The blue-green microalgae spirulina, used in daily diets of natives in Africa and America, has been found to be a rich natural source of proteins, carotenoids and other micronutrients. Experimental studies in animal models have demonstrated an inhibitory effect of spirulina algae on oral carcinogenesis. Studies among preschool children in India have demonstrated spirulina fusiformis to be a effective source of dietary vitamin A. We evaluated the chemoproventative activity of spirulina (1 g/day for 12 months) in reversing oral leukoplakia in pan tobacco chewers in Kerala, India. Complete regression of lesions was observed in 20 of 44 (45%) evaluable subjects supplemented with spirulina, as opposed to 3 of 43 (7%) in the placebo arm. When stratified by type of leukoplakia, the response was more pronounced in homogeneous lesions: complete regression was seen in 16 of 28 (57%) subjects with homogeneous leukoplakia, 2 of 8 with erythroplakia, 2 of 4 with verrucous leukoplakia, and 0 of 4 with ulcerated and nodular lesions. Within one year of discontinuing supplements, 9 of 20 (45%) complete responders with spirulina developed recurrent lesions. Supplementation with spirulina did not increase serum concentrations of retinal or beta carotene, nor was it associated with toxicity. This is the first human study evaluating the chemopreventive potential of spirulina. More studies in different settings and different populations are needed for further evaluations.

The bioavailability of total carotenes and beta carotene from spirulina was examined in apparently healthy preschool children and found to be comparable to those values reported for other plant sources like leafy vegetables and carrots. The study also showed spirulina is a good source of Vitamin A, as there was a significant increase in serum retinol levels. Researchers concluded spirulina can be used as a source of Vitamin A in the diet, is relatively inexpensive, has higher beta carotene than any other plant source and can be cultivated throughout the year.

A one year feeding program with 5,000 pre-school children showed a symptom of Vitamin A deficiency, "Bitot's spot", decreased from 80% to 10%. These rural children near Madras consumed 1 gram of spirulina a day for at least 150 days. This small amount provided the daily requirement of beta carotene (Vitamin A) which can help prevent blindness and eye diseases. In another study with 400 school children, a daily dose of beta carotene from spirulina increased their Vitamin A status to the same level as those administered pure Vitamin A. Spirulina was given to children in a unique way: extruded noodles, sweetened with sugar to preserve the beta carotene. Called "Spiru-Om", it was well accepted by the children. This project was sponsored by the Indian Government.

Thirty healthy men with high cholesterol, mild hypertension and hyperlipidemia showed lower serum cholesterol, triglyceride and LDL (undesirable fat) levels after eating spirulina for eight weeks. These men did not change their diet, except adding spirulina. No adverse effects were noted. Group A consumed 4.2 grams daily for eight weeks. Total serum cholesterol dropped a significant 4.5% within 4 weeks from 244 to 233. Group B consumed spirulina for four weeks, then stopped. Serum cholesterol levels decreased, then returned to the initial level. Researchers concluded spirulina did lower serum cholesterol and was likely to have a favourable effect on alleviating heart disease since the arteriosclerosis index improved.

Spirulina tablets were given to 21 patients with various nutritional deficiencies. They had suffered weight loss in conjunction with gastric resection, tubercular infection, chronic pancreatitis and gastritis, rheumatoid arthritis, anaemia and diabetes mellitus. With spirulina the patients gained weight and their proteinograms improved.

Immunoglobulin E (IgE) of children living in highly radioactive areas is greatly above normal. Studies with 270 children show that consuming about 5 grams per day of spirulina tablets normalized IgE within 6 weeks. Children not consuming spirulina did not change IgE levels. No side effects were observed. Spirulina lowers the amount of IgE in the blood, which in turn normalizes and reduces allergies.