Softgel capsules - the smooth, easy-to-swallow form of many medications and supplements - are increasingly popular for delivering everything from vitamins to omega-3s. These capsules, made of a liquid centre inside a soft, flexible shell, offer convenience and effectiveness. But they've also come under growing scrutiny for one surprising reason: plasticisers.
Author
- Craig Russell
Lecturer, Pharmacy, Aston University
To make the capsule shell soft and pliable, manufacturers often use plasticisers - chemicals called phthalates. While these help with flexibility and durability, they're also linked to a range of health concerns.
Phthalates are known as endocrine disruptors - substances that can interfere with hormone systems. Studies, particularly in animals, suggest they can affect reproductive development, fertility and hormone balance.
Some human studies have found associations with birth defects , allergies in children and even heart disease . But scientists are still trying to fully understand the risks, and how much exposure is too much.
One difficulty in assessing phthalate safety is that there isn't just one type. Phthalates are a large family of chemicals, each with different properties and risks. Not all are used in softgels, and many of the highest exposures come from other everyday sources such as vinyl flooring, shower curtains, perfumes and air fresheners.
But while phthalates in softgel capsules may not be the biggest contributor to our overall exposure, they're still worth paying attention to - especially for people who take many supplements daily.
Several phthalates are approved for pharmaceutical use, including diethyl phthalate (DEP), cellulose acetate phthalate, polyvinyl acetate phthalate and hypromellose phthalate.
DEP, the most common plasticiser in softgels, is considered to have relatively low toxicity and is used in small amounts. The others are typically used to help medicines survive stomach acid and are generally regarded as safe when used correctly.
However, some phthalates, such as dibutyl phthalate (DBP), have sparked more concern. DBP has been linked to reproductive and developmental issues and its use in medicines is now heavily restricted.
Others, like di-(2-ethylhexyl) phthalate and diisodecyl phthalate, are more commonly used in medical devices such as IV bags and are also tightly regulated .
Research suggests long-term exposure to these chemicals may increase the risk of conditions like insulin resistance, inflammation and cardiovascular disease - especially in children and pregnant women.
Regulated, but not always obvious
Health regulators including the European Medicines Agency and the US Food and Drug Administration have set clear guidelines for the use of phthalates in medicines. These include daily intake limits and ongoing safety monitoring.
But outside of prescription drugs, things can get murkier.
Many supplements are sold over the counter and taken without medical supervision. That means people could unknowingly exceed safe phthalate levels, especially when combined with other environmental exposures.
So, although phthalates in medicines are regulated, awareness is key. If you're concerned, check ingredient labels, ask your pharmacist, or look for phthalate-free alternatives.
And as science continues to evolve, regulators and manufacturers alike will need to keep reassessing how, and when, these chemicals are used.
Craig Russell receives funding from BBSRC
