Get more fiber. Eat fish for omega-3s. While following diet advice like this can improve your health, some folks get carried away.

"The belief that if some is good, more must be better is pretty common," says Maxine Siegel, R.D., who heads Consumer Reports' food-testing department. "But the truth is, there absolutely are nutrients and healthy foods you can overdo."

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In some cases, the fallout is relatively minor. For example, some orange fruits and vegetables can turn your skin a little orange if you eat too much of them. But it's a harmless side effect that will go away when you ease up on the carrots and pumpkin. It’s a result of the beta-carotene and other carotenoids that give them their rich color; those crucial antioxidants help your body make vitamin A.

But sometimes too much of a beneficial nutrient can be dangerous. For example, getting too much vitamin A from supplements (which most people should skip unless a doctor recommends them) can damage your liver, weaken bones, and cause birth defects.

When it comes to food, people tend to get themselves into trouble in one of three ways. The first mistake is focusing on too few foods or food groups and missing the essential nutrients that come with variety. The second and third mistakes are eating too many fortified foods and just eating too much, period. Even good-for-you foods can have plenty of calories. Here, then, are five things that are easy to go overboard on and why that’s a problem:

Protein

Sources: Meat, fish, poultry, eggs, legumes, tofu, nuts, and dairy, plus fortified foods, powders, drinks, and bars.

What happens if you overdo it: It can strain your kidneys, especially if they're already compromised because of kidney disease, and can also leech calcium from your bones. A big problem is fortified bars and drinks that contain far more protein than your body can use.

How to get the right amount: Adults need 0.4 grams of protein per pound of body weight per day. If you weigh 160 pounds, that’s 64 grams. To help prevent the muscle loss that naturally occurs with age, people 60 and older should get 0.6 grams per pound. And for weight loss, some research shows that 0.7 grams per pound is beneficial. Still, when you consider that a sandwich with 3 ounces of chicken and an 8-ounce glass of milk have about 40 grams, it’s easy to see why many of us get too much. For most people, three servings of protein-rich foods daily are plenty. Muscles need protein to recover from exercise, but unless you’re a pro athlete, you don’t need special muscle-building products, such as protein powders. Try half a turkey sandwich or an apple with a tablespoon of peanut butter. 

Fiber

Sources: Fruit, vegetables, nuts, beans, legumes, oats, and whole grains, plus fortified foods and supplements.

What happens if you overdo it: Fiber is important for good digestion, but too much can keep your body from properly absorbing minerals such as iron, zinc, magnesium, and calcium. The most common problems people have with fiber are gas, bloating, and diarrhea, and they often strike when you suddenly up your intake. Inulin, a kind of fiber made from chicory, is often used to fortify foods. It’s more likely to cause tummy trouble than natural fiber.

How to get the right amount: Aim for 25 to 30 grams daily. If you’re falling short, you can safely boost your intake without side effects by gradually adding more natural fiber sources. They’re the best because they have soluble and insoluble fiber as well as other nutrients. It’s not clear that synthetically fortified foods such as fiber-rich white bread have the same health benefits. 

Fish

Sources: The biggest risks come from eating too much of certain kinds of fish: king mackerel, shark, swordfish, tilefish, and albacore tuna.

What happens if you overdo it: You could be exposed to potentially high levels of a toxic kind of mercury. Even low-level exposure in pregnant women and young kids has been linked to problems with hearing, coordination, and learning ability. In adults, eating high-mercury fish too often might affect the nerves, heart, and immune system.

How to get the right amount: To consume a healthy dose of omega-3 fatty acids without too much mercury, stick with clams, oysters, pollock, Alaskan or wild-caught salmon (including canned), sardines, shrimp, and tilapia. Women of childbearing age and kids should eat certain fish less often.

Dried Fruit

Sources: In addition to apricots, prunes, and raisins, supermarkets now carry a wide variety. You can find dried boysenberries, guava, mango, and more.

What happens if you overdo it: The concentrated dose of fiber and fructose, the form of sugar found in dried fruits, can cause gas and bloating. Dried fruits are also high in sugar (and calories!) and can stick to your teeth, which can lead to decay.

How to get the right amount: Stick to small servings. Two tablespoons of dried cherries or blueberries, 1½ dried figs, or three dates contain about 70 calories each. Brush your teeth after snacking or at least drink some water.

Nuts

Sources: In addition to whole nuts and nut butters, they show up in all kinds of foods, including cereal, cookies, crackers, and ice cream.

What happens if you overdo it: You can pack on the pounds. The good news is that nuts probably don’t contribute as many calories as once thought, perhaps because some of their fat and calories aren't absorbed, according to recent research. But they're still calorie-dense. A 1-ounce serving of almonds (20 to 25 nuts), for example, has 129 calories.

How to get the right amount: Portion control helps. Put nuts into ¼-cup servings for snacking. A little nut flavor goes a long way. Try chopping nuts and toasting them for a few minutes in a nonstick skillet to bring out extra flavor before adding them to your dishes.