Dairy products a good dietary source of some types of vitamin K

June 2, 2017, Tufts University
Credit: CC0 Public Domain

Vitamin K, with its multiple forms, is among the lesser known nutrients. Now, new research from scientists at the Jean Mayer USDA Human Nutrition Research Center on Aging (USDA HNRCA) at Tufts University sheds new light on the vitamin and its significant presence in some dairy products available in the United States.

In the study, published June 1 in Current Developments in Nutrition, researchers quantified the activity of two natural forms of K in products of various fat contents and found that common U.S. dairy items, including milks, yogurts and cheeses, contain appreciable amounts of multiple forms of vitamin K. Vitamin concentrations varied by .

Vitamin K, which helps the blood to clot, is most commonly thought to come from leafy greens such as spinach, kale and broccoli. In fact, dietary sources of vitamin K are found in two natural forms: phylloquinone (PK, or vitamin K1), which is widely distributed through plant-based foods, and menaquinones (MK, or vitamin K2), which appear to be primarily in animal products and fermented foods. Almost all MK forms are also produced by bacteria in the human gut. Not much is known about MK amounts in U.S. dairy products.

"Dairy foods contain minute amounts of PK, the best known of the vitamin K forms, and so dairy is not commonly considered a rich dietary source for this nutrient. However, when it comes to MK forms, we found that dairy items already found in many peoples' refrigerators are indeed a good dietary source for vitamin K," said Xueyan Fu, Ph.D., first and corresponding author and scientist in the Vitamin K Laboratory at the USDA HNRCA.

Guidelines for adequate vitamin K intake are based only on PK intake without consideration for other forms of vitamin K. MK differ from PK in structure in that they are compounds with different numbers of isoprenoid units in the side chain, designated as MK4 through MK13. Which forms of MK are present reflects which bacteria might be in the dairy products. Lactic acid bacteria, for example, are widely used in dairy and fermented foods.

To understand the presence of MK and PK in dairy products, the researchers used 50 nationally collected dairy samples provided by the USDA Nutrient Data Laboratory and 148 dairy samples purchased in 2016 from Boston area retail outlets. The products were divided into categories based on dairy types and fat content: milks, yogurts, Greek yogurts, kefirs, creams, processed cheeses, fresh cheeses, blue cheeses, soft cheeses, semi-soft cheeses, and hard cheeses. The effect of fat content on total vitamin K in all forms was compared using a two-sample T-test. The vitamin K content of cream products, for which the researchers had a smaller sample size, was analyzed using a general linear model, with heavy cream as the reference group.

Among the findings:

  • All full-fat dairy products contained appreciable amounts of MK, primarily in the forms of MK9, MK10 and MK11. Combined, these three forms of MK accounted for approximately 90 percent of total vitamin K present in the foods tested.
  • In cheeses, the total vitamin K content varied by type, with soft cheese having the highest concentration, followed by blue cheese, semi-soft cheese, and hard . All of the cheeses contained MK9, MK10 and MK11, and modest amounts of PK, MK4, MK7, MK8 and MK12. Little MK5, MK6 or MK13 was measured in the majority of cheeses.
  • In milk, the vitamin K concentrations varied by fat content; both total vitamin K and individual MK concentrations in full-fat milk were significantly higher than in 2 percent milk. PK was only detected in full-fat milk. Only MK9-11 were detected in milk.
  • In yogurts, full-fat regular and Greek yogurts exhibited similar vitamin K concentrations as in full-fat milk; neither MK nor PK were detected in fat-free yogurt.

"Estimated intakes of PK and MK in dairy-producing countries in Western Europe suggest that between 10 and 25 percent of total vitamin K intake are provided by MK, and primarily from dairy sources. Additionally, observational data from Europe suggest that MK from dairy products have a stronger association with heart health benefits compared with PK intakes. This data from other countries highlights the need to analyze MK in commonly consumed foods in the U.S.," said Sarah L. Booth, Ph.D., last author on the study. Booth is senior scientist and director of the Vitamin K Laboratory at the USDA HNRCA, interim director of the USDA HNRCA, and professor at the Friedman School of Nutrition Science and Policy at Tufts University.

