Beltsville Human Nutrition Research Center
Beltsville Human Nutrition Research Center
News Article | June 2, 2017
BOSTON (June 2, 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. "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. For three decades, the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University has studied the relationship between good nutrition and good health in aging populations. Tufts research scientists work with federal agencies to establish the USDA Dietary Guidelines, the Dietary Reference Intakes, and other significant public policies.
News Article | February 1, 2016
“For me, a calorie is a unit of measurement that’s a real pain in the rear.” Bo Nash is 38. He lives in Arlington, Texas, where he’s a technology director for a textbook publisher. And he’s 5’10” and 245 lbs—which means he is classed as obese. In an effort to lose weight, Nash uses an app to record the calories he consumes and a Fitbit band to track the energy he expends. These tools bring an apparent precision: Nash can quantify the calories in each cracker crunched and stair climbed. But when it comes to weight gain, he finds that not all calories are equal. How much weight he gains or loses seems to depend less on the total number of calories, and more on where the calories come from and how he consumes them. The unit, he says, has a “nebulous quality to it”. Tara Haelle is also obese. She had her second son on St Patrick’s Day in 2014, and hasn’t been able to lose the 70 lbs she gained during pregnancy. Haelle is a freelance science journalist, based in Illinois. She understands the science of weight loss, but, like Nash, doesn’t see it translate into practice. “It makes sense from a mathematical and scientific and even visceral level that what you put in and what you take out, measured in the discrete unit of the calorie, should balance,” says Haelle. “But it doesn’t seem to work that way.” Nash and Haelle are in good company: more than two-thirds of American adults are overweight or obese. For many of them, the cure is diet: one in three are attempting to lose weight in this way at any given moment. Yet there is ample evidence that diets rarely lead to sustained weight loss. These are expensive failures. This inability to curb the extraordinary prevalence of obesity costs the United States more than $147 billion in healthcare, as well as $4.3 billion in job absenteeism and yet more in lost productivity. At the heart of this issue is a single unit of measurement—the calorie—and some seemingly straightforward arithmetic. “To lose weight, you must use up more calories than you take in,” according to the Centers for Disease Control and Prevention. Dieters like Nash and Haelle could eat all their meals at McDonald’s and still lose weight, provided they burn enough calories, says Marion Nestle, professor of nutrition, food studies and public health at New York University. “Really, that’s all it takes.” But Nash and Haelle do not find weight control so simple. And part of the problem goes way beyond individual self-control. The numbers logged in Nash’s Fitbit, or printed on the food labels that Haelle reads religiously, are at best good guesses. Worse yet, as scientists are increasingly finding, some of those calorie counts are flat-out wrong—off by more than enough, for instance, to wipe out the calories Haelle burns by running an extra mile on a treadmill. A calorie isn’t just a calorie. And our mistaken faith in the power of this seemingly simple measurement may be hindering the fight against obesity. The process of counting calories begins in an anonymous office block in Maryland. The building is home to the Beltsville Human Nutrition Research Center, a facility run by the US Department of Agriculture. When we visit, the kitchen staff are preparing dinner for people enrolled in a study. Plastic dinner trays are laid out with meatloaf, mashed potatoes, corn, brown bread, a chocolate-chip scone, vanilla yoghurt and a can of tomato juice. The staff weigh and bag each item, sometimes adding an extra two-centimetre sliver of bread to ensure a tray’s contents add up to the exact calorie requirements of each participant. “We actually get compliments about the food,” says David Baer, a supervisory research physiologist with the Department. The work that Baer and colleagues do draws on centuries-old techniques. Nestle traces modern attempts to understand food and energy back to a French aristocrat and chemist named Antoine Lavoisier. In the early 1780s, Lavoisier developed a triple-walled metal canister large enough to house a guinea pig. Inside the walls was a layer of ice. Lavoisier knew how much energy was required to melt ice, so he could estimate the heat the animal emitted by measuring the amount of water that dripped from the canister. What Lavoisier didn’t realise—and never had time to find out; he was put to the guillotine during the Revolution—was that measuring the heat emitted by his guinea pigs was a way to estimate the amount of energy they had extracted from the food they were digesting. Until recently, the scientists at Beltsville used what was essentially a scaled-up version of Lavoisier’s canister to estimate the energy used by humans: a small room in which a person could sleep, eat, excrete, and walk on a treadmill, while temperature sensors embedded