Guest guest Posted February 24, 2005 Report Share Posted February 24, 2005 Hi All, For diet advice from Nature that is not in Medline yet, see the below. DECLAN BUTLER AND HELEN PEARSON Nature 433, 794 - 796 (24 February 2005) Dietary advice: Flash in the pan? Obesity is the main target in the US government's latest dietary guidelines. But can this advice really make a difference? Nature's reporters sift through the heady mix of politics and science to get a taste of things to come. " If you follow this diet, you're going to lose weight, you're going to be healthy and you're going to be able to improve your quality of life ... it's scientifically based, but it's also common sense. " Another diet guru flogging their snake-oil prescription for the servings of fat, carbohydrate, protein and other nutrients needed to be healthy and slim? No. This was Tommy , then US Secretary of Health, speaking on 12 January at the release of Uncle Sam's very own diet book, Dietary Guidelines for Americans 2005. The guidelines, revised every five years, inevitably amount to a compromise between nutrition advocates and the food and agriculture lobbies. Yet this time they largely have pleased even staunch critics of government food policy. " They look to me like the strongest dietary guidelines yet produced, " said son, who heads the Center for Science in the Public Interest, a nutrition advocacy group in Washington DC, at a press conference after the release. But in the aftermath, a philosophical divide has emerged. On the one hand is the view, expressed by , that the government's role is to put out information about what constitutes healthy eating, but that it's up to individuals whether they follow the advice. The other take is that the government must do more, not only to educate people about food choice, but to ensure a food supply that accurately reflects its own dietary advice. For those who take this view, the guidelines don't go far enough — and they say that buried in the fine print are concessions to the food industry that threaten to weaken the impact of the advice. The guidelines — a joint effort by the Department of Health and Human Services (DHHS) and US Department of Agriculture (USDA) — were first issued in 1980, and form a reference for US eating habits. They underpin government nutritional policy and federal food programmes, including school meals. And they will be summarized graphically in a new 'food guidance system', which will be released within weeks to replace the 'food pyramid' introduced in 1992. Fat fighters Previous guidelines focused on cutting consumption of the saturated fats that cause chronic conditions such as heart disease. But the top priority now is to roll back the obesity epidemic that is causing a surge in conditions such as type-2 diabetes. About two- thirds of US adults are deemed overweight or obese by the Centers for Disease Control and Prevention in Atlanta, Georgia. Consequently, the biggest change in the new guidelines is the emphasis on restoring energy balance to people's diets. The message is that there is no getting round the laws of thermodynamics. If your calorie intake exceeds your energy output, you will gain weight. To this end, the guidelines advise a close watch on calories and 30–60 minutes of exercise most days of the week; 90 minutes to shed unwanted flab. The US government's guidelines for a healthy diet were released in January by Tommy , but some say influence from parties, such as the sugar industry, will compromise the advice. That's old hat to dieters, but the surprise this time was the explicit statement that the healthiest way to reduce calories is to avoid added sugars, certain fats and alcohol, all of which are high in calories but low in essential nutrients. In the past, such a message has been all but taboo. The previous guidelines say only that added sugars may contribute to weight gain. And in January 2004, the Bush administration lobbied against phrasing in the World Health Organization's dietary advice that urged people to eat fewer sugary and other high-calorie foods. To hammer its point home, the scientific advisory committee behind the guidelines turned to the concept of 'discretionary calories': the number of junk-food calories you can eat daily without gaining weight. A typical sedentary person who burns 2,200 calories per day needs to eat about 1,910 calories of healthy food to meet their basic nutritional needs. This leaves 290 calories for a treat, such as beer and potato crisps with late-night TV. The idea, say committee members, is to raise people's consciousness about overeating without denying them their favourite snacks. Even a relatively modest reduction of between 50 and 300 calories per day could prevent most new cases of obesity, particularly among children. " If we could achieve this it would be the major crowning achievement of the guidelines, " says Alice Lichtenstein, a cardiovascular researcher at Tufts University School of Medicine in Boston, Massachusetts, who sat on the scientific committee for the 2000 guidelines. Taste of the future Also new this year is an emphasis on fibre- and nutrient-rich whole grains instead of refined grains, and a recommendation to eat nearly twice the quantity of fruit and vegetables suggested in the 2000 version, as a way to lower the risk of certain cancers, type-2 diabetes, stroke and obesity. And the guidelines now clearly distinguish between different types of fat. Gone is the blanket low- fat creed of the past 20 years. In its place is advice to avoid saturated fats, which are found in red meat, for example, and trans- fats, which are abundant in processed foods. At the same time, moderate amounts of healthy fats, such as olive oil, are