MicronutrientVitamins and minerals

Micronutrients are the vitamins and minerals the body needs in small amounts: milligrams or micrograms a day rather than the tens or hundreds of grams that protein, carbohydrate and fat are measured in. Small does not mean minor. They are the cofactors that let the machinery run at all.

They matter because a shortfall shows up as something that looks like a training problem or a life problem rather than a nutrition problem. Iron deficiency degrades endurance well before it becomes anaemia. Low vitamin D affects bone and possibly muscle function. Inadequate B12 causes fatigue and, if prolonged, nerve damage.

The relationship between intake and benefit is a plateau, not a slope. Correcting a deficiency produces a real improvement; going above sufficiency produces nothing, and for a few nutrients it produces harm. Fat soluble vitamins accumulate, chronic high dose vitamin B6 can cause nerve damage, and too much iron is genuinely dangerous in people who do not need it.

That shape is why the multivitamin evidence is so unimpressive in well fed populations, and why the supplement industry sells insurance rather than outcomes. Someone with a shortfall gains; someone already replete does not.

Some groups have real reasons to supplement rather than guess: vegans need B12, people who see little daylight often need vitamin D in winter, menstruating and endurance athletes should have iron status checked rather than assumed, and folic acid before and during early pregnancy is one of the best evidenced supplements there is.

Food covers the rest, and does it better. Whole foods deliver micronutrients alongside fibre and the rest of the matrix, which is why nutrient density is a more useful idea than a pill count. A varied diet with plenty of plants is the unglamorous answer.

In practice, test rather than guess when you suspect a shortfall, correct what is actually low, and treat everything above sufficiency as spending without a return.