Dairy Products a Good Dietary Source of Some Types of Vitamin K

New study adds to knowledge about natural forms of vitamin K in dietary sources, their appreciable presence in commonly consumed foods

Newswise, July 10, 2017—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 vitamin K in dairy 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 fat content. 

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 cheese. 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.
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“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 dairy products, 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.

Additional authors on this study are Stephanie G. Harshman and Xiaohua Shen, Ph.D., Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University; David B. Haytowitz, Ph.D., Beltsville Human Nutrition Research Center, U.S. Department of Agriculture’s Agricultural Research Service; J. Philip Karl, Ph.D., alumnus of the Friedman School of Nutrition Science and Policy at Tufts University and formerly of the Jean Mayer USDA Human Nutrition Research Center on Aging, now at the U.S. Army Research Institute of Environmental Medicine; and Benjamin E. Wolfe, Ph.D., department of biology, School of Arts and Sciences at Tufts University.

This work was supported by the U.S. Department of Agriculture’s Agricultural Research Service and the National Dairy Council.

Time to Celebrate a Year-Round, Healthy Snack – the Strawberry

Newswise, May 2, 2017--- May is National Strawberry Month, a time to reflect on the history of this sweet, nutrition-packed fruit that grows well in Florida – and to extol its health benefits.

Strawberries originally grew in Europe. In France, people regarded them as the highest-quality aphrodisiac.

People believed Alpine strawberries provided various medicinal benefits. While some used the leaves, roots and fruits as a skin tonic, others ate berries to relieve diarrhea and an upset stomach. Folks also used the fruit’s juices to whiten teeth.

You can find these and other strawberry-related facts on a web page http://bit.ly/2q6hvB9 of the Gulf Coast Research and Education Center, part of the University of Florida Institute of Food and Agricultural Sciences.

Associate professor Vance Whitaker coordinates the strawberry breeding program at the UF/IFAS Gulf Coast REC. Whitaker and his lab recently came out with a new strawberry variety – ‘Florida Beauty’ – continuing the decades-long tradition of UF/IFAS scientists breeding the top-quality fruit.

Today, farmers grow them in the United States, Chile, Mexico and Russia, among other nations, and, in contrast to the early multiple uses for strawberries, consumers usually eat or drink the fruit.

In addition to Whitaker breeding disease- and pest-resistant strawberries, UF/IFAS experts shed light on some of the many benefits consumers enjoy by eating the fruit.

“The most important aspect of strawberries, aside from their wonderful taste, is their nutritional value,” said Linda Bobroff, a professor of nutrition and health with the UF/IFAS department of family, youth and community sciences. “With very few calories -- something that is important to many people -- strawberries pack a nutritional punch.”

Bobroff gave a list of examples of the nutrition value provided by 1 cup of strawberries:

• 3 grams of dietary fiber, something most Americans consume in insufficient amounts.
• 230 milligrams potassium -- a nutrient of concern in the U.S., which soon will appear on all nutrition facts panels.
• 90 milligrams of vitamin C

Also from a nutritional perspective, strawberries provide important non-nutritive compounds – known as polyphenols -- and antioxidants, said Anne Mathews, a UF/IFAS assistant professor of food science and human nutrition. Mathews gives interesting tips for ways to consume strawberries:

• Add them to cereal, oatmeal or a leafy salad, especially one with balsamic dressing.

• Consider swapping out a starch – such as white rice, roll or pasta for a serving of fruit with lunch or dinner.

The mission of the University of Florida Institute of Food and Agricultural Sciences is to develop knowledge relevant to agricultural, human and natural resources and to make that knowledge available to sustain and enhance the quality of human life. With more than a dozen research facilities, 67 county Extension offices, and award-winning students and faculty in the UF College of Agricultural and Life Sciences, UF/IFAS works to bring science-based solutions to the state’s agricultural and natural resources industries, and all Florida residents. Visit the UF/IFAS web site at ifas.ufl.edu and follow us on social media at @UF_IFAS.

No More ‘Superbugs’? Maple Syrup Extract Enhances Antibiotic Action

Newswise, April 20, 2017— Antibiotics save lives every day, but there is a downside to their ubiquity. High doses can kill healthy cells along with infection-causing bacteria, while also spurring the creation of “superbugs” that no longer respond to known antibiotics.

Now, researchers may have found a natural way to cut down on antibiotic use without sacrificing health: a maple syrup extract that dramatically increases the potency of these medicines.

The researchers will present their work at the 253rd National Meeting & Exposition of the American Chemical Society (ACS). ACS, the world’s largest scientific society, is holding the meeting here through Thursday. It features more than 14,000 presentations on a wide range of science topics.

“Native populations in Canada have long used maple syrup to fight infections,” says Nathalie Tufenkji, Ph.D. “I’ve always been interested in the science behind these folk medicines.”

The idea for the project really gelled when Tufenkji, who had been studying the antimicrobial effects of cranberry extracts, learned of the anti-cancer properties of a phenolic maple syrup extract.

“That gave me the idea to check its antimicrobial activity,” Tufenkji says. “So, I sent my postdoc to the store to buy some syrup.”

