Short-Term Effects of Spirulina Consumption on Glycemic Responses and Blood Pressure in Healthy Young Adults: Results from Two Randomized Clinical Trials

Abstract

The effects of spirulina consumption added in foods were investigated in two crossover clinical trials (n = 13 different healthy adults). In Trial-1 adults consumed cookies with-and-without spirulina (3.12 g per 100 g final product; 2.5 g spirulina per 50 g available carbohydrates) according to glycemic index (GI) methodology. In Trial-2, adults consumed 4 g, 6 g, and 8 g spirulina as beverage diluted in 50 g D-glucose vs. 50 g plain D-glucose. Capillary blood glucose samples were collected at 0, 15, 30, 45, 60, 90, and 120 min and blood pressure (BP) was measured at beginning and end of each visit in both trials. Trial-1: both cookies with and without spirulina provided medium GI values (59 and 60, respectively, on glucose-scale), but no significant differences were found for BP. Trial-2: both 4 g and 8 g spirulina lowered postprandial glucose at 120 min (95% CI: -1.64 to -16.12 and -1.23 to -15.87, respectively). The results explained 29% of variation. Only 8 g spirulina decreased significantly 90-120 min area under the curve (AUC) for glucose and systolic BP (-4%). No differences were found for fasting glucose. Adding spirulina to cookies did not affect glucose responses and BP. Only 8 g provided significantly lower 90-120 min-AUC for glucose and BP compared to 4 g, 6 g-and-D-glucose, indicating advantages to glycemic control and hypertension.

Keywords: appetite; blood pressure; cookies; dose; glycemic index; glycemic response; healthy adults; spirulina.

Figure 1

Flowchart of the two current investigations given as examples of the crossover, randomized procedure. Eligible participants were studied in separate days over a period of 3–9 weeks with an interval of no less than 40 h and more than 2 weeks between tests. Participants attended the sessions of around 3 h duration, separated by a wash-out period of at least two days. Abbreviations: GI = glycemic index; BP = blood pressure.

Figure 2

Changes from baseline (Δ) for capillary blood glucose concentrations (mg/dL) after the consumption of the test foods: plain cookies containing 50 g available carbohydrates, cookies containing 50 g available carbohydrates (2.5 g spirulina), white bread, and the reference food (D-glucose) (n = 13). Data are means ± SEM. Data were compared by post hoc analysis of repeated measures ANOVA. The models included the factors “subject” (id), “sequence” for inter-subject variation, and “period” and “treatments” to account for intra-subject variability.

Figure 3

Changes from baseline (Δ) for capillary blood glucose concentrations (mg/dL) after the consumption of test beverages, 50 g D-glucose with 4 g spirulina, 50 g D-glucose with 6 g spirulina, 50 g D-glucose with 8 g spirulina, and the reference beverage (50 g D-glucose) (n = 13). Data are means ± SEM. The asterisk denotes a statistically significant difference at the 0.05 level, as derived from repeated measures ANOVA followed by post hoc Tukey’s test. The models included the factors “subject” (id), “sequence” for inter-subject variation, and “period” and “treatments” to account for intra-subject variability. Between group effects were explored using multi-level random effects regression model, clustered by d and adjusted for time. Abbreviation: SPIR = spirulina.

Figure 4

Systolic blood pressure (SBP) at baseline and 120 min post-test beverage consumption. Beverages tested were 50 g D-glucose with 4 g spirulina, 50 g D-glucose with 6 g spirulina, 50 g D-glucose with 8 g spirulina, and the reference test beverage 50 g D-glucose (n = 13). Data are means ± SEM. Data were compared by repeated measures analysis using post hoc Tukey test with Bonferroni correction. * = p < 0.05. Abbreviations: SBP0: systolic BP at baseline. SBP120: systolic BP at 120 min post-test beverage.