Walking is an ideal exercise for many people—it doesn’t require any special equipment, can be done any time, any place, and it is generally safe. Also, many studies – including the Nurses’ Health Study, (1, 2) Health Professionals Follow-up Study, (3) Women’s Health Study, Harvard Alumni Health Study, (5) National Health Interview Survey, (6) Women’s Health Initiative, (7) Honolulu Heart Program, (8) Black Women’s Health Study, (9) and others (10, 11) – have demonstrated that this simple form of exercise substantially reduces the chances of developing heart disease, stroke, and diabetes in different populations.
The Forum at Harvard School of Public Health’s webcast, “Why We Overeat: The Toxic Food Environment and Obesity.”
This annual report integrates nutrition and public health, environmental stewardship and restoration, and social responsibility within the food service industry and beyond.
Food is a lens through which we see the world, and our vision is increasingly focused on not only our personal health, but also the health of our planet. Our food choices reflect our values and beliefs, and they also significantly impact the world around us. Food production has a larger impact on our planet than any other activity, affecting land, oceans, wildlife habitats, energy use, and greenhouse gas emissions.
A recent New York Times article by reporter Gina Kolata calls into question the national guidelines for daily sodium intake, citing a new Institute of Medicine report that examined consequences of sodium consumption and concluded there is insufficient evidence for the health benefits of reducing sodium below 2,300 mg. Many experts, including the American Heart Association, have suggested that all individuals should aim for the low level of 1,500 mg of sodium per day, the amount considered optimal for at-risk individuals but thought to be beneficial for all.
In honor of World Health Day – April 7, 2013 – Dr. Walter Willett, Harvard School of Public Health Department of Nutrition Chair, participated in a discussion with Dr. Anne Lusk, Research Scientist, and Dr. Morteza Asgarzadeh, Postdoctoral Research Fellow, about hypertension. The discussion, recorded and available as video here, explores the importance of regular physical activity and changes to the built environment that might make it easier to increase levels of physical activity. This video also provides information about how to prevent high blood pressure, and the best environments for fostering healthy behaviors.
Expert discussion at HSPH on the controversial JAMA article which claimed that being overweight leads to reduced mortality.
Harvard School of Public Health’s Department of Nutrition assembled a panel of health experts to elucidate inaccuracies in a recent high-profile JAMA article which claimed that being overweight leads to reduced mortality. In his opening remarks, HSPH Dean of Faculty Julio Frenk called for a deeper discussion of this matter given the conflicting reports on a topic of such fundamental importance to Americans’ health. Each panelist presented a clear, compelling case as to why the general public should not rely on these flawed study findings, giving attendees numerous reasons to question the validity of the study.
Here’s yet another reason why you should eat more fruits and vegetables and cut back on processed foods: A large new study finds that people who eat high sodium, low potassium diets have a higher risk of dying from a heart attack or from any cause. The study, which appears in the July 11, 2011 issue of Archives of Internal Medicine, (1) bolsters the already-substantial evidence that high salt diets have negative effects on health. (2-4) And it highlights a key dietary change people can make to lower their risk: Eat more fresh vegetables and fruits, which are naturally high in potassium and low in sodium—and eat less bread, cheese, and processed meat, since these and other processed foods are high in sodium and low in potassium.
“Much confusion was caused by a recent, widely quoted report concluding that lower salt intakes were associated with higher risk of cardiovascular disease,” says Dr. Walter Willett, chair of the Dept. of Nutrition at Harvard School of Public Health. “This new study is much larger and controlled for key factors that were ignored in the previous report.”
