conditions shows:
- Cancer. Findings on the benefits of vitamin D for cancer prevention are mixed. More studies are needed to determine whether vitamin D supplementation may reduce the risk of certain cancers.
- Cognitive health. Research shows that low levels of vitamin D in the blood are associated with cognitive decline. However, more studies are needed to determine the benefits of vitamin D supplementation for cognitive health.
- Inherited bone disorders. Vitamin D supplements can be used to help treat inherited disorders resulting from an inability to absorb or process vitamin D, such as familial hypophosphatemia.
- Multiple sclerosis. Research suggests that long-term vitamin D supplementation reduces the risk of multiple sclerosis.
- Osteomalacia. Vitamin D supplements are used to treat adults with severe vitamin D deficiency, resulting in loss of bone mineral content, bone pain, muscle weakness and soft bones (osteomalacia).
- Osteoporosis. Studies suggest that people who get enough vitamin D and calcium in their diets can slow bone mineral loss, help prevent osteoporosis and reduce bone fractures. Ask your doctor if you need a calcium and vitamin D supplement to prevent or treat osteoporosis.
- Psoriasis. Applying vitamin D or a topical preparation that contains a vitamin D compound called calcipotriene to the skin can treat plaque-type psoriasis in some people.
- Rickets. This rare condition develops in children with vitamin D deficiency. Supplementing with vitamin D can prevent and treat the problem.
The Role of Vitamin K
As mentioned above, vitamin D ensures that your blood levels of calcium are high enough to meet your body’s demands.
However, vitamin D does not fully control where the calcium in your body ends up. That’s where vitamin K steps in.
The Role of Vitamin K
Vitamin K regulates calcium in your body in at least two ways:
Vitamin K is a fat-soluble vitamin that comes in two forms. The main type is called phylloquinone, found in green leafy vegetables like collard greens, kale, and spinach. The other type, menaquinones, are found in some animal foods and fermented foods. Menaquinones can also be produced by bacteria in the human body. [1]
Vitamin K helps to make various proteins that are needed for blood clotting and the building of bones. Prothrombin is a vitamin K-dependent protein directly involved with blood clotting. Osteocalcin is another protein that requires vitamin K to produce healthy bone tissue.
Vitamin K is found throughout the body including the liver, brain, heart, pancreas, and bone. It is broken down very quickly and excreted in urine or stool. Because of this, it rarely reaches toxic levels in the body even with high intakes, as may sometimes occur with other fat-soluble vitamins.
Is Vitamin D Harmful Without Vitamin K?
Some people are concerned that a high vitamin D intake may promote blood vessel calcification and heart disease among those who are low in vitamin K.
Several lines of evidence partly support this idea:
- Vitamin D toxicity causes hypercalcemia: One symptom of extremely high vitamin D levels (toxicity) is hypercalcemia, a condition characterized by excessively high levels of calcium in the blood.
- Hypercalcemia leads to blood vessel calcification (BVC): In hypercalcemia, calcium and phosphorus levels become so high that calcium phosphate starts to accumulate in the lining of blood vessels.
- BVC is associated with heart disease: According to experts, blood vessel calcification is one of the main underlying causes of heart disease.
- Vitamin K deficiency is associated with BVC: Observational studies have linked low vitamin K levels to an increased risk of blood vessel calcification.
- High-dose vitamin K supplements prevented BVC in animals: A controlled study in rats at a high risk of calcification showed that a high-dose vitamin K2 supplement prevented BVC.
- Vitamin K supplements may reduce BVC in humans: One controlled study in older people showed that supplementing with 500 mcg of vitamin K1 every day for three years slowed BVC by 6%.
- High vitamin K intake may reduce the risk of heart disease: People who get high amounts of vitamin K2 from their diet are at a reduced risk of blood vessel calcification and heart disease.
Put simply, vitamin D toxicity may cause blood vessel calcification, while vitamin K may help prevent this from happening.
Although these strings of evidence may seem supportive enough, there are still a few missing puzzle pieces.
While extremely high doses of vitamin D may lead to dangerously high calcium levels and blood vessel calcification, it is still unclear if lower doses of vitamin D are harmful in the long term.
In 2007, one nutritionist proposed that high doses of vitamin D may deplete vitamin K, potentially causing vitamin K deficiency. More research is needed before the validity of this theory can be fully confirmed.
No strong evidence proves that moderate amounts of vitamin D are harmful without an adequate intake of vitamin K. However, research is ongoing, and the picture might become clearer in the near future.
SUMMARY: Scientists don’t know whether high vitamin D intake is harmful when vitamin K intake is inadequate. Evidence suggests it might be a concern, but a definite conclusion cannot be reached at this point.
How Do You Get Enough Vitamin K?
Vitamin K comes in many different forms, traditionally divided into two groups:
- Vitamin K1 (phylloquinone): The most common form of vitamin K. It’s found in plants, notably leafy greens like kale and spinach.
- Vitamin K2 (menaquinone): This form is much rarer in food and mainly found in animal-sourced food and fermented foods like natto.
Vitamin K2 is actually a large family of compounds, including menaquinone-4 (MK-4) and menaquinone-7 (MK-7).
- MK-4: Found in animal-sourced foods like liver, fat, egg yolk and cheese.
- MK-7: Formed by bacterial fermentation and found in fermented foods, such as natto, miso and sauerkraut. It is also produced by your gut bacteria.
The current dietary recommendations do not distinguish between vitamin K1 and K2. For people aged 19 and older, the adequate intake is 90 mcg for women and 120 mcg for men.
The two charts below show the richest sources of vitamins K1 and K2, as well as the amounts these foods provide in a 100-gram serving
Since vitamin K is fat-soluble, consuming it with fat can improve absorption.
For instance, you could add a little oil to your leafy greens or take your supplements with a meal that contains fat.
Fortunately, many foods rich in vitamin K2 are also rich in fat. These include cheese, egg yolks and meat.
Do not take very high doses of vitamin K supplements before speaking with your doctor, as they may interact with certain medications.
SUMMARY: Vitamin K1 is abundant in leafy, green vegetables, such as kale and spinach. Vitamin K2 is found in animal-sourced foods, such as liver, eggs and cheese, and fermented foods like natto.
The Bottom Line
Scientists are still investigating the functions of vitamins D and K.
They do not fully understand how they interact, but new pieces are gradually being added to the puzzle.
It’s clear that vitamin K benefits your heart and bones, but it’s unclear whether high-dose vitamin D supplements are harmful when you’re low in vitamin K.
Nevertheless, make sure to get adequate amounts of both vitamin D and K from your diet. Both of them are important.
curated by ozzie small
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