in the walls measured the heat given off and thus the calories burned. (We now measure this energy in calories. Roughly speaking, one calorie is the heat required to raise the temperature of one kilogram of water by one degree Celsius.) Today, those ‘direct-heat’ calorimeters have largely been replaced by ‘indirect-heat’ systems, in which sensors measure oxygen intake and carbon dioxide exhalations. Scientists know how much energy is used during the metabolic processes that create the carbon dioxide we breathe out, so they can work backwards to deduce that, for example, a human who has exhaled 15 litres of carbon dioxide must have used 94 calories of energy. The facility’s three indirect calorimeters are down the halls from the research kitchen. “They’re basically nothing more than walk-in coolers, modified to allow people to live in here,” physiologist William Rumpler explains as he shows us around. Inside each white room, a single bed is folded up against the wall, alongside a toilet, sink, a small desk and chair, and a short treadmill. A couple of airlocks allow food, urine, faeces and blood samples to be passed back and forth. Apart from these reminders of the room’s purpose, the vinyl-floored, fluorescent-lit units resemble a 1970s dorm room. Rumpler explains that subjects typically spend 24 to 48 hours inside the calorimeter, following a highly structured schedule. A notice pinned to the door outlines the protocol for the latest study: 6:00 to 6:45pm – Dinner, 11:00pm – Latest bedtime, mandatory lights out, 11:00pm to 6:30am – Sleep, remain in bed even if not sleeping. In between meals, blood tests and bowel movements, calorimeter residents are asked to walk on the treadmill at 3 miles per hour for 30 minutes. They fill the rest of the day with what Rumpler calls “low activity.. “We encourage people to bring knitting or books to read,” he says. “If you give people free hand, you’ll be surprised by what they’ll do inside the chamber.” He tells us that one of his less cooperative subjects smuggled in a bag of M&Ms, and then gave himself away by dropping them on the floor. Using a bank of screens just outside the rooms, Rumpler can monitor exactly how many calories each subject is burning at any moment. Over the years, he and his colleagues have aggregated these individual results to arrive at numbers for general use: how many calories a 120-lb woman burns while running at 4.0 miles an hour, say, or the calories a sedentary man in his 60s needs to consume every day. It’s the averages derived from thousands of extremely precise measurements that provide the numbers in Bo Nash’s movement tracker and help Tara Haelle set a daily calorie intake target that is based on her height and weight. Measuring the calories in food itself relies on another modification of Lavoisier’s device. In 1848, an Irish chemist called Thomas Andrews realised that he could estimate calorie content by setting food on fire in a chamber and measuring the temperature change in the surrounding water. (Burning food is chemically similar to the ways in which our bodies break food down, despite being much faster and less controlled.) Versions of Andrews’s ‘bomb calorimeter’ are used to measure the calories in food today. At the Beltsville centre, samples of the meatloaf, mashed potatoes and tomato juice have been incinerated in the lab’s bomb calorimeter. “We freeze-dry it, crush into a powder, and fire it,” says Baer. Humans are not bomb calorimeters, of course, and we don’t extract every calorie from the food we eat. This problem was addressed at the end of the 19th century, in one of the more epic experiments in the history of nutrition science. Wilbur Atwater, a Department of Agriculture scientist, began by measuring the calories contained in more than 4,000 foods. Then he fed those foods to volunteers and collected their faeces, which he incinerated in a bomb calorimeter. After subtracting the energy measured in the faeces from that in the food, he arrived at the Atwater values, numbers that represent the available energy in each gram of protein, carbohydrate and fat. These century-old figures remain the basis for today’s standards. When Baer wants to know the calories per gram figure for that night’s meatloaf, he corrects the bomb calorimeter results using Atwater values. This entire enterprise, from the Beltsville facility to the numbers on the packets of the food we buy, creates an aura of scientific precision around the business of counting calories. That precision is illusory. The trouble begins at source, with the lists compiled by Atwater and others. Companies are allowed to incinerate freeze-dried pellets of product in a bomb calorimeter to arrive at calorie counts, though most avoid that hassle, says Marion Nestle. Some use the data developed by Atwater in the late 1800s. But the Food and Drug Administration (FDA) also allows companies to use a modified set of values, published by the Department of Agriculture in 1955, that take into account our ability to digest different foods in different ways. Atwater’s numbers say that Tara Haelle can extract 8.9 calories per gram of fat in a plate of her favourite Tex-Mex refried beans; the modified table shows that, thanks to the indigestibility of some of the plant fibres in legumes, she only gets 8.3 calories per gram. Depending on the