Essential nutrients such as vitamins can act as pheromones to attract the opposite sex - at least in lizards.
The Iberian rock lizard may use vitamin D to attract mates
That is the conclusion of studies by a Spanish research team, who fed vitamin D supplement to male rock lizards.
Writing in the Royal Society journal Proceedings B, they report that females became excited by secretions from these males.
Whether or not vitamin D could play the same role in humans is not certain, the scientists say.
They suggest that in lizards, the presence of vitamins in male secretions may be a sign of good health, which from an evolutionary standpoint would be a useful signal to females selecting a mate.
"Most of the essential nutrients are also in the secretion," said Jose Martin from the National Museum of Natural Sciences in Madrid.
"The male lizard puts in the secretion what he has in his body, and this will be a reflection of his health," he told the BBC News website.
"In other lizard species, we have found a large amount of vitamin E in the secretion and we think that this will have a similar function as vitamin D."
Animals use pheromones as chemical communicators to attract the opposite sex for mating. Many pheromones belong to the steroid family of chemicals, and are odourless to humans.
Vitamin D is important to the immune system of Iberian rock lizards; it also facilitates calcium metabolism.
They are often unable to synthesise enough vitamin D in their skin, and so must obtain it through their diet.
Dr Martin's team found that males receiving vitamin D supplements secreted more provitamin D, a closely related compound, on their hind limbs. Provitamin D transforms into vitamin D after exposure to the Sun's ultraviolet radiation.
Animals have found many ways of signalling to the opposite species
The secretion from the male's hind limbs is smeared on the ground as it moves around its home, serving as a scent marking.
The secretion process may have a cost to the lizard in terms of energy, so healthy and well-fed individuals are probably likely to produce more.
Females were more excited by secretions from the supplemented males, which they signalled by increased tongue-flicking; they also spent more time in areas where a healthy vitamin-fed male had been.
Other essential nutrients are also used in nature for sexual attraction.
Birds and fishes use colours derived from carotenoid chemicals to be more visually attractive.
Whether or not provitamin D or vitamin D plays a role in other species, including humans, is not clear.
But the field contains many avenues for further research.
"We have to know more about the metabolism of these [pheromone] steroids and the effect of the hormones like the testosterones," said Dr Martin.
"Provitamin D is a steroid very similar to cholesterol and testosterone, and they are in the same metabolic route, so they can be converted from one to another.
"So these two things could be very similar."