recommended. The stronger wording in the new guidelines is partly the result of changes to the drafting procedure that gave scientific advisers greater autonomy. In 2003, the DHHS and USDA appointed 13 nutrition scientists to the Dietary Guidelines Advisory Committee and asked them to compile a report from the latest scientific literature. Bureaucrats at the two agencies then reviewed this report, published in the Federal Register in August 2004, and considered comments from interested parties. They drafted the guidelines themselves, and communications specialists transformed them into the slick, 84-page brochures released in January. Separating the two phases made the scientific basis of the guidelines more transparent, says Janet King, chair of the committee and a researcher at the Children's Hospital Oakland Research Institute in Oakland, California. In the past, the committee members had to write the actual guidelines, which forced them to consider factors such as how easy they were for a lay reader to understand. The previous committee spent ages, for example, debating whether to advise people to 'limit' or 'moderate' their salt intake, King says. The new set-up also made the committee less of a target for pressure from industry and policy-makers. " It shielded us, " she says. But the literature is far from definitive about the best diet. There are few long-term or well-controlled clinical nutrition trials available, so the committee relied heavily on epidemiological and observational studies (see 'How is science converted to dietary advice?' page 798 and Nature 428, 252–254; 2004). These uncertainties left plenty of room for quibbling about the wording of the guidelines, say critics of the process, who have been quick to point out the fingerprints of the food industry in the small print. One charge levelled at this and previous guidelines is that they tell consumers only what foods they ought to eat — such as lean cuts of meat and low-fat dairy products — without spelling out foods to avoid, such as processed snacks, fast food or red meat dripping with saturated fat. " They're saying the right thing but not quite giving it the teeth it needs, " says Camargo, himself a member of the scientific committee and an epidemiologist at the Harvard School of Public Health in Boston. Cream of the crop A more specific industry influence, critics contend, is the recommendation to consume more dairy products — the equivalent of three cups of milk a day, up from between two and three cups last time. They say that this increase provides most people with unnecessary calories, that it is possible to achieve recommended intakes of calcium and other nutrients through other means, and that it fails to take into account studies linking diets high in dairy products with an increased risk of prostate cancer. The increase is " one of the strongest influences of the food industry " in the report, says Walter Willett, a nutrition epidemiologist at the Harvard School of Public Health. Concerns have also been raised about the recommendation on trans- fats. The scientific report said that these should not exceed 1% of daily energy intake, but the guidelines say only that trans-fat intake should be kept " as low as possible " . According to Camargo, this was the most significant departure from the committee's recommendations, allowing those putting together school meals, for example, to make only a token effort to reduce the fat. Nutrition researchers critical of the food industry charge that the language was softened under industry pressure to avoid costly revamping of production processes that rely on cheap vegetable oils. For its part, the food industry says it is just trying to keep the guidelines fair. Industry representatives, as well as other interest groups, were invited to provide the committee with written and oral comments during the literature-review phase and to make comments after its report was published. The National Dairy Council, for instance, presented evidence supporting its argument that dairy foods help people meet their calcium and potassium requirements. And the Grocery Manufacturers of America argued that added sugars help increase the palatability of some nutritionally valuable foods. Reaping benefits But industry has other avenues of influence open to it. One is through USDA, which, by the nature of its mission, is more attuned to farmers' interests than to public-health needs. " It's the wrong agency to do this, and a blatant conflict of interest, " says n Nestle, a prominent critic of the food industry working at New York University. A second and more opaque route is through lobbying — an integral part of the US political system — where industry and others try to influence agency officials by, for example, providing them with relevant documents and making personal contacts. openly discussed industry's influence at the launch of the guidelines. " The food industry has spent a great deal of time and money appearing in and observing all of the negotiations and all of the testimonies that went into compiling the guidelines, " he said. " They come in and meet with me on a regular basis. " Although industry may have won key concessions, anyone who follows the guidelines strictly will probably end up in better health. The reason some nutrition experts are still not happy is that they anticipate little time or money will be put into spreading or enforcing the advice. " What is lacking is will on the part of the government and Congress to convert the guidelines into new health and agriculture policies and programmes, " says son. He asserts that doing so would step on major interests such as restaurants, as well as the corn, sugar, processed-food and salt