calorie-measuring method that a company chooses—the FDA allows two more variations on the theme, for a total of five—a given serving of spaghetti can contain from 200 to 210 calories. These uncertainties can add up. Haelle and Bo Nash might deny themselves a snack or sweat out another few floors on the StairMaster to make sure they don’t go 100 calories over their daily limit. If the data in their calorie counts is wrong, they can go over regardless. There’s also the issue of serving size. After visiting over 40 US chain restaurants, including Olive Garden, Outback Steak House and PF Chang’s China Bistro, Susan Roberts of Tufts University’s nutrition research centre and colleagues discovered that a dish listed as having, say, 500 calories could contain 800 instead. The difference could easily have been caused, says Roberts, by local chefs heaping on extra french fries or pouring a dollop more sauce. It would be almost impossible for a calorie-counting dieter to accurately estimate their intake given this kind of variation. Even if the calorie counts themselves were accurate, dieters like Haelle and Nash would have to contend with the significant variations between the total calories in the food and the amount our bodies extract. These variations, which scientists have only recently started to understand, go beyond the inaccuracies in the numbers on the back of food packaging. In fact, the new research calls into question the validity of nutrition science’s core belief that a calorie is a calorie. Using the Beltsville facilities, for instance, Baer and his colleagues found that our bodies sometimes extract fewer calories than the number listed on the label. Participants in their studies absorbed around a third fewer calories from almonds than the modified Atwater values suggest. For walnuts, the difference was 21 per cent. This is good news for someone who is counting calories and likes to snack on almonds or walnuts: he or she is absorbing far fewer calories than expected. The difference, Baer suspects, is due to the nuts’ particular structure: “All the nutrients—the fat and the protein and things like that—they’re inside this plant cell wall.” Unless those walls are broken down—by processing, chewing or cooking—some of the calories remain off-limits to the body, and thus are excreted rather than absorbed. Another striking insight came from an attempt to eat like a chimp. In the early 1970s, Richard Wrangham, an anthropologist at Harvard University and author of the book Catching Fire: How cooking made us human, observed wild chimps in Africa. Wrangham attempted to follow the entirely raw diet he saw the animals eating, snacking only on fruit, seeds, leaves, and insects such as termites and army ants. “I discovered that it left me incredibly hungry,” he says. “And then I realised that every human eats their food cooked.” Wrangham and his colleagues have since shown that cooking unlaces microscopic structures that bind energy in foods, reducing the work our gut would otherwise have to do. It effectively outsources digestion to ovens and frying pans. Wrangham found that mice fed raw peanuts, for instance, lost significantly more weight than mice fed the equivalent amount of roasted peanut butter. The same effect holds true for meat: there are many more usable calories in a burger than in steak tartare. Different cooking methods matter, too. In 2015, Sri Lankan scientists discovered that they could more than halve the available calories in rice by adding coconut oil during cooking and then cooling the rice in the refrigerator. Wrangham’s findings have significant consequences for dieters. If Nash likes his porterhouse steak bloody, for example, he will likely be consuming several hundred calories less than if he has it well-done. Yet the FDA’s methods for creating a nutrition label do not for the most part account for the differences between raw and cooked food, or pureed versus whole, let alone the structure of plant versus animal cells. A steak is a steak, as far as the FDA is concerned. Industrial food processing, which subjects foods to extremely high temperatures and pressures, might be freeing up even more calories. The food industry, says Wrangham, has been “increasingly turning our food to mush, to the maximum calories you can get out of it. Which, of course, is all very ironic, because in the West there’s tremendous pressure to reduce the number of calories you’re getting out of your food.” He expects to find examples of structural differences that affect caloric availability in many more foods. “I think there is work here for hundreds and probably thousands of nutritionists for years,” he says. There’s also the problem that no two people are identical. Differences in height, body fat, liver size, levels of the stress hormone cortisol, and other factors influence the energy required to maintain the body’s basic functions. Between two people of the same sex, weight and age, this number may differ by up to 600 calories a day—over a quarter of the recommended intake for a moderately active woman. Even something as seemingly insignificant as the time at which we eat may affect how we process energy. In one recent study, researchers found that mice fed a high-fat diet between 9 AM and 5 PM gained 28 percent less weight than mice fed the exact same food across a 