"Does sodium benzoate cause cancer?"

"There's no direct evidence that sodium benzoate at food-use levels causes cancer. The cancer concern comes from benzene, a carcinogen that can form when sodium benzoate reacts with vitamin C. FDA testing found benzene in some beverages, but at levels well below the EPA's drinking water standard of 5 ppb in most products."

"What foods contain sodium benzoate?"

"Sodium benzoate is most common in acidic foods and beverages: sodas, fruit juices, salad dressings, pickles, condiments like hot sauce and ketchup, and some fermented products. It has to appear on ingredient labels in the US."

"What is the acceptable daily intake for sodium benzoate?"

"The FDA's acceptable daily intake (ADI) for sodium benzoate is up to 5 mg per kilogram of body weight per day. For a 154-pound (70 kg) adult, that's 350 mg/day. Most people consume well under 10 mg/day from food, putting typical exposure far below the limit."

Sodium Benzoate: Preservative Safety Explained

Sodium benzoate has been in the food supply since the early 1900s. It’s one of the most widely used preservatives in the world. It’s also one of those ingredients that shows up on “scary additives” lists alongside warnings that don’t always reflect what the evidence actually shows. Here’s the real picture.

What Sodium Benzoate Is

Sodium benzoate is the sodium salt of benzoic acid. Benzoic acid occurs naturally in many foods, including cranberries, prunes, cinnamon, and cloves. The commercial version used as a preservative is synthesized industrially, though the molecule is identical to what you’d find in nature.

When you add sodium benzoate to an acidic solution, it partially converts back to benzoic acid. That conversion is what makes it work as a preservative.

How It Works

Sodium benzoate is only effective in acidic environments, specifically foods with a pH below about 4.5. This is why you find it in sodas, fruit juices, vinegar-based condiments, and pickled foods, but not in neutral-pH products like plain water or milk.

The mechanism is straightforward. Benzoic acid is lipid-soluble in its protonated (acid) form. It passes through the cell membranes of yeast and bacteria. Inside the cell, where pH is closer to neutral, it ionizes and can’t get back out. The accumulated acid disrupts the cell’s ability to regulate its internal pH, interfering with enzyme function and eventually killing the microorganism.

It’s particularly effective against yeasts and molds, which makes it useful in beverages and condiments where those are the main spoilage organisms. It’s less effective against bacteria, especially at the concentrations used in food.

At typical food concentrations (0.03-0.1% by weight), sodium benzoate extends shelf life significantly without altering flavor in most applications.

The Benzene Problem

This is the most legitimate chemical concern about sodium benzoate.

Benzene is a known human carcinogen. Under certain conditions, sodium benzoate can react with ascorbic acid (vitamin C) to form benzene. The reaction is catalyzed by heat, UV light, and the presence of certain metal ions like iron and copper.

The pathway looks like this: ascorbic acid donates an electron to reduce iron(III) to iron(II). The iron(II) then reacts with benzoic acid through a Fenton-type reaction, producing benzene as a byproduct (Gardner and Winkler, 2008).

This isn’t a theoretical concern. The FDA tested beverages in 2005-2007 and found detectable benzene in some products that combined sodium benzoate and vitamin C. Most were below the EPA’s drinking water limit of 5 parts per billion (ppb). A handful exceeded it. The FDA worked with manufacturers to reformulate those specific products.

Deeper look: How to interpret the benzene numbers

The EPA’s 5 ppb drinking water standard is set with a large safety margin built in. The risk level used to derive that number assumes lifetime daily consumption. Occasional consumption of a beverage with 5-10 ppb benzene doesn’t translate to the same risk as drinking benzene-contaminated water every day for 70 years.

For context, benzene is also present in ambient air, particularly in urban environments. The typical person inhales roughly 200 micrograms of benzene per day from air alone (ATSDR, 2007). The amounts contributed by an occasional soda with trace benzene are small relative to that background exposure.