industries. What is needed, he says, are hard-hitting, mass-media campaigns to help shift consumer demand to healthier products. Some also advocate legislation to subsidize healthy foods, regulate advertising aimed at children, and to require calorie information to be displayed on restaurant menus. So far there is little sign that strong implementation is coming. Instead, the US administration has emphasized that diet is a matter of personal choice. " It's up to the individual to make the right decisions, " said in January. But Uauy, an expert on health and nutrition at the London School of Hygiene and Tropical Medicine, argues that it is nearly impossible to choose carbohydrates or fats " wisely " , as the guidelines recommend, when many children's cereals contain as much as 40% sugar, for instance, and processed foods account for 80% of the trans-fats that people eat. Nor is it easy for people to choose foods with little salt — as the guidelines advise to lower blood pressure — when 80% of their salt intake comes from processed foods. Hard to swallow Indeed, the US diet will have to change radically to meet the new advice. At present, many Americans eat a diet that resembles the food pyramid turned upside down, with too much salt and added sugars and fats, and not enough grains, fruit and vegetables. Without substantial changes in the practices of the food industry the guidelines will have little impact, predicts Uauy. " If people want French fries and a double cheeseburger we're gonna give them that. " Others say that the food industry is already going through a period of evolution spurred in part by consumer demand. The public discussion of obesity and related health problems has led to increased awareness among consumers and greater scrutiny of the industry by nutrition advocates and the media. Many fast-food chains have updated their image with healthier fare such as salads and yoghurts. Last year, Mc's phased out its 'supersize' meal options. And PepsiCo has removed trans-fats from some of its snacks and has introduced a greater range of bottled waters and fruit juices as alternatives to sugary drinks. At the same time, food companies are not about to abandon their calorie-laden products as long as demand for them exists. " If people want French fries and a double cheeseburger we're gonna give them that, " says Bob Goldin, executive vice-president of Technomic, a food- industry consulting and research firm based in Chicago. But industry experts say that the shift towards healthier foods is more than cosmetic. Health and whole foods are one of the biggest growth areas in an otherwise saturated market, and companies are scrambling for a share of it. They predict that consumer demand for healthier food will grow, partly as a result of the dietary guidelines. " It will be a driving factor in the industry going forward, because that is what the consumer will ultimately want, " Goldin says. Certainly Americans are hungry for food advice, if $2 billion in diet book sales last year is any indication. But whether it will take more than a few books and a gentle nudge from their federal health department to get them to eat better and slim down is still up in the air. http://www.healthierus.gov/dietaryguidelines JONATHAN KNIGHT Nature 433, 797 (24 February 2005) Around the world in three square meals In China, it's a pagoda; in Canada, a rainbow. But despite the diversity of design to be found in pictorial food guides from around the world, the core advice remains the same: eat your peas and porridge, limit your bacon and eggs. In Canada's rainbow, for instance, breads and cereals occupy the outermost — and therefore longest — curve of the arc. This band is coloured golden yellow to represent grain. Vegetables and fruit are next in green, followed by dairy in blue and meat in the diminutive, innermost red band. Of course, in real rainbows, even Canadian ones, red comes before yellow. Putting the colours in that order comes a bit closer to what real Canadians eat. According to data from the United Nations Food and Agriculture Organization, Canadians, like other North Americans, get more than twice as many calories from meat and fish as from fruit and vegetables. That ratio is fairly common in parts of the world where meat is readily available. The Chinese, avid consumers of pork, have a similar proportion in their diets. This is despite the advice of the Food Guide Pagoda, which has grain in its foundation level, and fruit and veg just above it. Nearly every official food guide emphasizes grains and cereals as the foundation of a healthy diet, and that's one recommendation the world as a whole has no trouble living up to. In the United States and Europe, grains and cereals make up about a quarter of the average diet. In Asia, where rice is a staple, they are anywhere from 50% to 60% of daily calories. Diets in most other regions fall somewhere in the middle. Although the basic recommendations are the same, each pyramid, rainbow or circle tends to reflect the nation's unique food culture. The Mexican food circle has an entire wedge devoted to beans. The Chinese pagoda's food depictions include a bowl of rice and a head of bok choy, and the German food circle features photographs of hearty whole-grain breads. But no food guide seems to take adequate account of the irrepressible human sweet tooth. Sweets are listed along with fats as only for occasional consumption in most guides. And several make no mention of sweets at all, including those from China, Sweden, Germany and Portugal (see J. Painter, J.-H. Rah and Y.-K. Lee J. Am. Diet. Assoc. 