Which foods are good for what

Wheat bran and prunes are good for regularity. But they’re the exceptions. Most foods don’t have a unique feature that prevents or cures disease.

It’s usually not a single food, but a class of foods or an entire diet, that protects against (or promotes) a disease. It’s not just spinach, but all lutein-rich green leafy vegetables, that may protect your eyes. And it’s not just bananas or other potassium-rich foods, but a DASH diet (which is rich in fruits and vegetables and low in saturated fat and added sugars), that may lower your blood pressure.

Here’s what we know about which foods lower (or raise) the risk of some key health problems.

Lowering Cholesterol

“Can help reduce cholesterol,” promise boxes of Honey Nut Cheerios. “Proven to help reduce cholesterol,” claim cartons of Minute Maid Heart Wise Orange Juice.

What gives you the biggest bang for your buck when it comes to lowering LDL (“bad”) cholesterol? Cheerios gets the most air time, but the soluble fiber in oats isn’t exactly Lipitor.

“The soluble fiber in any single food has only a modest impact on LDL cholesterol,” explains Alice Lichtenstein, director of the Cardiovascular Nutrition Laboratory at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University in Boston.

“However, if you’re eating beans, fruits, vegetables, oats, and other foods with soluble fiber instead of burgers, pizza, and shakes, it adds up to a sizeable benefit.”

The plant sterols that are added to some juices, margarines, and yogurts make a bigger dent. “There’s good evidence that they decrease LDL cholesterol levels on average by about 10 percent,” notes Lichtenstein. “That’s very significant. You get maximal lowering with about two grams a day. With three grams a day, you don’t get much more.”

But neither soluble fiber nor plant sterols matters the most. “The important thing is when saturated or trans fat is replaced by unsaturated fat,” says Lichtenstein, who is vice chair of the Expert Panel that is now updating the National Heart, Lung, & Blood Institute’s Clinical Guidelines on the Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults.1

“Polyunsaturated fats win out over monounsaturated fats because they lower LDL a bit more,” explains Lichtenstein. “But that’s fine tuning.”

That means replacing butter with highpoly oils like soybean, corn, and sunfl ower or with high-mono oils like canola, olive, and saffl ower. It also means replacing red meat and cheese with poultry and fish.

However, you don’t want to swap a steak for a high-carb dish like a plate of pasta.

“If you’re going to decrease saturated and trans fat, you don’t want to substitute Carbohydrates, because they can raise triglycerides,” notes Lichtenstein.

When triglycerides go up, HDL (“good”) cholesterol typically goes down. “It’s a sort of ying-yang metabolically,” she says. People with high triglycerides and low HDL have a higher risk of heart disease.2

“Carbohydrates are more likely to raise triglycerides in some people than in others,” adds Lichtenstein. “People who are overweight tend to be more carbsensitive.”

Does that apply to all carbs?

“No one has done the ultimate study,” says Lichtenstein. “People assume that whole grains are not as bad as refined grains, but the literature is very thin.”

In any case, it’s smarter to cut back on sodas, sweets, and refined grains than on healthier carbs.

“You’d hate to see somebody decrease fruits and vegetables, beans, and non-fat dairy because of their carbs,” she says. “But you can prepare the beans with some oil or put salad dressing on vegetables.”

Just don’t get carried away, says Lichtenstein. The key word is “replace.”

“Just pouring some soybean oil over a hot fudge sundae is not going to help,” she cautions. “You need to make sure the oil is replacing an equal number of calories from some other food.”

Otherwise, you’ll gain weight. “That will increase LDL, decrease HDL, prompt insulin resistance, and increase blood pressure,” she points out. “Since the majority of people are already overweight, that’s the last thing you want to do.”

The same holds true for margarine with added sterols. “You can’t just decide, ‘I’m going to use this great margarine to lower my cholesterol, so boy, I can really spread it on,’” she says. “That’s the concern I always have when we say that any food is good for you.”

Nuts are rich in polyunsaturated fats, but they pose the same problem. “People think of them as add-ons, and that’s the way they’re advertised,” says Lichtenstein. “Throw some on your salad, throw them In your yogurt, throw them in your cereal in the morning.”

But just a quarter cup of most nuts has 150 to 230 calories.

“They’re extremely calorie-dense. So pouring some out of a bottle, especially if they’re salted, you have to be very careful.”

What’s worst for your cholesterol? Both saturated and trans fat.

