What Does Science Say You Should Eat

What Does Science Say You Should Eat - Article 13 What Does...

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Unformatted text preview: Article 13 What Does Science Say You Should Eat? Most diets aren’t realistic or advisable, including the US. agriculture department’s famous food pyramid. Instead, a Harvard scientist recommends a new way of eating based on the world’s largest and longest food study. By Brad Lemley America clearly needs dietary guidance—More than 44 million people are clinically obese compared with 30 million a decade ago, putting them at increased risk for heart dis— ease, stroke, type 2 diabetes, and breast, prostate, and colon cancers. In the meantime, the noun diet seems to attract a different adjective every week, including Atkins, Ornish, Cooper, grapefruit, rice, protein, Scarsdale, South Beach, Beverly Hills, Best Chance, Eat Smart, and Miracle, not to mention Help, I’m Southern and I Can’t Stop Eating. While some of these plans overlap, others seem to specifically contradict each other, notably the meat—inten— sive regime of the late Robert Atkins versus the near—vegetarian program of Dean Ornish.—No wonder Amer- icans are tempted to follow Mark Twain’s admonition to “eat what you like and let the food fight it out inside.” But still, we wonder: Is there really an optimum way to eat?—Al- though debate rages, academic nu— trition researchers have begun to form a consensus around a plan with an important advantage—it is based On a preponderance of sound sci— ence. The regime does not as yet have a name, but it might well be Called the Willett diet, after its lead— ing proponent, Walter Willett, chair— man of the department of nutrition at the Harvard School of Public Health.—~Featuring abundant fruits, vegetables, whole grains, and vege— table oils, as well as optional por- tions of fish and chicken, Willett’s plan resembles the much-touted Mediterranean diet shown in several studies to reduce the risk of heart disease. Nonetheless, Willett resists the comparison. "The Mediterra— nean diet is specific to a certain cli— mate and culture," he says, adding that by focusing on healthy ingredi— ents rather than specific dishes, "anyone can adapt this plan to his own tastes.” The results: stable blood—sugar levels, easier weight- control, clearer arteries, and overall better health. In this case it’s hard science, not just opinion. Willett’s plan is based on the largest long—term dietary sur— vey ever undertaken: the 121,700- participant Nurses’ Health Study, begun in 1976 by Harvard Medical School professor Frank Speizer, with dietary assessments supervised by Willett since 1980. The study isn’t just big: Willett carefully crafted it so that he and others could extract spe— cific recommendations about food intake. Participants even surrender blood and toenail samples so that Willett can track absorption of trace elements and other nutrients. If a participant reports a major illness, such as heart attack or cancer, "we write for permission to obtain medi— 31 _l\ cal records for further details,” says Willett. To ensure that the data in- clude both sexes and two genera~ tions, Willett and several colleagues also launched the Health Profession- als Follow‘Up Study, which includes 52,000 men, and the Nurses’ Health Study H, a survey of 116,000 younger women. In the past, nutritional scientists have largely relied on studies of ani— mals, small groups of people, and/ or petri-dish biochemistry that may not reflect the vagaries of human metabolism, although Willett uses such studies when he deems it ap— propriate. His access to a unique quarter—million-person pool of hu— mans who carefully track both their diets and their health lends added credibility to his research. "When you put animal, metabolic, and epi- demiological studies together and they all point in the same direction, you can be pretty confident about your conclusions,” Willett says. ’Nutrition used to be like religion. Everyone said, I have the truth, everyone else is wrong’ While soft—spoken and self—effac- ing in person, Willett isn’t shy about using this formidable database to take on the federal establishment. ———I———————————m r ANNUAL EDITIONS WILLETT VS. ORNISH VS. ATKINS Walter Willett’s dietary recommenda- tions are similar in many ways to those advanced by another duetor~nutrition« ist, Dean Omish, who pioneered an'ul— tralow—fat, near~vegetarian r regime that has been shown to halt 0r reduce coronary blockage in most heart patients. Both Wil— lett and Ornish emphasize whole grains, fruits, and vegetables, and both minimize animal proteins. But they part ways on fats: Willett recommends replacingsatw rated fats in the American diet withunsat— urated ones, while Ornish suggests sharply cutting fat intake altogether, espe- cially for those at risk for heart disease. "No one has shown that the kind of diet that Walter Willett recommends can re- verse heart disease,” says Omish. ’ For his part, Willett insists that “re— - placing saturated fats withunsaturated fats is a safe, proven, and delicious way to cut the rates of heart disease.” He says the Lyon Diet Heart study,:a French trial that tracked heart—attack survivors on an oil-rich Mediterranean diet versus those on the low—fat American Heart Associa- tion diet, showed a significant drop in second attacks for the Lyon group. Or- nish responds that the drop in "deaths in His Healthy Eating Pyramid differs radically from the Food Guide Pyra— mid pushed by the US. Department of Agriculture, ’,’,At,,b8,st,,,,,ths USDA, , pyramid offers wishy—washy, scien- tifically unfounded advice,” Willett argues in his book, Eat, Drink, and Be Healthy: The Harvard Medical School Guide to Healthy Eating. At worst, he adds, “the misinformation contrib— utes to overweight, poor health, and unnecessary early deaths." The numbers back him up. Men and women in Willett’s studies whose diets most closely paralleled the Healthy Eating Pyramid’s guide— lines lowered their risk of major chronic disease by 20 percent and 11 percent respectively, according to an article published in the December 2002 issue of The American journal of Clinical Nutrition. That compares with reduced risks of 11 percent and 3 percent for those whose diets most that study was most likely due to in— creasing heart—healthy omega-3 fats and decreasing intake of omega-6 fats, satu— rated fats, animal protein, and choles- terol, not to high overall consumption of fat. Ornish recommends that everyone consume three grams of omega?) fats daily, either through eating fishor tak- ing supplements. * . V In contrast with both Willett and Or— nish, the late RObert Atkins recom- mended a meat—intensive, protein~rich regime. "Studies at Duke University, the University of Cincinnati, and the Uni- versity of Pennsylvania all show that people can lose significant weight, lower their triglycerides, andimprove their HDL [high—density lipoprotein] choles- terol levels by consuming protein and limiting carbohydrates,”. says Stuart Trager, an orthopedic surgeon who as— sumed the spokesman's mantle for the " diet after Atkins’sdeath in April 2003." ' " Trager belieVes the real strength of the Atkins dietis that "it is something peo— ple are willing and able to‘do.” Willett concedes th'atAtkins "was re— ally onto something. Hebelieved, cor- rectly, that most people can; better control closely mirrored the USDA pyra- mid’s guidelines. “Nutrition used to be like religion. Everyone said, ’I have the truth, ev- eryone else is wrong,’ and there wasn’t much data to refute that,” says Willett. “Now we're starting to have a real scientific basis for understanding what you should eat." JUST INSIDE THE DOOR OF WILLETT'S OFFICE AT the Harvard School of Public Health in Boston sits his bicy- cle, mud~spattered from his daily commute over the Charles River from his home in Cambridge. Past that, on top of a pile of medical jour— nals, perches a plastic bag full of plump, homegrown cherry toma— toes, a late—season—harvest gift from his administrative assistant. Willett knows good tomatoes. As a member ofa fifth-generation Michigan farm- ing family, he paid his undergradu— 52 their weight by reducing the glycemic load of the diet than by other means, But there is evidence that the tradi— tional Atkins diet, which is high in an: imal fat, is not optimal. There are benefits to having cereal in one's diet. " There'is relief’frorn'constipation, and we do see [in the Nurses’ Health Study] some benefit for heart disease and diabetes. This is probably par- tially from the fiber in whole grains, and also partly from the other miner— als and vitamins that come along with A whole grains that are in short supply ‘ in many people’s diets.” While at first blush the three ap- proaches seem sharply divergent, Trager sounds a conciliatory note. "No one has ever bothered to point out that we are compatriots on many points,” he says. All three nutrition- ists’ share an emphasis on' reducing bloodisugarspikes by reducing the glycemic load. Moreover, all three condemn trans fats, white flour, and sugar. "There really is universal agreement that you should cut those things out of your diet," Trager says. —Brad Lemley ate tuition at Michigan State by raising vegetables, and today he grows “as much as possible" in his tiny urban backyard. y Behind the cluttered desk sits Wil— ' lett himself, trim, toned, and turned out in a sharp gray suit. "All you ‘ have to do is take a look at Walter to _ see the value of his research. The proof is in the pudding," says David Jenkins, a nutrition researcher at the University of Toronto. Willett vigor- ously follows his own plan and at age 58 reports that his weight, cho- lesterol, and triglycerides are all where they should be. He is, in short, the picture of where applied nutri- tional science might deliver us all, if we had the proper information. That's the problem. In recent years, Willett says, the American public has been victimized by dodgy advice. Notionly has obesity sky‘ rocketed