Do We Really Need Magnesium?

Magnesium is everywhere right now. People say it helps you sleep, it helps the body, it fixes this and that. A lot of it is true. But a lot of people are confused, especially when they walk into a pharmacy in Lagos, Abuja or Port Harcourt and see five different bottles that all say “magnesium.” Oxide, citrate, glycinate. Which one? How much? Do you even need it?

So this week we want to go through it slowly. What magnesium does in the body, how much you need, whether you may already be getting it from the food you eat every day, the different forms you’ll see on the shelf, which claims have actually been proven, and how to take it without wasting your money or clashing with your other drugs.

What does magnesium do in the body?

Think of magnesium as a helper. Your body is doing thousands of chemical reactions every second, and magnesium is needed to make a lot of them work. The US National Institutes of Health says it takes part in more than 300 of them. In simple terms, here is what it does:

Makes energy. The energy your cells use (it’s called ATP) needs magnesium to be made and to be used.
Works your muscles and nerves. It helps muscles contract and then relax, and it helps nerves pass signals. Calcium helps the muscle tighten, magnesium helps it let go.
Keeps the heartbeat steady. The heart is a muscle too.
Handles blood sugar. It plays a part in how your body uses insulin and moves sugar into your cells.
Helps blood pressure. It helps blood vessels relax.
Builds bones. A good amount of the magnesium in your body is stored in your bones.
Builds proteins and DNA.

So when someone says “magnesium does everything,” they’re not far off. But here is the real question: does taking extra magnesium give you extra benefit? That depends on whether you were low to begin with.

How much magnesium do you need?

The daily amounts recommended by the NIH Office of Dietary Supplements (this counts what you get from food and drink):

Men 19 to 30: 400 mg
Men 31 and above: 420 mg
Women 19 to 30: 310 mg
Women 31 and above: 320 mg

Pregnant women and teenagers have slightly different numbers, so check the NIH fact sheet if that’s you.

Now, here is something that should interest you. A team from the University of Ibadan and Babcock University, among others) studied what 732 adults in Abuja and Ogun State actually eat, and worked out how much magnesium they were getting from their food. The average was about 389 mg a day. That is inside the recommended range. Roughly 3 in 10 people were below the recommended amount, which is not nothing, but the authors said magnesium intake was not a big worry in the group. Read the study (Shokunbi et al., Heliyon, 2023).

Two things to remember about that study. It was two places only, not the whole country. And it counted food only. So it does not mean everyone is fine, but it does mean that a regular diet can get you close.

True magnesium deficiency is not common in healthy people with healthy kidneys. It is more likely in people with certain stomach and gut problems, type 2 diabetes, heavy alcohol use, and people on some long-term drugs (we’ll come to those). Signs of low magnesium can include muscle cramps or twitching, tremors, tiredness, and numbness or tingling. But these signs show up in many other conditions too, so don’t diagnose yourself from a list. A blood test and a doctor can help.

Where does magnesium come from in Our food?

The same study measured magnesium in 141 foods as they are actually eaten. Here are some of the results, per 100 grams:

Food (as eaten)	Magnesium (mg per 100 g)
Crayfish, roasted	416
Cashew nuts, roasted	326
Groundnut, roasted	272
Stockfish	229
Donkwa	181
Lagos spinach (soko) soup with egusi	155
Groundnut, boiled	147
Catfish, roasted	133
African spinach (tete) soup	113
Fried ugu (fluted pumpkin leaves)	94
Beans (olo), boiled	87
Akara (white beans)	77
Garri (eba)	28
Pounded yam	28
Rice, boiled (long grain)	14

Source: Shokunbi et al., Heliyon, 2023, values rounded.

A few things stand out. Our soups, your beans, your groundnut and cashew, and your fish are doing the heavy lifting. The swallow and the rice are not. Eba, pounded yam and white rice have very little magnesium. So a plate that is mostly swallow or rice with a thin soup will give you less than a plate with beans, ugu and egusi soup, and fish.

One note on crayfish: it tops the list, but you only use a small amount in a pot of soup, so it won’t give you 416 mg. Same with any food in the table. What counts is how much you actually eat.

The different forms of magnesium supplements

When you buy magnesium, the magnesium is attached to something else. That “something else” is the name on the label: oxide, citrate, glycinate and so on. It matters, because it changes how well your body absorbs it and how your stomach reacts.