Sodium and potassium have opposite effects on heart health: High salt intakes increase blood pressure, ultimately leading to heart disease; high potassium intakes can help relax blood vessels and decrease blood pressure. Our bodies need far more potassium each day than sodium, and most Americans should limit their sodium intake to 1,500 milligrams per day, the amount in about two-thirds of a teaspoon of table salt. (5) But the typical US diet—heavy on the processed foods, light on the produce—is just the opposite: Americans average about 3,300 milligrams of sodium per day, about 75 percent of which comes from processed foods, while only getting about 2,900 milligrams of potassium each day. (3,6)
The newest study, which is based on diet reports from participants in the National Health and Nutrition Examination Survey, followed just over 12,000 men and women for an average of 15 years. Sodium intakes averaged about 4,300 milligrams per day in men and 2,900 milligrams a day in women.(1) Potassium intakes averaged a good bit lower (3,400 milligrams and 2,400 milligrams), and substantially lower than the 4,700 milligrams per day that the US government recommends. (7)
People with the highest sodium intakes had a 20 percent higher risk of death from any cause than people with the lowest sodium intakes. People with the highest potassium intakes had a 20 percent lower risk of dying than people with the lowest intakes. But what may be even more important for health is the relationship of sodium to potassium in the diet: People with the highest ratio of sodium to potassium in their diets had double the risk of dying of a heart attack than people with the lowest ratio, and they had a 50 percent higher risk of death from any cause. (1)
Given that processed foods are responsible for much of people’s sodium intake in the US and Europe, governments have started working with the food industry to lower sodium levels. Finland and the United Kingdom have led successful sodium reduction efforts, (8) and in the US, the Institute of Medicine has recommended that the Food and Drug Administration regulate the amount of salt in commercially prepared food—a recommendation that’s likely to receive pushback from the salt industry, which continues to argue that salt has little influence on blood pressure. (9) Encouragingly, some manufacturers have voluntarily agreed to cut back on sodium by 20 percent over the next five years, as part of New York City’s National Salt Reduction Initiative. (10) Walmart has also pledged to cut back on sodium and decrease the prices of fresh produce in its stores. It remains to be seen whether the food industry will be able to deliver on these pledges. (Campbell Soup reportedly announced in early July 2011 that it was raising the salt levels in some of its soups, blaming its previous salt reduction efforts—and the resulting changes in product taste—for sagging sales.
It could take a decade for any US regulatory changes to take effect. In the meantime, there are steps that consumers can take to curb sodium intake and boost potassium.
1. Yang Q, Liu T, Kuklina EV, et al. Sodium and Potassium Intake and Mortality Among US Adults: Prospective Data From the Third National Health and Nutrition Examination Survey. Arch Intern Med. 2011;171:1183–91.
2. Strazzullo P, D’Elia L, Kandala NB, Cappuccio FP. Salt intake, stroke, and cardiovascular disease: meta-analysis of prospective studies. BMJ. 2009;339:b4567.
3. Brown IJ, Tzoulaki I, Candeias V, Elliott P. Salt intakes around the world: implications for public health. Int J Epidemiol. 2009;38:791–813.
4. World Cancer Research Fund, American Institute for Cancer Research. Food, Nutrition, Physical Activity, and the Prevention of Cancer: A Global Perspective. London; 2007.
5. Application of lower sodium intake recommendations to adults—United States, 1999–2006. MMWR Morb Mortal Wkly Rep. 2009;58:281–3.
6. Dietary Guidelines for Americans Scientific Advisory Committee. 2010. Report of the Dietary Guidelines Advisory Committee on the Dietary Guidelines for Americans, 2010, to the Secretary of Agriculture and the Secretary of Health and Human Service.
7. Institute of Medicine. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. Washington, D.C.: National Academies Press; 2005.
8. He FJ, MacGregor GA. A comprehensive review on salt and health and current experience of worldwide salt reduction programmes. J Hum Hypertens. 2009;23:363–84.
9. Institute of Medicine. Strategies to Reduce Sodium Intake. Washington, D.C.: National Academies Press; 2010.
10. National Salt Reduction Initiative – Statement of Commitment by Health Organizations and Public Agencies. 2011.
Why you should take the latest sodium study with a huge grain of salt
A new study would have you believe that low-salt diets raise your risk of dying from heart disease—a surprising finding, and one that’s sure to grab headlines worldwide. The only problem is that the study’s conclusions are most certainly wrong.
Walmart, the largest retailer in the U.S., has pledged to cut the trans fat, salt, and sugar from thousands of its grocery products by 2015 in the U.S.—and to cut prices on produce and other healthy foods.
