Natural beta-carotene and cancer prevention
Cancer is the number two cause of premature deaths in Americans. Increasing cancer rates seem to be caused by environmental factors, especially diet. Scientists are examining foods and substances having protective factors. Beta-carotene is one of the most well known natural anti-cancer substances. Over the past twenty  years, cancer health authorities, National Cancer Institute and dozens of publicized studies have shown evidence that eating vegetables rich in beta-carotene reduces the risk of all kinds of cancer.
Beta-carotene is the main source of vitamin A for humans. Our bodies convert beta-carotene to vitamin A as we need it. Although very high dosages of vitamin A supplements are toxic, high amounts of beta-carotene from foods and supplements are safe. Spirulina is the richest beta-carotene food known, having over ten  times more beta-carotene than any other food, including carrots.
Beta-carotene is one of the most effective substances for deactivating free radicals, which damage the cells, leading to cancer. Free radicals are molecular fragments from environmental pollution, toxic chemicals, drugs, and physical and emotional stress.
Beta-carotene prevents free radicals from reacting, and decreases incidence of lung pre-chromosome damage and enhances immunological resistance.
Over 100 animal studies confirm Vitamin A and Beta-carotene inhibit the development of various cancers and tumours. Many human epidemiological studies correlated high Vitamin A intake with decreased cancer risks. 12 Beta-carotene (and not the preformed Vitamin A from animal sources) correlated with lower cancer rates. 13
Over 15 studies from 1975-1986 correlated lower incidence of lung cancer with beta-carotene and vitamin A. One study found the lower the serum level of beta-carotene, the higher the incidence of lung cancer. 14 Nine  studies from 1974-1986 correlated lower digestive tract cancer (oral, stomach, colon, gastrointestinal) with beta-carotene and vitamin A. Two  studies with women correlated lower breast cancer and cervix cancer. A five  year study in China completed in 1993 with 29,000 people daily dosages of beta-carotene, vitamin E and selenium reduced the incidence of cancer deaths by 13%. 15
In 1982, the famous monograph “Diet, Nutrition and Cancer” published by the US National Research Council reviewed this overwhelming literature. It concluded, “the epidemiological evidence is sufficient to suggest that foods rich in carotenes or Vitamin A are associated with a reduced risk of cancer.” The study recommended a diet including beta-carotene rich vegetables to reduce cancer risks. 16
In 1987 Israeli study demonstrated natural beta-carotene is more effective than synthetic. The body better assimilates natural beta-carotene because it contains the 9-cis Caroteniods isomer, lacking in synthetic carotene molecules. This means beta-carotene in algae and vegetables greater antioxidant power than synthetic beta-carotene. 17
Controversy arose in 1995 when synthetic beta-carotene was found ineffective preventing cancer in Finnish and US smokers, and could even be harmful. Yet, these studies were flawed. Researches chose only synthetic beta-carotene lacking the cis isomer and gave high mega doses, which may have caused nutrient imbalance. These studies reinforced the interest in natural carotenoids in whole foods.
12.Petro, R. et al. Can dietary beta-carotene reduce human cancer rates? Nature, 1981.290:201-208.
13.Shekelle, R. B. et al. Dietary Vitamin A and risk of cancer in Western Electric study. Lancer, 1981. 8257:1185-1189.
14.Menkes, et al. Serum Beta-carotene, vitamins A and E, selenium, and risk of lung cancer. Johns Hopkins, N.E. Journal of Medicine, Nov 1986, p. 1250
15.Blot. William. Journal of National Cancer Institute. Sept. 15. 1993.
16.National Research Council. Diet, Nutrition and Cancer. National Academy Press Washington DC, 1982.
17.Ben Amotz, A. Presentation to Polysaccharides from microaglae workshop. Duke University, 1987
Anti-cancer tumour effects
Because it is the richest natural beta-carotene food, Spirulina has been tested for anti-vcancer effects. The Harvard University School of Dental Medicine reduced oral cancer cells with Spirulina extracts. A beta-carotene solution applied to cancerous tumors in mouths of hamsters reduced the number and size of tumors or caused them to disappear. 18 When beta-carotene extracts was fed to twenty  hamsters pre-treated to develop mouth cancer, none developed the disease. Tissue samples contained an immune stimulating substance believed to have destroyed cancer cells before they could multiply.19
In 1995, Spirulina reversed oral cancer in pan tobacco chewers in Kerala, India. Complete regression of oral leukoplakia was found in 45% of those using one gram a day for one  year, compare to only 7% with a placebo. Within one  year of discontinuing Spirulina, 45% of the lesions returned. This was the first human study of its chemo preventive potential.20
Evidence linking natural beta-carotene and cancer prevention is impressive. For those who do not eat 4-9 servings of fruit and vegetables daily, Spirulina will add natural carotene insurance.