“I’m not willing to say one is worse than the other because the amount of saturated fat you get in foods like meat, cheese, cream, and butter is much higher than the amount of trans you get in partially hydrogenated oils,” says Lichtenstein. “If you directly compared 10 grams of each, the trans fat would be worse, but that’s not what happens in food.”

In recent years, much of the trans fat in supermarket foods has disappeared. But it still shows up in some pie crusts, microwave popcorns, frozen pizzas, biscuits, margarines, and cookies. And it’s still in all the major brands of frosting.

And restaurant foods—from some pastries, pies, and cookies to some fried potatoes, fried chicken, and fried fish—still have trans because there are no Nutrition Facts labels to spill the beans.

“These cupcakes that are popping up in stores may be a good poster child for bad fats,” says Lichtenstein. “It doesn’t matter if they’re made with butter or partially hydrogenated oils. Both are bad.”

And those bad fats come with refined fl our and sugar. “The cupcakes look like they’re half frosting,” she notes. “And they’re a concentrated source of calories.”

Protecting Eyes

What’s good for your eyes is good for the rest of you. “Eat a variety and abundance of colorful plant foods,” advises Julie Mares, professor of ophthalmology at the University of Wisconsin School of Medicine and Public Health.

But what if you had to single out one group of foods? “At the top of my list are dark leafy greens,” says Mares. That means spinach, kale, collards, and Swiss chard. Peas, broccoli, and other green vegetables may also help.

That’s because dark leafy greens are rich in lutein and its cousin, zeaxanthin (see “Seeing Lutein”). “They’re the predominant carotenoids in both the lens and the retina, and specifically in the cone-rich area of the macula,” says Mares. “That’s the part of the retina that’s used to see fine detail, like reading a pill bottle or newspaper.”

Age-related macular degeneration is the major cause of blindness in older people. And the lens is where cataracts form.

“By age 75, half of us will either have a visually significant cataract or have already had one extracted,” says Mares. “It’s the number-one cause of poor vision among people aged 65 to 74.”

A number of studies have found a lower risk of cataracts and advanced macular degeneration in people who consume more lutein and zeaxanthin (see “See Food,” May 2009) .3,4

“There’s strong, compelling evidence for a potential protective effect of these carotenoids,” notes Mares. But it’s not a done deal. Something else in leafy greens could Explain their link to healthy eyes.

“They’re nutritional powerhouses,” explains Mares. “They’ve got gobs of antioxidants.”

Another possibility: “Lutein may be a marker for people who eat healthy plantrich diets,” she suggests. And something else about those diets—or the people who eat them—may explain their lower risk of eye disease.

Second on Mares’s list of possible eye protectors: “I would add oily fish.” That means foods like salmon, sardines, and mackerel.

“There is a strong, consistent body of evidence that people who eat fish of this type are less likely to have macular degeneration,” she notes.5 “People are jumping to the conclusion that it’s their omega-3s that matter, but it may also be other things, like their vitamin D or selenium or both.”

What might boost your risk of cataracts and macular degeneration, other than smoking and excess sunlight?

“Refined sugars and starches,” offers Mares. “The most compelling reason is that they’re strongly associated with poor diets,” she explains. In other words, their empty calories replace nutrientrich foods.

For example, “If you had one 500-calorie Dunkin’ Donuts blueberry muffin a day in place of nutrient-dense foods, the muffin would reduce your lutein and zeaxanthin every day to 75 percent of what it would be otherwise.” You’d also get less of the vitamins and minerals that are in the healthier foods that you gave up.

“It’s not that Refined sugars or white bread are bad,” adds Mares. “It’s that they go along with a reduced intake of many nutrients. So in my mind, they’re anti-vitamins.”

And if you ate the 500-calorie muffin— or bagel or scone or cupcake or whatever —in addition to your ordinary diet, you’d gain weight. “Obesity leads to the infl ammatory and oxidative stress that also increases your risk of eye disease,” says Mares. “That’s absolutely a problem.”

Dodging Colon Cancer

“Milk probably reduces colorectal cancer risk,” concluded the World Cancer Research Fund and the American Institute for Cancer Research in May.6 (The WCRF and AICR periodically convene a panel of scientists to review the scientific evidence on lifestyle and cancer.)

However, they added, “AICR does not make a recommendation to consume more dairy foods because the evidence for overall cancer risk remains unclear.”

Back story: In 2007, the AICR cautioned that diets high in calcium (at least 1,500 milligrams a day) might raise the risk of prostate cancer (see “Dairy: Hero or Villain?” Jul./Aug. 2011). Yet prostate cancer is not a worry for all of us, needless to say. And the evidence on colorectal cancer is consistent.