102, 483–489; 2002). Even so, North Africans get 9% of their calories from sugar, Europeans 11%, and Americans a cloying 18%. Achim Schneider Nature 433, 798 - 799 (24 February 2005); doi:10.1038/433798a Food FAQs Eating a healthy diet is hard work. There are hundreds of guides out there — often providing conflicting instructions. Deciding what advice to take means wrestling with a number of tough questions. How is science converted to dietary advice? To make the jump from scientific data to specific recommendations for a healthy diet — that everyone should now eat nine servings of fruit and vegetables a day, for instance — the scientists on the US Dietary Guidelines Advisory Committee turned to computer modelling. They mixed and matched foods from the traditional groups — fruits, vegetables, grains, meat and beans, dairy foods, fats and sweets — to come up with combinations that met nutritional requirements put forward by the Institute of Medicine's Dietary Reference Intakes. This gave them a series of food patterns for a range of daily calorie intake levels from 1,000 to 3,200, in increments of 200. These model diets were designed to boost nutrients that are often too low in US diets, such as vitamin E, calcium, magnesium, potassium, fibre and vitamin A. In a twist, the nutritional value of each food group was calculated to reflect what Americans actually eat, rather than as a simple average of all the foods in the group. For example, broccoli accounts for more than half of the greens Americans eat, and spinach about a fifth, according to the 1999–2002 National Health and Nutrition Examination Survey. So the value of the greens group as a whole was calculated as having 0.53 of the nutritional values of broccoli and 0.20 of those of spinach. The remainder was taken as the combined average of other greens. Committee members say that this approach allowed them to make recommendations with practical value to Americans, who are not likely to radically shift the proportions of foods they eat within the food groups. But the result did not entirely satisfy nutrition professionals. Dena Bravata, a physician and obesity researcher at Stanford University in California, says that although the guidelines are valuable she would have preferred them to be " based more on the scientific evidence rather than this hybrid approach " . The average US diet is hardly ideal, she says, and knowing what food combinations are optimal would allow patients and clinicians to create individualized diets based on the best available evidence. The approach has its disadvantages, the committee admits. Many people in the United States don't get enough vitamin E, for example, so one might have expected the guidelines to recommend eating more nuts and oils, which are rich in this vitamin. But Americans eat very few real nuts (peanuts, although popular, are actually legumes) and use oils that are low in vitamin E, so nuts and oils ended up with low vitamin E scores in the computation. This meant acrobatic accounting to boost other food groups with average levels of vitamin E. Which countries or cultures have the best diets? Several groups are in the running. Many people consider the traditional Mediterranean diet to be one of the healthiest. But times are changing. With the globalization of the food market, processed foods are creeping into traditional diets at the same time that physical activity is declining in many parts of the world. More and more, the people with the best diets are those who make a concerted effort. In collaboration with the Harvard School of Public Health, Oldways, a Boston-based non-profit organization that promotes healthy eating, has assembled several traditional diets into food-guide pyramids, following the shape of the official eating guide set out by the US Department of Agriculture. These take traditional dietary patterns into account, as well as data from clinical and epidemiological research. The Oldways Mediterranean pyramid is based on the diet of Greece, Italy, Portugal and Spain around 1960, a time when people in those countries lived longer than their northern European neighbours and were less likely to develop heart disease. Their daily fare included wholegrain bread, pasta, rice, fruit, beans, vegetables, cheese, yoghurt and that quintessential Mediterranean ingredient, olive oil. They also ate fish, poultry, eggs and sweets weekly. But red meat, with its artery-clogging saturated fat, was consumed less often. Today, these eating habits are gradually being abandoned, and at the same time the Mediterranean advantage in life expectancy has decreased1 and obesity is on the rise2. But the diet itself remains popular among those who try to eat right. As a result, diet-conscious people in places that lack strong nutritional traditions may be candidates for the best eaters today. " Middle-aged, educated women in California eat particularly healthy diets, " says Martijn Katan, nutrition scientist at the Wageningen Centre for Food Sciences in the Netherlands. If effort is essential, certainly few countries have tried harder to eat right than Finland. In the early 1970s, Finnish men had the highest rate of heart disease in the world. Their diet consisted of large amounts of whole milk, cheese and salt, with very little in the way of fruit and vegetables. A national programme of education and changes to the food supply over three decades has vastly improved the national diet. Today, the mortality from coronary heart disease in working-age men has been reduced to a quarter of what it was in the 1970s (ref. 3). There must be a natural diet for humans — what did we evolve to eat? The good news is that evolution teaches us that humans can eat just about any mix of the basic food groups. During evolution, we have colonized almost every ecosystem on Earth, and adapted to what was available; from