Getting enough? What-you don't eat can hurt you.
Too much sugar. Too much salt. Too much saturated fat. We eat too much of all three. And we eat too much, period.
Yet we also eat too little.
Many Americans fall short of the recommended intakes of a handful of nutrients. Several key players--potassium, magnesium, vitamin D, and vitamin B-12--may make or break your risk of high blood pressure, diabetes, and brittle bones. For some of those nutrients, only foods--not pills--can make up the shortfall. For others, only a pill will do.
Here's why and how to get the nutrients you may be missing.
Here are four key nutrients you may lack--and where to get them.
The numbers are staggering:
* One in three adults in the United States has high blood pressure, or hypertension. Among those over 65, it's two out of three. And another one out of four adults has pre-hypertension.
* Of the 74.5 million Americans with hypertension, 56 percent don't have it under control. That includes 22 percent who don't even know they have it.
* Roughly three out of four people who suffer a stroke, a heart attack, or congestive heart failure have hypertension.
Too much salt, too much weight, too little exercise, too much alcohol, and other risk factors can raise blood pressure. Potassium can trim it.
"It's absolutely clear that potassium can lower blood pressure," says Frank Sacks, professor of cardiovascular disease prevention at the Harvard School of Public Health in Boston.
In 1988, the INTERSALT study of 52 large populations reported that people with higher potassium intakes had lower blood pressures. (1) By 1997, a meta-analysis of 33 studies found that potassium supplements (2,300 milligrams a day) lowered systolic blood pressure by an average of 3.3 points. (2) (Systolic pressure is the higher of the two blood pressure numbers.)
"That meta-analysis conclusively showed that potassium supplements reduce blood pressure," says Lydia Bazzano, assistant professor of epidemiology at the Tulane School of Public Health in New Orleans.
In animal studies, potassium protects rats from stroke. (3) "And in human population studies, low potassium is a predictor for stroke," adds Sacks.
For example, in a study that tracked 43,000 men for eight years, those who consumed the most potassium (4,300 mg a day) were 38 percent less likely to suffer a stroke than those who consumed the least (2,400 mg a day). (4)
Potassium matters because it seems to counter the damage caused by sodium. "If people are eating high amounts of sodium, potassium will lower blood pressure more," explains Sacks. "The higher the sodium, the more potassium helps."
And when researchers tracked 2,275 participants in the Trials of Hypertension Prevention for 10 to 15 years, they found that the risk of heart attack or stroke depended more on potassium and sodium than on either one alone. (5)
Scientists aren't sure exactly how potassium lowers blood pressure. Among the possibilities: it makes the larger blood vessels more flexible. (6)
"The flexibility of the big arteries like the aorta or carotid arteries is very important in maintaining a nice, lower, youthful blood pressure," explains Sacks. "In older people, arteries are less elastic." And that boosts blood pressure.
Potassium may also lower blood pressure by dilating the small blood vessels. (6) "You don't want the tiny vessels clenched," says Sacks. "Resistance to blood flow will increase blood pressure."
What's clear is that a healthy, potassium-rich diet can revitalize arteries, big or small. "Conditions we thought were permanent with age can be reversed in four weeks," says Sacks. "Four weeks of a lower-sodium, potassium-rich DASH diet completely reverses the effect of age on blood pressure."
A DASH (Dietary Approaches to Stop Hypertension) diet is rich in potassium, thanks to 11 (modest) servings a day of fruits and vegetables, with two servings of low-fat dairy foods, and with low levels of saturated fat, added sugars, and refined flour (see p. 7).
"Potassium may account for half of the effect of the overall DASH diet," says Sacks.
The citrate that's usually bound to the potassium in fruits and vegetables could also help. Potassium citrate lowers blood pressure more than the potassium chloride that is in some salt substitutes, supplements, and potassium-fortified foods. (7)
Another reason to get potassium from food: high-dose potassium supplements--far more than the amounts that occur naturally in food--can be hazardous.
"If you have kidney disease and don't know it, you could potentially end up with too much potassium in your blood, and that's life-threatening," explains Bazzano. "It can stop your heart."
Bonus: getting potassium citrate from fruits and vegetables may prevent kidney stones.
