Still not getting it? 10 messages that don't seem to stick.
Those messages probably ring a bell (whether or not you actually follow through on them).
But others just don't stick. Maybe that's because we haven't heard them enough or because they're controversial. Maybe it's because there's only so much you can remember and only so much you can think about when you're deciding what to have for lunch.
Here's a refresher on 10 topics that may have gone in one ear and out the other.
We're doing some things right. As a nation, we've cut back on sugar and soft drinks. We've replaced much of our shortening with oil. We've switched from whole milk to lower-fat milk. We've swapped much of our beef for chicken. And we're eating more vegetables (not counting potatoes). Clearly, some messages are getting through, loud and clear.
But others, not so much. Here are 10 things that many of us have heard before, yet they just don't seem to sink in.
1 Extra weight increases your risk of cancer.
If you asked a thousand people why it's unhealthy to gain weight, what would you expect to hear? Maybe that extra pounds boost your odds of getting diabetes or a heart attack or a stroke.
Fewer people would guess that excess weight may increase your risk of cancer. Yet in January, the American Cancer Society (ACS) released the latest update of its Guidelines on Nutrition and Physical Activity for Cancer Prevention. (1) One of its key recommendations: "Be as lean as possible throughout life without being underweight."
Obesity is clearly linked to breast cancer in postmenopausal women, adenocarcinoma of the esophagus, and cancers of the colon, rectum, uterus, kidney, and pancreas. Evidence is growing that obesity is also linked to cancers of the gallbladder, liver, cervix, and ovary, along with non-Hodgkin lymphoma, multiple myeloma, and aggressive prostate cancer.
"After tobacco cessation, maintaining healthy body weight through physical activity and diet is one of the main ways people can reduce their risk of developing cancer," says Marjorie McCullough, strategic director of nutritional epidemiology at the ACS and co-author of the Guidelines.
Losing excess weight (after treatment) may also raise your odds of keeping some cancers (like breast, colon, and prostate) from returning, says the ACS's new Nutrition and Physical Activity Guidelines for Cancer Survivors. (2) How?
"The obesity-inflammation connection is likely to be relevant for both risk and recurrence of cancer," said Andrew Dannenberg, director of the Weill Cornell Cancer Center in New York, at a recent workshop on "The Role of Obesity in Cancer Survival and Recurrence" held by the Institute of Medicine. (3)
Other culprits may also play a role.
"Insulin could be a major player, not just as an indicator of insulin resistance, but actually as a hormone that is driving cancer growth," suggested Derek Leroith of the Mount Sinai School of Medicine in New York at the same workshop. (When you're insulin resistant, your insulin doesn't work properly.)
To prevent cancer, the ACS doesn't just recommend that people lose excess weight, but that they avoid putting on pounds in the first place.
"For most adults, a reduction of 50 to 100 calories per day may prevent gradual weight gain," says the Prevention guidelines.
"It's so easy to inadvertently add 50 to 100 calories to your diet," notes McCullough. "It can really add up if you do the math. So it makes sense to start cutting back a little bit."
That way, you can stay lean, rather than try to return to your old leaner self.
"People who maintain a healthy weight have a lower risk of cancer than people who have gained and then lost weight," McCullough points out. "So the ideal thing is not to gain in the first place."
But if you're already overweight, it's still worth trying to lose. Even if you repeatedly lose and regain the weight, your risk of dying of cancer, heart disease, or other illness is no higher than that of someone who started at the same weight. (4)
"Yo-yo dieting isn't dangerous," says McCullough. "So you might as well try to lose weight rather than not try at all."
2 Subtle cues can make you eat more (or less).
"Bet you can't eat just one," dared the classic Lay's potato chip ads. In fact, how many chips--or other foods--you eat may depend on cues below your radar.
A case in point: Researchers gave nearly 100 students at two colleges tubes of Lay's Stackables potato chips to eat while they watched a movie. (5) Half the students got tubes of ordinary chips and half got tubes with a red (tomato-basil flavored) chip inserted after every four (or six, nine, or 13) ordinary chips.