“Through 2010, 16 of 17 cohort studies found a decreased risk in people with a higher calcium intake,” notes Amanda Cross, an investigator in the Division of Cancer Epidemiology & Genetics at the National Cancer Institute in Bethesda, Maryland.

Similarly, a meta-analysis of 19 studies found a lower risk of colon cancer in people who consume more milk.7 (An 8 oz. Glass of milk has 300 mg of calcium, so people who consume more dairy tend to get more calcium.)

What’s more, when researchers gave calcium (1,200 mg a day) to people with a history of colon polyps—which can turn into tumors—they were 20 percent less likely to get new polyps than similar people who were given a placebo.8 And the calcium takers still had a lower risk of polyps five years after the trial stopped.9

How might milk or calcium protect the colon? “It may lower cell proliferation” In the lining of the colon, says Cross. “Increased proliferation can elevate cancer risk.”

The AICR also decided that “foods containing dietary fiber, such as fruits, vegetables, whole grains and beans, reduce risk of colorectal cancer.” (Note that the statement doesn’t apply to the inulin, maltodextrin, polydextrose, wheat fiber, oat fiber, and other isolated fibers that companies add to foods so that they can make “high fiber” claims.)

However, when the Polyp Prevention Trial told people with a history of colon polyps to eat less fat and more whole grains, beans, fruits, and vegetables, they had no fewer new polyps.10 And in the Wheat Bran Fiber Trial, people who were Told to eat a wheat bran cereal had no fewer new polyps than those who were told to eat a low-fiber cereal.11

“It’s possible that their fiber intake didn’t increase enough,” says Cross. (The wheat bran group ate 28 grams of fiber per day, while the control group ate 18 grams.)

Her research focuses on the potential harm from red meat (beef, pork, and lamb) and processed meats (like ham, bacon, pastrami, salami, hot dogs, and sausages), each of which the AICR calls a “convincing” cause of colon cancer.

“The recommendation from the WCRF and AICR is to limit red meat to 18 ounces per week and to avoid processed meats,” Notes Cross, who was a reviewer for the AICR’s 2011 report.

How might they harm the colon?

“Meat is a source of heterocyclic amines, polycyclic aromatic hydrocarbons, and N-nitroso compounds,” explains Cross. “All have been shown to induce tumors in animal models.”

The first two (HCAs and PAHs) can show up in any meat, poultry, or seafood. “They’re formed when meat is cooked well done by high-temperature methods like barbecuing,” says Cross.

“The N-nitroso compounds are formed in processed meats that are made with nitrites or nitrates,” she adds. “But they can also form within the body after consuming any red meat.”

Red meats are worse than poultry or fish, possibly because meats contain more iron that’s bound to the hemoglobin in blood (see “The Real Cost of Red Meat,” June 2009).12 “Heme iron can increase the formation of N-nitroso compounds,” says Cross.

“If a person eats 3.5 ounces of red meat every day (24.5 ounces per week), their risk of colorectal cancer will be 17 percent higher than someone who eats no red meat,” noted the AICR. Doubling the amount of meat would double the risk. But processed meats are worse.

“If a person eats 3.5 ounces of processed meat every day,” said the AICR, “their risk of colorectal cancer will be 36 percent higher than someone who eats no processed meat.”

Staying Regular

What’s the best food for staying regular?

“Wheat bran is at the top of the list, followed by other brans like rye, corn, and oat,” says Joanne Slavin, professor of food science and nutrition at the University of Minnesota.

That’s because much of the fiber in wheat bran—celluloses and hemicelluloses— survives the trip through your gut. “Probably half is still there at the end,” explains Slavin. “And they bind to water, so they have the most effect on stool weight.”

But all wheat brans are not alike. “The coarser ones increase stool weight more,” says Slavin. “If you grind bran up into Smaller particles, it doesn’t have as much of an effect.”

Stool weight is a better way to gauge a food’s impact on regularity than transit time—the time it takes for food to go from one end of the GI tract to the other.

“Transit time is difficult to measure, and it doesn’t tell you much because most people are in the 24-to-48-hour normal range,” explains Slavin.

After brans come beans. “Beans have far more fiber than fruits or vegetables,” she notes. “Some have 6 or 7 grams of fiber in a half cup.” A serving of most fruits or vegetables has only 2 or 3 grams of fiber. “That’s because they’re mostly water.”

What’s lowest on Slavin’s list?

“White fibers that are purified, like pectin and inulin.” Fiber One Yogurt, Kellogg’s Fiber Plus Bars, and other “high fiber” bars get much of their fiber from inulin.