In the Health Professionals Follow-Up Study of more than 45,000 men, those who consumed the most potassium (about 4,300 mg a day) had roughly half the risk of kidney stones over 14 years of those who ate the least (roughly 2,700 mg). (8)
"If you eat more fruits and vegetables, your urine citrate goes up, and that should reduce the risk of kidney stones," says study coauthor Gary Curhan, associate professor of epidemiology at the Harvard School of Public Health.
"But it's probably the citrate or some other alkali, not the potassium."
How does citrate prevent kidney stones?
"It forms soluble complexes with calcium, so it keeps the calcium from sticking to oxalate or phosphate," says Curhan. "So it's less likely that oxalate or phosphate crystals will form."
Preventing calcium oxalate crystals is key. "More than 80 percent of kidney stones are made of calcium oxalate," says Curhan.
And there may be a bonus for bones, he adds. "Citrate should reduce urine calcium excretion as well."
Scientists used to think that potassium could lower the risk of osteoporosis, but no longer.
"Potassium isn't the key to bone health," says Bess Dawson-Hughes, director of the Bone Metabolism Laboratory at the Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging at Tufts University in Boston. "It's the alkaline accompaniment of potassium that's good."
The Bottom Line
Whether it's blood pressure, stones, or bones you're worried about, the message is clear: "Eat potassium-rich fruits and vegetables like you'd get in a DASH diet," says Tulane's Lydia Bazzano.
Osteoporosis, or brittle bones, takes a huge toll on the public's health:
* One in two women and one in four men over age 50 will break a bone because of osteoporosis. (9)
* Osteoporosis caused more than 2 million fractures in 2005, including roughly 297,000 hip fractures, 547,000 spine fractures, 397,000 wrist fractures, 135,000 pelvic fractures, and 675,000 fractures at other sites.
* Half of all women and 30 percent of all men over 50 have osteopenia (low bone mass) in their hips, which often leads to osteoporosis. (10)
* Six months after a hip fracture, only 15 percent of patients can walk across a room without help.
If you ask people how to strengthen bones, the nutrient they're most likely to mention is calcium. But, in fact, average calcium intakes are now close to the recommended levels, in part because 43 percent of Americans get some calcium from a supplement. (11)
What many people don't know is that calcium may not prevent fractures if you don't get enough vitamin D, which helps the body absorb calcium.
"It's looking like the combination of calcium and vitamin D is effective," says Tufts' Bess Dawson-Hughes.
In a 2007 meta-analysis, calcium supplements alone didn't lower the risk of fractures. (12)
"But when you look at calcium plus vitamin D, the risk reduction was significant," says Dawson-Hughes. "So we should absolutely aim for the recommended levels of both."
Calcium plus D could also protect young bones. In a study of 3,700 young female U.S. Navy recruits, those who were given calcium (2,000 mg a day) and vitamin D (800 IU a day) were 20 percent less likely to be diagnosed with stress fractures during eight weeks of training than those who got a placebo. (13)
How much vitamin D is enough?
"My interpretation of current evidence is that our blood levels should not be lower than 30 nanograms per milliliter," says Dawson-Hughes. "If you look at data from the National Health and Nutrition Examination Survey, about 70 percent of older adult men and women were lower than that."
To reach adequate blood levels, most older people need more vitamin D than is now recommended (400 IU a day from age 51 to 70, and 600 IU over 70).
"The vast majority of the older global population would need 800 to 1,000 units of vitamin D a day," from food or a supplement, explains Dawson-Hughes. She led a group of experts who came up with new guidelines for the International Osteoporosis Foundation. (14)
"And high-risk older people--those who have no effective sun exposure or don't absorb vitamin D well or who have very dark skin or osteoporosis--would need more than 800 to 1,000 units a day to get to desired serum levels," she adds.
It's tough to get even 800 IU of vitamin D from foods. A cup of milk is fortified with only 100 IU, and a tablespoon of fortified margarine has 60 IU. Unless you eat fish like red salmon (800 IU per 3 oz. of cooked fish) almost every day, you won't reach those levels.
Getting enough vitamin D may protect more than bones. Evidence suggests that it may lower the risk of colon cancer, heart attacks, stroke, Type 2 diabetes, falls, and some autoimmune diseases (see cover story, Nov. 2009).
