What should be avoided with magnesium?

The habits to avoid, which matter more than any substance on a folklore list

What should be avoided with magnesium is, for most readers, a question about habits rather than substances, the medicines that magnesium is spaced from having their own page and the folklore's substances, coffee, calcium, zinc, turning out to be irrelevant at ordinary doses, so this page gives the habits list. Avoid heavy alcohol, or at least know its cost: alcohol raises urinary magnesium loss and chronic heavy drinking is the commonest cause of deficiency in fed adults, the depleters page's top entry, so a lifter whose weekends are heavy is draining what the capsule fills, and the supplement cannot outrun the habit. Avoid a fasted dose of the wrong salt: magnesium's laxative effect is osmotic and worse in an empty gut with nothing to slow it, citrate and oxide carrying most of it, so a citrate on an empty stomach, and any magnesium before a run or a session, is the habit the gut punishes, bisglycinate with a meal being the version that avoids it, the with-food and empty-stomach pages' finding. Avoid totals over the level: the UK supplemental guidance of about 400mg a day is a sum across every source, and the hidden ones, a magnesium-hydroxide antacid, a milk-of-magnesia laxative, a multivitamin's line, an electrolyte drink, add to a 300mg glycinate without announcing it, the every-night audit's one real risk, so the habit to avoid is not counting. Avoid a new salt or dose on a race or competition day: nothing new starts on the day, the runner's rule, and a change of magnesium salt is a change of gut behaviour. Avoid the fasted bedtime ritual of ZMA marketing: zinc fasted causes nausea and magnesium fasted gains nothing, both belonging with the evening meal.

The one food interaction, phytate, at its true size, the substances the folklore names and their real status, and the list filed

The one food interaction worth naming is phytate, and it is named at its true size: phytic acid in wholegrains, legumes, nuts and seeds binds magnesium, zinc and iron in the gut and reduces their absorption from the same meal, a real effect that matters for a marginal diet relying on those foods for its minerals and barely at all for a supplemented one, since a 300mg elemental dose is large against the fraction phytate binds and the same foods are also the diet's best magnesium sources, so the phytate note is that a reader on a marginal, unsupplemented diet may absorb less magnesium from an all-bran breakfast than the table suggests, and a supplemented reader ignores it, soaking, sprouting and fermenting reducing phytate for anyone who cares. The substances the folklore names, at their real status: coffee has a small diuretic effect and its main magnesium cost is the sleep it steals, not a reason to avoid it with the capsule; calcium competes only at gram-scale doses, a yoghurt or a modest tablet being fine beside magnesium; zinc competes only above 100mg, adequacy doses of 10 to 25mg being fine at dinner; iron has no meaningful interaction; and fibre binds a little through the phytate above and is otherwise a friend of the gut the laxative effect is not. The medicines are spaced rather than avoided and belong on the not-with page, levothyroxine, bisphosphonates and the tetracycline and quinolone antibiotics by hours, and proton-pump inhibitors and diuretics for a pharmacist's word. The list filed: avoid heavy alcohol, a fasted dose of a laxative salt, uncounted totals over 400mg, a new salt on race day and the fasted bedtime ritual, note phytate only on a marginal diet, ignore the folklore's coffee, calcium, zinc and iron at ordinary doses, and space the medicines, the worked example avoiding the gut problem by design, bisglycinate with the evening meal at 300mg elemental, £19.99 for 90 days at 22p.

The verdict, habits to avoid and folklore to ignore

What should be avoided with magnesium: habits more than substances, heavy alcohol that drains it, a fasted dose of citrate or oxide that the gut punishes, totals over 400mg across antacids, laxatives, multivitamins and drinks that go uncounted, a new salt on race day and the fasted bedtime ritual, with phytate noted only for a marginal unsupplemented diet, the folklore's coffee, calcium, zinc and iron ignored at ordinary doses, and the medicines spaced on their own page. The salt and meal that avoid the gut problem by design: Futuro Labs Magnesium Glycinate, bisglycinate, two capsules with the evening meal, 300mg elemental at 80% NRV, £19.99 for 90 days at 22p a day.

What to check on the label

Questions people also ask

What foods should I avoid when taking magnesium?

None in practice: the one real food interaction, phytate in wholegrains, legumes and seeds binding some magnesium at the same meal, matters only for a marginal unsupplemented diet and is irrelevant against a 300mg elemental dose.

Should I avoid coffee with magnesium?

No: coffee has a small diuretic effect that regular drinkers adapt to, and its main magnesium cost is the sleep it steals when taken late, which is a caffeine curfew question rather than a magnesium one.

What is the biggest thing to avoid with magnesium?

Heavy alcohol: it raises urinary magnesium loss and is the commonest cause of deficiency in fed adults, so the supplement cannot outrun a heavy weekend.

Why should I not take magnesium on an empty stomach?

Because the laxative effect is worse in an empty gut with nothing to slow it, citrate and oxide especially, so magnesium goes with a meal as bisglycinate, and never before a run or a session.

Do I need to avoid calcium or zinc with magnesium?

Not at ordinary doses: calcium competes only at gram-scale amounts and zinc only above 100mg, so a yoghurt, a modest calcium tablet or 10 to 25mg of zinc beside magnesium at dinner is fine.

Sources

1. The alcohol and magnesium literature: alcohol increases urinary magnesium excretion acutely and chronic heavy drinking is the commonest cause of clinical magnesium deficiency in otherwise well-fed adults. PubMed record
2. The phytate literature: phytic acid in wholegrains, legumes and seeds binds magnesium, zinc and iron in the gut and reduces their absorption from the same meal, an effect that matters for marginal diets and barely for supplemented ones. PubMed record
3. The calcium and magnesium interaction literature: calcium and magnesium share intestinal transport, and very high calcium doses can modestly reduce magnesium absorption, while ordinary supplemental amounts taken together show no meaningful effect. PubMed record
4. Expert Group on Vitamins and Minerals. Safe Upper Levels for Vitamins and Minerals. Food Standards Agency, 2003 (magnesium guidance level 400mg a day from supplements). https://cot.food.gov.uk/sites/default/files/vitmin2003.pdf

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