Hexane, propylene glycol, and ethanol—terms you might have last encountered in high school chemistry class—are examples of chemical solvents used in a food processing technique called solvent extraction. Solvent extraction is a process commonly used to create natural flavors, oils, and extracts from nuts, seeds, fruits, and herbs.

The Problem?

Trace amounts of solvents can remain in the final products we consume. Some solvents, like hexane, are particularly concerning, as they are hazardous chemicals linked to reproductive and neurological damage.

To better understand why trace amounts of solvents, aka residual solvents, can remain in the final product, let’s take a simplified look at how solvent extraction can be used to make vegetable oil:

1. Prepare the Seeds: Seeds such as sunflower, canola, or soybeans are prepared and processed.
2. Mix the Seeds with a Solvent: The processed seeds are combined with a solvent, like hexane, which dissolves the oil from the solids, leaving behind unwanted materials and an oil/hexane mixture.
3. Separate the Oil: The oil is separated from the hexane using a separation process, such as vaporization or distillation.
4. Refine the Oil: The oil is further processed, bleached, and deodorized to make it shelf-ready.

Aren’t Residual Solvents Regulated?

The U.S. Food and Drug Administration (FDA) doesn’t set specific limits for the quantity of residual solvents allowed in all end products, only a select few. For example, the FDA sets limits for the amount of hexane in fish protein isolate (5 mg/kg), hop extract (25 mg/kg), and spice resins (25 mg/kg). The European Union (EU) has more extensive regulations in place across a range of end products, but I’m writing from the perspective of someone living in the United States.

Are Trace Amounts Really a Concern?

Yes, I believe trace quantities matter, especially considering how much hexane an individual might consume over a lifetime. Using vegetable oil as an example, an individual could ingest nearly two-thirds of a teaspoon of hexane throughout their lifetime. This estimate considers the EU standard for allowable residual hexane (1 mg/kg) and the OECD-FAO Agricultural Outlook’s estimate for average vegetable oil consumption (40 kg/year).

While two-thirds of a teaspoon may not seem like a lot, it’s important to note that this estimate only considers exposure from one food product: vegetable oil. Additionally, this estimate assumes that U.S. products meet EU standards, when in reality, the levels of residual hexane in U.S. products could be much higher. All I can sarcastically think is “a spoonful of vegetable oil helps the hexane go down.” Add other food products to the mix, like flavorings, hops, and soy protein, it’s no wonder we’re a “sick society.”

How Can You Reduce Your Exposure?

A big culprit of chemical solvent exposure is industrial seed oils, aka vegetable oils. To reduce exposure to these oils, cut back on processed foods and limit dining out at restaurants—two major sources of them. If you want to go a step further, look for labels that specify “cold-pressed” or “organic” when purchasing products like oil, beer, cocoa, or soy, which could contain residual solvents. Cold-pressed refers to a chemical free extraction method and organic products are not allowed to contain volatile synthetic solvents.