And a 2007 meta-analysis of 18 trials found a 7 percent lower risk of dying over six months to seven years when people were given vita min D (usually to reduce the risk of bone fractures). (15)
However, a recent study raised the possibility that high blood levels of vitamin D could increase the risk of pancreatic cancer. (16) The higher risk was only seen in people from states with low sun exposure (Michigan, Minnesota, and Wisconsin, in this study), and it wasn't linked to how much vitamin D people were getting from supplements, so it's somewhat of a mystery.
"The government has funded a huge vitamin D intervention trial giving people 2,000 IU a day or a placebo," says Dawson-Hughes. "So that will give us more information."
(Most women over 65 or men over 60 are eligible to join the VITAL trial, which is also testing fish oil. If you're interested, call 1-800-388-3963 or go to vitalstudy.org.)
"We're looking at cancer, heart disease, stroke, diabetes, high blood pressure, vision, bone density, memory loss, depression, and autoimmune outcomes," says JoAnn Manson, a professor of medicine at the Harvard Medical School who is leading the trial.
Too much calcium without vitamin D may also pose a risk. In July, British researchers reported that high doses of calcium from supplements--l,000 mg a day in most cases--without vitamin D raised the risk of heart attacks, but only in people who were already getting more than 800 mg of calcium from food. (17) (The average adult gets 1,000 to 1,200 mg of calcium a day from foods and supplements combined. (11))
"I would not go a whole lot above the recommended intake because it adds no value and could be adding risk," says Dawson-Hughes. (The researchers didn't look at people who were given calcium plus vitamin D, citing evidence that vitamin D would lower death rates.)
The Bottom Line
Shoot for 800 to 1,000 IU of vitamin D a day from foods and supplements if you're over 60, and 400 IU a day if you're younger. Shoot for 1,200 mg of calcium a day from food and supplements if you're over 50, and 1,000 mg a day if you're a younger adult.
An estimated 23.6 million Americans--including one out of four people aged 60 or older--have Type 2 diabetes. Roughly 5.7 million of them don't know it. And 57 million others have pre-diabetes.
The disease takes a heavy toll:
* Adults with diabetes are two to four times more likely than others to have a stroke or to die of heart disease.
* Diabetes is the leading cause of new cases of blindness among people 20 to 74 and the leading cause of kidney failure.
* More than 60 percent of people with diabetes have nervous system damage.
* Each year, about 70,000 Americans with diabetes have a foot or leg amputated. (18)
Type I diabetes, which typically strikes in childhood, occurs when the body's immune system destroys beta-cells in the pancreas that make insulin, the hormone that controls blood sugar levels. Type 1 accounts for 5 to 10 percent of diabetes cases.
In Type 2 diabetes (which this article will refer to simply as "diabetes"), the body's cells don't use insulin properly. As the need for insulin rises, the pancreas gradually loses its ability to make enough, and blood sugar levels climb.
What causes diabetes?
Extra pounds are by far the biggest risk factor. Genes, lack of exercise, and diet also play a role. Whole grains, fiber-rich foods, and coffee (decal or regular) seem to lower the risk. Sugar-sweetened beverages, processed meats, and white potatoes seem to raise it.
One nutrient that often gets overlooked: magnesium.
