Safety Of Single Cell Oils

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The arrival of SCO on the food scene is a relatively recent event - the first commercial SCO (Oil of Javanicus) not being produced commercially until 1985 (see Section - well after regulations and regulatory bodies relating to food safety were in place. Therefore the safety of these food products had to be determined and proven to the regulatory authorities and the general public. The safety of Oil of Javanicus was relatively easy to confirm as both the producing organism (Mucor circinelloides) and the active ingredient (y-linolenic acid) have long been part of the human diet and were therefore deemed safe by historical association with food products.

y-Linolenic acid was the PUFA responsible for the therapeutic activity of evening primrose oil, the high value plant oil that Oil of Javanicus was developed to compete against. Evening primrose oil has been taken for centuries as a folk remedy for a number of ailments, the most well documented of which is premenstrual syndrome. Indeed, its reputed efficacy against general illnesses was such that it was also known as "King's Cure All."

The filamentous fungus Mucor circinelloides (the production organism for Oil of Javanicus) has a long documented association with human foods, being the organism used in the fermentative production of the oriental food tempeh. This historical connection and evidence of long term (hundreds if not thousands of years) human consumption without reported adverse effects was instrumental in proving the safety of Oil of Javanicus, and was one of the major factors (other than y-linolenic acid productivity) involved in selection of Mucor circinelloides as the production organism of choice. Having a whole organism that was historically demonstrated non-toxogenic made it fairly easy to argue that a cellular constituent of that organism (the oil) would also be safe for human consumption. Likewise, as the methods used to extract and process the oil from Mucor circinelloides were essentially identical to those used to prepare vegetable oils for human consumption (14), it was evident that the processing of the fungal biomass to release the oil would not introduce any deleterious qualities to the final product.

Unlike Oil of Javanicus, the safety of ARA-rich SCO from Mt alpina could not be inferred by the association of the producing organism with any traditional foodstuff. Furthermore, there were even reports suggesting the potential harmful effects of an increase in the dietary intake of arachidonic acid (48). As a result extensive safety data had to be generated before ARASCO™ could be considered safe for human consumption, especially as its primary application is as an ingredient in baby formula. As a result ARA-rich SCO, along with DHASCO™, are probably the most extensively safety tested edible oils currently on the market. The safety of ARASCO™ has been reported by numerous authors who have assessed this oil from a number of different perspectives. The safety of ARASCO™ (the ARA-rich SCO produced by Martek Biosciences Corp) was even the topic of an entire symposium at the AOCS meeting in Indianapolis in 1996 (49).

For some years the inclusion of high levels of ARA in the human diet was considered undesirable, due to potential adverse effects on blood clotting (48). However the apparent lack of toxicity in animal models prompted a major study at the Western Human Nutrition Research Center, San Francisco, USA, of the effect of dietary supplementation with ARASCO™. During an intensive and prolonged study (in which human volunteers lived in a "metabolic ward" to decrease the effect of external influences) the inclusion of 1.5 g ARA/day (3 g ARASCO™/day) did not cause any significant adverse effects on any of the test individuals. Factors examined included blood coagulation, immune response, and the production of arachidonic acid derived signal molecules. The conclusion of the study was that the inclusion of 3 g/day ARASCO™ did not have any toxic effects on adult humans and that this oil should be considered safe as a human food ingredient (50-53).

Further studies have been undertaken in Europe to determine the safety of ARASCO™ as a nutritional supplement specifically in relation to its intended use in infant formula. A review of the literature was carried out to determine if the production organism (Mort. alpina) was, or had ever been, associated with human disease (33). This study concluded that this fungus had never been unequivocally linked to human disease (due largely to the fact it is unable to grow at human body temperature) and that there were no reports of mycotoxin production. As Mt. alpina is a ubiquitous soil fungus and therefore in common contact with humans it was argued that it was clearly a completely benign organism and should be considered safe for the production of human food material.

Animal studies employing rats as a mammalian model system have failed to demonstrate acute toxicity of ARASCO™ at levels up to 20 ml/kg body weight, (corresponding to a 75 kg human taking 1.5 l of ARASCO™ in a single dose). The only negative finding was that test animals experienced diarrhea the day following administration! Likewise, subchronic studies using a range of ARASCO™ doses in the rat model found that while >2 g/kg body weight/day caused some physiological changes in terms of blood lipid composition and organ weights. These changes are associated with high-lipid diets in general and are not specific to ARASCO™ consumption in particular. No obvious pathological changes were seen (i.e., none of the animals became ill). Furthermore, reproductive function was unaffected and the pups from the ARASCO™-fed group did not demonstrate any ill effects (54,55).

This detailed examination of ARASCO™, in terms of the producing organism and the SCO derived from it, demonstrated unequivocally that this SCO presents no greater danger to infant and human health than any other typical vegetable oil. It should also be pointed out that most of today's commodity and speciality plant oils have never undergone the extensive scrutiny to which SCOs have been subjected. We assume that such esoteric oils as walnut oil, macadamia oil, and sesame seed oil are intrinsically safe, as indeed they probably are; but these have never gone through the extensive examination that SCO have had to.

The DHA-rich SCO from C. cohnii, like Oil of Javanicus, does not contain a LC-PUFA with questionable toxicological effects. Diets very rich in DHA are documented for several human populations - this DHA is invariably derived from ingestion of sea fish and sea mammals and has never been associated with any adverse effects. Indeed it was the supposed health benefits of the diets enjoyed by populations of Iceland and Japan (who have a very low incidence of cardiovascular disease, despite a high fat diet, and a low incidence of premature infant deliveries) that first highlighted the potential therapeutic effects of DHA. Ironically, the high intake of sea fish is now being suggested to represent a health risk to these same populations due to the presence in fish meat and especially oil of pollutants released into the marine environment by man (56,57).

As a result of the accepted inherent safety of an oil rich in DHA, the safety issues related to DHA-rich SCO were restricted to a demonstration of the safety of the microbi-ally derived oil. In many studies, fish oils have been used as a negative control (i.e., "safe" oil) with which to compare DHA-rich SCO. The safety of DHASCO™, the DHA-rich SCO that is used on a commercial scale as a infant formula additive as part of the DHASCO™/ARASCO™ blend, has been comprehensively studied both by the manufacturer (Martek Biosciences Corp.), and by formulae manufacturers. These studies have looked at the possible in vitro effects of DHASCO™ to test for mutagenic and clasto-genic (chromosome damaging) effects, animal studies and human feeding studies (Tables 17.8, 17.9). Animal studies using rats as a model system have checked acute toxicity at doses up to the maximum dose physically possible to administer (~20 g/kg body wt). Additionally, sub-acute studies, where DHASCO™ was fed at several times the anticipated human doses for prolonged periods (up to 90 days), have also studied the effect of DHA supplementation of female animals prior to and during pregnancy as well as to the offspring. None of these studies found any indication of toxicological problems and the LD50 for DHASCO™ (if one exists) was found to exceed the maximum possible dose.

Table 17.8

In Vitro and Animal (in Vivo) Studies on the Safety of DHASCO™ Produced by Martek Biosciences Corporation

Table 17.8

In Vitro and Animal (in Vivo) Studies on the Safety of DHASCO™ Produced by Martek Biosciences Corporation


Max DHASCO™ Dose

Model System Employed



Ames mutagenicity test

5 mg/plate


Not mutagenic

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  • ali
    Is single cell oil safe for human consumption?
    2 years ago

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