Key Points

  • Many foods commonly thought to be healthy in Japan can cause problems depending on portion, preparation, or contamination.
  • Potential risks include allergies, added sugars, pesticides, anti-nutrients, heavy metals, and imbalanced fatty acids.
  • Simple practical measures—like choosing fermented products, eating whole fruits, rinsing/soaking rice, and favoring smaller fish—can reduce those risks.
  • This article highlights specific items (milk, 100% fruit juice, aojiru, brown rice, hijiki, tuna) and offers safer alternatives and tips.

Introduction: Why "Healthy Foods" Can Sometimes Be Problematic

We tend to easily assume that "traditional foods equal safe and healthy," but due to the impacts of modern production, processing, and environmental pollution, this isn't always the case. In Japan, the perception that "Japanese food is healthy" is particularly strong, which can unintentionally lead to overconsumption or the accumulation of harmful substances. Here, we'll share 10 foods that are commonly consumed on a daily basis, what to watch out for, and tips for making reasonable adjustments. We'll also include some practical measures that our team has actually tried.

10 Foods Often Mistaken as "Healthy" in Japan

1. Milk

For those with lactose intolerance or milk allergies, milk can cause indigestion and inflammation. There are also points raised that low-fat milk isn't necessarily a cure-all, and the benefits and risks of milk are debated by institutions like Harvard Medical School. As an alternative, trying fermented dairy (like yogurt or kefir) or unsweetened plant-based milks can make a noticeable difference. We also noticed our stomachs felt much better after switching to yogurt.

2. White Rice and Brown Rice

Both are high in carbohydrates. White rice can be an issue for blood sugar management, while brown rice raises concerns about phytic acid inhibiting mineral absorption and the accumulation of arsenic from the rice. Practically, you can reduce these risks by mixing in millet, barley, or sprouted brown rice, and by washing and soaking your rice thoroughly.

3. Aojiru (Kale-based Green Juice Powder)

Processed products can sometimes contain added sugars and additives, and pesticide residue can be a concern with kale and spinach. It's also important to keep oxalates and other "anti-nutrients" in mind. Rather than relying on aojiru, we recommend getting a balanced intake of raw and steamed vegetables.

4. Tomatoes (Nightshade Vegetables)

Tomatoes, eggplants, and bell peppers contain compounds called lectins, which can trigger indigestion or inflammation in sensitive individuals. While they aren't a problem for most people, if you're experiencing chronic discomfort, it might be worth temporarily removing them from your diet to see how your body reacts.

5. Tuna and Other Large Fish

Heavy metals like mercury, which concentrate through the food chain, can be a problem. Pregnant women and young children need to be especially careful. By moderately incorporating smaller, fatty fish like sardines and mackerel, you can get your omega-3s while lowering the risks.

6. Soy Products (When Overconsumed)

Soy is a healthy source of protein, but you need to be careful about overconsumption or eating it in an unfermented state due to phytic acid and isoflavones (phytoestrogens). Fermented foods like natto and miso are highly recommended as they are much easier to digest.

7. 100% Fruit Juice

Even though it comes from fruit, it's high in fructose and can be equivalent to sugary soft drinks from a sugar perspective. There's also the issue of pesticide residue. If possible, it's better to eat whole fruits to get the dietary fiber, which helps prevent sudden spikes in blood sugar.

8. Sesame Oil and Other Oils Heavy in Omega-6

Too much omega-6 fatty acid can lead to a tendency for chronic inflammation. Sesame oil is flavorful and easy to use, but it's wise to use it alongside oils like olive oil to maintain a good balance of omega-3 and omega-6.

9. Hijiki (Seaweed)

Hijiki is rich in iron, but it's also known to have a high inorganic arsenic content,