There are many super healthy foods out there.
However, it’s important to keep in mind that more is not always better.
Some foods can be good for you in moderation, but seriously harmful in large amounts.
Here are 8 incredibly healthy foods that can harm you if you eat too much of them.
1. Omega-3 and Fish Oils
Omega-3 fatty acids are essential for our health.
They fight inflammation in the body, play an important role in brain development and reduce the risk of heart disease, to name a few (1, 2, 3).
Since most diets are low in omega-3, supplements have been gaining popularity (4).
The most common supplements include omega-3 capsules produced from fish, fish liver and algae.
However, too much omega-3 may be harmful. The usual dose ranges from 1–6 grams per day, but taking as much as 13–14 grams per day may have blood-thinning effects in healthy individuals (5, 6).
This may be risk, especially for people who are prone to bleeding or are taking blood-thinning medications (7).
Furthermore, taking high amounts of fish liver oil may result in excessive vitamin A intake, which may cause vitamin A toxicity. This is of particular concern for children and pregnant women (8, 9).
Bottom Line: Omega-3 fatty acids are essential for good health. However, excess omega-3 may have blood-thinning effects. Fish oil is also very high in vitamin A, which can be dangerous in large amounts.
2. Tuna (Both Fresh and Canned)
Tuna is a fatty fish that is usually considered to be very healthy. It is a good source of omega-3 fatty acids and is very high in protein.
However, tuna may also contain high levels of an environmental pollutant called methylmercury (10).
At higher levels, methylmercury is a neurological toxin that may cause many adverse health effects. These include developmental delays in children, vision problems, lack of coordination and impaired hearing and speech (11,12).
Large tuna fish contain the most mercury, since it builds up in their tissues over time. These big tunas are very likely to be served to you as premium fish steaks or used in sushi.
Smaller tunas contain lower amounts of mercury, and are more likely to be canned.
There are two main types of canned tuna, and their mercury content differs (13, 14):
- White tuna: Light in color and usually comes from albacore fish. White tuna contains 4–5 times the amount of mercury found in light tuna.
- Light tuna: Light tuna contains much less mercury than white tuna. It is darker in color and usually doesn’t come from albacore fish.
The upper safety limit of methylmercury for humans is 0.1 micrograms per kilogram of body weight.
This means that a 25 kg (55 lb) child could only eat one 75 g (2.6 oz) serving of canned, white tuna every 19 days. Any more than this would exceed the recommended upper limit (13).
Pregnant women and children are advised to limit their intake of seafood containing mercury to no more than two times per week (15).
There are several other types of fish that are also rich in omega-3 fatty acids, but less likely to be contaminated with mercury. These include salmon, mackerel, sardines and trout.
Bottom Line: Tuna contains many important nutrients. However, it may also be contaminated with methylmercury due to pollution of the oceans.
3. Cinnamon
Cinnamon is a delicious, widely-used spice that may have some medicinal properties.
It is high in antioxidants and has been shown to fight inflammation and lower blood sugar levels. Eating cinnamon has also been linked to a reduced risk of heart disease, diabetes, cancer and neurodegenerative diseases (16, 17, 18, 19, 20).
However, cinnamon contains high amounts of a compound called coumarin, which may be harmful in large doses.
There are two main types of cinnamon, with different amounts of coumarin (21, 22,23, 24):
- Cassia: Also known as regular cinnamon, Cassia cinnamon contains a relatively high amount of coumarin.
- Ceylon: Known as the true cinnamon, Ceylon is the less common of the two. It is much lower in coumarin.
The tolerable daily intake of coumarin is 0.1 mg per kg of body weight. Consuming much more than that may cause liver toxicity and cancer (25).
Based on the tolerable daily intake, it is not recommended to consume more than 0.5–2 grams of Cassia cinnamon each day. However, you can eat up to 5 grams (1 teaspoon) of Ceylon cinnamon per day.
Eating more than that is fine occasionally, such as if a certain recipe calls for it. But large amounts should not be eaten too frequently.
Ceylon cinnamon is available in many health food stores, and there is also a broad selection on Amazon.
Bottom Line: Cinnamon is antioxidant-rich and linked to several health benefits. Yet it also contains coumarin, which may be harmful in large doses. Of the two types of cinnamon, Ceylon cinnamon contains less coumarin.
4. Nutmeg
Nutmeg is a spice with a very unique taste. It is often used in Christmas foods like eggnog, cakes and puddings.
Nutmeg contains a compound called myristicin, which is a psychoactive substance.
In lower doses, nutmeg provides flavor to meals without affecting health. But in large doses, nutmeg may cause myristicin poisoning.
The effects of myristicin poisoning include seizures, heart arrhythmias, nausea, dizziness, pain and hallucinations (26, 27).
Eating more than 10 grams of nutmeg in one sitting is not recommended. Higher doses than that have been shown to cause symptoms of toxicity (28).
Bottom Line: Nutmeg is used to flavor many foods. In low doses, it does not affect health. However, nutmeg contains myristicin, which can cause poisoning in large doses.