"Students who ate from tubes with the red chip dividers cut their consumption by more than 50 percent," says co-author Brian Wansink of Cornell University. "That meant that they consumed about 250 fewer calories."
Another benefit: "The dividers made students much better at estimating how many potato chips they ate," notes Wansink. "On average, those without red divider chips underestimated their intake by 13 chips, while those with divider chips were off by less than one chip."
Wansink, author of Mindless Eating (Bantam, 2007), has found that all sorts of below-the-radar cues influence how much we eat. For example, people tend to consume more from larger plates and bowls and when food is visible and within reach. (See "Under the Influence," May 2011.)
What to do? Create your own dividers. "Repackage food into small containers, bowls, or haggles," suggests Wansink. "Don't say, 'Now that I know, it won't influence me.' Set up your environment so that you mindlessly eat less."
3 We're eating too many grains.
Too many grains? We've all heard the advice to switch to whole grains, to eat less sugar and bad fat, and to cut back on excess calories. But why less grains?
In 1970, the average American got 430 calories a day from wheat, corn, oats, rye, and other grains. By 2009, we were up to 620 calories a day. (6)
Chalk up the increase to more bread, pasta, rice, tortillas, crackers, cereal, pancakes, pizza crust, pretzels, pastries, and other foods made with grain. And an estimated 90 percent of the grain we eat is refined flour.
"Refined grains are a big part of the imbalance in our diets," says Susan Krebs-Smith of the National Cancer Institute, who analyzed diet data on more than 16,000 Americans. (7)
The other parts: We eat too many servings from the "meat" group (which also includes poultry, fish, and eggs) and too few servings of fruits, vegetables, and low-fat dairy. We also don't come close to making at least half of our grains whole. And we eat too much of what health authorities call SOFAS (solid fats and added sugars).
"Refined grains are not only consumed in excess, but tend to be carriers of SoFAS," says Krebs-Smith. "They show up in grain-based desserts, cakes, cookies, grain-based chips, and snacks."
And the U.S. Department of Agriculture may be too generous when it recommends six servings a day of grains for a 2,000-calorie diet. (A serving is just a half cup of cooked pasta or rice or one slice of bread.)
The healthiest diets in the OmniHeart study--which lowered blood pressure, triglycerides, and LDL ("bad") cholesterol--had only four servings of grains a day (see October 2009, p. 1). (8) Instead, the diets' carbs came from fruits, vegetables, and beans. But that's a quibble when most people get far more than six servings of grains a day.
"It's not as though people were having either extra grains or extra solid fats and added sugars," says Krebs-Smith. "People were having quite a bit extra of all three."
4 Animal protein can help, not hurt, bones.
Does animal protein leach calcium from bones, as some people claim?
"Protein does increase calcium excretion," says Sue Shapses, professor of nutrition at Rutgers University in New Jersey. "But with a higher protein intake, there's also a higher absorption of calcium."
Whether that leads to a net loss or gain in bone seems to depend on how much calcium you consume.
Researchers divided more than 3,700 residents of Framingham, Massachusetts, by how much calcium they got from food and supplements. Among residents who consumed less than 800 milligrams of calcium a day (they averaged about 500 mg), those who ate the most animal protein had nearly three times the risk of a hip fracture than those who ate the least animal protein.
However, among those who consumed at least 800 mg of calcium a day (they averaged about 1,000 mg), those who ate the most animal protein had an 85 percent lower risk of a hip fracture than those who ate the least animal protein. (9)
"As long as there's adequate calcium, protein is good for bones," says Shapses.
Shapses has also looked more closely at what protein does to bone in dieters.
"In the past, we found that there's a decrease in calcium absorption when you're dieting," she notes. "And when you're dieting, you may be decreasing your calcium and protein intake, too."
