According to the Institute of Medicine – IOM, the vitamin K recommendation for women is 90 mg/day and for men it is 120 mg/day. However, a lack of information leads people to take inappropriate supplements, which can pose health risks. For this reason, Dr. Iana Mizumukai de Araújo, nutritionist at the Brazilian Association of Bone Evaluation and Osteometabolism – ABRASSOcomes to clarify important points backed by science about vitamin K2.
1. What is the main function of vitamin K2 in the body?
Vitamin K2, also known as menaquinone, is one of three types of vitamin K, in addition to phylloquinone (K1) and menadione (K3). The main function of vitamin K in the body is to act on blood clotting, helping to activate essential proteins for the clotting process. Furthermore, she also plays a role in bone health. Osteocalcin, involved in the bone mineralization process, is dependent on vitamin K, as is the matrix protein GLA (a protein found in cartilage).
2. What are the main food sources of vitamin K2?
Specifically, vitamin K2 is produced during the fermentation process, such as in natto, a fermented soybean widely consumed in Japan. We can also find this vitamin in dairy products and organ meats, such as liver. In general, The main food sources of vitamin K include dark green vegetables (kale, broccoli, spinach), lettuce, cabbage, asparagus, okra, cucumber, cauliflower, cheeses, vegetable oils (soybean, canola, olive oil), margarine, lentils, soybeans, egg yolks , milk and, as previously mentioned, in fermented foods.
3. How does vitamin K2 affect bone health?
Vitamin K plays a fundamental role in bone health by activating the matrix protein Gla, present in cartilage. Its importance is due to the regulation of calcium, ensuring that it goes to the bones and not to soft tissues, such as the arteries. A study with mice that did not have this protein showed that these animals showed spontaneous calcification of arteries and cartilage (Luo G, Ducy P, McKee MD, et al. Spontaneous calcification of arteries and cartilage in mice lacking Matrix GLA protein. Nature. 1997 386 (6620):78–81). It also activates osteocalcin, the main non-collagenous protein in bone, ensuring that adequate bone mineralization occurs.
Some studies relate vitamin K to the maintenance and improvement of bone mineral density in postmenopausal women with osteoporosis, as shown in the meta-analysis by Zhou M and colleagues (J Bone Miner Metab. 2022 Sep;40(5):763 -772. ). On the other hand, a review study found that vitamin K supplementation appears to have little effect on bone mineral density in postmenopausal women or women with osteoporosis (Osteoporos Int. 2019 Aug;30(8):1543-1559). Given this conflicting data, the studies are promising, but still We need more in-depth studies to consider vitamin K supplementation..
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4. Is there any relationship between vitamin K2 and the absorption of calcium in the body?
There is no direct relationship between vitamin K and calcium absorption. But as mentioned above, vitamin K plays an important role in activating osteocalcin, ensuring that calcium is directed to the bones and does not accumulate in other tissues, reducing, for example, the risk of arterial calcifications.
5. Is there a specific group that should pay more attention to vitamin K2 supplementation?
People with a diet low in vitamin K, that is, people who do not consume foods rich in vitamin K, such as fermented products, organ meats, dark leafy vegetables, among other foods mentioned above, can benefit from supplementation. However, we must be aware that these are rare situations and should be evaluated by a qualified health professional.
6. What are the possible contraindications or side effects of vitamin K2 supplementation?
Vitamin K supplementation is generally safe, but there are some contraindications and possible side effects that should be considered, such as interactions with blood thinners, gastrointestinal reactions in sensitive individuals, and allergic reactions. Besides, There are no studies on the safety of supplementation doses in pregnant and lactating women. and for people in general, caution is necessary to avoid toxicity.
