Bio-Strath® (commonly referred to as Swiss Strath) is a liquid or tablet supplement produced in Switzerland since 1961 by Bio-Strath AG. Its primary ingredient is plasmolysed herbal yeast — a preparation of Saccharomyces cerevisiae grown on a substrate of 61 culinary herbs, then subjected to a plasmolysis process that releases the nutritional content of the yeast cells. The result is a product with an extensive nutrient profile including B vitamins, amino acids, minerals, beta-glucans, nucleotides, and coenzymes.
Strath is sold as a vitality tonic, traditionally recommended for fatigue, convalescence, concentration difficulties, and immune support. It has been a mainstay of Swiss, German, and Irish health shops for decades. The plasmolysis manufacturing process is the key differentiator claimed by its manufacturer — and it's worth understanding what this means biochemically.
Plasmolysis is the process by which cells lose water due to osmotic pressure — when a cell is placed in a hypertonic solution, water diffuses out through the cell membrane, causing the cytoplasm to shrink and pull away from the cell wall. In yeast cell processing, plasmolysis is used deliberately to rupture or permeabilise the cell membrane, releasing intracellular contents (amino acids, nucleotides, vitamins, coenzymes) that would otherwise remain trapped inside the intact yeast cell wall.
This is meaningful for bioavailability: the thick cell wall of Saccharomyces cerevisiae (composed primarily of glucan and mannan polysaccharides) is indigestible by human enzymes. Intact yeast cells pass through the GI tract largely undigested, releasing relatively little of their intracellular nutrient content. Plasmolysis pre-ruptures the cells, theoretically making the intracellular nutrients available for absorption without requiring cellular digestion in the gut.
This is a technically legitimate rationale for why plasmolysed yeast might offer better bioavailability than standard dried yeast or brewer's yeast preparations. The question is whether this claimed advantage is validated in clinical studies.
Bio-Strath has sponsored a number of clinical studies examining its product for concentration, learning performance, physical fatigue, and immune function. The most widely cited is a Swiss RCT by Grundmann et al. (2002) — a double-blind, placebo-controlled trial in 51 adults with chronic fatigue or mental exhaustion. Participants received Bio-Strath liquid (3 teaspoons daily, approximately 18 ml/day) or placebo for 12 weeks. The Strath group showed significantly greater improvements in self-reported fatigue, concentration, and general wellbeing compared to placebo.
A separate children's RCT (Landes 1999) found improved learning performance and concentration in children taking Bio-Strath versus placebo over 12 weeks, with some supporting neuropsychological assessment data.
A study examining Strath in athletic performance (Reiter et al. 2003) found that cyclists taking Strath supplementation showed improved maximal oxygen uptake (VO2 max) and reduced lactate accumulation during exercise compared to placebo over 16 weeks — suggesting a possible ergogenic effect.
The key limitation throughout the Strath research portfolio is that most studies are funded by or conducted in collaboration with Bio-Strath AG, the manufacturer. Independent replication is sparse. This does not mean the results are fabricated, but it does mean the evidence base cannot be considered fully independent. Trial sizes are also modest.
| Claim | Evidence Level | Source |
|---|---|---|
| Plasmolysis releases intracellular yeast nutrients | Strong (mechanism) | Established cell biology; well-characterised process |
| Reduces fatigue and improves wellbeing | Moderate | Grundmann et al. 2002 RCT (n=51, double-blind) |
| Improves concentration in children | Limited | Landes 1999 — manufacturer-funded; no independent replication |
| Athletic performance improvement | Limited | Reiter et al. 2003 — small, manufacturer-affiliated study |
| Immune support / reduced infection frequency | Limited | Anecdotal and manufacturer-funded data |
Bio-Strath provides a broad spectrum of B vitamins (B1, B2, B6, biotin, folic acid, pantothenic acid), essential amino acids, beta-glucans, co-enzymes, and minerals. For people with dietary gaps — particularly those in convalescence, vegetarians/vegans with B vitamin concerns, or elderly people with reduced appetite — the broad nutritional coverage of a plasmolysed yeast preparation like Strath may offer practical supplementation support across multiple deficiencies simultaneously.
The liquid form of Strath contains a small amount of alcohol (from the fermentation process — typically around 0.3% per serving) which may be relevant for those avoiding all alcohol for medical or religious reasons.
Standard dosing for the liquid form is 1 teaspoon (5 ml) three times daily before meals, diluted in water or juice. The tablet form is typically 3 tablets three times daily. A general tonic course is 1–3 months, though Strath is also used long-term as a daily supplement. It has a distinctly flavoured, slightly earthy taste that most people find mild and acceptable.
Bio-Strath has an excellent safety profile over 60+ years of use. Yeast-based supplements can provoke reactions in people with Candida overgrowth sensitivity or yeast allergies — though Strath uses Saccharomyces cerevisiae, which is a different species from Candida. Side effects are rare; mild GI discomfort occasionally reported at the start of use.
Due to the B vitamin content (including B12 in some formulations), Strath should not be combined with megadose B vitamin supplements without consideration of total intake. No significant drug interactions are documented.
Swiss Strath is a well-made, historically established product with a credible technical rationale for its bioavailability claims. The clinical evidence for fatigue and vitality is positive, if limited by manufacturer funding and small study sizes. It is best viewed as a broadly nutritious supplement with a good safety record and a genuine biochemical basis for the plasmolysis claim. The evidence doesn't place it in the category of treatments for medical conditions — but as a nutritional tonic, it has more scientific grounding than many competitors.