In a study funded by the National Institute on Aging, Shapses and her colleagues assigned 47 overweight postmenopausal women to either a high-protein or a normal-protein diet. (10) All the women cut 500 to 600 calories a day and got 1,200 mg a day of calcium (from food and supplements) and 400 IU of vitamin D. The protein came mostly from fish, lean meat, poultry, beans, and dairy foods.
After one year, the high-protein group lost less bone from the hip, spine, and wrist.
"All three are high-risk sites for fracture," notes Shapses, who adds that "I think the results would be even more significant in older people. Fractures don't generally begin until after 70 years of age, so they were still a youngish group for osteoporosis." (The average age was 58.)
"And older people may not eat enough protein," notes Shapses. That can lead to loss of muscle too.
Even the women in her study had trouble getting enough protein.
"Our goal was to have the higher-protein group get 30 percent of their calories from protein, but they only reached 24 percent," says Shapses. They averaged 86 grams of protein a day, while the normal-protein group got 18 percent of their calories from protein, or 60 grams a day.
Shapses' bottom line: "Getting about 25 percent of your calories from protein seems like a good target to reduce bone loss."
5 Eating 3,500 fewer calories doesn't mean you'll lose a pound.
"If you google how many calories are in a pound, you'll get something like 11 million hits, and they all basically say the same thing," explained Kevin Hall at the 2012 annual meeting of the American Association for the Advancement of Science in Vancouver in February.
"They all say there's 3,500 calories in a pound," continued Hall, who is an obesity researcher and physicist at the National Institute of Diabetes and Digestive and Kidney Diseases.
For decades, people have used the 3,500-calorie rule to estimate how much weight they'll lose.
The usual assumption: If you cut, say, 500 calories a day from your diet, said Hall, "then after a week, I'm going to get one pound of weight change, and that will keep going forever." But that's not what happens (see graph). Why?
The 3,500-calorie rule assumes "that there's going to be no change in the number of calories that you're expending," said Hall. In fact, the body starts burning fewer calories as you lose weight. (11)
"The resting metabolic rate drops," Hall noted. Resting metabolic rate--the rate at which your body burns calories to keep you alive at rest--accounts for 60 to 75 percent of the calories that a typical person burns.
When you lose weight, your resting metabolic rate drops because your body thinks you're starving, so it tries to burn fewer calories. And that's not all.
"The physical activity cost also drops," added Hall. That's because your body doesn't need to burn as many calories to move the new, lighter you.
What happens if you don't just cut calories, but get out and walk or run a few miles every day?
"Let's say I start cranking up my physical activity and start burning a lot more calories," said Hall. "In some people, that's going to cause them to eat more, and our model doesn't know how much that's going to be, because in other people, that's going to cause them to eat less."
In carefully controlled studies where people participate in supervised exercise, weight loss varies. The studies "see this large range of weight changes, from people who gain weight ... to people who lose more weight than would be expected," said Hall.
The bottom line: Don't expect to lose weight quickly.
"We have a new weight-loss rule of thumb, which is 10 calories per day per pound of weight change," said Hall. "About half of this weight change will occur after one year and about 95 percent will occur after three years."
So if you want to lose, say, 10 pounds, you have to permanently cut 100 calories a day. After a year you will have lost 5 of the 10 pounds and after three years you will have lost nearly all 10 pounds.
To estimate how long it will take to reach your weight goal, try using Hall's body weight simulator (bwsimulator.niddk.nih.gov).
6 We don't get enough potassium.
How much potassium are you supposed to get? The Recommended Dietary Allowance (RDA) is 4,700 milligrams a day. The average American gets roughly half that much.
And potassium matters. "Many randomized trials have shown that an increase in potassium intake lowers blood pressure," says Graham MacGregor, professor of cardiovascular medicine at the London School of Medicine and Dentistry. (12)
But potassium may do more than help blood pressure.