but “the incidence of heart f disease is also not going down any- more. It has really stalled.” What happened? In Willett's view, things began to go awry in the mid-19805, when a National Insti- tutes of Health conference decreed that to prevent heart disease, all Americans except children under 2 years old should reduce their fat in— take from 40 percent to 30 percent of their total daily calories. The press touted the recommendation as re— vealed truth, and the USDA’S Food Guide Pyramid, released in 1992, re- flects this View, calling for 6 to 11 servings of bread, cereal, rice, and pasta daily, while fats and oils are to be used “sparingly.” Too bad, says Willett. “The low- fat mantra has contributed to obe— sity. The nutrition community told people they had to worry only about counting fat grams. That encouraged the creation of thousands of low—fat products. I call it ’the SnackWell revolution."’ Blithely consuming low—fat foods full of carbohydrates is a prescription for portliness, says Willett, adding that any farmer knows this. “If you pen up an animal and feed it grain, it will get fat. Peo- ple are no different.” The problem with overeating re— fined carbohydrates such as white flour and sucrose (table sugar) is that amylase, an enzyme, quickly con- verts them into the simple sugar called glucose. That goads the pan- creas to overproduce insulin, the sub- stance that conducts glucose into the cells. But excessive sugar is toxic to cells, so after years of glucose and in- sulin overload, the cells can become insulin resistant and may no longer allow insulin to easily push glucose inside them. That keeps blood glu- cose levels high, forcing the pancreas to make even more insulin in a des- perate attempt to jam the stuff through cell membranes. Willett lik- ens the effect to an overworked, un— dermaintained pump that eventually Wears out. Type 2 diabetes canlbe one result, but Willett contends that insu- ljII-resistant people who don't de— velop full—blown diabetes still face Significant health risks. Article 13. What Does Science Say You Should Eat? Other researchers agree. Stanford endocrinologist Gerald Reaven coined the term Syndrome X to describe the constellation of health problems that spring from insulin resiStance. Until the late 19805, Reaven says, “the com— mon scientific View was that insulin resistance only mattered if it led all the way to type 2 diabetes. Looking at the N data, it’s clear that most people who are insulin resistant don’t get diabetes but are greatly at risk for coronary heart disease, hypertension, non—alco— holic-type liver disease, polycystic ovary syndrome, and several kinds of cancer." In the case of heart disease, Reaven says that high blood concentrations of insulin and glucose can damage the endothelium that lines coronary ar- teries and set the stage for the forma— tion of plaques. “A big problem is the lack of drugs to treat this problem,” he adds. “A lot of doctors’ education comes from drug companies. They know about cholesterol because ev— eryone is pushing their statin. They know about hypertension because there are multiple hypertensive drugs. But they know a lot less about insulin resistance and its conse— quences, and that’s unfortunate.” Syndrome X, also known as meta— bolic syndrome or insulin—resistance syndrome, is largely unknown to the public as well. While many people avoid cholesterol foods, few understand the threat posed by carbohydrate excess. That needs to change, says Willett. “Cho- lesterol is relevant, but the danger is' overblown,” he says. “Syndrome X is the global public-health problem of the let century. Almost certainly the vast majority of Americans have a higher degree of insulin resistance than is optimal." The Willett plan aims to even out the glucose roller coaster through an emphasis on foods with low glyce— mic loads—foods that convert to glu- cose slowlyMlike whole grains, plant oils, and vegetables. This keeps blood glucose levels relatively con- stant, sparing the pancreas over— work. Steady blood glucose also helps keep the appetite in’check, ' " 53 and fat-laden ’ 7 which makes maintaining a healthy weight easier, says Willett. So in— stead of high carb, low fat, one might summarize the Willett plan’s direc- tive as good carb, good fat. "People are being told to reduce fat and eat more carbohydrates. For many people, particularly over— mweight people with ahigh degree of insulin resistance, that produces ex- actly the opposite of what they need," says Willett. Randomized tri— als, he says, show that people on low-fat diets generally lose two to four pounds after several weeks but thenigain back the weight even while continuing the diet. “Most of them would be better off reducing carbs, switching to better carbs, and in— creasing their intake of healthy fats.” ’Instead of high carb, low fat, one might summarize the Willet plan’s directive as good carb, good fat’ WILLETT, LIKE VIRTUALI.Y EVERY OTHER NUTRITION researcher, advises eating vegetables in