A dietary cholesterol challenge study to assess Chlorella supplementation in maintaining healthy lipid levels in adults: a double-blinded, randomized, placebo-controlled study

Background: Previous animal studies suggested that Chlorella, a unicellular green alga, has a preventive role in maintaining serum cholesterol levels against excess dietary cholesterol intake. This study aimed to conduct a pioneering investigation to clarify this issue in healthy subjects by adopting a dietary cholesterol challenge, which has not been used previously in similar studies of Chlorella in hypercholesterolemia. Methods: In this double blind, randomized, placebo-controlled study, 34 participants ingested 510 mg of dietary cholesterol from three eggs concomitantly with a usual dose of Chlorella (5 g/d) or a matched placebo for 4 weeks. Results: The dietary cholesterol challenge induced consistently higher concentrations of serum total cholesterol (TC, P < 0.001), LDL-C (P = 0.004), and HDL-C (P = 0.010) compared with baseline values, suggesting that the challenge was reliable. Thus, we observed a preventive action of Chlorella in maintaining serum TC versus placebo levels (3.5 % versus 9.8 %, respectively; P = 0.037) and LDL-C versus placebo levels (1.7 % versus 14.3 %, respectively; P = 0.012) against excessive dietary cholesterol intake and in augmenting HDL-C versus placebo levels (8.3 % versus 3.8 %, respectively). Furthermore, serum alpha-carotene showed the best separation between the placebo and Chlorella groups ((RX)-X-2 and (RY)-Y-2 > 0.5; Q(2) > 0.4). Conclusion: The results suggest that a fully replicated dietary cholesterol challenge may be useful in assessing the effectiveness of dietary supplements in maintaining the serum lipid profiles of adults whose habitual diets are high in cholesterol.