Unveiling the company’s plans at an event with First Lady Michelle Obama on January 20, 2011, Walmart executives said they would work with suppliers to
- remove all of the remaining industrial trans fats from its grocery products, including the small amounts that fall beneath the FDA food labeling threshold;
- cut back on sodium by 25 percent in foods that are often hidden sources of sodium, including bread and baked goods, lunch meats and fresh meats, cheese, condiments, chips, soups, and boxed and frozen meals; and
- cut back on added sugar by 10 percent in foods that consumers often don’t realize are high in added sugar—such as breakfast cereals and snack bars, pancakes and waffles, flavored milk and yogurt, condiments and sauces, and fruit drinks; it will not, however, change the added sugar content of sugary treats or sugar-sweetened soft drinks.
The changes reportedly will apply to Walmart’s house-branded products, and Walmart executives say they will encourage other product suppliers to follow suit.
In addition to making its grocery foods healthier, Walmart is trying to make healthy foods more affordable. Executives say they will cut prices on fresh fruits and vegetables and “better-for-you” packaged food items, such as whole grain pastas and reduced sodium meals, so that the healthy foods are no pricier than their less-healthful counterparts. And they announced their intention to open stores in “food deserts”—neighborhoods, often urban, that don’t currently have easy access to affordable, fresh healthy foods.
These changes will take time and effort. To cut prices on produce, Walmart will need to increase its local sourcing of fruits and vegetables and wring unnecessary costs out of its supply chain. To achieve its other nutrition goals, Walmart’s suppliers will have to stealthily reformulate their products to cut back on salt and sugar without sacrificing taste.
Given Walmart’s size—its 4,300 Walmart and Sam’s Club stores draw more than 140 million U.S. customers per week—and its clout in the food and grocery industry, the planned changes promise to have a major impact on foods sold at other grocery stores across the country.
“This new initiative has the potential to transform the marketplace and help Americans put healthier foods on their table every day,” said Mrs. Obama, speaking at the Walmart announcement. The First Lady has spearheaded the “Let’s Move!” initiative, which is working to curb U.S. childhood obesity rates, and Let’s Move! staff worked with Walmart on the development of its plan. Reportedly, this is the first time that the First Lady has given this type of support to a single company’s nutrition efforts.
The announcement represents an important victory for public health activists who have been working for more than a decade to eliminate heart-harmful trans fats from the food supply, and who have been intensifying efforts to curb added sodium.
Most Americans get the majority of their daily sodium, on the order of 75 percent, from processed and prepared foods, many of which don’t even taste salty. (1) High sodium diets increase the risk of high blood pressure, heart disease, and stroke, and it’s been estimated that curbing Americans’ excessive sodium intakes—on average, 3,400 milligrams per day, more than double what’s recommended for most adults—could save billions of healthcare dollars and upwards of 90,000 lives annually. (2, 3)
Still, there are some who think that Walmart could have gone farther with its planned changes. Walmart’s initiative does not address the biggest source of added sugar in Americans’ diets—the billions of gallons of sugar-sweetened soft drinks that Americans consume each year and that contribute mightily to the obesity and diabetes epidemics. (4–10) (The rationale for not addressing sugary soft drinks, according to Walmart executives: Consumers can already choose sugar-free beverages from Walmart’s shelves.)
Similarly, a 25 percent sodium reduction may sound like a lot, but other food producers have already begun reducing sodium by similar amounts. Walmart could have made a bigger impact by adopting stricter food category-specific sodium thresholds, similar to what has been proposed in New York City.
Walmart executives positioned this as a customer-driven initiative, saying that customers have been asking for healthy foods that are more affordable—and asking for help identifying healthy options. So Walmart also plans to create front-of-package nutrition labels that make it easier for consumers to spot healthy foods. Front-of-package nutrition labels have been a source of consumer confusion, and the focus of government attention, with an independent Institute of Medicine Panel working to propose standards that companies must follow. Walmart said that its labeling would complement, rather than compete with, industry efforts.
“Even though some of us had hoped that Walmart might go a bit farther, this is a very important step in the right direction,” says Dr. Walter Willett, Fredrick John Stare Professor of Epidemiology and Nutrition and chair of the Department of Nutrition at Harvard School of Public Health. “Very importantly, Walmart promises to remove the price difference between healthier and regular versions of the same food, which will be hugely beneficial for those with low incomes, who are often forced to purchase products they know are not good for the well being of their families. We hope that other grocery stores will follow this lead, and go even further in helping Americans have better lives.”
