Your body, by the numbers
Your body runs on a small, specific set of vitamins and minerals. Iron is how oxygen gets from your lungs to the rest of you. Vitamin B12 keeps your nerves passing messages along without dropping any. Vitamin D regulates mood and bone. Magnesium does muscles and sleep. When one of these runs short, the engine doesn't break, it just doesn't sing.
There are twenty-seven essentials on the UK list. Most get cleared without you thinking about it: a varied weekly shop covers about twenty-two of them. The trouble lands on the same four every time, and they happen to be the four most likely to leave you exhausted.
01Iron carries oxygen
If climbing a flight of stairs leaves you oddly out of breath, or your heart flutters after a brisk walk, iron is the first place to look. Tiredness, breathlessness, a paler look about you, sometimes a sore tongue. Heavy periods speed it up. Your body uses iron to ferry oxygen around in your blood, and when supply drops the whole system slows down to compensate.
Adult women aged 19 to 50 need 14.8mg a day. After 50 and for men of any age, 8.7mg. American sites quote 18mg; that's their figure, not ours.
02B12 keeps your nerves talking
B12 shares tiredness with iron, but it has a few signs of its own. Pins and needles in your hands or feet. A sore, red, oddly smooth tongue. Mouth ulcers. Mood changes that don't have a cause. If the breathless thing isn't really you but the tingling and the bad mood is, B12 is the suspect.
The UK target is small: 1.5µg a day, easy to clear if you eat meat, fish, eggs, or dairy in any quantity. The genuine gap is for vegans, where animal foods do most of the carrying. Fortified plant milks, nutritional yeast and fortified cereals fill the gap. So does a B12 supplement if those aren't part of your week.
03Vitamin D holds your mood up
Vitamin D is harder to feel until it's been low for a while. The pattern is persistent low mood, a bit too much bone or muscle ache, getting ill more often, hair feeling thinner. The reason the NHS hands out a recommendation rather than waiting for symptoms is that low vitamin D doesn't ring an obvious bell until it's been quiet for a season.
The UK target is 10µg a day. From October to March there isn't enough daylight here to make enough of it from skin, so the NHS recommends a 10µg daily supplement through autumn and winter for everyone aged four and over. That one is worth taking. The rest of the year, food and a bit of sun cover it.
04Magnesium calms muscles and sleep
Magnesium is the one most likely to show up in your sleep. Calf cramps that wake you. Restless legs. A sleep that's plenty long but somehow not quite restful. Some people notice anxiety or irritability with low magnesium too. If you've fixed the sleep itself and things still feel off, magnesium is worth a look.
The UK targets are 300mg a day for men, 270mg for women. A varied diet usually clears it without effort. Two foods do disproportionate work for their size: a handful of pumpkin seeds and a small square of dark chocolate. Both make it easy.
Seeing it without a spreadsheet
Twenty-seven nutrients tracked daily against UK targets sounds like a spreadsheet, the kind of thing nobody does for more than a fortnight. So we built it into the food diary. You log what you actually ate, the way you would jot it down anyway, and a small ticker at the top of the page tots up your day across all twenty-seven against the UK target for each one.
Anything running short shows up in red. Tap one and the app pulls up the foods that move that number, at portions you might actually eat, drawn from the same UK food composition data the NHS works against. Then you carry on with your week, having seen something it would otherwise take a nutritionist's appointment to see.
