Vitamin K
Vitamin K is not just one substance but is actually a group of substances identified as naphthoquinones. Most of the human’s sources of vitamin K come from plant sources, particularly the green leafy vegetables.
| Food | Serving Size | Vitamin K (mcg) | Food | Serving Size | Vitamin K (mcg) |
|---|---|---|---|---|---|
| Kale, cooked | 1/2 cup | 531 | Parsley, raw | 1/4 cup | 246 |
| Spinach, cooked | 1/2 cup | 444 | Spinach, raw | 1 cup | 145 |
| Collards, cooked | 1/2 cup | 418 | Collards, raw | 1 cup | 184 |
| Swiss chard, cooked | 1/2 cup | 287 | Swiss chard, raw | 1 cup | 299 |
| Mustard greens, cooked | 1/2 cup | 210 | Mustard greens, raw | 1 cup | 279 |
| Turnip greens, cooked | 1/2 cup | 265 | Turnip greens, raw | 1 cup | 138 |
| Broccoli, cooked | 1 cup | 220 | Broccoli, raw | 1 cup | 89 |
| Brussels sprouts, cooked | 1 cup | 219 | Endive, raw | 1 cup | 116 |
| Cabbage, cooked | 1/2 cup | 82 | Green leaf lettuce | 1 cup | 71 |
| Asparagus | 4 spears | 48 | Romaine lettuce, raw | 1 cup | 57 |
| Table from "Important information to know when you are taking: Warfarin (Coumadin) and Vitamin K", Clinical Center, National Institutes of Health Drug Nutrient Interaction Task Force.[1] | |||||
Vitamin K1 is found chiefly in leafy green vegetables such as spinach, swiss chard, and Brassica (e.g. cabbage, kale, cauliflower, broccoli, and brussels sprouts); some fruits such as avocado, kiwifruit and grapes are also high in vitamin K. By way of reference, two tablespoons of parsley contain 153% of the recommended daily amount of vitamin K. Some vegetable oils, notably soybean, contain vitamin K, but at levels that would require relatively large calorific consumption to meet the USDA recommended levels. Colonic bacteria synthesize a significant portion of humans' vitamin K needs; this is one of the reasons why newborns often receive a vitamin K shot at birth - in order to tide them over until day 5-7 when their colon becomes colonized.
It is believed that phylloquinone's tight binding to the thylakoid membranes in the chloroplasts is the reason behind the poor bioavailability of vitamin K in green plants. For example, cooked spinach has a 5% bioavailability of phylloquinone. However when one adds fat to the spinach, the bioavailability increases to 13% due to the increased solubility of vitamin K in fat.
Vitamin K2 (Menaquinone-4) is synthesized by animal tissues and is found in meat, eggs, and dairy products. Menaquinone-7 is synthesized by bacteria during fermentation and is found in fermented soybeans (natto).
Special Precautions of Vitamin K
Although allergic reaction from supplementation is possible, there is no known toxicity associated with high doses of the phylloquinone (vitamin K1) or menaquinone (vitamin K2) forms of vitamin K and therefore no tolerable upper intake level (UL) has been set. Blood clotting (coagulation) studies in humans using 45 mg per day of vitamin K2 (as MK4)[25] and even up to 135 mg/day (45 mg three times daily) of K2 (as MK4),[50] showed no increase in blood clot risk. Even doses in rats as high as 250 mg/kg body weight did not alter the tendency for blood-clot formation to occur. However, a synthetic form of vitamin K, vitamin K3 (menadione), is demonstrably toxic. In fact, the FDA has banned this synthetic form of the vitamin from over-the-counter supplements because large doses have been shown to cause allergic reactions, hemolytic anemia, and cytotoxicity in liver cells. [edit]Drug interactions
Phylloquinone (K1)or menaquinone (K2) are capable of blocking the blood thinning action of anticoagulants like warfarin, which work by interfering with the action of vitamin K. They also reverse the tendency of these drugs to cause arterial calcification in the long term.
The benefits of Vitamin K are
- Vitamin K1—phylloquinone, also known as phytonadione : Vitamin K1 makes up 90% of the vitamin K found in the Western diet. Vitamin K1 is a necessary and important contributor to bone growth and overall bone health. Vitamin K1 is best known in its ability to promote blood clotting. In fact, the letter “K” comes from the German term, koagulation.
- vitamin K2—also known as menaquinone—is very different. Vitamin K2 is essential for your cardiovascular health because of its amazing ability to utilize calcium. Calcium belongs in our bones, not in our blood. When our vitamin K2 levels are low, calcium collects in our blood and can lead to calcification in our arteries.
- Vitamin K3—menadione synthetic variant : This synthetic form of vitamin K is NOT for human consumption. It offers no benefits and comes with possibly risky side effects. Unfortunately, many vitamin manufacturers offer vitamin K3 as a supplement, so it is advisable to steer clear of these supplements!
- Vitamin K has more functions other than clotting; vitamin K is also beneficial in protecting the bones from fractures and in helping women in their menopausal stage from having unhealthy bones. The link between bone health and vitamin K has been researched extensively. Primary to this is the ability of vitamin K, in its menaquinone form, to impede the formation of osteoclasts. Osteoclasts are responsible for removing the minerals in the bone for proper body functioning. While these minerals are important in the body, we do not want too much of the osteoclastic activity as it can result to bone demineralization. Therefore, if vitamin K is increased, there will be less demineralization of bones, less chances of getting fractures.
Males require 120 micrograms of vitamin K, while females only need 90 micrograms daily. The excellent source of vitamin K is boiled kale and boiled spinach, which can provide over 1000 percent of the nutrients daily value per 1 cup of the vegetable.
