Men with good levels of vitamin D in their bachelor years are more likely to have healthy children when they start a family.

That is according to a new study by University College Dublin, which found a direct link between a child's height and weight at five years old, and their father's pre-conception vitamin levels.

While previous studies have shown maternal vitamin D intake before pregnancy affects a baby's health, this is one of the first to study the same in men.

Scientists in Ireland found men with good levels of vitamin D in their bachelor years are more likely to have healthy children when they start a family (file image)

The researchers analyzed data on 213 father-child pairs from the Lifeways Cross-Generation Cohort Study - a unique longitudinal database in Ireland - when the children were aged five and nine years old.

They carried out a questionnaire to assess a number of factors.

These included paternal age, energy intake height, weight, and being the biological father; maternal age, vitamin D and energy intake height, and weight.

They also analyzed the child's sex, age, vitamin D and energy intake, and summer outdoor physical activity aged five.

Compiling all the data, they found paternal vitamin D intake directly impacted their child's height and weight in their early years - a crucial point of development.

The correlation dropped off when the child aged into double figures.

To the scientists' surprise, they found no association between a mother's vitamin D intake during the first and second trimester of pregnancy and children's weight and height at either age five or nine years.

There were other factors that bolstered a child's height and muscle strength - such as absorbing their own healthy dose of vitamin D.

Skin exposure to sunlight is essential for the body to produce vitamin D, so the authors also looked at the number of hours children aged five spent playing outdoors during summer.

They found that spending three or more hours playing outdoors during weekends was related to increased height at five years old.

The authors concluded: 'Paternal vitamin D intake was positively and prospectively associated with offspring's height and weight at 5 years old, independent of maternal characteristics, meriting further investigation of familial dietary pathways.'

'One reason this may occur is that father's nutrition status may somehow influence the health, quality and function of their germ cells, which are involved in reproduction,' they added.

'Thus, maternal nutrition may not be the only key factor in offspring's growth development and health'.