October 09, 2003
A reader asks about squalene - a chemical in olive oil. He is an herbalist who is trying to make products for the treatment of psoriasis. He has heard that squalene can reduce the inflammation of psoriasis and that the two main sources of squalene are shark oil and olive oil. The shark product can smell of shark so he is interested in a source of squalene derived from olive oil.
Isn't olive oil an amazing product that it can incidentally contain a product which can treat a terrible human skin condition? Actually it isn't such an accident, it is an artifact of the age old war between plants and animals. Trees have very large genomes and are capable of cranking out thousands of different chemicals, far more than a human. Trees became chemical factories throughout evolution to protect themselves from herbivorous animals, fungi and bacteria. It has been estimated that up to 40% of the dry weight of most plants is toxic chemicals created to deter herbivores. After all, these tress can't exactly run away from their tormentors.
Olive trees create squalene, which is a precursor of other sterols, and many other sterol type chemicals. In animals these chemicals are hormones which signal sexual differentiation, pupation, and other developmental stages. In the biological warfare between plants and animals, toxins are not as effective as hormones which prevent normal insect development. After all, an insect can evolve a new enzyme to break down a toxin but it would be difficult for it to break down or ignore its own sex or developmental hormone and get to the next stage of its life cycle.
In humans, the sterols include the "cortisone" type substances, many of which have anti-inflammatory actions. Psoriasis is an auto-immune disease. The body gets confused and attacks certain body structures, thinking they are foe instead of friend. Anti-inflammatory medications are a mainstay of treatment. They can be given orally or spread on the skin.
But does squalene really help psoriasis? While thousands of websites and nutraceutical vendors claim that a variety of fats and oils will "promote skin health", I was unable to find any hard evidence in the form of double blinded scientific studies which can prove or disprove this treatment. An excellent website which helps sort through the medical misinformation found on the web is http://www.cochrane.org. "It is an international organization that aims to help people make well informed decisions about health care by preparing, maintaining and ensuring the accessibility of systematic reviews of the effects of health care interventions."
Olive Oil contains the largest percentage of squalene among the common vegetable oils. For instance, olive oil has 136-708 mg/100g of squalene compared to 19-36 for corn oil (Gutfinger and Letan). Squalene would be found in fresh extra virgin olive oil. Olive oil which is rancid or has unacceptable flavors is deodorized using distillation. The resultant oil is called "Pure" or "Refined" olive oil. Squalene is removed during the refining process and is concentrated in the distillate. According to Bondioli et al, squalene can be recovered in yields of up to 90% from the distillate using a supercritical carbon dioxide process. The squalene is sold to the cosmetics industry as an emollient or moisturizer and to the nutraceutical industry.
In Europe and North Africa, a good portion of the olive oil ends up getting refined. They have large chemical facilities to handle this so there is a squalene industry there. Here in California, most of the oil made is sold as extra virgin and we don't really have a large refining capacity, so I don't know that the reader will find squalene being made here. Its not that we're throwing it away, we just don't remove it from the olive oil in the first place.
Bondioli, P. Squalene recovery from olive oil deodorizer distillates, J. Am. Oil Chem. Soc 70:763 (1993) Gutfinger and Letan. Studies of unsaponifiables in several vegetable oils. Lipids magazine 9:658 (1974)
Gutfinger and Letan. Studies of unsaponifiables in several vegetable oils. Lipids magazine 9:658 (1974).