“The purified fibers are pretty much all broken down by the end,” explains Slavin. “There’s zero fiber left in fecal samples, so they don’t have a big role in increasing stool weight.”

Wheat bran generates 5 grams of fecal weight for every gram of fiber you consume, while oat, corn, and rye bran generate 3 or 4 grams, says Slavin. Fruit and vegetable fiber yields about 2½ grams, but each gram of inulin or pectin yields only about 1 gram of fecal weight.

The isolated fibers “generate some microfl ora that binds to water, but it’s much less than what you get from wheat bran,” says Slavin.

Worse yet, isolated fibers cause more gas. “With wheat bran, some of the fiber is fermented, but it happens slowly throughout the colon,” notes Slavin. “Fibers like inulin are completely broken down really quickly high in the colon, so they cause more intestinal gas and bloating.”

What about those old standbys, prunes and prune juice? “Prunes absolutely work,” says Slavin. In a pilot study she never published, stool Frequency increased in 10 people who consumed either 5 prunes or 6 ounces of prune juice every day. But it’s not just fiber that explains the magic of prunes. Their naturally occurring sugar alcohol sorbitol may also make a difference.

“Sorbitol is a possibility because the sugar alcohols absolutely have an effect on laxation,” explains Slavin. “However, prunes significantly increase fl atulence.”

That would seem to leave wheat bran in the lead. “All-Bran cereal works,” says Slavin. “Psyllium also works.” That’s the fiber in Metamucil and in cereals like Bran Buds.13

“As for food, I’d go with whole grain,” she says. But not foods that are “made with whole grain,” which are mostly white fl our.

That doesn’t mean the sky’s the limit. “Many people are eating whole-grain cookies, cereals, and breads that are high in calories,” notes Slavin. “They aren’t going to get healthier—they’re going to gain weight.”

Her only other caution: “Bran works well for healthy people, but you’d never want to give a bunch of bran to someone who is constipated. There are studies where people take way too much bran, and it gets impacted because nothing moves. You have to deal with the constipation before you get back to fiber. Prevention is better than the cure.”

What’s worst for regularity? Foods don’t have much impact, says Slavin. But “iron supplements—and many medications— are constipating.”

Lowering Blood Pressure

High blood pressure—or hypertension— boosts your odds of having a heart attack or stroke (a “brain attack”). And the odds are that your blood pressure will someday be too high. Among people who still have normal pressure at age 55, nine out of 10 eventually end up with hypertension.

What foods help keep blood pressure in check? “I would emphasize fresh fruits and vegetables that are high in potassium,” says Norman Kaplan, professor of internal medicine at the University of Texas Southwestern Medical Center in Dallas.

Topping the list are green leafy vegetables (like spinach, Swiss chard, and beet greens) and deep orange vegetables (like butternut squash and sweet potatoes). Bananas, cantaloupe, and mushrooms are also potassium-packed. So are fish, beans, milk, and yogurt.

The DASH (Dietary Approaches to Stop Hypertension) diet—which is rich in fruits, vegetables, and low-fat dairy foods but low in saturated fat, added sugars, and refined fl our—is also rich in calcium and magnesium.14 (See “What Should I Eat?” October 2009.)

“But when researchers looked at just calcium or magnesium, they didn’t have much effect on blood pressure,” says Kaplan, whose classic textbook, Kaplan’s Clinical Hypertension, is in its tenth edition.

In contrast, a meta-analysis of 33 studies showed that potassium supplements (2,300 milligrams a day) lowered blood pressure by an average of 3.3 points.15 What’s more, people who consume more potassium-rich foods have a lower risk of stroke.16

How does potassium work? “It’s hard to say for sure, but if you lower potassium levels inside cells experimentally, it makes blood vessels constrict,” explains Kaplan. Stiff, infl exible arteries are a major cause of high blood pressure, especially in older people.

What’s bad for blood pressure is a nobrainer: too much salt. But how?

“Primarily, the mechanism is that sodium expands the volume of blood in the circulation,” says Kaplan. “As volume increases, pressure goes up. When we go on a lower-sodium intake, the overall volume goes down.”

Diuretics lower blood pressure because they lower blood volume. “You can either take less sodium in or take a drug that increases the excretion of sodium,” says Kaplan.

And swallowing less sodium isn’t a matter of which foods, but how they’re prepared. “There are no natural foods that are high in sodium,” notes Kaplan.

“If we stay away from processed foods, we could achieve a lower-sodium intake without going to a lot of trouble.”