24-hour period. The researchers suggested that irregular feedings affect the circadian cycle of the liver and the way it metabolises food, thus influencing overall energy balance. Such differences would not emerge under the feeding schedules in the Beltsville experiments. Until recently, the idea that genetics plays a significant role in obesity had some traction: researchers hypothesised that evolutionary pressures may have favoured genes that predisposed some people to hold on to more calories in the form of added fat. Today, however, most scientists believe we can’t blame DNA for making us overweight. “The prevalence of obesity started to rise quite sharply in the 1980s,” says Nestle. “Genetics did not change in that ten- or twenty-year period. So genetics can only account for part of it.” Instead, researchers are beginning to attribute much of the variation to the trillions of tiny creatures that line the coiled tubes inside our midriffs. The microbes in our intestines digest some of the tough or fibrous matter that our stomachs cannot break down, releasing a flow of additional calories in the process. But different species and strains of microbes vary in how effective they are at releasing those extra calories, as well as how generously they share them with their host human. In 2013, researchers in Jeffrey Gordon’s lab at Washington University tracked down pairs of twins of whom one was obese and one lean. He took gut microbes from each, and inserted them into the intestines of microbe-free mice. Mice that got microbes from an obese twin gained weight; the others remained lean, despite eating the exact same diet. “That was really striking,” said Peter Turnbaugh, who used to work with Gordon and now heads his own lab at the University of California, San Francisco. “It suggested for the first time that these microbes might actually be contributing to the energy that we gain from our diet.” The diversity of microbes that each of us hosts is as individual as a fingerprint and yet easily transformed by diet and our environment. And though it is poorly understood, new findings about how our gut microbes affect our overall energy balance are emerging almost daily. For example, it seems that medications that are known to cause weight gain might be doing so by modifying the populations of microbes in our gut. In November 2015, researchers showed that risperidone, an antipsychotic drug, altered the gut microbes of mice who received it. The microbial changes slowed the animals’ resting metabolisms, causing them to increase their body mass by 10 per cent in two months. The authors liken the effects to a 30-lb weight gain over one year for an average human, which they say would be the equivalent of an extra cheeseburger every day. Other evidence suggests that gut microbes might affect weight gain in humans as they do in lab animals. Take the case of the woman who gained more than 40 lbs after receiving a transplant of gut microbesfrom her overweight teenage daughter. The transplant successfully treated the mother’s intestinal infection of Clostridium difficile, which had resisted antibiotics. But, as of the study’s publication last year, she hadn’t been able to shed the excess weight through diet or exercise. The only aspect of her physiology that had changed was her gut microbes. All of these factors introduce a disturbingly large margin of error for an individual who is trying, like Nash, Haelle and millions of others, to count calories. The discrepancies between the number on the label and the calories that are actually available in our food, combined with individual variations in how we metabolise that food, can add up to much more than the 200 calories a day that nutritionists often advise cutting in order to lose weight. Nash and Haelle can do everything right and still not lose weight. None of this means that the calorie is a useless concept. Inaccurate as they are, calorie counts remain a helpful guide to relative energy values: standing burns more calories than sitting; cookies contain more calories than spinach. But the calorie is broken in many ways, and there’s a strong case to be made for moving our food accounting system away from that one particular number. It’s time to take a more holistic look at what we eat. Wilbur Atwater worked in a world with different problems. At the beginning of the 20th century, nutritionists wanted to ensure people were well fed. The calorie was a useful way to quantify a person’s needs. Today, excess weight affects more people than hunger; 1.9 billion adults around the world are considered overweight, 600 million of them obese. Obesity brings with it a higher risk of diabetes, heart disease and cancer. This is a new challenge, and it is likely to require a new metric. One option is to focus on something other than energy intake. Like satiety, for instance. Picture a 300-calorie slice of cheesecake: it is going to be small. “So you’re going to feel very dissatisfied with that meal,” says Susan Roberts. If you eat 300 calories of a chicken salad instead, with nuts, olive oil and roasted vegetables, “you’ve got a lot of different nutrients that are hitting all the signals quite nicely,” she says. “So you’re going to feel full after you’ve eaten it. That fullness is going to last for several hours.” As a result of her research, Roberts