1. Brown IJ, Tzoulaki I, Candeias V, Elliott P. Salt intakes around the world: implications for public health. Int J Epidemiol. 2009; 38:791-813.
2. Palar K, Sturm R. Potential societal savings from reduced sodium consumption in the U.S. adult population. Am J Health Promot 2009; 24:49-57.
3. Bibbins-Domingo K, Chertow GM, Coxson PG, et al. Projected effect of dietary salt reductions on future cardiovascular disease. N Engl J Med. 2010; 362:590-9.
4. Beverage Digest. Beverage Digest Fact Book 2008: Statistical Yearbook of Non-Alcoholic Beverages. Bedford Hills, New York, 2008.
5. Bleich SN, Wang YC, Wang Y, Gortmaker SL. Increasing consumption of sugar-sweetened beverages among US adults: 1988-1994 to 1999-2004. American Journal of Clinical Nutrition. 2009; 89:372-81.
6. Wang YC, Bleich SN, Gortmaker SL. Increasing caloric contribution from sugar-sweetened beverages and 100% fruit juices among US children and adolescents, 1988-2004. Pediatrics. 2008; 121:e1604-14.
7. Schulze MB, Manson JE, Ludwig DS, Colditz GA, Stampfer MJ, Willett WC, Hu FB. Sugar-sweetened beverages, weight gain, and incidence of type 2 diabetes in young and middle-aged women. Journal of the American Medical Association. 2004; 292:927-934.
8. Malik VS, Schulze MB, Hu FB. Intake of sugar-sweetened beverages and weight gain: a systematic review. American Journal of Clinical Nutrition. 2006; 84:274-288.
9. Malik VS, Willett WC, Hu FB. Sugar-sweetened beverages and BMI in children and adolescents: reanalyses of a meta-analysis. American Journal of Clinical Nutrition. 2009; 89:438-9; author reply 439-40.
10. Vartanian LR, Schwartz MB, Brownell KD. Effects of soft drink consumption on nutrition and health: a systematic review and meta-analysis. American Journal of Public Health. 2007; 97:667-675.
The U.S. Department of Agriculture (USDA) has come under fire from politicians and potato lobbyists over its proposal to cut back on French fries and potatoes in school lunch and offer broccoli and other vegetables instead. Yet its plan is based on sound science—and could help turn around this country’s obesity and diabetes epidemics.
The USDA’s proposal is a straightforward switch: Cap the amount of potatoes and other starchy vegetables that school lunch can serve at one cup per week—the equivalent of a medium baked potato—and promote a wider variety of vegetables, especially dark green and orange varieties, such as broccoli, spinach, and carrots. (1) The recommendation is part of a 76-page proposed overhaul of the nutrition standards in U.S. school meal programs, and the agency is on solid scientific footing: It’s following the recommendations from an expert panel at the Institute of Medicine (IOM), which spent a year reviewing research on children’s nutrient needs, as well as food choices that prevent obesity and chronic disease. (2)
Read more about the health benefits of vegetables and fruits.
U.S. children, on average, only eat about 40 percent of the government’s daily recommended vegetable intake—and 29 percent of that comes from potatoes, most of them fried. (2) Children are especially low in their intake of dark green vegetables, orange vegetables, and legumes (dried beans), getting less than 20 percent of the recommended intake.
By limiting starchy vegetables at lunch, and setting new requirements for dark green and orange vegetables, the IOM was trying to steer children’s diets in a healthier direction: “The committee anticipates that…with repeated exposures and high-quality food preparation, students will learn to value the vegetable items offered.” (2, p. 170) In other words, over time, kids will get used to eating broccoli, carrots, and other colorful vegetables—and may even start to like them.
Potatoes don’t count as a vegetable on Harvard’s new Healthy Eating Plate, and with good reason: They are very high in carbohydrate—in particular, the kind of carbohydrate that the body digests rapidly, causing blood sugar and insulin to surge and then dip. (The scientific term for this is that they have a high glycemic load.) In the short term, this roller coaster-like effect on blood sugar and insulin can lead people to feel hungry again, soon after eating—and this, in turn, can lead to overeating. (3) Over the long term, diets high in potatoes and similarly rapidly-digested, high carbohydrate foods can contribute to obesity, diabetes, and heart disease. (4–9)
Potatoes do contain important nutrients—vitamin C, potassium, and vitamin B6, to name a few. But the potato is not the only source of these nutrients, nor is it the best: Cup for cup, for example, broccoli has nearly nine times as much vitamin C as a potato, and white beans have about double the potassium. Yet a cup of potatoes has a similar effect on blood sugar as a can of Coca Cola or a handful of jelly beans. (10) That’s a high metabolic price to pay for nutrients that children can easily get from other sources.