For four weeks, MacGregor and his colleagues gave an extra 2,500 milligrams of potassium a day or a placebo to 42 people with high blood pressure who were already getting about 2,200 mg of potassium from their food. (13) The participants' arteries were less stiff when they got the extra potassium than when they got the placebo.
People with stiffer arteries have a higher risk of heart attacks, strokes, and memory loss. (See "Keep it Supple," October 2010.)
What's more, they also had less thickening of the heart muscle when they were given potassium. A thicker muscle around the left ventricle--left ventricular hypertrophy--is linked to a higher risk of heart disease. (The left ventricle is the chamber of the heart that pumps oxygen-rich blood throughout the body.)
"High blood pressure and left ventricular hypertrophy are both important risk factors for heart failure," says MacGregor, who heads World Action on Salt and Health, which is working to gradually reduce salt intake in 85 countries.
In a U.S. study of 1,000 healthy young adults without high blood pressure, those who consumed more potassium and less sodium also had less thickening of the heart muscle. (14)
"The best way to increase potassium intake is to increase the consumption of fruits and vegetables," says MacGregor.
Why? Fruits and vegetables have other nutrients that may lower blood pressure, and they displace foods with more saturated fat and cholesterol. The OmniHeart diets, which lowered blood pressure and LDL ("bad") cholesterol, included 11 (half-cup) servings of fruits and vegetables a day. (8)
And don't forget salt. "For the most effective blood pressure control, reduce sodium intake and increase potassium intake," says MacGregor.
7 Don't expect vitamins to prevent cancer.
"With bone & breast health support," says the One A Day Women's Formula multivitamins box.
"Supplementing with [selenium] may decrease your prostate cancer risk," says GNC's Web site. ("GNC provides the information as a service but does not endorse it," notes the site. The information comes from Aisle7, an "integrated wellness marketing" firm that promises to "drive in-store sales." How convenient.)
In fact, few studies have found that multivitamins, selenium, or other supplements prevent cancer. Yet half of all U.S. adults take them.
"Undoubtedly, use is driven by a common belief that supplements can improve health and protect against disease, and that at worst, they are harmless," wrote five cancer researchers in the Journal of the National Cancer Institute in April. (15)
But that belief may be wrong. For example, selenium (200 micrograms a day) raised the risk of squamous cell skin cancer in one trial. (16) And high doses of beta-carotene (33,000 to 50,000 IU a day) raised the risk of lung cancer in heavy smokers in two others. (17)
"Antioxidants may well be a two-edged sword," wrote the researchers, because they "could serve as pro-oxidants or interfere with any of a number of protective processes."
But so far, it appears that most supplements are neither harmful nor helpful.
"For most people, who are basically well nourished, these supplements don't have the role in preventing cancer that people expect," says John Baron, professor of medicine at the University of North Carolina and one of the article's authors.
Granted, the studies testing supplements may have been too short for a disease that can take a decade to develop.
"Trials on vitamin C or E found no benefit after five or six years," notes Baron. "It's conceivable that there's some benefit after a longer period, but it's unlikely."
That's not to say that all supplements are dangerous or useless. In one of Baron's trials, for example, calcium lowered the risk of precancerous colon polyps. (18) And trials are under way to find out if vitamin D can lower the risk of several different cancers.
Just remember: when you see claims that a vitamin "maintains a healthy prostate" or "supports breast health," what it really means is "there's no good evidence that the vitamin lowers the risk of prostate or breast cancer."
8 Omega-6 fats don't cause inflammation.
"The anti-inflammatory diet counteracts the chronic inflammation that is a root cause of many serious diseases that become more frequent after age 60," explains Dr. Andrew Weil's Web site.
"We now know that inflammation also plays a causative role in heart disease, Alzheimer's and Parkinson's diseases," the site adds, "as well as other age-related disorders, including cancer."
One cause of inflammation, says Weil: "Most people consume an excess of omega-6 fatty acids from which the body synthesizes hormones that promote inflammation."
