Does a contest-prep diet run short on vitamins and minerals?

Short answer

Food alone often falls short. The fewer calories people ate, the more vitamin D, calcium, zinc and iron fell below recommended amounts. Supplements filled the gap, but too many pushed some nutrients past the safe upper limit.

Does a contest-prep diet run short on vitamins and minerals?
'Fewer calories → fewer vitamins and minerals → your body suffers' — does this formula hold?
Contest prep often means months of small portions of the same few foods, like chicken, rice and vegetables. The common claim is that vitamins and minerals run short. We checked studies that analyzed real competitors' diets.
Those eating the least ran short first
The 11 women got 52% of the calcium they needed
Researchers recorded the diets of 24 competitors at a drug-tested national championship. The 11 women got 0% of the recommended vitamin D, 52% of calcium and 76% of zinc. The 13 men were short on vitamin D at 46% but had enough of everything else.
With enough calories, the gaps stayed filled right up to the show
16 people were above the targets for almost everything 1 week out
Researchers checked 16 competitors 10-12 weeks out and again 1 week out. Intake of most nutrients dropped by the final week, yet almost every vitamin and mineral was still well above the recommended amount. Even within contest prep, how much you eat made the difference.
Counting food alone, more than half fell short
Over half of 41 people missed several targets
When the diets of 41 competitors were analyzed from food alone, more than half ate less than the recommended amount of several vitamins and minerals. The women averaged 1,794 kcal a day, and those who just hit macro targets got more vitamins C, E and K than those on a strict fixed-food diet.
Calories and supplements made the difference
75% vs 11.5% met the iron target
In 30 people eating low-calorie diets, those who ate more calories were more likely to meet the targets for calcium, iron, folate and vitamin B12. Among supplement users, 75% met the iron target versus 11.5% of non-users. For vitamin D it was 56.3% versus 0%.
Supplements filled the gap, and sometimes overshot
Some nutrients hit 10 times the target
In a survey of 227 competitors, everyone used supplements. Those in prep ate about 1,780 kcal a day, yet average vitamin and mineral intake including supplements was above the target for every nutrient. An analysis that pooled 385 competitors found supplements pushed some nutrients to about 1,000% of the target, past the safe upper limit.
Bottom line: cut calories and food alone often falls short
Vitamin D, calcium, zinc and iron go first
The harder people cut calories, the more food alone left vitamin D, calcium, zinc and iron below the targets. People who added supplements met the targets, and those who took a lot went past the upper limit. Topping up only what is missing, to the recommended amount, is enough.