Paramylon (PM), a type of β-glucan, functions like dietary fiber, which has been suggested to exert a protective effect against obesity. We evaluated the potential beneficial effects of PM powder on obesity in mice. Male C57BL/6J mice were fed a high-fat diet supplemented with either 2.5 or 5% PM powder, extracted from Euglena gracilis, for 74 days. Growth parameters, abdominal fat content, serum biochemical markers, hepatic lipid accumulation and hepatic mRNA expression were measured. Dietary supplementation with PM resulted in decreased food efficiency ratios and abdominal fat accumulation. Dose-dependent decreases were observed in postprandial glucose levels, serum low-density lipoprotein (LDL)-cholesterol, and serum secretary immunoglobulin A (sIgA) concentrations. PM supplementation increased peroxisome proliferator-activated receptor α (PPARα) mRNA expression in the liver which is suggested to induce β-oxidation through activation of acyl-coenzyme A oxidase (ACOX), carnitine palmitoyltransferase (CPT) and fatty acid transport protein 2 (FATP2) mRNA expression. Changes in fatty acid metabolism may improve lipid and glucose metabolism. In conclusion, a preventive effect against obesity was observed in mice given a PM-enriched diet. The mechanism is suggested to involve a reduction in both serum LDL-cholesterol levels and the accumulation of abdominal fat, in addition to an improvement in postprandial glucose concentration.

Euglena gracilis EOD-1, a microalgal strain known for high yields of the β-1, 3-glucan paramylon, is suggested to function as a dietary fiber and enhance immunity. Here, we aimed to investigate the effects of E. gracilis EOD-1 biomass (EOD1BM) ingestion on immunoglobulin A (IgA) antibody titers in saliva, its reactivity, and the health-related quality of life (QOL) in humans. Reacting human immunoglobulin preparations and saliva with paramylon granules revealed the presence of anti-paramylon antibodies in the blood and saliva. We conducted a placebo-controlled, double-blind, crossover study involving 13 healthy subjects who ingested the placebo or EOD1BM for 4 weeks. Saliva was collected from each subject before and after ingestion, and IgA titers and E. gracilis EOD-1 paramylon (EOD1PM) reactivity were compared. In the EOD1BM Ingestion group, the anti-EOD1PM IgA content and titer increased after EOD1BM ingestion. No such change was observed in the Placebo group. Furthermore, the health-related QOL, especially mental health, increased in the EOD1BM Ingestion group. Thus, EOD1BM ingestion led to the production of paramylon (PM)-specific IgA antibody and increased salivary IgA antibody titers. We demonstrate that EOD1BM ingestion enhanced the immunity in the mucosal surface, evoked an antigen-specific response, and increased the health-related QOL, thereby contributing to health improvement.

Euglena gracilis EOD-1, a kind of microalgae, is known to contain a high proportion of paramylon, a type of β-1,3-glucan. Paramylon derived from E. gracilis EOD-1 is presumed to suppress cellular oxidative injury and expected to reduce fatigue and fatigue sensation. Therefore, we aimed to examine whether food containing paramylon derived from E. gracilis EOD-1 (EOD-1PM) ingestion reduced fatigue and fatigue sensation in healthy adults. We conducted a randomized, double-blind, placebo-controlled, parallel-group comparison study in 66 healthy men and women who ingested a placebo or EOD-1PM daily for 4 weeks (daily life fatigue). Furthermore, at the examination days of 0 and 4 weeks, tolerance to fatigue load was evaluated using mental tasks (task-induced fatigue). We evaluated fatigue sensation using the Visual Analogue Scale, the work efficiency of the advanced trail making test and measured serum antioxidant markers. The EOD-1PM group showed significantly lower levels of physical and mental fatigue sensations and higher levels of work efficiency as well as serum biological antioxidant potential levels than the placebo group. These results indicate that EOD-1PM ingestion reduced fatigue and fatigue sensation, which may be due to an increase in antioxidant potential and maintenance of selective attention during work.

Background/Objective: Dietary polysaccharides are increasingly recognized as functional nutritional components that support human health through modulation of immune function. However, clinical evidence linking their intake to site-specific upper respiratory mucosal immune health in humans remains limited. This study investigated whether dietary β-1,3/1,6-glucan (SC-BG) from baker’s yeast may support upper respiratory mucosal immune health in healthy adults. Methods: Following in vitro assays on human dendritic cells (DCs), a randomized, double-blind, placebo-controlled parallel-group trial was performed in healthy adults (18–69 years) who consumed either SC-BG or placebo capsules for 12 weeks in Japan. The primary outcome was circulating DC activation. Secondary outcomes were mucosal immune markers including secretory immunoglobulin A (s-IgA) and lysozymes from site-specific mucosal swabs (posterior oropharyngeal wall/nasopharynx) and salivar, and self-perceived upper respiratory tract symptoms. Results: SC-BG increased CD80 expression in DCs in vitro. In the clinical trial, 40 participants were randomized (n = 20 per group), and 39 (SC-BG: n = 19, placebo: n = 20) were analyzed. At week 8, the SC-BG group showed higher cDC1 CD80 expression than placebo. SC-BG intake also attenuated declines in s-IgA levels in the posterior oropharyngeal wall and nasopharynx and increased salivary lysozyme concentrations. Participants receiving SC-BG reported fewer cumulative days with upper respiratory tract-related local and systemic symptoms. No test food-related adverse events were observed. Conclusions: These findings provide preliminary clinical and mechanistic observations suggesting that dietary SC-BG may enhance circulating cDC1 activation and may help support upper respiratory local mucosal immune health in healthy adults, highlighting the potential of dietary polysaccharides as functional nutritional strategies for maintaining immune resilience.