In contrast, he continues, "omega-3 fatty acids have an anti-inflammatory effect and are found in oily fish, walnuts, flax, hemp, and to a smaller degree in soy and canola oils and sea vegetables."
Weil's advice: "Avoid regular safflower and sunflower oils, corn oil, cottonseed oil, and mixed vegetable oils." Instead, he recommends olive or canola oils, which are lower in omega-6 fats than those other oils. (Oddly, he implies that soy oil is largely omega-3s, even though it's much higher in omega-6s.)
Well isn't alone in his criticism of omega-6 fats.
"If you've got too much omega-6, inflammation wins," explains Dr. Mehmet Oz on his Web site. "Not only do you lose the power of the omega-3s ... but you do serious damage to your body."
Only one problem: omega-6 fats don't seem to promote inflammation.
"Eating less omega-6 vegetable oils doesn't matter for two reasons," explains William Harris of the University of South Dakota Sanford School of Medicine.
"First, the body converts so little of the omega-6's linoleic acid into arachidonic acid that its levels don't budge." (Arachidonic is the fatty acid that supposedly leads to inflammation.)
"And second, the body converts arachidonic acid into both pro- and anti-inflammatory compounds, so it can't be pigeonholed as one or the other," adds Harris.
In a recent Swedish study, 61 people with abdominal obesity were fed a diet that got 15 percent of its calories from either saturated fat (butter) or omega-6 fat (sunflower oil). (19) The omega-6 diet had 14 times as much omega-6 as omega-3 fat.
Yet after 10 weeks, the researchers saw no rise in inflammation or in arachidonic acid in either group. What's more, the people eating the omega-6 diet had less liver fat, which suggests that their insulin was working better.
Similar findings led the American Heart Association to caution consumers in 2009 not to cut back on omega-6 oils. (20)
"So far, there is no good evidence that omega-6 fats cause inflammation in people," says Harris, who chaired the panel of scientists who wrote the Heart Association's advice.
"Eating less omega-6 fats is more likely to increase than to decrease the risk of heart disease," adds Harris. One reason: omega-6 fats lower LDL ("bad") cholesterol.
It's still important to get omega-3 fats from fatty fish (like salmon) or, if you're a vegetarian, from DHA pills made from algae or yeast. Omega-3s lower LDL and may also lower the risk of heart disease in other ways. (See "From Sun & Sea," Nov. 2009.)
And don't worry that the omega-6 fats from the soybean oil in most salad dressings, mayonnaise, and restaurant foods cause inflammation.
9 You need to cut calories as you get older.
Still eating the same-size sandwich, plate of pasta, or bowl of cereal that you always have? Maybe that's why your waist is starting to spread out.
"Food lover that I am, the worst part about getting older is that I can't eat as much as I used to without putting on weight," says Marion Nestle, professor of nutrition, food studies, and public health at New York University.
"I hate this," she adds. "But the reality is that bodies change with age in ways that reduce calorie needs."
Resting metabolism--the rate at which we burn calories to keep our lungs, heart, kidneys, brain, and other organs running--starts to drop appreciably at around age 40 in men and age 50 in women.
"Muscle mass is replaced by fat--which burns fewer calories than muscle--and people generally become less active," notes Nestle. Exercise helps, "but some of the change seems to be inevitable," she adds. "I consider this the worst dirty trick about aging."
The only consolation: You're not alone.
"Every postmenopausal woman I know complains about how hard it is to maintain weight," says Nestle. "It's no fun to feel as though you can't even look at food without adding on pounds."
That's one of the topics she addresses in Why Calories Count: From Science to Politics (University of California Press, 2012), her new book co-authored by Malden Nesheim, professor emeritus of nutritional sciences at Cornell University.
"We wrote the book in part to help everyone realize that we are all in this together," says Nestle.
10 Magnesium may lower your risk of diabetes.
Want to avoid type 2 diabetes? Lose extra pounds, exercise daily, and limit sweets, especially sugary drinks. That's no surprise.
