What is BHT and Why is it in Centrum?


Butylated Hydroxytoluene (BHT) is a synthetic preservative used to prevent the oxidation and subsequent spoilage of oils and fats. Typically added to fat-containing foods in an effort to increase their shelf-life, it is also commonly used in the supplement, cosmetic, and manufacturing (rubber, petroleum, and plastics) industries for similar purposes.

Fat spoilage can dramatically alter the appearance, taste, and smell of a product, making it an unattractive purchasing option. But is BHT our best and safest option for fat preservation? Clinical study has been mixed regarding the safety of BHT–with evidence of increased risk of cancer in some studies and a decreased risk of cancer in others. Butylated hydroxyanisole (BHA), also a fat preservative and BHT’s chemical relative, “is reasonably anticipated to be a human carcinogen,” according to the National Toxicology Program. Is it worth noting that the vast majority of efficacy/toxicity studies have been conducted in animals and test tubes, providing no definitive human data. These studies do, however, increase the legitimacy and likelihood of the observed effects occurring in humans.

In LabDoor’s multivitamin analysis, for example, BHT was used exclusively in Centrum products (present in 5/6 tested Centrum multivitamins) while the majority of tested products used vitamin E, a natural fat preservative. Rosemary extract, also a natural preservative, was a less common alternative.

BHT & Health

BHT is as a synthetic antioxidant–preferentially reacting with oxygen before it is capable of reacting with fatty acids, a process that leads to their oxidation and eventual rancidity.

Because BHT acts as an antioxidant, it may also offer anti-carcinogenic protection. Some animal studies have noted that both BHA and BHT–at both high and low levels–are able to scavenge free radicals or aid in the production of enzymes known to detoxify carcinogenic compounds. The question of risk still remains: is there a cost to taking this compound for its purported antioxidant effects? In one animal study, for example, BHT was shown to enhance thyroid hyperplasia’s, but simultaneously reduced incidence of colon and kidney tumors.

According to the International Agency for Research on Cancer (IARC), there is no conclusive scientific evidence indicating the BHT causes cancer in humans. It has, however, shown carcinogenic, genotoxic, and tumor-promoting effects in limited animal testing. The compound may also act as a mild endocrine disruptor–specifically interacting with and inhibiting androgen signaling–and affect lung, liver, kidney and thyroid function.

Final Words & Suggestions

While BHT has shown promise of anti-carcinogenic effects, it has also been associated with carcinogenesis, tumor promotion, and organ dysfunction in animal testing. Further scientific testing is needed to reach conclusive results, but it may be best to keep the preservative out of your supplement cabinet and limit how much you consume in your diet. Let me be clear: a compound whose toxicity results are mixed is not your best safety bet.

If you choose to eat preserved foods, a natural preservative such as vitamin E (alpha-tocopherol) may be a better option. Vitamin E has also shown antioxidant and anti-carcinogenic benefit, and is not associated with any health risk at the levels typically used in foods. Eating more minimally processed and fresh foods is the best way of avoiding controversial additives and minimizing risk of disease.