Subchronic toxicity study in mice fed Spirulina maxima

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Abstract

The purpose of this study was to evaluate the toxicity of Spirulina maxima, a blue–green alga used as food supplement and food coloring, after 13 weeks of treatment. Groups of ten mice of each sex were given S. maxima in the diet at concentrations of 0 (control), 10, 20 or 30% (w/w) for 13 weeks. The alga ingestion had no effect on behavior, food and water intake, growth or survival. Terminal values in hematology and clinical chemistry did not reveal differences between treated and control groups. However, male and female mice showed significant changes in serum cholesterol levels at 20 and 30% algal concentrations, but a toxic effect of S. maxima was excluded. Post-mortem examination revealed no differences in gross or microscopic findings. Our results show that S. maxima up to high feeding levels did not produce adverse effects in mice after subchronic treatment.

Introduction

Spirulina maxima is an unbranched, helicoidal and filamentous blue–green alga found as an almost unialgal culture in many alkaline lakes (Belay et al., 1993). This cyanobacterium has been extensively grown to provide a high-protein commodity used as food supplement and food colorant (Belay et al., 1997).

Studies have been conducted to explore the potential of S. maxima as a nutrient source and have demonstrated that the crude protein content of this alga varies from 60 to 77% according to the strain (Dillon and Phan, 1993, Tranquille et al., 1994), with a nutritional value equivalent to proteins from conventional plant origins (Becker and Venkataraman, 1984). It has been regarded as a rich source of vitamins, minerals, essential fatty acids such as γ-linoleic acid, and antioxidant pigments such as carotenoids (Belay et al., 1997).

Some therapeutic properties, such as a hypocholesterolemic effect (Nakaya et al., 1988), antiherpes simplex virus activity (Hayashi et al., 1993), body weight reduction in obese patients (Becker et al., 1986), antimutagenic potential (Qishen et al., 1989) and other pharmacological properties, have indicated an added advantage of an algal-protein diet for human and animal consumption (Belay et al., 1993). Nevertheless, several toxic effects in humans and animals produced by certain blue–green algae have been reported (Fox, 1996). The signs of poisoning in mice after intraperitoneal injection were piloerection, paresis of the hindlimbs, tachypnea, pallor and cold peripheries (Aldridge, 1996, Pabst et al., 1978b). Moreover, Pabst et al. (1978a), Pabst et al. (1978b)in a multigenerational study demonstrated that mice were sensitive to toxic effects of the microalga Scenedesmus acutus.

Any form of single cell protein for human consumption or animal feeding should be subjected to detailed toxicological investigations as recommended by international organizations such as the Protein Advisory Group of the United Nations (Becker, 1995). These tests include short-term and long-term feeding studies with rodents and other species, as well as multigenerational, teratogenic and mutagenic studies (Becker, 1988).

Reproductive toxicity and mutagenicity tests have been performed in several rodent species with S. maxima, and it was concluded that the alga diet used in these experiments did not cause any toxic effect (Chamorro et al., 1985, Chamorro et al., 1987, Chamorro and Salazar, 1996, Chamorro et al., 1997).

Because of its importance in xenobiotic toxicity research (Voss et al., 1995), the objective of the present study was to obtain subchronic data on S. maxima in order to increase the confidence in extrapolating safety to humans, particularly with reference to its use as a dietary complement.

Section snippets

Test material

S. maxima (Oscillatoriaceae) was supplied by Sosa Texcoco (Mexico City). It was spray-dried and of a standardized quality, being part of a bulk production batch. The alga was identified by Prof. Catalina Mendoza González at the ENCB Herbarium of the National School of Biological Sciences, National Polytechnic Institute, Mexico City, where a voucher herbarium specimen (12584) is kept.

The dried alga was incorporated into the experimental diets at levels of 0 (control), 10, 20 and 30%

Results

All mice survived to the end of the 13-week study. No abnormalities of condition or behavior were detected. In all cases the feces of the experimental animals were darkly colored.

Average feed and water consumption by male and female mice in the 30% of algae concentration group was slightly depressed compared to the control group (data not shown); however, all other treatment groups were similar to the control group and within the normal range for mice. Total body weight gains over the whole

Discussion and conclusions

Some authors have suggested that subchronic data may be sufficient to predict the hazard of long-term, low-dose exposure to a particular compound (McNamara, 1976). This kind of experiment has already been carried out for the toxicological evaluation of single-cell proteins, mainly in rats, as well as in the target (farm) animals (Pabst et al., 1978b).

Our studies demonstrated that S. maxima feeding at levels up to 30% of the diet for up to 13 weeks was not toxic for CF1 mice. There were no

Acknowledgements

This work was supported in part by the Postgraduate Studies and Research Section, National Polytechnic Institute, Mexico. The authors thank Violeta Pardı́o from Pesticide Research Laboratory, Veracruz University, for her assistance in the revision of the manuscript.

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