The common ones:

Magnesium oxide. Usually the cheapest and the one with the big number on the label. But it is one of the poorly absorbed forms, and the one most likely to give you loose stool. It is better for short-term constipation or heartburn than for fixing low magnesium.
Magnesium citrate. Absorbs well, and also works as a mild laxative. Good if you are also dealing with constipation. If you aren’t, higher doses can upset the stomach.
Magnesium glycinate. Magnesium attached to glycine, an amino acid. It is absorbed well and is usually gentle on the stomach, which is why many people choose it for daily use and for sleep. To be fair, its main edge over citrate looks like stomach comfort, not some huge difference in absorption.
Magnesium chloride, lactate and aspartate. Also reasonably well absorbed.
Magnesium sulfate (Epsom salt). Mostly for baths or as a laxative, not for daily supplements.
Magnesium L-threonate. Sold for brain health and memory. More on this in the claims section.

There is one more form you may already know without knowing it: the magnesium in some antacids and laxatives, like Milk of Magnesia. The NIH points out that some laxatives and some heartburn products contain magnesium. So if you take those often, count it.

One more thing about labels. The big number on the front is not always the real amount of magnesium. Look for “elemental magnesium” on the supplement facts panel. That is the actual magnesium in the pill, and it’s the number to compare with the daily limit. A 500 mg magnesium oxide tablet does not give you 500 mg of magnesium, and because oxide is poorly absorbed, your body takes in even less.

Which claims are backed by evidence, and which aren’t?

Every day somebody is making a new claim about magnesium. Most of them are not lying. But “popular” is not the same as “proven.” And it’s not like because there’s no paper on something yet, then it doesn’t work. It only means we don’t know yet. Here is where things stand.

Reasonably supported

Blood pressure. A big review of 34 randomized trials found that magnesium supplements lowered the top blood pressure number by about 2 mmHg on average. That is real, but small. It is a helper, not a replacement for your BP drugs. Especially here in Nigeria, where studies have put hypertension in adults at roughly 28 to 29 percent in some estimates, and where the Ibadan study found people eating about double the recommended sodium (salt, seasoning cubes, restaurant stews). Cutting salt will do more for your BP than any magnesium pill. Read the magnesium review (Zhang et al., 2016) and the Nigerian hypertension estimate (Adeloye et al., 2015).

Migraine prevention. Doctors do use magnesium as an option to help prevent migraine, usually 400 to 600 mg a day, and some people get fewer attacks. That dose is above the supplement limit we mention below, so this one is for doing with your doctor. Read the review (Dolati et al., 2020).

Blood sugar in type 2 diabetes. A 2021 review of 25 trials found that magnesium supplements lowered fasting blood sugar in people with type 2 diabetes. It does not replace diabetes medication.

Fixing a real deficiency. If your magnesium is actually low, supplementing helps. Nobody disputes that.

Mixed or weak evidence

Sleep. This is the one everyone is talking about, so let’s be honest about it. People with higher magnesium intake tend to report better sleep. But when researchers give magnesium to people in controlled trials, the results are not consistent. One review of trials in older adults with insomnia found people fell asleep about 17 minutes faster on magnesium, but the studies were small and of low quality, and the authors said the evidence is not strong enough for firm advice. Read that review. A broader 2023 review reached a similar conclusion. Read it here. So it may help some people, especially if they were low, but it is not a proven sleeping pill.

Muscle cramps. This one is often oversold. A Cochrane review found that magnesium is unlikely to give meaningful relief for ordinary cramps in older adults. Read it here. For leg cramps in pregnancy the results are mixed. If a doctor finds your magnesium is low, that is a different story.

Anxiety, mood and stress. There is some early and promising research, but nothing solid enough to say it treats anxiety or depression.

Not yet supported (but not disproven)

Magnesium L-threonate for memory and brain health. The idea makes sense in theory and it’s popular, but the human evidence is still thin.

Absorbing magnesium through the skin (sprays, creams, Epsom salt baths). Lots of people enjoy these, and a warm bath is relaxing anyway. But good proof that enough magnesium gets into your body this way is lacking.

We say “not yet supported” on purpose. It is not the same as “false.” It just means that when you see these claims, you should know the proof isn’t there yet.

How to take magnesium

How much is safe?

The NIH sets an upper limit of 350 mg a day of magnesium from supplements and medications for adults. This limit does not apply to magnesium from food, so you don’t need to worry about eating too much groundnut or beans. Going above it from supplements can cause diarrhea, nausea and stomach cramps. People with kidney problems are at higher risk of magnesium building up to dangerous levels, so if you have kidney disease, do not take magnesium supplements without your doctor’s approval.