18.Shwartz, J. Scklar, G. Suda, D. Inhibition of experimental oral carcinogen sis by topical beta-carotene. Harvard School of Dental Med. Carcinogen sis, May 1986, 7(5) 711-715.
19.Shwartz, J. Scklar, G. Suda, D. Growth, inhibition and destruction of oral cancer cells by extracts of Spirulina. Cancer & Nutrition. 6/88.
20.Babu, M. et al. Evaluation of Chemo prevention of oral cancer with Spirulina. Nutrition and Cancer V. 24, No. 2 p. 197-202, 1995
Polysaccharides enhance the immune system
In 1979, Russian scientists published initial research on the immune stimulating effects on rabbits from lip-polysaccharides in Spirulina.24 More recent studies in China and Japan have shown polysaccharide extracts increase macrophage function, antibody production and infection fighting T-cells.
In 1991-94 in China, polysaccharides and Phycocyanin from Spirulina increased immunity in mice by enhancing bone marrow reproduction, growth of thymus and spleen and biosynthesis of serum protein. 25,26,27,28 In 1993 in Japan, hamsters treated with a polysaccharide extract had better recovery rates when infected with a herpes virus. 3 In 1996, a water extract unique to Spirulina, Calcium Spirulan, inhibited replication of HIV-1, Herpes Simplex and other viruses, yet was very safe for human cells.2
In the USA, a water-soluble extract increased macrophage activity in chickens. In further 1993-96 studies, chickens fed a diet with less than 1% Spirulina showed improved immune performance without any adverse side effects. The whole immune system array of killer cells, helper cells antibody production was supercharged. 29,30 Similar benefits were found for cats. 31
Researches are testing the theory that Spirulina and its extracts act much like a broad spectrum vaccine against bacteria. Because it is a safe natural food, this research has created a sensation among animal scientists. They are scrambling to replace ineffective antibiotics with probiotics that strengthen the immune system and prevent disease. Based on this animal research, as little as 3 grams per day may be effective for humans. 32
In 1996, US scientists announced on-going research, documenting that a water extract of Spirulina inhibits HIV-1 replication in human derived T-cells and in human blood mononuclear cells.1 HIV-1 is the AIDS virus. Small amounts of the extract reduce viral replication, while higher concentration totally stopped its reproduction. The extract seemed to prevent the virus from penetrating the cell membrane, therefore the virus was unable to replicate. This Spirulina extract was non-toxic to human cells. The scientists said this was only preliminary research, to be followed by animal and human studies.
24.Besednova, T. et al. Immunune-ostimulating activity of lip polysaccharides in blue-green algae. Zhumal Mikrobiologii, Epidemiologii, immunobiologii, 56 (12) p. 75-79. 1979
25.Baojiang, G. et. Al. Study on effect and mechanism of polysaccharides of Spirulina on body immune function improvement. Second Asia-Pacific Conference on Algal Biotechnology. Singapore, April 1994. p. 24.
26.Zhang Cheng-Wu, et. Al. Effects of polysaccharides and Phycocyanin from Spirulina on peripheral blood and haematopoietic system of bone marrow in mice. Second Asia Pacific Conf. Ibid, April. 1994.
27.Qishen, P. et. Al. End nuclease activity and repair DNA synthesis by polysaccharide of Spirulina. Acta Genetics Sinica (Chinese J. of Genetics) V.15(5) p. 374-381. 1988
28.Lisheng, L. et. al. Inhibitive effect and mechanism of polysaccharide of Spirulina on transplanted tumor cells in mice. Marine Sciences, Qindao, China. N.5. 1991. p. 33-38
29.Qureshi, M. et. Al. Spirulina extract enhances chickens macrophage functions after in vitro exposure. J. Nutritional Immunology, V.3(4) 1995. p. 35-45.
30.Qureshi, M.. et. Al. Dietary Spirulina enhances humoral and cell-mediated immune functions in chickens immunopharmacology and Immunotoxicology, 1996
31.Qureshi, M. et. Al. Spirulina exposure enhances macrophage phagocytic function in cats. Immunopharmacology and Immunotoxicology, 1996.
32.Belay, A., Henson, R., Ota, Y. Potential Pharmaceutical Substances from Aqua culturally Produced Spirulina. Earthrise Farms, Cal-patria CA. presented to World Aquaculture Society, New Orleans. Jan. 1994