Commonly consumed dietary foods contain natural forms of vitamin K, reveals a recent study
Vitamin K helps in the clotting of blood which is usually thought to be present in leafy greens like kale, spinach and broccoli. In dietary sources, vitamin K is found naturally in two forms namely phylloquinone (PK, or vitamin K1) and menaquinones (MK, or vitamin K2). PK forms are found in plant-based foods and MK forms are present in animal products and fermented food items. Nearly, every MK forms are also made by gut bacteria in human body. But information about MK forms present in U.S dairy products is less known.
“Dairy foods have little amounts of PK, the well known of the vitamin K forms, and thus dairy is not generally considered a good dietary source for this nutrient. But, in the case of MK forms, we discovered that dairy items already seen in many peoples’ refrigerators are really a rich dietary source for vitamin K,” noted Xueyan Fu, Ph.D., principal and corresponding author of this study and scientist in the Vitamin K Laboratory at the USDA HNRCA.
Presence Of Vitamin K In Dairy Products
To identify the presence of MK and PK in dairy products, the researchers made use of 50 nation-wide collected dairy samples offered by the USDA Nutrient Data Laboratory and 148 dairy samples purchased in 2016 from Boston area retail stores. The products were separated into categories based on dairy types and fat content such as milks, yogurts, Greek yogurts, creams, kefirs, fresh cheeses, blue cheeses processed cheeses, soft cheeses, semi-soft cheeses, and hard cheeses. The impact of fat content on total vitamin K in all forms was analyzed using a two-sample T-test. For cream products, the researchers had a smaller sample size, was compared by means of a general linear model, with heavy cream as the reference group.
The full-fat dairy products had remarkable amounts of MK, mainly in the forms of MK9, MK10 and MK11. Together, these three forms of MK estimated for approximately 90 percent of total vitamin K found in the foods tested.
When it comes to cheeses, the total vitamin K content changed by type, with soft cheese contain the highest concentration, followed by blue cheese, semi-soft cheese, and hard cheese. All these kinds of cheeses had MK9, MK10 and MK11, and modest amounts of PK, MK4, MK7, MK8 and MK12. Little MK5, MK6 or MK13 was present in the most of the cheeses.
In milk, the vitamin K concentrations changed along with fat content; both total vitamin K and individual MK concentrations in full-fat milk were remarkably higher than in 2 percent milk. PK was only found in full-fat milk. Only MK9-11 was present in milk. In yogurts, full-fat regular and Greek yogurts showed same concentrations of vitamin K as in full-fat milk; neither MK nor PK were found in fat-free yogurt.
“Measured intakes of PK and MK in dairy-producing countries in Western Europe propose that between 10 and 25 percent of total vitamin K intakes are given by MK, and mainly from dairy sources. Also, observational data from Europe propose that MK from dairy products have a stronger relation with heart health benefits in comparison to with PK intakes. This information from other countries emphasizes the need to estimate MK in regularly consumed foods in the U.S.,” explained Sarah L. Booth, Ph.D., last author on the study.