Spirulina is reported to be effective for improving blood lipid profiles (Torres et al., 1998
), enhancing immune capacity, and reducing oxidative stress (Shklar & Schwartz, 1998
). Since dyslipidemia, oxidative and inflammatory stress are considered to be the contributing factors for diabetes, spirulina is the most likely candidate as functional food for management of type 2 diabetes.
) reported that spirulina supplementation to healthy elderly people with normal fasting blood glucose (FBG) brought a significant reduction in mean FBG from 105.1 mg/dl to 100.0 mg/dl. On the contrary, the spirulina supplementation in patients with type 2 diabetes in this study did not result in a reduction in the plasma levels of FBG, hemoglobin A1c, and insulin. The subjects in this study were type 2 diabetes mellitus (DM) patients with FBG>126 mg/dl. Therefore spirulina may not have beneficial effect on blood glucose concentration for DM patients.
Many animal and human studies have repeatedly reported the lipid-lowering effects of spirulina. Park and Kim (2003
) reported that the plasma levels of triglyceride, total cholesterol, and LDL-cholesterol in Korean elderly people were significantly decreased after spirulina supplementation for 24 weeks. Also, spirulina supplementation to type 2 diabetic patients resulted in a significant decrease in plasma concentrations of triglyceride, total cholesterol and LDL-cholesterol (Iyer et al., 2001
). In an animal study, rats fed a 20% water-soluble fraction of spirulina showed a significant reduction in LDL/HDL ratio (Hosoyamada et al., 1991
). In our study, no changes were observed in plasma concentrations of total cholesterol, LDL-cholesterol, and HDL-cholesterol after spirulina intervention, however, a significant lowering effect on plasma triglyceride concentration was shown. The less profound cholesterol lowering effect in this study may be due to baseline lipid concentration of the subjects. The cholesterol concentrations of our subjects at baseline were in normal ranges, however, the baseline lipid profile of the previous study (Park & Kim, 2003
) was higher with triglyceride of 168.2 mg/dl, and total cholesterol of 231.3 mg/dl, and LDL-cholesterol of 154.6 mg/dl. Correlation analysis in this study revealed that subjects with higher initial blood levels of triglycerides and cholesterol showed a higher reduction in lipid concentration, blood pressure and inflammatory cytokine. Therefore, spirulina supplementation was probably more effective for lowering total cholesterol in subjects with higher blood cholesterol level before intervention.
Hypotriglyceridemic and blood pressure lowering effects of spirulina have been reported. Iwata et al. (1990
) postulated that the hypotriglyceridemic effect of spirulina might be due to its effect on the metabolism of lipoproteins. They reported that rats fed a diet containing spirulina showed a significant increase in the activity of lipoprotein lipase compared to rats fed a high fructose diet. The mechanisms of spirulina on blood pressure are not well understood. However, Guan et al. (2007
) have proposed that the high potassium content of spirulina may have a lowering effect on blood pressure.
Oxidative stress may play an important role in the etiology of diabetic complications (Giugliano et al., 1996
). Kim and Kim (2005
) reported that healthy elderly subjects received spirulina supplementation for 8 weeks showed improved antioxidant status as evidenced by increased total antioxidant status and decreased thiobarbituric acid reactive substance. In accordance with these studies, spirulina supplementation in this study resulted in a significant decrease in MDA level from 2.57 µM/L to 1.85 µM/L. Also, a significant increase in plasma adiponectin concentration was observed in this study after spirulina supplementation. An increase in adpionectin concentration with a decrease in oxidative stress would play a role in the prevention of DM complication.
In conclusion, spirulina intervention brought in favorable effect on blood lipids, anti-oxidant capacity, and inflammatory response in Korean patients with type 2 diabetes. Our results also suggest that spirulina is a promising agent as a functional food for the management of diabetes. Further studies with larger sample size and longer duration are required to ascertain the mechanism of spirulina's actions on lipid profiles, immune variables, and antioxidant capacity.