What the Research Says About the Seven Ingredients

Guarana: 100 mg of extract from a domesticated vine

Paullinia cupana is a perennial climbing plant of the soapberry family, domesticated in the central Amazon basin. The Sateré-Mawé have cultivated and prepared its seeds for centuries — roasted, ground, pressed into bars, then grated into water against a rough stone. European sources first described this daily practice in 1669.

The chemistry is dominated by methylxanthines. Caffeine is the main component, accompanied by theobromine and theophylline, along with condensed tannins, saponins and catechins. A review in the Journal of Agricultural and Food Chemistry looked at the published literature on phytochemistry, pharmacology and safety. Its conclusion: no causal links to serious health risks are currently known when the seed is consumed properly (“Safety of Guarana Seed as a Dietary Ingredient”, J Agric Food Chem, 2019).

A pharmacological review makes a second point bluntly: what can be observed from guarana traces back to its caffeine — and the caffeine content of commercial products is not always declared transparently (Drug Ther Bull, 2012). That criticism is an argument for declaring every individual amount, not against it.

Apple cider vinegar: two fermentation stages, two groups of micro-organisms

Vinegar is one of the oldest preserved foods there is. It’s made in two separate steps. First, yeasts — usually Saccharomyces cerevisiae — convert the fruit sugars in apple juice into ethanol in the absence of oxygen. Then acetic acid bacteria, chiefly Acetobacter, Gluconobacter and Komagataeibacter, oxidise that ethanol into acetic acid in the presence of air. Vinegar sold for the table ends up at four per cent acetic acid or more.

This group of bacteria is unusually versatile. It shapes not just vinegar but kombucha, kefir, sour beer and fermented cocoa and coffee beans, and the mother of vinegar, that gelatinous layer, is cellulose made by the bacteria themselves. A 2024 review shows how strongly the end product depends on how those micro-organisms interact (“A Review on the Interaction of Acetic Acid Bacteria and Microbes in Food Fermentation”, Foods, 2024). Reta3 contains 100 mg of apple cider vinegar extract — the dried form, bound to a carrier, with no taste of its own and none of the acidity that liquid vinegar brings into contact with tooth enamel.

Inulin from Jerusalem artichoke: a fructan of variable chain length

Helianthus tuberosus is a North American member of the daisy family, brought to France by Samuel de Champlain in 1605. Its German name traces back to the Brazilian Tupinambá people, while the English “Jerusalem artichoke” is most likely a mangling of the Italian girasole, sunflower.

The tuber stores its carbohydrates as inulin rather than starch: linear chains of β(2→1)-linked fructose units capped by a terminal glucose. Inulin can make up as much as 85 per cent of the tuber’s dry weight. Two enzymes build the molecule — 1-SST starts the chain, 1-FFT extends it — while fructan exohydrolases break it down again when the tuber sprouts (Characterisation of fructan metabolism during germination, Front Plant Sci, 2018). The degree of polymerisation determines solubility and processing behaviour, which is why turning it into powder is a piece of process engineering in its own right (Preparation of inulin powder from Jerusalem artichoke tubers, 2015).

One number is worth stating plainly. Reta3 contains 100 mg of inulin. Dietary fibre research works in gram quantities — that’s a gap of two orders of magnitude.

L-glutamine: the most abundant free amino acid in the body

Glutamine circulates in blood at roughly 0.5 to 0.7 mmol/l, two to a hundred times higher than the concentration of other amino acids. Hans Adolf Krebs showed in the 1930s that mammalian tissue can both break glutamine down and build it up — the start of a field that hasn’t stopped growing since.

The body makes its own glutamine, which is why it counts as non-essential. Under heavy catabolic stress, though, demand can outstrip that internal supply — which is why it’s classed as conditionally essential. Between organs, the amino acid works as a nitrogen shuttle: lung, liver, brain, skeletal muscle and adipose tissue synthesise it, while the intestinal mucosa, leukocytes and renal tubule cells consume it (Newsholme et al., Proc Nutr Soc, 2023). Reta3 contains 50 mg.

L-leucine: discovered in cheese in 1818

Leucine was one of the first amino acids ever isolated. Joseph Louis Proust obtained it from cheese in 1818; two years later Henri Braconnot isolated it from muscle and wool by acid hydrolysis and named it after the Greek leukós, white, because of the pale flakes it formed. Nobody worked out its structure until 1891.

These days leucine is studied mainly as a signalling molecule. It acts on mTORC1 — the cell’s central nutrient-sensing complex — more strongly than any other amino acid. A cell culture study on human myotubes found that leucine transiently increased phosphorylation of mTOR and p70S6K independently of insulin (Gran & Cameron-Smith, BMC Physiol, 2011). Leucine is an essential branched-chain amino acid, so it has to come from the diet. Reta3 contains 50 mg.

Zinc: from a single enzyme to three thousand proteins

As early as 1869, Jules Raulin showed that the mould Aspergillus niger will not grow without zinc. The biochemical breakthrough came in 1939, when David Keilin and Thaddeus Mann found zinc in carbonic anhydrase — the first known zinc metalloenzyme. More than 300 zinc-dependent enzymes have since been described, covering all six enzyme classes, and sequence analyses estimate that the human genome encodes around 3,000 zinc proteins (Maret, Adv Nutr, 2013).

The 1980s brought a second kind of role with the discovery of zinc fingers, where the ion stabilises protein domains that bind DNA. The coordination geometry is usually a distorted tetrahedron, and that variety of binding sites is exactly what makes the element interesting for protein design (Zastrow et al., Biochemistry, 2014). Reta3 provides 15 mg of zinc as citrate, equal to 150% of the Nutrient Reference Value.

Chromium: a finding in torula yeast, 1959

Klaus Schwarz and Walter Mertz fed rats a semi-synthetic diet based on torula yeast and observed impaired glucose tolerance. Brewer’s yeast stopped it happening. The factor that one yeast contained and the other didn’t was described in 1959 as the “glucose tolerance factor” — with trivalent chromium identified as its active component.

Attention later turned to an oligopeptide. Chromodulin binds four chromium(III) ions and was named by analogy with calmodulin, since both molecules dock onto kinases in response to a flux of metal ions. Chromodulin binds to the activated insulin receptor and stimulates its tyrosine kinase activity (Vincent, J Nutr, 2000). A later review shows what slow going the field has been: chromium deficiency is hard to produce in humans and was first documented only in 1977, in patients on long-term parenteral nutrition (Vincent, Proc Nutr Soc, 2004). Picolinate became the standard form because it produces a neutral, stable complex. Reta3 contains 40 µg of chromium, exactly 100% of the Nutrient Reference Value.

What counts as a claim in law — and what doesn’t

An interesting research history is one thing. A claim you’re allowed to advertise is quite another. In Great Britain, only officially authorised health claims may be used for foods. Of the seven ingredients in Reta3, two meet that condition:

• Chromium contributes to normal macronutrient metabolism.
• Chromium contributes to the maintenance of normal blood glucose levels.
• Zinc contributes to normal macronutrient metabolism.

No authorised claim exists for guarana, apple cider vinegar extract, inulin, L-glutamine or L-leucine. For the plant extracts, that’s down to an assessment process for botanicals that has been stalled for years; for the two amino acids, the applications that were submitted didn’t succeed. Inulin does have an authorised claim, but it is tied to chicory inulin and to a daily intake of 12 g — Reta3 meets neither condition and therefore cannot use it.