Arctic populations eating almost exclusively animal protein, to villagers in the peaks of the Andes living largely on grains and cereals. We evolved as " flexible eaters " , says Leonard, an anthropologist at Northwestern University in ton, Illinois, and an expert on diet in evolution. Taken from this evolutionary vantage point, arguments in diet books over whether a low-fat, high- carbohydrate diet is better than a high-protein, low-carb diet make no sense, he says. Alice Lichtenstein, a cardiovascular researcher at Tufts University School of Medicine in Boston who sat on the scientific committee that produced the 2000 US dietary guidelines, agrees. " A variety of diets are possible from an evolutionary point of view, " she says. The bad news is that evolution has also left us with a genetic legacy: our brains and genes are hardwired to seek out as much energy as possible for the least physical effort. This served humans well during millennia when starvation was a constant threat to our survival, but is not adapted to the modern world where high-calorie foods are a phone order or short drive away. Evidence for this can be found in the Arctic, for instance. Indigenous people who maintain a traditional lifestyle eat a great deal of meat, yet they have low blood lipid levels, which is a risk factor in heart disease, and enjoy good cardiovascular health. The explanation, Leonard proposes, is that their rate of metabolism is raised as a result of vigorous physical activity and in response to their frozen environment. But their relatives who have adopted a more sedentary way of life, and a Western diet that has more processed foods and less meat, have significantly increased blood lipid levels and higher rates of obesity and cardiovascular disease4. Such findings have implications for the hunt for 'fat genes'. Although some genes may be linked to the risk of getting fat, obesity is less the result of individual genetic propensities than of the shift in environmental conditions, says Uauy, an expert on public health and nutrition at the London School of Hygiene and Tropical Medicine. " The past 50 years is too short to modify our evolutionary trajectory. " Do we have enough of the right kind of food for everyone on the planet? Certainly if one considers the world's chronically undernourished, who now number some 850 million people5, the answer is no. But the surprise is that many of those who are better off or who live in countries with abundant food supplies still fail to get the nutrients they need, and may even be overweight in spite of this. The problem of chronic hunger occurs almost entirely in poor countries. The condition is particularly lethal to children, of whom more than 3.7 million died in 2002 from the health consequences of being underweight. Another estimated 850,000 died because their diet — although sufficiently rich in calories — did not contain enough vital components such as iron, vitamin A and zinc5. That lack of proper nutrients is also a phenomenon in wealthy countries, where food insecurity, if not starvation, is surprisingly common. In the United States, for example, 12.6 million households (about 11%) fall short of basic food needs at some point during the year. In about a quarter of those cases, people fail to get government food aid or find private charities to make up the difference, and so go hungry6. Ironically, poverty and obesity often go hand in hand in developed countries7. " Obesity is a disease of the poor in rich countries, whereas in poor countries obesity is a disease of the rich, " says Katan. A key factor is that junk food tends to offer the most calories for the least money. " This is the single most important factor influencing food choice, " says n Nestle, professor of nutrition, food studies and public health at New York University. In US supermarkets, for instance, a 270-calorie doughnut costs about 75¢, the same as 125-calorie apple. The ready availability of processed and fast foods in many corners of the globe is now making them the natural choice, particularly for the poor and uneducated. Apart from being cheap, they have a natural appeal, Nestle says. " Eating highly refined food rich in sugar and fat is a kind of joy, which poor people do not frequently have, " she says. Although it is true that wholesome foods are also available throughout the industrialized world, evidence suggests that even slight inconvenience is enough to put people off buying them. A representative study involving participants in the US food-stamp programme shows that people tend to buy more fruit the closer they live to a supermarket8. References 1. Trichopoulos, D. & Lagiou, P. Public Health Nutr. 7, 949–951 (2004). | Article | PubMed | 2. Padez, C., Fernandes, T., Mourão, I., Moreira, P. & do, V. Am. J. Hum. Biol. 16, 670–678 (2004). | Article | PubMed | ChemPort | 3. Puska, P. Acta Cardiol. 55, 213–220 (2000). | PubMed | ChemPort | 4. Leonard, W. R. et al. Annu. Rev. Anthropol. 34, (in the press). 5. The State of Food Insecurity in the World 2004 (UN Food and Agriculture Organization, Rome, Italy, 2004); available at: ftp://ftp.fao.org/docrep/fao/007/y5650e/y5650e00.pdf. 6. Nord, M., s, M. & Carlson, S. Food Assistance and Nutrition Research Report no. 42: Household Food Security in the United States, 2003 (USDA Economic Research Service, Washington DC, 2004); available at: http://www.ers.usda.gov/publications/fanrr42. 7. Drewnowski, A. & Specter, S. E. Am. J. Clin. Nutr. 79, 6–16 (2004). | PubMed | ChemPort | 8. Rose, D. & s, R. Public Health Nutr. 7, 1081–1088 (2004). | Article | PubMed | Cheers, Al Pater. Quote Link to comment Share on other sites More sharing options...
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