But eating more magnesium-rich foods like leafy greens, beans, whole grains, nuts, and wheat bran may also help. Yet many people fall short. A typical woman gets 250 milligrams of magnesium a day, but should get 320 mg. A typical man gets 335 mg, but should get 420 mg.
"We have very consistent evidence from population studies that higher magnesium status is associated with lower risk of type 2 diabetes," says Yiqing Song, assistant professor of medicine at Harvard Medical School.
For example, in a meta-analysis of seven studies that tracked more than 286,000 people for 4 to 17 years, the risk of diabetes was 15 percent lower for each 100 mg a day of magnesium that people reported eating. (21) That's how much you'd get in four slices of whole wheat bread, one cup of beans, a quarter cup of most nuts, half a cup of cooked spinach, or half a cup of Original All-Bran cereal.
Still, questions remain because those studies weren't designed to prove cause-and-effect. Something else about people who eat magnesium-rich foods may lower their risk of diabetes.
So researchers have tried to give people magnesium to see if it lowers their blood sugar or makes their insulin work better.
For example, a recent German study gave either magnesium (365 mg a day) or a placebo to 52 overweight people with insulin resistance. (22) (If you're insulin resistant, your insulin doesn't work efficiently, and you have a higher risk of diabetes and heart disease.)
After six months, the magnesium takers had lower fasting blood sugar levels and less insulin resistance than the placebo takers.
Magnesium hasn't worked in all studies, though. "We have inconsistent results from small trials," says Song.
"But they used different doses and most were short term and tested people who already have diabetes. We'd like to do a larger and longer trial in people who don't have diabetes to see if magnesium supplementation prevents the disease."
How might magnesium keep diabetes at bay? Some enzymes that regulate blood sugar need magnesium to work.
"Magnesium is also anti-inflammatory," says Song. "And its antioxidant function may protect beta-cells."
Diabetes occurs when blood sugar rises because beta-cells in the pancreas can no longer secrete enough insulin.
In the meantime, "we don't have direct and conclusive evidence to recommend that people take magnesium supplements for preventing type 2 diabetes," says Song.
"But it's safe to consume magnesium-rich foods like green leafy vegetables, which are beneficial for many chronic diseases."
(1) CA Cancer J. Clin. 62: 30, 2012.
(2) CA Cancer J. Clin. DOI:10.3322/caac.21142.
(3) www.iom.edu/Reports/2012/The-Role-of-Obesity-in-Cancer-Survival-and- Recurrence.aspx.
(4) Am. J. Epidemiol. 175: 785, 2012.
(5) Health Psych. DOI:10.1037/a0027221, 2012.
(6) www.ers.usda.gov/Data/FoodConsumption/ FoodGuideSpreadsheets.htm#calories.
(7) J. Nutr. 140: 1832, 2010.
(8) JAMA 294: 2455, 2005.
(9) J. Bone Min. Res. 25: 2770, 2010.
(10) J. Bone Min. Res. 26: 1339, 2011.
(11) Lancet 378: 826, 2011.
(12) JAMA 277: 1624, 1997.
(13) Hypertension 55: 681, 2010.
(14) Hypertension 58: 410, 2011.
(15) J. Natl. Cancer Inst. 104: 1, 2012.
(16) J. Natl. Cancer Inst. 95: 1477, 2003.
(17) N. Engl. J. Med. 330: 1029, 1994.
(18) N. Engl. J. Med. 340: 101, 1999.
(19) Am. J. Clin. Nutr. 95: 1003, 2012.
(20) Circulation 119: 902, 2009.
(21) J. Intern. Med. 262: 208, 2007.
(22) Diab. Obes. Metab. 13: 281, 2011.
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|Title Annotation:||on common health myths|
|Publication:||Nutrition Action Healthletter|
|Article Type:||Cover story|
|Date:||Jun 1, 2012|
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