has created a weight-loss plan that focuses on satiety rather than a straight calorie count. The idea is that foods that help people feel satisfied and full for longer should prevent them from overeating at lunch or searching for a snack soon after cleaning the table. Whole apples, white fish and Greek yoghurt are on her list of the best foods for keeping hunger at bay. There’s evidence to back up this idea: in one study, Roberts and colleagues found that people lost three times more weight by following her satiety plan compared with a traditional calorie-based one—and kept it off. Harvard nutritionist David Ludwig, who also proposes evaluating food on the basis of satiety instead of calories, has shown that teens given instant oats for breakfast consumed 650 more calories at lunch than their peers who were given the same number of breakfast calories in the form of a more satisfying omelette and fruit. Meanwhile, Adam Drewnowski, a epidemiologist at the University of Washington, has his own calorie upgrade: a nutrient density score. This system ranks food in terms of nutrition per calorie, rather than simply overall caloric value. Dark green vegetables and legumes score highly. Though the details of their approaches differ, all three agree: changing how we measure our food can transform our relationship with it for the better. Individual consumers could start using these ideas now. But persuading the food industry and its watchdogs, such as the FDA, to adopt an entirely new labelling system based on one of these alternative measures is much more of a challenge. Consumers are unlikely to see the calorie replaced by Roberts’s or Drewnowski’s units on their labels any time soon; nonetheless, this work is an important reminder that there are other ways to measure food, ones that might be more useful for both weight loss and overall health. Down the line, another approach might eventually prove even more useful: personalised nutrition. Since 2005, David Wishart of the University of Alberta has been cataloguing the hundreds of thousands of chemical compounds in our bodies, which make up what’s known as the human metabolome. There are now 42,000 chemicals on his list, and many of them help digest the food we eat. His food metabolome database is a more recent effort: it contains about 30,000 chemicals derived directly from food. Wishart estimates that both databases may end up listing more than a million compounds. “Humans eat an incredible variety of foods,” he says. “Then those are all transformed by our body. And they’re turned into all kinds of other compounds.” We have no idea what they all are, he adds—or what they do. According to Wishart, these chemicals and their interactions affect energy balance. He points to research demonstrating that high-fructose corn syrup and other forms of added fructose (as opposed to fructose found in fruit) can trigger the creation of compounds that lead us to form an excess of fat cells, unrelated to additional calorie consumption. “If we cut back on some of these things,” he says, “it seems to revert our body back to more appropriate, arguably less efficient metabolism, so that we aren’t accumulating fat cells in our body.” It increasingly seems that there are significant variations in the way each one of us metabolises food, based on the tens of thousands—perhaps millions—of chemicals that make up each of our metabolomes. This, in combination with the individuality of each person’s gut microbiome, could lead to the development of personalised dietary recommendations. Wishart imagines a future where you could hold up your smartphone, snap a picture of a dish, and receive a verdict on how that food will affect you as well as how many calories you’ll extract from it. Your partner might receive completely different information from the same dish. Or maybe the focus will shift to tweaking your microbial community: if you’re trying to lose weight, perhaps you will curate your gut microbiome so as to extract fewer calories without harming your overall health. Peter Turnbaugh cautions that the science is not yet able to recommend a particular set of microbes, let alone how best to get them inside your gut, but he takes comfort from the fact that our microbial populations are “very plastic and very malleable”—we already know that they change when we take antibiotics, when we travel and when we eat different foods. “If we’re able to figure this out,” he says, “there is the chance that someday you might be able to tailor your microbiome” to get the outcomes you want. None of these alternatives is ready to replace the calorie tomorrow. Yet the need for a new system of food accounting is clear. Just ask Haelle. “I’m kind of pissed at the scientific community for not coming up with something better for us,” she confesses, recalling a recent meltdown at TGI Friday’s as she navigated a confusing datasheet to find a low-calorie dish she could eat. There should be a better metric for people like her and Nash—people who know the health risks that come with being overweight and work hard to counter them. And it’s likely there will be. Science has already shown that the calorie is broken. Now it has to find a replacement. This story originally appeared on Mosaic with the headline, "Why the calorie is broken." It is published under a CC BY 4.0 license.
