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Stainless steel travel mugs seem like a practical choice for coffee, but there’s one reason to avoid them: Stainless steel releases nickel and cadmium into acidic liquids and foods.
Coffee is acidic. One analysis of commercial beverages measured coffee at a pH of about 5.1, well below the neutral pH of 7.
That matters because acidity can increase the release of metals from stainless steel.
With nickel toxicity on the rise — and nickel causing more skin allergies than any other metal — regularly drinking coffee from stainless steel can become a significant source of nickel exposure, just as cooking with stainless steel pots and pans can. Removing these sources of exposure is an important step toward reducing the body’s nickel burden.
Learn about low nickel foods here.
Stainless steel contains nickel
Many common food-grade stainless steels contain substantial amounts of nickel. For example, 18/8 stainless steel contains roughly 8% nickel, while 18/10 contains roughly 10%.
The nickel isn’t simply sitting loosely on the surface. It’s incorporated into the stainless-steel alloy. However, that doesn’t mean none of it can migrate into food or beverages.
Researchers have repeatedly demonstrated that stainless steel releases measurable nickel when it comes into contact with acidic substances. One study specifically tested stainless-steel frying pans, bowls and tumblers with citric, tartaric and lactic acids and found both nickel and chromium in the resulting liquids.
Another study concluded that organic acids attack stainless-steel cookware and cause iron, chromium and nickel to migrate from the metal into food.
Switch your pots and pans
For safer cookware alternatives, try these pots and pans, which I own and have found to be both good quality and a great value, or consider these glass pots.
You may also want to replace your stainless steel water bottle with a glass one. We use and like this one.
Acid makes the difference
A particularly useful study compared stainless-steel pots under different pH conditions. Researchers found that nickel and chromium release increased at low pH. Release also increased with longer heating times and varied considerably between manufacturers.
This gives us a simple principle for the kitchen: The more acidic the food or beverage, the less I want it sitting against nickel (and chromium)-containing stainless steel.
For example, researchers cooked acidic tomato sauce in stainless steel and measured nickel and chromium migration. After repeated cooking cycles, the cookware was still contributing measurable amounts of both metals to the tomato sauce. New stainless steel produced the greatest increases.
The same principle makes us question putting hot coffee into a stainless-steel travel mug and allowing it to sit there for 30 minutes to a couple of hours while someone drinks it.
Nickel exposure isn’t necessary
Excess nickel exposure can cause health problems for everyone (it builds up and causes disease). Reducing nickel is particularly important for people with nickel allergy or sensitivity.
Research has shown that oral nickel exposure can trigger dermatitis in susceptible individuals, which is one reason researchers study nickel migration from cookware in the first place.
A striking recent example makes the concern especially tangible. In 2026, physicians published a case report about nickel leaching. The conclusion: Acidic liquids interact with stainless steel, nickel leaches from the metal, and that exposure matters for everyone, especially those who drink from stainless steel regularly and those who already have contact dermatitis.
A simple alternative
If you’re trying to reduce unnecessary heavy toxic metal exposure (I think that’s everyone?!), don’t store acidic drinks and foods in nickel-containing stainless steel.
For coffee, I prefer glass or ceramic. I would also use extra caution with other acidic liquids and foods — including lemon water, tomato sauce, vinegar-based foods, kombucha, yogurt/kefir and citrus drinks — especially when they will remain in contact with stainless steel for extended periods.
3 Ceramic or Glass coffee travel/to-go mug options:
- With silicone lid and handle, comes in a variety of colors
- Handmade look, silicone lid, no handle, comes in a variety of colors
- Tempered glass, with no-splash lid
Stainless steel may be durable, natural and convenient, but convenience isn’t the only consideration. When an acidic food or beverage sits against nickel-containing metal for hours, choosing glass or ceramic is an easy way to eliminate that particular source of nickel exposure.
Related topics
- If you have a stainless steel coffee maker, even a French press with a metal press, consider replacing it with a glass coffee maker, such as the Chemex.
- 3 Best Coffee Alternatives
- Basic Bulletproof Coffee Recipe
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