Potatoes seem to be a particular culprit for weight gain and diabetes. A recent study from Harvard School of Public Health that tracked the diet and lifestyle habits of 120,000 men and women for up to 20 years looked at how small food-choice changes contributed to weight gain over time. People who increased their consumption of French fries and baked or mashed potatoes gained more weight over time—an extra 3.4 and 1.3 pounds every four years, respectively. (6) People who decreased their intake of these foods gained less weight, as did people who increased their intake of other vegetables. A similar long-term study found that high potato and French fry intakes were linked to a greater risk of diabetes in women, and that replacing potatoes with whole grains could lower diabetes risk. (5)
For people who are lean and active, potatoes likely don’t exact such a severe metabolic toll. But one out of three children and two out of three adults in the U.S. are overweight or obese, and many do not get enough daily physical activity. That’s all the more reason to use potatoes sparingly in our meals, if at all.
“Eating more than two servings of potatoes a week may be okay for people who dig their own,” says Walter Willett, Professor of Epidemiology and Nutrition and chair of the Department of Nutrition at HSPH. “But today, few Americans get the amount of physical activity our ancestors did 80 years ago, and that means our metabolism responds poorly to high amounts of starch.”
Some politicians and potato lobbyists have raised concerns that replacing potatoes with a wider variety of vegetables would add $6.8 billion to the cost of school lunches over the next five years. (11) But that appears to be a short-sighted point of view: Obesity costs this country an estimated $152 billion a year in healthcare expenses, and those could rise to an estimated $319 billion by 2020. (12) That makes the cost of this school lunch upgrade seem like just a drop in the potato bucket.
1.U.S. Department of Agriculture. Nutrition Standards in the National School Lunch and School Breakfast Programs: A Proposed Rule by the Food and Nutrition Service on 01/13/2011. Federal Register. 2011;76:2494–2570.
2. Institute of Medicine. School Meals: Building Blocks for Healthy Children. Washington, D.C.: National Academies Press; 2009.
3. Abete I, Astrup A, Martinez JA, Thorsdottir I, Zulet MA. Obesity and the metabolic syndrome: role of different dietary macronutrient distribution patterns and specific nutritional components on weight loss and maintenance. Nutr Rev. 2010;68:214-31.
4. Halton TL, Willett WC, Liu S, et al. Low-carbohydrate-diet score and the risk of coronary heart disease in women. N Engl J Med. 2006;355:1991-2002.
5. Halton TL, Willett WC, Liu S, Manson JE, Stampfer MJ, Hu FB. Potato and french fry consumption and risk of type 2 diabetes in women. Am J Clin Nutr. 2006;83:284-90.
6. Mozaffarian D, Hao T, Rimm EB, Willett WC, Hu FB. Changes in diet and lifestyle and long-term weight gain in women and men. N Engl J Med. 2011;364:2392-404.
7. Barclay AW, Petocz P, McMillan-Price J, et al. Glycemic index, glycemic load, and chronic disease risk–a meta-analysis of observational studies. Am J Clin Nutr. 2008;87:627-37.
8. Beulens JW, de Bruijne LM, Stolk RP, et al. High dietary glycemic load and glycemic index increase risk of cardiovascular disease among middle-aged women: a population-based follow-up study. J Am Coll Cardiol. 2007;50:14-21.
9. Chiu CJ, Liu S, Willett WC, et al. Informing food choices and health outcomes by use of the dietary glycemic index. Nutr Rev. 2011;69:231-42.
10. The University of Sydney. Glycemic Index Database. Accessed October 8, 2011.
11. Huang, J. USDA wants to limit potatoes in school lunches. National Public Radio. October 5, 2011.
12. Dor AF, Langwith C, Tan E. A heavy burden: The individual costs of being overweight and obese in the United States. The George Washington University School of Public Health and Health Services Department of Health Policy, 2010.