Using the same extraction approach as other researchers have in the past, Tufenkji’s team at McGill University separated the sugar and water from the syrup’s phenolic compounds, which contribute to maple syrup’s signature golden hue.

In an initial test, the team exposed several disease-causing bacterial strains to the extract, but they didn’t see much of an effect. Rather than give up on maple syrup altogether, Tufenkji decided to check whether the extract could enhance the antimicrobial potency of the commonly used antibiotics ciprofloxacin and carbenicillin.

When her team mixed the phenolic extract with either of these medicines, they indeed found a synergistic effect, allowing them to get the same antimicrobial effect with upwards of 90 percent less antibiotic.

The approach worked on a variety of bacterial strains, including E. coli, which can cause gastrointestinal problems; Proteus mirabilis, responsible for many urinary tract infections; and Pseudomonas aeruginosa, which can cause infections often acquired by patients in hospitals.

Building on this work, Tufenkji’s team next tested the extract in fruit flies and moth larvae. The researchers dosed fly food with pathogenic bacteria and antibiotic, with and without the phenolic extract.

Flies with meals doused in maple syrup extract lived for days longer than those denied the syrupy topper. The researchers observed a similar outcome with the moth larvae.

To figure out how the extract makes antibiotics work better, the researchers investigated whether the extract changed the permeability of bacterial cells. The extract increased the permeability of the bacteria, suggesting that it helps antibiotics gain access to the interior of bacterial cells.

Another experiment suggested that the extract may work by a second mechanism as well, disabling the bacterial pump that normally removes antibiotics from these cells.

Currently, the researchers are testing the maple syrup extract in mice. While it is likely to be years before it would be available to patients as a prescribed medical protocol, and a pharmaceutical company would likely need to purify the extract further to avoid any potential allergic reactions, Tufenkji says, she’s hopeful that it may have an edge over other would-be medications thanks to its source.

“There are other products out there that boost antibiotic strength, but this may be the only one that comes from nature,” she says.

Tufenkji acknowledges funding from Canada Research Chairs, the Natural Sciences and Engineering Research Council of Canada and the William and Rhea Seath Award at McGill University.

The American Chemical Society is a nonprofit organization chartered by the U.S. Congress. With nearly 157,000 members, ACS is the world’s largest scientific society and a global leader in providing access to chemistry-related research through its multiple databases, peer-reviewed journals and scientific conferences. ACS does not conduct research, but publishes and publicizes peer-reviewed scientific studies. Its main offices are in Washington, D.C., and Columbus, Ohio.

New Measurement Technique Lowers Estimated Vitamin D Recommended Daily Allowance

Newswise, April 3, 2017—After re-measurement of vitamin D by improved technology, the Recommended Dietary Allowance (RDA) for vitamin D intake drops from 800 to 400 International Units (IU) per day, new research reports. The results of the study were presented at the annual scientific meeting of the Endocrine Society, in Orlando, Fla.

"The RDA is easily achievable with a supplement of 400 IU in winter, when vitamin D levels are lowest in North America," said principal investigator J. Christopher Gallagher, M.D., professor and director of the Bone Metabolism Unit in the Division of Endocrinology of Creighton University School of Medicine in Omaha, Neb.

"This has important ramifications for public health recommendations. The amount of vitamin D needed, 400 IU daily, is less than the figure recommended by Institute of Medicine," said Gallagher, the study's principal investigator.

"In estimating the RDA for vitamin D intake, the laboratory method used for measuring serum 25-hydroxyvitamin D ̶ 25(OH)D ̶ can affect the results," he said. "The estimated RDA based on the older immunoassay (DiaSorin S.p.A., Salugia, Italy) system was 800 IU daily, whereas the newer liquid chromatography tandem-mass spectrometry (LC-MS/MS) technique estimated that 400 IU daily would meet the RDA."

In their earlier double-blind dose-response clinical trial in the winter and spring of 2007 to 2008, Gallagher and his colleagues enrolled 163 healthy postmenopausal Caucasian women 57 through 90 years of age with vitamin D insufficiency and followed them for 1 year.

The women were at least 7 years postmenopausal and they had vitamin D insufficiency based on the World Health Organization cutoff (serum 25(OH)D 20 ng/ml or lower).

The participants were randomized to one of seven vitamin D3 doses: 400, 800, 1600, 2400, 3200, 4000, 4800 IU/day or placebo, for 1 year, and all the women were given calcium supplements to maintain a total calcium intake.

After analyzing the samples and estimating the RDA using the older immunoassay, the authors reported that 800 IU daily would meet the vitamin D intake requirement for 97.5 percent of the population.

But now that liquid chromatography mass spectrometry (LC-MS/MS) has become the gold standard for measuring 25(OH)D, the researchers have reanalyzed the original samples using this new technology.

Able to determine a more precise dose-response curve, they have calculated the RDA for vitamin D to be 400 IU daily.

"Remember, this RDA is for bone health only," Gallagher cautioned. "It may be different for other diseases. Although trials looking into cancer, diabetes, and other diseases are ongoing, we do not have information about this yet."