That said, the benzene-formation reaction is avoidable. It requires both sodium benzoate and a vitamin C source in the same acidic product. Manufacturers that reformulate to separate these ingredients (or replace sodium benzoate with potassium sorbate, which doesn’t react the same way) eliminate the issue entirely.

Storage matters too. The reaction speeds up with heat and light. A bottle of juice left in a hot car will have higher benzene formation than one stored cold and dark.

The ADHD and Hyperactivity Question

In 2007, a team of researchers published what became known as the Southampton study (McCann et al., 2007) in The Lancet. They gave children aged 3 and 8-9 two different drink mixes. One contained a combination of artificial food dyes plus 45 mg of sodium benzoate. The other was a placebo.

Parents and teachers (blinded to the assignment) rated children’s behavior. The researchers found a statistically significant increase in hyperactivity measures in children who consumed the dye and benzoate mixture.

The UK’s Food Standards Agency responded by recommending that manufacturers voluntarily remove the six specific dyes studied (now called the “Southampton six”) from their products. The European Food Safety Authority issued a similar advisory. The EU later required warning labels on products containing those dyes.

The FDA reviewed the same evidence and concluded it wasn’t sufficient to mandate changes. Their position was that the effect size was modest, the study used a mixture rather than individual ingredients, and the evidence didn’t prove causation.

The design problem is that sodium benzoate wasn’t tested alone. It was always combined with artificial dyes. You can’t separate the individual contributions of sodium benzoate versus the color additives from this study’s results. Later research examining sodium benzoate in isolation has been limited. Learn more about the dye side of this story in our article on food dyes and behavior.

Where You’ll Find Sodium Benzoate

Product Type	Common?	Notes
Sodas and fizzy drinks	Very common	Often paired with citric acid (not Vit. C)
Fruit juices and drinks	Common	Watch for added ascorbic acid on same label
Salad dressings	Common	Acidic pH makes it effective
Pickles and relishes	Common	Works alongside vinegar acidity
Hot sauce and condiments	Common	Most acidic sauces use it
Soy sauce	Sometimes	Traditional fermented versions usually don’t
Medications	Common	Liquid medications and cough syrups

In the US, sodium benzoate must appear on ingredient labels. It can’t be hidden inside “natural flavors” or similar catch-all terms. If you want to avoid it, label reading is straightforward.

How It Compares to Alternatives

Potassium sorbate is the most common alternative. It works across a similar pH range and doesn’t carry the benzene-formation concern because it’s a different chemistry entirely. Many manufacturers have shifted to potassium sorbate specifically to address the benzene issue. It’s slightly more expensive but functionally similar.

Sodium benzoate’s continued use often comes down to cost, its effectiveness against yeasts specifically, and the fact that at normal temperatures and with careful formulation, benzene formation is minimal.

What the Regulatory Picture Looks Like

The FDA has maintained GRAS status for sodium benzoate with an established acceptable daily intake (ADI) of 5 mg per kilogram of body weight. Most people consume far less than that from food. Even heavy soda drinkers typically land well below the limit.

The European Food Safety Authority (EFSA) last reviewed sodium benzoate in 2016 and set an ADI of 5 mg/kg, consistent with the FDA position.

The concern about sodium benzoate isn’t that it’s clearly harmful at the doses in food. The concern is that two specific scenarios, the benzene-formation reaction and the possible contribution to hyperactivity in sensitive children, introduce enough uncertainty to warrant a “caution” rather than a clean pass.

Sodium Benzoate and Gut Health

One additional area of emerging research is whether sodium benzoate affects the gut microbiome. A 2021 animal study (Patel et al., 2021) showed changes in gut bacterial composition at relatively high doses. Human data is sparse. This is worth watching but doesn’t currently change the practical advice. For more on how food additives interact with gut bacteria, see our overview of gut microbiome basics.

Keeping foods at proper temperatures, as covered in our temperature danger zone guide, is relevant here: heat accelerates benzene formation in sodium benzoate-containing drinks, which is one more reason proper storage matters.