England Sets Purity Rules for Magnesium L-threonate
If you have ever looked at a supplement label and wondered who decides what is allowed inside, this small piece of law gives part of the answer. On 22 June 2026, ministers made the Food Supplements Purity Criteria (Magnesium L-threonate monohydrate) (England) Regulations 2026, with the new rules due to come into force on 13 August 2026. The change is narrow. It deals with one chemical form used as a source of magnesium in food supplements. But this is exactly how much of food law works in practice: not through dramatic announcements, but through careful, technical standards that decide what can be sold and how it should be described.
According to the text published on legislation.gov.uk, this is a statutory instrument. That means it is not a brand-new Act of Parliament. Instead, it is a detailed rule made under powers that Parliament has already given to ministers through earlier legislation. In this case, those powers come from the Nutrition (Amendment etc.) (EU Exit) Regulations 2019. If that sounds dry, it is still worth noticing. After Brexit, many food and nutrition rules had to be carried across, adjusted and managed in UK law, and statutory instruments like this are one of the main ways that happens.
The process matters too. The instrument says there was open and transparent consultation, following the food law rules set out in Regulation (EC) No 178/2002. It also says a draft was laid before Parliament and approved by both Houses before it was made. So this was not simply signed off behind a closed door. Sharon Hodgson, a Parliamentary Under-Secretary of State at the Department of Health and Social Care, signed it on 22 June 2026 by authority of the Secretary of State, but the legal route included consultation and parliamentary approval first.
There is one legal detail that often confuses readers, and it is a useful one to pause on. The regulations extend to England and Wales, but apply only to England. In everyday terms, that is about where the law formally sits and where it has practical effect. In UK law, those are not always the same thing. The main legal change appears in the schedule. It sets the purity criteria for magnesium L-threonate monohydrate at 7.2% to 8.3% magnesium and 82% to 91% L-threonate.
That does not mean the government is telling you how much magnesium to take each day. It means that if a manufacturer uses this substance as a magnesium source in a food supplement, the substance itself must match clear composition standards. These percentages help define what the ingredient is supposed to be. For you, **what this means** is simple: purity criteria are about consistency, identity and trust. They help regulators, laboratories and manufacturers check that an ingredient matches the legal standard, rather than drifting into a weaker, altered or poorly described version.
The official note says no impact assessment was produced because no significant effect on the private, voluntary or public sector is expected. That tells you the government sees this as a technical update, not a major shake-up for shops, charities or public bodies. Even so, technical rules are still public-interest rules. They shape the quiet standards behind the products people buy, often without most of us ever seeing the law underneath them. For teachers, students and curious readers, this is a good reminder that food safety is often built from small decisions, not only big headline laws.
The Explanatory Memorandum published alongside the instrument is there to help readers understand the purpose behind the legal wording. That matters, because documents like this can look intimidating when they begin with powers, schedules and chemical names. A helpful way to read a statutory instrument is to ask what substance is being regulated, who had the power to do it, and what changes on the date it comes into force. Here, the answer is clear. From 13 August 2026, England will have legal purity criteria for magnesium L-threonate monohydrate as a source of magnesium in food supplements.