abundance, con— suming alcohol in moderation, and taking a daily multivitamin to cover nutritional gaps. He also touts fish as a source of protein and. heart-protec~ tive n—3 fatty acids, which are also "’krtown"aS’ omeg‘aLB acidsr" (Those who worry about mercury contami- nation in fish got some good news recently: In one study conducted in the Seychelles, a group of islands in theIndiachean, scientistsfrom the University of Rochester Medical Center tracked pregnant women who ate an average of 12 fish meals a week, about 10 times the quantity of fish eaten by the average American. “We've found no evidence that the low levels of mercury in seafood are harmful," said lead author Gary My- ers. Moreover, various tests indi— cated that the women’s children suffered no adverse cognitive, be— havioral, or neurological effects.) High on the list of food ingredi— ents Willett counsels avoiding are hydrogenated fats, often referred to ANNUAL EDITIONS GOOD CARBS/BAD CARBS Theglycemic index (G1) is a way of measuring how quickly the H carbohydrate in a given fOOdraises the levelfo blood sugar. So eating a low~GI food causes a slow, mild rise, while the same quantity of carbohydrate in arhigh¥GI fOOdLWill trigger a faster, bigger rise. A GI of 55 or less-is considered low, 56 "to 69 is me- dium, and 70 or more is high; ' ‘ J 1 , 7 [But the GI is of limited use in the real World of pears, pork, aandipvudding because it'ignores hoW‘that food a per— : eats. A few years ago,~Walter pioneei‘ed the concept 1; efythe glycemic load (CL), a meaSurernentr'that factors in the (quantity of carbohydrates eaten ina singleserving Of a particu- . lar food-The carbohydrates in parsnips, for example, are quickly ‘ converted to glucose, so parsnipsihavea rather high index of 97, a plus, Or minus 19 (the numbers xey'somefimes imprecise because ' they are based onrfeeding foods ‘to‘ftesti-subjects and monitoring “theirblood-sugar response, whichcan‘vary, for many reasons). ,-parsnips have a CL of juSt;12,7becauS‘e a Single 80—gram ' serving contains a relatively small’amount of, carbohydrate. A I CL of 10 or less is considered 11 to 19 is medium, and, 20 ' or more is Consistently eating low-CL foods evens out ' 'blood-‘sugarspeaks and valleys, which Willett says helps-'kéeppg, appetite and weight under control. Eating low-CL foods also, reduces the risk of developing type 2 diabetes. When Willett ’ ’ ' ’says “ goodtarbsfil he is essentiallyreferringr torfiber—vrich, lot/v-5," GL foods. 5 I I I I I K , _ Generally,whole grains have lower glycemic loads than re;- fined grains. For example, a 150-gram serving of brOwn rice T has a CL of 18, While the same serving of quick-cooking white} rice has a CL" of ‘29.]Although the photographs in this story: V tally the "sugar equivalence” of the carbohydrates in"vario‘u5’iri American-foods,theglycemic index and glycemic load of each of theSe foods‘needslto be considered as well. The [glycemic ~i numbersaccontpanying the photographs in thisarticleifi'are ‘ from Janette Brand-Miller of the University of Sydney, based on a table published in the July 2002 issue of The Alfiericahi? journal of Clinibal Nutrition. An adaptation of that table Canbe; f seen a at ~ diabetes . about . com/l ibrary/mendosagi/E, ngilistsbtm} H L as trans fats, which are found in shortening, margarine, deep-fried foods, and packaged baked goods. That advice was controversial when Willett published a groundbreaking paper on the subject in 1991, but it has since become close to dogma. "Both controlled—feeding studies that have examined the effects of trans fat on blood cholesterol and ep- idemiological studies of trans—fat in— take in relation to the risk of heart disease and diabetes indicate they are considerably worse than satu— rated fats,” he says. Daily exercise is essential, Willett adds, and he confirms the often-cited advice that walking is the best choice for many people. The Nurses’ Health Study revealed a “very strong link” between walking and protection against heart disease: Women who walked an average of three hours a week were 35 percent less likely to have a heart attack over an eight— year period than those who walked less. It may seem odd that Willett in- cludes exercise in his Healthy Eating Pyramid, but he is adamant that ex— ercise and diet cannot be teased apart. "It doesn't have to be extreme. I run along the Charles for 25 min— utes most mornings.” A half hour daily of moderate activity offers "im- pressive health benefits,” he says, but there is “added benefit for greater intensity for longer times.” Willett’s more iconoclastic con— clusions include the heretical notion that soywtouted as a miracle food that fights cancer, obesity, and virtu— ally every other human ill—may have "a dark side." He points to a British study in which 48 women with suspicious breast lumps were randomly assigned to receive either no supplement or one containing soy isoflavones (a compound in soy- beans molecularly similar to estro— gen) for 14 days. Those taking the supplement