Posted by Cameron Webb
on May 03, 2026
Every ingredient was chosen for a specific reason, dosed to reflect what the clinical evidence actually supports, and selected in a form that the body can meaningfully use. Here is the thinking behind each one.
Ashwagandha (7% Withanolides) at 300mg
Ashwagandha is one of the most researched adaptogenic herbs we have, with a growing body of well conducted clinical evidence. The extract in ARC is standardised to 7% withanolides, which are the pharmacologically active constituents responsible for its effects on the stress response. The concentration of Withanolides is also higher than what is typically seen in the industry. Standardisation is important here because the withanolide content varies considerably between products and without it you have no reliable sense of what you are actually taking.
Its primary role in ARC is supporting healthy cortisol regulation. Chronic stress keeps the HPA axis in a state of sustained activation, maintaining cortisol at levels that make it very difficult to wind down in the evening. In a 60 day double blind placebo controlled trial, this standardised extract was associated with a 23% reduction in morning serum cortisol. That is a meaningful effect, and it is the foundation on which the rest of ARC's sleep support is built.
Magnesium Bisglycinate at 750mg (148mg Elemental Magnesium)
Magnesium is involved in hundreds of enzymatic processes, several of which are directly relevant to sleep. It regulates GABA A receptor activity, supports parasympathetic nervous system function, plays a role in melatonin synthesis, and helps modulate the stress response via the HPA axis. Low magnesium is consistently associated with elevated cortisol, increased sleep fragmentation, and reduced time in slow wave sleep.
The form matters significantly. Magnesium oxide, which appears in many lower cost products, has bioavailability of around 4%. Bisglycinate, chelated to the amino acid glycine, absorbs substantially better and is far gentler on the digestive system. The 750mg of bisglycinate in ARC provides 148mg of elemental magnesium, a genuinely useful contribution, particularly given how common magnesium insufficiency is in the UK adult population.
L Theanine at 500mg of a 40% Extract (200mg Active)
This is something worth explaining clearly because it is often misrepresented on product labels. The 500mg figure refers to the weight of the extract, which is standardised to 40%, meaning the active L theanine content is 200mg. That is the dose with clinical relevance and it sits at the upper end of the range used in published research.
L theanine works by increasing alpha band EEG activity, the brain wave pattern associated with calm and relaxed alertness. It also supports GABA and serotonin activity. Practically speaking, it is particularly helpful for people who find that their mind stays active even when they are physically tired. It eases cognitive arousal without causing sedation, which makes it well suited to the wind down period before sleep.
Apigenin at 50mg
Apigenin is a flavonoid found in high concentrations in chamomile, which goes some way to explaining why chamomile has been associated with sleep and relaxation for so long. It has affinity for GABA A receptors, contributing to the GABAergic calming effect alongside the magnesium and L theanine in the formula. At 50mg as a standardised extract, the dose is meaningfully higher than anything achievable through dietary chamomile consumption alone. Alongside the other ingredients in ARC, it helps create a multi pathway approach to supporting the body's transition toward sleep.
P5P (Vitamin B6) at 2.5mg
P5P is pyridoxal 5 phosphate, the active coenzyme form of B6. Unlike standard pyridoxine, it does not require hepatic conversion, making it immediately available as a cofactor. Its role in ARC is at the level of serotonin synthesis: P5P is required for the conversion of tryptophan to serotonin, and serotonin is in turn the precursor to melatonin. Supporting this upstream step means the body has what it needs to produce melatonin naturally.
P5P also carries EU authorised health claims for contributing to normal psychological function and the reduction of tiredness and fatigue, which is why its role in ARC is associated with morning clarity rather than wind down. The 2.5mg dose is intentionally modest. This is a cofactor, and exceeding physiological need serves no additional purpose.
Every choice in this formula came from asking what the body actually needs to sleep well, not from what looks good on a label.
