What is Nickel and Why is it in Food?
Nickel is a naturally occurring metallic element found throughout the environment, including in soil and water. Because plants absorb nutrients and elements from the soil as they grow, nickel ends up in a wide variety of foods. While the nickel content of food can vary based on the specific soil composition and the environment, some food types consistently contain higher levels than others.
For most people, ingesting trace amounts of nickel poses no health risk. However, a significant portion of the population has a nickel allergy, and for these individuals, dietary nickel can trigger symptoms like dermatitis, eczema flare-ups, and gastrointestinal issues. Following a low-nickel diet is a common strategy to manage these symptoms.
The Foods Highest in Nickel
Certain food categories are well-documented to contain higher levels of nickel, making them key items to monitor for those with a sensitivity.
Legumes and Pulses
- Soybeans and Soy Products: This includes tofu, soy milk, and fermented soybean paste.
- Beans: Canned and dried varieties of black beans, red kidney beans, chickpeas, and haricot beans are known to be high in nickel.
- Lentils and Peas: Both fresh and dried lentils and peas can have elevated nickel levels.
Nuts and Seeds
- Nuts: Almonds, walnuts, hazelnuts, cashews, and peanuts are all noted for their high nickel content.
- Seeds: Flaxseeds, sunflower seeds, poppy seeds, and sesame seeds are also significant sources.
Grains and Cereals
- Oats: Oatmeal, oat bran, and other oat-based products are often high in nickel.
- Whole Grains: Whole wheat, rye, and buckwheat contain higher levels than their refined counterparts.
Cocoa and Chocolate Products
- The cacao bean is naturally high in nickel, meaning that cocoa powder and dark chocolate contain substantial amounts. The higher the cacao percentage, the higher the nickel content.
Seafood
- Certain types of fish and shellfish can be high in nickel, including tuna, herring, mackerel, salmon, and mussels.
Other High-Nickel Foods
- Canned Foods: The canning process can cause nickel to leach from the metal container into the food, raising its overall content.
- Certain Vegetables: While most vegetables are low, some, including spinach, onions, and asparagus, can contain moderate to high levels.
- Dried Fruits: Dried fruits, such as prunes and raisins, are also often high in nickel.
Factors Influencing Nickel Content
Beyond the natural content, several factors can influence the amount of nickel present in food. These include:
- Soil and Water: The concentration of nickel in the soil and water where the food is grown directly impacts how much the plant absorbs.
- Cooking Utensils: Cooking acidic foods (like tomatoes or vinegar-based sauces) in stainless steel cookware can increase the nickel content of the meal, as the acid can cause the metal to leach from the utensils. Using glass, ceramic, or enamel cookware is recommended for those with a sensitivity.
- Processing: Industrial food processing using stainless steel machinery can add trace amounts of nickel.
Comparison of High vs. Low Nickel Foods
Here is a quick comparison of common food items to help with dietary choices.
| Food Category | High Nickel Content (mg/kg) | Low Nickel Content (mg/kg) |
|---|---|---|
| Grains | Oats, Whole Wheat, Buckwheat | Refined Rice, Cornflakes, White Flour |
| Nuts & Seeds | Almonds, Cashews, Peanuts, Sunflower Seeds | Fresh Fruits (most), Vegetables (most) |
| Protein | Soybeans, Mussels, Tuna, Herring | Meat, Poultry, Eggs, Dairy Products |
| Sweets | Dark Chocolate, Cocoa Powder | Milk, Honey |
| Canned Items | Canned Beans, Canned Fish | Fresh or Frozen Alternatives |
Conclusion
For those with a nickel sensitivity, being aware of which foods are highest in nickel is the first step toward managing symptoms through diet. Legumes, nuts, whole grains, and dark chocolate are consistently identified as major sources, while animal products and most fruits and vegetables are typically lower. However, the exact nickel content can vary widely depending on growing conditions and cooking methods. Consulting with a healthcare professional or allergist is recommended for a proper diagnosis and guidance on developing a personalized low-nickel diet plan. For further reading on managing systemic nickel allergy, the National Institutes of Health provides detailed resources.