"We have a lot of evidence from observational studies that magnesium is beneficial for preventing Type 2 diabetes,"
Potassium on Tape If you're like 90 percent of men and 99 percent of women, you get less potassium than experts recommend (4,700 mg a day). Go for fruits and vegetables so you can eat bigger servings --these are small-without piling on calories. Potassium Calories % IOM * Clams (4 oz. cooked) 170 15 Beet greens (1/2 cup cooked) 20 14 Yellowfin tuna or Halibut (4 oz. cooked) 160 14 Pacific cod (4 oz. cooked) 120 12 Non-fat or Low-fat plain yogurt (8 Oz.) 135 12 Swiss chard (1/2 cup cooked) 20 10 Acorn squash (1/2 cup cooked) 55 10 Sweet potato with skin (1/2 cup cooked) 90 10 Lima beans (1/2 cup cooked) 110 10 Edamame, shelled (1/2 cup cooked) 130 10 Wild Coho salmon (4 oz. cooked) 160 10 Spinach (1/2 cup cooked) 20 9 Tomato sauce (1/2 cup) 30 9 Banana (1) 105 9 Orange juice (1 cup) 120 9 Low-fat fruit yogurt (8 oz.) 225 9 Farmed Atlantic salmon (4 oz. cooked) 235 9 Cantaloupe (1/4) 45 8 Dried apricots (1/4 cup) 80 8 Non-fat or Low-fat milk (1 cup) 90 8 Kidney beans or Lentils (1/2 cup cooked) 115 8 Avocado (1/2 cup) 120 8 Navy or Pinto beans (1/2 cup cooked) 125 8 Tomato paste (2 Tbs.) 25 7 Baked potato with skin (1/2 cup cooked) 55 7 Great Northern beans (1/2 cup cooked) 105 7 Prunes (1/4 cup) 105 7 Pistachios (1/4 cup) 180 7 Tomato (1) 20 6 Beets (1/2 cup cooked) 35 6 Butternut squash (1/2 cup cooked) 40 6 Peach or Nectarine (1) 60 6 Raisins (1 cup) 110 6 Brussels sprouts (1/2 cup cooked) 30 5 Artichoke hearts (1/2 cup cooked) 45 5 Spinach (1 cup raw) 5 4 Grapes (1 cup) 60 4 Apple (1) 95 4 Boston or Romaine lettuce (1 cup raw) 10 3 * Percent of the daily intake (4,700 milligrams) recommended by the Institute of Medicine (IOM). Sources: USDA and manufacturers. Chart compiled by Amy Ramsay, Danielle Hazard, and Melissa Pryputniewicz. A Mouthful of Magnesium 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. The Daily Value (DV) is 400 mg. Here's how to get more magnesium without overdoing the calories. Magnesium Calories % DV * Pumpkin seed kernels 1/4 cup) 170 41 Brazil nuts (1/4 cup) 220 31 Halibut (4 oz. cooked) 160 30 Kellogg's Original All-Bran cereal (1/2 cup) 80 25 Almonds (1/4 cup) 205 25 Cashews (1/4 cup) 195 22 Spinach (1/2 cup cooked) 20 20 Swiss chard (1/2 cup cooked) 20 19 Soybeans (1/2 cup cooked) 150 19 Yellowfin tuna (4 oz. cooked) 160 18 Lima beans (1/2 cup cooked) 105 16 Quinoa (1/2 cup cooked) 110 15 Black beans (1/2 cup cooked) 115 15 Dark chocolate (1.4 oz.) 220 15 Haddock (4 oz. cooked) 125 14 Peanuts (1/4 cup) or Peanut butter (2 Tbs.) 195 14 Hazelnuts (1/4 cup) 210 14 Beet greens (1/2 cup cooked) 20 12 Okra (1/2 cup cooked) 25 12 Black-eyed peas (1/2 cup cooked) 100 12 Navy beans (1/2 cup cooked) 125 12 Semisweet chocolate (1.4 oz.) 190 12 Walnuts (1/2 cup) 195 12 Oat bran (1/2 cup cooked) 45 11 Great Northern beans (1/2 cup cooked) 105 11 Kidney or Pinto beans (1/2 cup cooked) 115 11 Non-fat plain yogurt (8 oz.) 125 11 Brown rice or Lentils (1/4 cup cooked) 110 10 Garbanzo beans (1/4 cup cooked) 135 10 Low-fat plain yogurt (8 oz.) 145 10 Sunflower seed kernels (1/4 cup) 190 10 Tofu (1/2 cup raw) 95 9 Pistachios (V4 cup) 175 9 Oatmeal (1/2 cup cooked) 85 8 Post Original Shredded Wheat (1/2 cup) 85 8 Canned light tuna in water (4 oz.) 130 8 Low-fat fruit yogurt (8 oz.) 225 8 Bulgur (1/2 cup cooked) 75 7 Non-fat milk (1 cup) 85 7 Spinach (1 cup raw) 5 6 Whole wheat bread (1 slice, 1 oz.) 70 6 * Percent of the Daily Value (400 milligrams). Sources: USDA and manufacturers. Chart compiled by Amy Ramsay, Danielle Hazard, and Melissa Pryputniewicz.