showed substantially more cell growth in the tissue re- mOved than the women who were not taking the soy. Another trou- bling study showed memory loss and other cognitive declines in eld— erly Japanese men in Hawaii who stuck to their traditional soy-based diet, as opposed to those who switched to a more of a Western diet. “In moderation, soy is fine," says Willett. “Stuffed into everything, you could get into trouble.” And soy isoflavone supplements, he coun- sels, should be regarded as "totally untested new drugs.” Willett also counsels that dairy products—which supply concen- trated calories and saturated fat»— are not the best way to get calcium 54 and that the recommended daily in- take of 1,200 milligrams daily for adults over 50 appears to be more than what’s needed. His advice: Eat Tj calcium—bearing vegetables, includ- 7 ing leafy greens, take calcium sup- plements if you’re a woman, and exercise. "The evidence for physical activity being protective against fractures is huge,” he says. ’No research has ever shown that people who eat more eggs have more heart attacks than people .who eatfewer eggs’ And he defends eggs. Although cholesterol fears have caused Amer- i ican per capita egg consumption to drop from 400 to 250 per year, “no research has ever shown that people who eat more eggs have more heart attacks than people who eat fewe eggs," Willett says. A 2001 Kansas State University study identified a type of lecithin called phosphatidyl choline in eggs that interferes wit cholesterol absorption, which may a explain why many studies have? found no association between egg 7, intake and blood cholesterol level. If f the breakfast menu option is a white- flour bagel or an egg fried in vegeta— ble oil, says Willett, “the egg is the better choice.” Perhaps the most comprehensive studies Willett has assembled com- pare the health consequences of eat- ing saturated versus unsaturated fat. The term saturated means that every available site along each fat mole- cule’s carbon chain is filled with a hydrogen atom; such fats—includ- ing butter and animal fat—are solids at room temperature. There are two types of unsaturated fats: monoun— saturated fats such as olive oil, which are missing one pair of hydro— gen atoms, and polyunsaturated fats such as soy, corn, and canola oils, which lack more than one pair. Both sorts are liquid at room temperature. Some researchers have ques— tioned whether saturated fat is dan- gerous. In his book, The Cholesterol Myths: Exposing the FallcTCy That Sata— rated Fat and Cholesterol Cause Heart Disease, Swedish physician Uffe Ravnskov asserts that as of 1998, 27 studies on diet and heart disease had been published regarding 34 groups of patients; in 30 of those groups in- vestigators found no difference in' ~ Article 13. What Does Science Say You Should Eat? animal fat consumption between those who had heart disease and those who did not. "Anyone who reads the literature in this field with an "openinind' soon discovers ' that the emperor has no clothes, ’1 r Ravn: skov writes. Willett turns to his Nurses’ Health mega-study for the definitive word. ' " "The amounts of specific fats did make a difference," he says. "Women who ate more unsaturated fat instead of saturated fat had fewer heart problems.” Willett calculated that replacing 5 percent of saturated fat calories with unsaturated would cut the risk of heart attack or death from heart disease by 40 percent. Other studies—notably the French Lyon Diet Heart study, begun in l988—show a similar correlation. A HEALTHY DIET PLAN 13 WORTHLESS IF PEOPLE won’t stick to it, and Susan Roberts, director of the energy me— tabolism laboratory at Tufts Univer— sity, contends that Willett’s regimen is too severe. “Most people would sayw hisw rrecemmendationseare healthy but that other, less difficult diets are healthy too,” she says. Difficult is in the palate of the eater. The last half of Willett’s book aims to dispel any taint of Calvinism with recipes that verge on the syba— ritic, including pork tenderloin with pistachio-gremolata crust, chicken enchilada casserole, and grilled salmon steaks with papaya-mint salsa. On the other hand, some re- solve might be required to soldier through a few of the other dishes listed there, including hearty oat— wheat berry bread or the onion- crusted tofu—steak sandwich. But most people, Willett believes, can summon the willpower to substitute ’ Whole—wheat flour for white and plant oils for shortening or lard, and eat less sugar overall. “I think what I suggest is not severely restrictive, because it can be achieved mainly by substitution,” rather than slavishly following recipes, Willett says. In any case, “it does not mean you can— not eat any of those foods but rather that they should be de-emphasized.” So take heart. Even Willett has a little chocolate new and then. M From Discover, February 2004, pp. 43-49. Copyright © 2004 by Brad Lemley. Reprinted by permission ofthe author. ...
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