Wu M.,University of Maryland University College |
Kang M.M.,University of Maryland University College |
Schoene N.W.,Beltsville Human Nutrition Research Center |
Cheng W.-H.,University of Maryland University College
Journal of Biological Chemistry | Year: 2010
Selenium chemoprevention by apoptosis has been well studied, but it is not clear whether selenium can activate early barriers of tumorigenesis, namely senescence and DNA damage response. To test this hypothesis, we treated normal and cancerous cells with a gradient concentration of sodium selenite, methylseleninic acid and methylselenocysteine for 48 h, followed by a recovery of 1-7 days. Here we show that selenium compounds at doses of ≤LD 50 can induce cellular senescence, as evidenced by the expression of senescence-associated β-galactosidase and 5-bromo-2-deoxyuridine incorporation, in normal but not cancerous cells. In response to clastogens, the ataxia telangiectasia mutated (ATM) protein is rapidly activated, which in turn initiates a cascade of DNA damage response. We found that the ATM pathway is activated by the selenium compounds, and the kinase activity is required for the seleniuminduced senescence response. Pretreatment of the MRC-5 non-cancerous cells with the antioxidant N-acetylcysteine or 2,2,6,6-tetramethylpiperidine-1- oxyl suppresses the seleniuminduced ATM activation and senescence. Taken together, the results suggest a novel role of selenium in the activation of early tumorigenesis barriers specific in non-cancerous cells, whereby selenium induces an ATM-dependent senescence response that depends on reactive oxygen species.
Panickar K.S.,University of Maryland, Baltimore |
Panickar K.S.,Beltsville Human Nutrition Research Center
Molecular Nutrition and Food Research | Year: 2013
Polyphenols are natural substances and are enriched in vegetables, fruits, grains, bark, tea, and wine. Some polyphenols have insulin-potentiating and anti-inflammatory effects, both of which are important in obesity. Dietary supplementation with polyphenolic compounds is associated with reduced diet-induced obesity and/or metabolic syndrome in animal and human studies. Insights into mechanisms that regulate food intake and satiety have led to an increased understanding of obesity but the pathogenesis underlying obesity is lacking. Food intake is subject to a complex regulation by the hypothalamus and other brain centers including the brain stem and the hippocampus. An intricate network of interacting feedback mechanisms that involve the aforementioned neural centers along with the stomach, gut, liver, thyroid, and adipose tissue in the periphery, influence the eventual outcome of food intake and satiety. Key peripheral signals, such as leptin, insulin, and ghrelin, have been linked to hypothalamic neuropeptide systems in energy regulation. This review will examine the neural centers important in food intake, the role of various neuropeptides, and the neurohormonal influence on food intake. The potential role of polyphenols in influencing the neuroregulatory factors, the neural signaling pathways and/or the peripheral feedback mechanisms that modulate food intake will also be examined. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Wang Z.,Ohio University |
Chen P.,Beltsville Human Nutrition Research Center |
Yu L.,University of Maryland University College |
De Harrington P.B.,Ohio University
Analytical Chemistry | Year: 2013
Basil plants cultivated by organic and conventional farming practices were accurately classified by pattern recognition of gas chromatography/mass spectrometry (GC/MS) data. A novel extraction procedure was devised to extract characteristic compounds from ground basil powders. Two in-house fuzzy classifiers, i.e., the fuzzy rule-building expert system (FuRES) and the fuzzy optimal associative memory (FOAM) for the first time, were used to build classification models. Two crisp classifiers, i.e., soft independent modeling by class analogy (SIMCA) and the partial least-squares discriminant analysis (PLS-DA), were used as control methods. Prior to data processing, baseline correction and retention time alignment were performed. Classifiers were built with the two-way data sets, the total ion chromatogram representation of data sets, and the total mass spectrum representation of data sets, separately. Bootstrapped Latin partition (BLP) was used as an unbiased evaluation of the classifiers. By using two-way data sets, average classification rates with FuRES, FOAM, SIMCA, and PLS-DA were 100 ± 0%, 94.4 ± 0.4%, 93.3 ± 0.4%, and 100 ± 0%, respectively, for 100 independent evaluations. The established classifiers were used to classify a new validation set collected 2.5 months later with no parametric changes except that the training set and validation set were individually mean-centered. For the new two-way validation set, classification rates with FuRES, FOAM, SIMCA, and PLS-DA were 100%, 93%, 97%, and 100%, respectively. Thereby, the GC/MS analysis was demonstrated as a viable approach for organic basil authentication. It is the first time that a FOAM has been applied to classification. A novel baseline correction method was used also for the first time. The FuRES and the FOAM are demonstrated as powerful tools for modeling and classifying GC/MS data of complex samples, and the data pretreatments are demonstrated to be useful to improve the performance of classifiers. © 2013 American Chemical Society.
