Nutritionists are continually spouting the benefits of foods like tomatoes, avocados and fish, but overdoing it on these healthy foods actually can be harmful.
"Even nutritious food can be too much of a good thing if you eat it in too large a quantity or too often," said Elisa Zied, New York-based dietitian, nutritionist and author of "Younger Next Week." "For one, anything that has calories — even if they're quality calories — can add up if your portion gets too big. Also, if you overdo any one food, you will leave less room for other foods that provide a different mix of nutrients."
Here are some ways to find the right balance so you don't eat too much of a good thing.
Why it's good for you: A major component of the healthful Mediterranean diet, it lowers the risk of heart disease, stroke and high blood pressure because it contains monounsaturated fatty acids (as opposed to saturated fats or trans fats). A study published in Neurology found that older people who regularly consume olive oil have a 41 percent lower risk of stroke compared with those who never consume it. Other studies have found that it helps maintain healthy cholesterol levels, protects against Alzheimer's disease, prevents acute pancreatitis and protects the liver from oxidative stress, in addition to other diseases.
Too much of a good thing: "Because olive oil is looked upon as a healthy fat, people think they should not be concerned about calories," said Andrea Giancoli, a Los Angeles-based registered dietitian and nutrition consultant. "But calories count."
Stick to this: Giancoli recommends sticking to one tablespoon daily, which is 120 calories. If you want more than one tablespoon, you should cut calories in other areas of your diet that day.
Why it's good for you: Agave was promoted as being on the low-glycemic index and doesn't spike your blood sugar like regular sugar does — so it's a good alternative for diabetics. It's also natural.
Too much of a good thing: Agave is mostly fructose, and it has more calories than sugar (1 teaspoon of sugar has 16 calories while 1 teaspoon of agave has 21), Giancoli said. Fructose may increase your risk for heart disease and metabolic syndrome, and it is converted into belly fat faster.
Stick to this: The American Heart Association recommends limiting sweets to 6 teaspoons daily for women and 9 teaspoons for men. Giancoli suggests treating agave like sugar. "If you're not going to put a tablespoon of sugar into your coffee, then don't do this for agave," she said.
Why it's good for you: It's high in monounsaturated fat, which reduces bad cholesterol, lowers your risk of stroke, heart disease and cancer — and may promote a healthy body weight. It also contains about 4 grams of protein and is high in vitamins K, B, C and E.
Too much of a good thing: "Each one also contains 322 calories and 29 grams of fat," said Allison Parker, registered and licensed dietitian for Mariano's, a Roundy's brand grocery story.
Stick to this: Parker has ¼ to 1/3 of a medium avocado as a service of fat in her meals or snacks — essentially using the avocado as a replacement for another fat, like butter or mayonnaise.
Tomato and orange
Why they're good for you: Tomatoes are high in vitamins A, B6, E and K, and they're also a good source of copper, potassium, fiber and phosphorus. Oranges are packed with vitamin C, phytochemicals and flavonoids, which have anti-inflammatory properties — and they are only about 80 calories.
Too much of a good thing: "If you overdose on them, one thing that comes to mind is tooth enamel," Zied said. "Too much acidity can wear it away, so it's good to eat acidic fruits and vegetables for their nutrients and water content but to also choose other options in those categories (for example hard, crunchy fruits like apples, carrots and celery that stimulate the flow of saliva and neutralize the acids in foods that can erode enamel)."
Stick to this: ½ to 1 cup of tomatoes, an orange or a clementine is great per day.
Why they're good for you: Most nuts boast a good dose of monounsaturated fat that, when used to replace saturated fats and trans fats, can reduce blood cholesterol and lower heart disease and stroke risk, Zied said. "Nuts also provide polyunsaturated fats, which are essential fats our bodies need from the diet since it can't make them," Zied said.
Too much of a good thing: They're easy to overdo because they're a concentrated source of calories (a lot of calories in a small portion), Zied said.
Stick to this: 1 ounce of nuts per day — or up to 1 ½ ounces if you can afford the calories. Mix the types of nuts so you get a different mix of nutrients and flavors in your diet. An ounce of almonds is 24 whole almonds or 4 tablespoons chopped. An ounce of walnuts is 14 halves or 4 tablespoons chopped. An ounce of pistachios is 48 pistachios.
Large fish (such as tuna, swordfish or mackerel)
Why it's good for you: It's lean protein and high in B12, vitamin D, calcium and iron. It also has high amounts of omega-3 fatty acids, which have been associated with everything from reducing inflammation and heart disease to warding off depression.
Too much of a good thing: These types of fish contain relatively high levels of mercury, and while this is particularly concerning in pregnant and lactating women, it's not good for anyone to ingest too much mercury, Parker said.
Stick to this: No more than 6 ounces of large fish weekly.
Why it's good for you: This is a great way to get in an extra dose of fruits, vegetables and possibly low-fat dairy.
Too much of a good thing: The calories add up, Parker said. "If you wouldn't eat them all together in one sitting, consider modifying your recipe to incorporate a more realistic service."
Stick to this: 1 cup of spinach, half of a banana and ½ cup assorted frozen berries. You may also add milk or yogurt to increase the protein and provide some added calcium, Parker said.
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