A sensible way to do it: start low, well under the limit, see how your stomach reacts, and only go up if needed. Count the elemental magnesium, and count the magnesium in any antacid or laxative you also use.

Which form is best?

It depends on what you want it for:

Daily use or for sleep: glycinate is a common choice because it is absorbed well and gentle on the stomach.
If you also have constipation: citrate.
To fix a real deficiency: talk to your doctor and choose a well-absorbed form, not oxide.
Oxide: better for short-term constipation or heartburn than for raising your magnesium level.

A form you can tolerate and take every day will beat a “better” form that upsets your stomach and that you stop after three days.

What’s the best time to take it?

Honestly, there is no strong research saying one time of day is best. Taking it consistently matters more. A few practical points:

If you’re taking it for sleep, the evening makes sense.
If it upsets your stomach, take it with food.
If you need a higher dose, splitting it into two smaller doses is usually easier on the stomach than one big dose.
Keep it away from certain drugs and supplements, covered next.

What to be careful about when taking magnesium

Magnesium does not work alone. It can clash with other minerals and with some drugs. Most of the time the fix is simple: take them at different times.

Minerals and supplements

Zinc. Very high doses of zinc (around 142 mg a day or more) can interfere with how your body absorbs magnesium. Normal zinc supplement doses are far below this, so it’s only a problem if you’re taking a lot.
Calcium. High doses of calcium and magnesium can compete for absorption if taken together. If you take both, space them a few hours apart. And note: the Ibadan study found that most people were eating far less calcium than recommended, so don’t drop your calcium because of magnesium. Just don’t take big doses of both at the same time.

Drugs that magnesium can interfere with. Magnesium can stop some medicines from being absorbed properly. The common ones:

Tetracycline-type and fluoroquinolone antibiotics (for example doxycycline and ciprofloxacin, which many people buy at the chemist)
Bisphosphonates (osteoporosis drugs)
Levothyroxine (thyroid medication)
Gabapentin

The usual advice is to leave a gap of at least two hours, and some antibiotics need several hours. Ask your pharmacist for the exact timing for your drug.

Drugs that can lower your magnesium. Long-term use of acid-reducing drugs (proton pump inhibitors like omeprazole and esomeprazole) and some water pills (loop and thiazide diuretics like furosemide) can drain magnesium from the body. On the other side, some other diuretics (the potassium-sparing type, like spironolactone) can make the body hold on to magnesium. If you are on any of these, tell your doctor before you start a supplement.

Buying magnesium safely

Fake and unregistered products are a real problem here, and supplements are not exempt. Some tips:

Look for the NAFDAC registration number, the manufacturer’s name and address, the batch number and the expiry date on the pack.
Don’t stop at the number. NAFDAC itself warns that counterfeiters copy registration numbers from genuine products. Check the number on the NAFDAC Greenbook or its online verification platforms to see that it matches the product.
Buy from a registered pharmacy, not from a roadside seller or a random online page.
If something looks wrong, you can report it to NAFDAC.

Read NAFDAC’s guidance on spotting and reporting fake products.

The short version

Magnesium really does matter. It is involved in hundreds of reactions in your body.
Many of us can get a good part of what they need from food. Beans, ugu, egusi and other soups, groundnut, cashew and fish all help. Swallow and white rice don’t give much.
Oxide is poorly absorbed, citrate also acts as a laxative, and glycinate is gentle and well absorbed.
Best supported: fixing a real deficiency, a small drop in blood pressure, migraine prevention, and blood sugar in type 2 diabetes.
Sleep, cramps and mood: mixed or unproven. It might help, but don’t expect miracles.
For supplements, stay under 350 mg of elemental magnesium a day unless your doctor says otherwise, and be careful if you have kidney problems.
Watch the timing with antibiotics, bone drugs, thyroid medication, and very high doses of zinc or calcium.
Check that any product you buy is genuine.

This newsletter is for general information and is not a replacement for medical advice. If you are on medication, pregnant, or have a health condition, check with your doctor or pharmacist before starting a supplement.

Where to read more

🧠 CURIOSITY FACTS OF THE WEEK

🥜 A study of 732 adults in Abuja and Ogun State found their food gave them about 389 mg a day, inside the recommended range
🍲 Beans, ugu, egusi soup, groundnut and fish help most. Eba and white rice give very little
😴 Sleep and cramps: the evidence is mixed
💊 For supplements, stay under 350 mg of elemental magnesium a day unless your doctor says otherwise

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What does magnesium do in the body?

How much magnesium do you need?

Where does magnesium come from in Our food?

The different forms of magnesium supplements