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8 Healthy Foods That Can Be Risky in Excess

Close up of broccoli florets

Most people know that foods high in calories, sugar and unhealthy fats can increase the risk of obesity, heart disease and diabetes. But did you know that some healthy foods can also be harmful in larger amounts?

“It’s true,” says Jacob Wolf, LAc, a naturopathic doctor at University Hospitals Connor Whole Health. “When developing a healthy diet plan, it’s important to remember that more of a good thing is not necessarily better.”

Here are eight foods to consume in moderation:

  1. Broccoli & Other Cruciferous Vegetables

    Cruciferous vegetables such as broccoli, cauliflower, Brussels sprouts, kale, cabbage and bok choy are packed with nutrients and help protect against cancer and heart disease. However, they also contain chemical compounds called thiocyanates.

    “When consumed in very large amounts, thiocyanates can block or limit the body’s ability to absorb iodine, a mineral found in some foods,” says Dr. Wolf. “The body needs iodine to produce thyroid hormones, which regulate many functions including metabolism, growth and energy use.” If iodine levels are too low, it can lead to or aggravate an underactive thyroid gland or hypothyroidism.

    If you have a thyroid disorder, limit your intake of cruciferous vegetables to 2-3 cups per week, including those used in smoothies. “Sensitive individuals can further lower their risk by steaming, roasting or sautéing cruciferous veggies to reduce the compounds that affect thyroid function,” suggests Dr. Wolf.

  2. Cinnamon

    Cinnamon is high in antioxidants and may help fight inflammation and lower blood sugar levels. Some studies show it reduces the risk of heart disease, diabetes and cancer.

    “Cinnamon is delicious and healthy when used in moderation,” says Dr. Wolf. “However, it contains a chemical compound called coumarin, which can cause liver toxicity at high amounts. Some studies also suggest high doses of coumarin can increase cancer risk.” Fortunately, cinnamon is typically used in small quantities. If possible, choose Ceylon cinnamon over the more common Cassia cinnamon, which contains higher levels of coumarin.

  3. Coffee

    Coffee, in general is a very healthy beverage. It’s full of antioxidants and other compounds that lower the risk of liver disease, type 2 diabetes and neurological diseases.

    “As most people know, regular coffee contains caffeine, a stimulant that can cause insomnia, irritability, muscle tremors and heart palpitations if taken in excess,” says Dr. Wolf. “A maximum of 3-4 cups of coffee a day is generally safe, but some people are more sensitive to the side effects of caffeine. For optimal health benefits, coffee is best enjoyed without added sweeteners or cream.”

  4. Liver

    Organs meats like liver are rich in iron, B vitamins and choline. However, the high nutrient density means you should avoid eating organ meats too often.

    “One 3-4 ounce serving of beef liver contains over six times the recommended daily allowance (RDA) of vitamin A, a fat-soluble vitamin that is stored in the body. Too much vitamin A can cause vision problems, bone pain, nausea and an increased risk of fractures. A serving of liver also contains seven times the RDA of copper. Consuming too much copper can lead to neurodegenerative changes and an increased risk of Alzheimer’s disease,” says Dr. Wolf.

    “Liver should not be eaten daily,” he adds. “One serving per week provides all the nutritional benefits without the risks.”

  5. Nutmeg

    Like cinnamon, nutmeg is a popular spice rich in antioxidants and safe when ingested in small amounts. In large doses, nutmeg contains a psychoactive compound called myristicin, which can be toxic.

    Symptoms of myristicin poisoning include seizures, irregular heartbeat, nausea, dizziness and hallucinations. Dr. Wolf recommends that nutmeg be used according to specified recipe amounts to avoid toxicity and serious side effects.

  6. Nuts

    Nuts and seeds are healthy when eaten in moderation to replace other snack foods like chips and sweets. An optimal daily snack is typically 1-2 ounces with one notable exception – Brazil nuts. They can produce toxic effects after eating just a few nuts.

    “Just one Brazil nut contains up to 95 micrograms of selenium, an essential trace element,” says Dr. Wolf. “The daily recommended amount of selenium is 50-70 micrograms. And the upper safe limit is about 300 micrograms per day for adults, or 3-4 Brazil nuts.” Symptoms of selenium toxicity can include hair loss, digestive problems and memory difficulties, so Brazil nuts should only be enjoyed occasionally and in very small quantities.

  7. Omega-3 Supplements

    Omega-3 fatty acids are anti-inflammatory, support brain health and reduce the risk of heart disease. Food sources include flaxseed oil, fatty fish (salmon, mackerel, sardines & trout) and walnuts. However, many people prefer omega-3 supplements.

    “It’s important to watch your dosage if you take a supplement,” says Dr. Wolf. “Too much omega-3 can thin the blood and increase the risk of bleeding. This is particularly true for people already taking blood thinners.”

    Omega-3 supplements made from cod liver oil also contain high levels of vitamin A, which can be toxic in large amounts. Dr. Wolf recommends you ask your healthcare provider if omega-3 supplements are appropriate for you and how much you can safely take.

  8. Tuna

    Tuna is a good source of omega-3 fatty acids and protein. However, because of ocean pollution, tuna may contain high levels of toxins, including methylmercury, which can cause developmental delays in children, vision problems, lack of coordination and impaired hearing and speech.

    Canned tuna is typically a healthier option than large, fresh tuna streaks or sushi. And be sure to choose light, not white canned tuna. It contains much less mercury than other types of tuna.

    “I recommend that pregnant women and children eat little to no tuna.” says Dr. Wolf. “Other nutritious fish options include fresh or canned salmon, mackerel, sardines and trout which are less likely to be contaminated with mercury.”

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The clinical dietitians and whole-health practitioners at University Hospitals can help you develop an eating plan that is both nutritious and safe for your whole family.