There is a lot to be learned from the vegan approach to eating, says dietitian Sarah Keogh of the Early Feeding Clinic in Dublin, but "to be brutally honest it is not a diet I would recommend . . . it is not a healthy diet, you can't get the nutrition you need from it."

However her clinic, which specialises in nutrition from pre-conception, through pregnancy and into early childhood, helps clients who are intent on keeping their households vegan to make sure their children have a balanced diet. And she says “the vast majority of vegan parents are really well educated, know what they are doing and are willing to spend the money on the supplements”. She thinks it is telling that none of the vegan dietitians she knows is raising children vegan, preferring to start them vegetarian.

The American Dietetic Association believes "that appropriately planned vegetarian diets, including total vegetarian or vegan diets, are healthful, nutritionally adequate, and may provide health benefits in the prevention and treatment of certain diseases. Well-planned vegetarian diets are appropriate for individuals during all stages of the life cycle, including pregnancy, lactation, infancy, childhood and adolescence and for athletes."

Here the Food Safety Authority of Ireland (FSAI), in its "best practice" guide to infant feeding, from pre-conception to the end of the first year, says that "in general, restrictive diets are not recommended" for babies and it urges parents following a vegetarian/ vegan diet to consult a dietitian.

“Don’t do this on your own – no matter how much as an adult you know about vegan diets,” agrees Keogh. “With babies in particular you have to be really careful.”

While most vegan parents breastfeed, if they can’t, there is no baby formula milk that is 100 per cent vegan – even soya formula is fortified with vitamin D3, which is made from lanolin (a grease produced by sheep’s skin and extracted from their wool).

Other dietary challenges when raising vegan children include:

Vitamin B-12

Any vegan will have to supplement their diet with this, according to Keogh. “The damage that can be done without it, particularly for a growing body, is crucial.”

Iron

If a vegan diet is done well, contrary to popular belief there should be no problem with iron. Beans and lentils, for example, are rich sources.

Calories

The high-fibre nature of vegan foods can make it hard for small children to consume enough to meet their energy requirements and sometimes adding oil to their food is recommended to increase the calorie count.

Vitamin D

Everybody has a problem getting enough of the “sunshine vitamin”. However, while eggs and oily fish are natural food sources, vegans must rely on fortified foods and supplements.

Calcium

It is “extraordinarily difficult” to get sufficient calcium from vegetables according to Keogh, who says a child would have to eat 16 servings of broccoli a day to get enough. For this reason, she encourages vegans to consider including dairy for the first 10 years or so of a child’s life.

Fortified soya and almond milk are sources of calcium if they drink enough of them – and calcium supplements are also an option.

Lack of fish

While there are a lot of positives around a vegan diet, Keogh says her one hesitation about it is down to the lack of fish, which has a specific omega-3 called DHA that is “absolutely essential for brain development”. The FSAI recommends that vegan women take fish-oil supplements when pregnant. There is omega-3 in plants but it is ALA and will not do the job, she warns.

However recently a DHA supplement has been developed from algae which, although she has not seen it in Ireland yet, should solve the issue.

Iodine

We don’t have a huge amount of iodine in the soil here, so while vegetables grown in some other countries may have significant levels of this chemical element, in Ireland the two main dietary sources are milk and fish. Iodine supplementation is needed for vegan children and adults, she adds.