Pre-Race Nutrition Mistakes UK Runners Make (And How to Avoid Them)

Most pre-race nutrition disasters share one root cause: trying something new on race morning instead of in training. It's an easy mistake to make when race-day nerves push you toward wanting to do "everything right" — but that instinct is exactly what causes the problem, and it's one of the most consistently repeated pieces of advice across coaching, nutrition and sports medicine circles for a reason.

Mistake 1: trying something new on race day

A new gel, a new breakfast, a new pre-race supplement — anything untested carries a real risk of an unpredictable stomach reaction under race-day stress, even if it would have been fine on an ordinary Tuesday long run. Race-day adrenaline changes how your gut behaves compared to a calm training run, which is exactly why something that felt fine in training can still cause problems on the day if the underlying routine itself was never actually tested.

Mistake 2: too much fibre or fat too close to the start

Both slow digestion and increase the risk of GI discomfort mid-race — a pre-race breakfast is not the moment for a big fibre-rich bowl of porridge with all the toppings, however healthy it normally is. Simpler, lower-fibre, lower-fat carbohydrate-focused options in the two to three hours before a race tend to sit far better under race-day stress than your normal, healthier daily breakfast.

Mistake 3: under-drinking because of nerves

Race-morning nerves often reduce normal fluid intake without runners noticing — starting a race mildly dehydrated because you were too anxious to eat or drink properly is common and entirely avoidable with a planned routine written down in advance, rather than relying on how you happen to feel on the morning itself.

Mistake 4: stacking caffeine sources without realising it

Coffee, a gel, and a pre-race supplement can add up to a much higher caffeine dose than intended, particularly if none of them are dosed with the others in mind — overstimulation from stacked caffeine sources is a genuinely common and avoidable cause of a rough race-morning experience, including jitteriness and an elevated, anxious feeling that has nothing to do with race nerves themselves.

Mistake 5: ignoring your usual routine because "it's race day"

Some runners deliberately change their normal pre-run habits for race day, assuming the occasion calls for something special — when in fact the opposite is true. The best race-morning routine is almost always simply your best-tested training routine, repeated on a day that happens to matter more.

The fix: test everything in training first

RunnerVits' Pre-Race Performance (3,000mg Citrulline Malate, 100mg measured caffeine) is designed to be trialled in training well before race day, not introduced for the first time on the start line — the same principle British Athletics and most coaching guidance emphasise for any race-day nutrition decision, whatever product or brand you end up using.

Quick answers

How many times should I test my race-day routine before the actual race?

Ideally across at least three to four long training runs in the final two months before race day, so timing, dosing and any stomach response are well understood before it matters.

What should I eat on the morning of the race itself?

Something simple, familiar, carbohydrate-focused and low in fibre and fat, eaten with enough time (generally two to three hours) before the start for digestion to settle.