Vitamin K on a plant-based diet. What does it do, what foods have vitamin K, and what are the types of vitamin K you should know about?
Vitamin K isn’t necessarily a nutrient of concern, but that doesn’t mean it doesn’t deserve some attention.
Understanding what vitamin K does for health can help you make sure a variety of good sources are included in your family’s diet.
What is vitamin K?
Vitamin K is a fat-soluble vitamin, alongside vitamins A, D, and E.
That means it doesn’t dissolve in water and its absorption is boosted with dietary fat intake.
Vitamin K plays a role in a number of health functions, primarily by activating proteins involved in:
- Blood clotting
- Promoting strong bones and maintaining skeletal health
- Supporting heart health by preventing calcium deposits from building up in arteries; helping to prevent heart disease
- Aiding in overall health and disease prevention, potentially including certain cancers
While most vitamin K comes from diet, some studies indicate that our gut bacteria also produce some K2, and even have the ability to convert some dietary K1 into K2.
In fact, a 2002 study showed that when breastfeeding mothers were supplemented with vitamin K1, their bodies produced vitamin K2.
And an older study noted that our intestines may produce more K2 when our diet is lacking, to make sure we have enough.
Types of vitamin K
While often grouped together, there are actually two types of vitamin K: K1 and K2, the latter of which has several subtypes of its own.
- Vitamin K1 (phylloquinone) is produced by plants.
- Vitamin K2 (menaquinones, named MK-4 to MK-13 based on their chemical structures) are made by bacteria.
More research has been done on the roles of K2 in recent years, suggesting that we should pay more attention to where it may be found in our diet.
Vitamin K foods
Most of the dietary sources of vitamin K we eat are K1.
The best places to find it are whole plant foods, particularly dark leafy greens (e.g. kale, Swiss chard, romaine lettuce, spinach).
And of course, incorporating a wide variety of plant foods can help make sure you’re getting both K1 and K2, both directly and from conversion.
Good sources of K1 include:
- Leafy greens
- Cruciferous veggies, like broccoli, Brussels sprouts, and cabbage
- Bok choy
On the other hand, Vitamin K2 is found primarily in animal products, like poultry, egg yolks, certain cheeses, and butter. This is because their intestinal flora produce K2.
However, certain fermented plant foods – like tempeh, sauerkraut, and a Japanese fermented soybean dish called natto – also have some, because the bacteria in them produce K2.
Overall, it appears that eating enough vitamin K1 can be adequate for K2 as well, since your body converts some of it, but more research is needed here.
Vitamin K deficiency
Between the widespread dietary sources of vitamin K1 and intestinal production, deficiency is very rare in Western countries, even on a plant-based diet.
Plus, vitamin K is routinely provided to infants at birth via a single injection, to prevent deficiency that could cause bleeding issues.
Instances that could increase risk of vitamin K deficiency are liver disorders and malabsorption conditions. Some studies suggest long-term antibiotic use could also raise risk, as it may kill off good K2-producing bacteria.
The most apparent symptoms of vitamin K deficiency are easy bruising or bleeding. If suspected, a lab test called prothrombin time (PT) may be done to evaluate blood clotting capability.
Most people can avoid vitamin K deficiency with a healthy and balanced diet.
Getting enough vitamin K
General vitamin K needs for kids are as follows:
- 0-6 months: 2 mcg/day
- 7-12 months: 2.5 mcg/day
- 1-3 years: 30 mcg/day
- 4-8 years: 55 mcg/day
- 9-13 years: 60 mcg/day
- 14-18 years: 75 mcg/day
To give you an idea, a 1/2-cup serving of spinach contains approximately 68 mcg, and a 1/4-cup serving of raw broccoli offers around 25 mcg.
Plus, eating vitamin K alongside a source of dietary fat – like roasted broccoli in olive oil – can help optimize its absorption.
Some supplements specifically made for babies contain a small amount of K2. For example, Live Wise Naturals D3 Vegan Drops for Baby contains K2 because it helps boost absorption of vitamin D.
That being said, supplementation is generally not necessary for the purpose of meeting vitamin K needs.
In conclusion, it’s pretty easy to find enough vitamin K on a plant-based diet. Understanding what foods have vitamin K and the types of vitamin K can help you incorporate great sources of this nutrient in your family’s diet.
Chime in: What sources of vitamin K1 and K2 does your family eat?
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