Novotny J.A.,Beltsville Human Nutrition Research Center |
Baer D.J.,Beltsville Human Nutrition Research Center |
Khoo C.,Ocean Spray Cranberries Inc. |
Gebauer S.K.,Beltsville Human Nutrition Research Center |
Charron C.S.,Beltsville Human Nutrition Research Center
Journal of Nutrition | Year: 2015
Background: Cardiometabolic risk is the risk of cardiovascular disease (CVD), diabetes, or stroke, which are leading causes of mortality and morbidity worldwide. Objective: The objective of this study was to determine the potential of low-calorie cranberry juice (LCCJ) to lower cardiometabolic risk. Methods: A double-blind, placebo-controlled, parallel-arm study was conducted with controlled diets. Thirty women and 26 men (mean baseline characteristics: 50 y; weight, 79 kg; body mass index, 28 kg/m2) completed an 8-wk intervention with LCCJ or a flavor/color/energy-matched placebo beverage. Twice daily volunteers consumed 240 mL of LCCJ or the placebo beverage, containing 173 or 62 mg of phenolic compounds and 6.5 or 7.5 g of total sugar per 240-mL serving, respectively. Results: Fasting serum triglycerides (TGs) were lower after consuming LCCJ and demonstrated a treatment 3 baseline interaction such that the participants with higher baseline TG concentrations were more likely to experience a larger treatment effect (1.15 ± 0.04 mmol/L vs. 1.25 ± 0.04 mmol/L, respectively; P = 0.027). Serum C-reactive protein (CRP) was lower for individuals consuming LCCJ than for individuals consuming the placebo beverage [ln transformed values of 0.522 ± 0.115 ln(mg/L) vs. 0.997 ± 0.120 ln(mg/L), P = 0.0054, respectively, and equivalent to 1.69 mg/L vs. 2.71 mg/L back-transformed]. LCCJ lowered diastolic blood pressure (BP) compared with the placebo beverage (69.2 ± 0.8 mm Hg for LCCJ vs. 71.6 ± 0.8 mm Hg for placebo; P = 0.048). Fasting plasma glucose was lower (P = 0.03) in the LCCJ group (5.32 ± 0.03 mmol/L) than in the placebo group (5.42 ± 0.03 mmol/L), and LCCJ had a beneficial effect on homeostasis model assessment of insulin resistance for participants with high baseline values (P = 0.035). Conclusion: LCCJ can improve several risk factors of CVD in adults, including circulating TGs, CRP, and glucose, insulin resistance, and diastolic BP. This trial was registered at clinicaltrials.gov as NCT01295684. © 2015 American Society for Nutrition.
Panickar K.S.,Beltsville Human Nutrition Research Center |
Anderson R.A.,Beltsville Human Nutrition Research Center
International Journal of Molecular Sciences | Year: 2011
Polyphenols are natural substances with variable phenolic structures and are elevated in vegetables, fruits, grains, bark, roots, tea, and wine. There are over 8000 polyphenolic structures identified in plants, but edible plants contain only several hundred polyphenolic structures. In addition to their well-known antioxidant effects, select polyphenols also have insulin-potentiating, anti-inflammatory, anti-carcinogenic, anti-viral, anti-ulcer, and anti-apoptotic properties. One important consequence of ischemia is neuronal death and oxidative stress plays a key role in neuronal viability. In addition, neuronal death may be initiated by the activation of mitochondria-associated cell death pathways. Another consequence of ischemia that is possibly mediated by oxidative stress and mitochondrial dysfunction is glial swelling, a component of cytotoxic brain edema. The purpose of this article is to review the current literature on the contribution of oxidative stress and mitochondrial dysfunction to neuronal death, cell swelling, and brain edema in ischemia. A review of currently known mechanisms underlying neuronal death and edema/cell swelling will be undertaken and the potential of dietary polyphenols to reduce such neural damage will be critically reviewed. © 2011 by the authors; licensee MDPI, Basel, Switzerland.
