All about Preservatives

Commercial pet foods have a relatively long shelf life. Processing is partly responsible for this, but preservatives are also used. Many premium pet food manufacturers use natural anti-oxidants in place of artificial preservatives. However, some pet foods and pet food ingredients are still artificially preserved.

There is no denying that artificial preservatives are cheaper and more effective at increasing shelf-life, but we can’t be sure how safe they are.

The 3 most common artificial preservatives used in pet food are:

• Ethoxyquin (EQ)
• Butylated hydroxyanisol (BHA)
• Butylated hydroxytolulene (BHT)

These are all approved for use in US and European pet foods, if within the recommended limit.

Animal fats in pet food are susceptible to lipid peroxidation, which makes them go ‘off’. Preservatives used on fat sources are usually listed in the ingredients. However, Protein sources may also contain fat, and the amount of preservative used here is sometimes not disclosed on the label!

Animal meals (such as fish, beef, chicken and lamb) are commonly used protein sources. Often these are treated with preservatives before they’re added to pet food.

EQ

EQ is THE most common and most effective artificial preservative used in pet food(1). Despite this, direct treatment with EQ has been reported to possibly cause the following dysfunctions in dogs:

• Liver
• Kidney
• Thyroid
• Reproductive system

It has also been suggested that EQ may cause allergic reaction and increase the risk of cancer, but there is insufficient data to validate this (i.e. it may not be the case)(2). The effects of EQ on dog health have not been properly investigated as a result of dietary exposure.

A recent report of the European food safety authority (EFSA) concluded that levels of ’50 mg ethoxyquin/kg (bodyweight) and 11 mg ethoxyquin/kg complete feed might be’ safe for dogs….

…EFSA could not confirm their findings due to insufficient data(3).

BHA & BHT

Neither BHA nor BHT has been proven to cause disease in dogs. Studies in other mammalian species suggest that BHA and BHT may increase the risk of certain types of cancer, while inhibiting others(4,5) — but we can’t really draw much from this.

BHA has been shown to increase the liver weight of dogs over time(6,7,8). Possibly due to increased action of the liver removing BHA from the blood

The take-home message

There is a clear lack of research investigating the effects of artificial preservatives in dogs, more so for BHT and BHA. We do not know whether the levels present in dog foods will cause disease over time. EQ may have the potential to cause disease in dogs based on some reports. Gaps in our knowledge mean that we cannot rule out long-term toxicity. Dog foods containing artificial preservatives should be treated with caution.

M. A. Crisci

References

1. Błaszczyk, A., Augustyniak, A. and Skolimowski, J., 2013. Ethoxyquin: an antioxidant used in animal feed. International journal of food science, 2013, pp.1–12
2. Dzanis, D.A., 1991. Safety of ethoxyquin in dog foods. The Journal of nutrition, 121(11 Suppl), pp.S163-S164.
3. EFSA, 2015. Safety and efficacy of ethoxyquin (6-ethoxy-1,2-dihydro-2,2,4-trimethylquinoline) for all animal species. EFSA Journal, 13(11), p.4272
4. Ito, N., Fukushima, S. and Tsuda, H., 1985. Carcinogenicity and modification of the carcinogenic response by BHA, BHT, and other antioxidants. CRC Critical Reviews in Toxicology, 15(2), pp.109–150.
5. Hilton, J.W., 1989. Antioxidants: function, types and necessity of inclusion in pet foods. The Canadian Veterinary Journal, 30(8), p.682.
6. Wilder, O.H.M., Ostby, P.C. and Gregory, B.R., 1960. Food Additives, Safety, Effect of Feeding Butylated Hydroxyanisole to Dogs. Journal of Agricultural and Food Chemistry, 8(6), pp.504–506.
7. Tobe, M., Furuya, T., Kawasaki, Y., Naito, K., Sekita, K., Matsumoto, K., Ochiai, T., Usui, A., Kokubo, T., Kanno, J. and Hayashi, Y., 1986. Six-month toxicity study of butylated hydroxyanisole in beagle dogs. Food and Chemical Toxicology, 24(10–11), pp.1223–1228.
8. Ikeda, G.J., Stewart, J.E., Sapienza, P.P., Peggins, J.O., Michel, T.C., Olivito, V., Alam, H.Z. and O’Donnell, M.W., 1986. Effect of subchronic dietary administration of butylated hydroxyanisole on canine stomach and hepatic tissue. Food and Chemical Toxicology, 24(10–11), pp.1201–1221.