Additional research is needed to determine the role of microbes used in production of , and their impact on MK content. The researchers also say there is a need to determine the relative bioavailability of all MK forms given their abundance in the U.S. diet.

The researchers acknowledge limitations of the study, including the reliance on food labels for fat content instead of direct measurement of fat content. Additionally, whereas the dairy product samples obtained from the USDA Nutrient Data Laboratory were geographically representative of the U.S. diet, those purchased in the Boston region were not. However, items purchased locally were selected from retail outlets with national representation.

Explore further: Low vitamin D levels if you're lactose intolerant

More information: Xueyan Fu et al, Multiple Vitamin K Forms Exist in Dairy Foods, Current Developments in Nutrition (2017). DOI: 10.3945/cdn.117.000638

Related Stories

Low vitamin D levels if you're lactose intolerant

May 23, 2017
Those with a genetic intolerance to lactose may suffer from a vitamin D deficiency. That's according to a recent study conducted at the University of Toronto and published in the Journal of Nutrition.

Researchers find lactose intolerance related to low vitamin D levels

May 15, 2017
New research from the University of Toronto shows that people genetically intolerant to lactose, the main sugar found in dairy, have lower blood levels of vitamin D than the general population.

To lose weight, start with dairy swaps

May 29, 2017
(HealthDay)—Losing weight comes down to simple arithmetic: Eat fewer calories than you burn off.

Research shines light on lesser known form of vitamin D in foods

July 19, 2016
Some people worry that they aren't getting enough vitamin D, which is critical for bone health, but they may be consuming more than they think.

Older bones benefit from dairy plus vitamin D

March 1, 2017
(HealthDay)—A combination of vitamin D supplements and certain dairy foods may protect against age-related bone loss, a new study indicates.

New review article suggests sheep milk may be the next functional dairy food

January 24, 2017
A paper published in Comprehensive Reviews in Food Science and Food Safety explored the physicochemical and nutritional characteristics of sheep milk and development of sheep milk dairy products containing prebiotics and/or ...

Recommended for you

Teens get more sleep with later school start time, researchers find

December 12, 2018
When Seattle Public Schools announced that it would reorganize school start times across the district for the fall of 2016, the massive undertaking took more than a year to deploy. Elementary schools started earlier, while ...

Large restaurant portions a global problem, study finds

December 12, 2018
A new multi-country study finds that large, high-calorie portion sizes in fast food and full service restaurants is not a problem unique to the United States. An international team of researchers found that 94 percent of ...

Receiving genetic information can change risk

December 11, 2018
Millions of people in the United States alone have submitted their DNA for analysis and received information that not only predicts their risk for disease but, it turns out, in some cases might also have influenced that risk, ...

Yes please to yoghurt and cheese: The new improved Mediterranean diet

December 11, 2018
Thousands of Australians can take heart as new research from the University of South Australia shows a dairy-enhanced Mediterranean diet will significantly increase health outcomes for those at risk of cardiovascular disease ...

Effect of oral alfacalcidol on clinical outcomes in patients without secondary hyperparathyroidism

December 11, 2018
Treatment with active vitamin D did not decrease cardiovascular events in kidney patients undergoing hemodialysis, according to a research group in Japan. They have reported their research results in the December 11 issue ...

Licence to Swill: James Bond's drinking over six decades

December 10, 2018
He may be licensed to kill but fictional British secret service agent James Bond has a severe alcohol use disorder, according to an analysis of his drinking behaviour published in the Medical Journal of Australia's Christmas ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

michbaskett
5 / 5 (1) Jun 02, 2017
I had long been under the impression the amount of vitamin K we get from our diet is a mere suplement to what is synthesized in our livers that could eaily be discounted. I also never knew there are so many chemical variations of vitamin K. Time for some runny Brie with my lunch.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.