Panickar K.S.,University of Maryland Baltimore County |
Panickar K.S.,Beltsville Human Nutrition Research Center
Central Nervous System Agents in Medicinal Chemistry | Year: 2013
Herbs and spices have been used since ancient times to not only improve the flavor of edible food but also to prevent and treat chronic health maladies. While the scientific evidence for the use of such common herbs and medicinal plants then had been scarce or lacking, the beneficial effects observed from such use were generally encouraging. It is, therefore, not surprising that the tradition of using such herbs, perhaps even after the advent of modern medicine, has continued. More recently, due to an increased interest in understanding the nutritional effects of herbs/spices more comprehensively, several studies have examined the cellular and molecular modes of action of the active chemical components in herbs and their biological properties. Beneficial actions of herbs/spices include anti-inflammatory, anti-oxidant, anti-hypertensive, gluco-regulatory, and anti-thrombotic effects. One major component of herbs and spices is the polyphenols. Some of the aforementioned properties are attributed to the polyphenols and they are associated with attenuating the metabolic syndrome. Detrimental changes associated with the metabolic syndrome over time affect brain and cognitive function. Metabolic syndrome and type-2 diabetes are also risk factors for Alzheimer's disease and stroke. In addition, the neuroprotective effects of herbs and spices have been demonstrated and, whether directly or indirectly, such beneficial effects may also contribute to an improvement in cognitive function. This review evaluates the current evidence available for herbs/spices in potentially improving the metabolic syndrome, as well as their neuroprotective effects on the brain, and cognitive function in animal and human studies. © 2013 Bentham Science Publishers.
Lin L.-Z.,Beltsville Human Nutrition Research Center
Journal of Agricultural and Food Chemistry | Year: 2010
A liquid chromatography-mass spectrometry (LC-MS) profiling method was used to characterize the phenolic components of 17 leafy vegetables from Brassica species other than Brassica oleracea. The vegetables studied were mustard green, baby mustard green, gai choy, baby gai choy, yu choy, yu choy tip, bok choy, bok choy tip, baby bok choy, bok choy sum, Taiwan bok choy, Shanghai bok choy, baby Shanghai bok choy, rapini broccoli, turnip green, napa, and baby napa. This work led to the tentative identification of 71 phenolic compounds consisting of kaempferol 3-O-diglucoside-7-O-glucoside derivatives, isorhamnetin 3-O-glucoside-7-O-glucoside hydroxycinnamoyl gentiobioses, hydroxycinnamoylmalic acids, and hydroxycinnamoylquinic acids. Ten of the compounds, 3-O-diacyltriglucoside-7-O-glucosides of kaempferol and quercetin, had not been previously reported. The phenolic component profiles of these vegetables were significantly different than those of the leafy vegetables from B. oleracea. This is the first comparative study of these leafy vegetables. Ten of the vegetables had never been previously studied by LC-MS.
Byrdwell W.C.,Beltsville Human Nutrition Research Center
JAOCS, Journal of the American Oil Chemists' Society | Year: 2015
The Updated Bottom Up Solution (UBUS) was recently applied to atmospheric pressure chemical ionization (APCI) mass spectrometry (MS) of triacylglycerols (TAG). This report demonstrates that the UBUS applies equally well to atmospheric pressure photoionization (APPI) MS and to electrospray ionization (ESI) MS. Critical Ratio 1 (CR1), the [MH]+/∑[DAG]+ or [MNH4]+/∑[DAG]+ ratio, does not exhibit the same strongly sigmoidal shape as it does by APCI-MS. CR1 varies more widely for APPI-MS than by APCI-MS, having a maximum value of 11.8, indicating a much greater effect of unsaturation on ion ratios in APPI-MS than APCI-MS. Critical Ratio 2, the [AA]+/[AB]+ ratio for Type II TAG or [AC]+/([AB]++[BC]+) ratio for Type III TAG, allows quantification of regioisomers of TAG, and shows good agreement for APPI-MS to regioisomer quantification determined by APCI-MS. Critical Ratio 3, the [BC]+/[AB]+ ratio for Type III TAG, reveals new trends relating the degree of unsaturation by APPI-MS, and shows that structural assignments made by ESI-MS are in good agreement to APCI-MS data. In addition to providing valuable structural information, the Critical Ratios also constitute a reduced data set that allows APPI-MS or ESI-MS mass spectra to be reconstructed when processed through the UBUS. Quantification by APPI-MS of Vitamin D in the gelcaps gave values of 42.90 ± 0.83 μg, or 1716 ± 33 international units, in good agreement with APCI-MS. © 2015 AOCS (outside the USA).