How was the study conducted?
The
paper, published in the American Journal of Clinical Nutrition,
examined the differences in children aged five to ten years of age in
Poland.
They looked at 187 healthy children between 2014 and
2016 who had been on their respective diets for at least one year: 72
children were omnivores (meat eaters), 63 were vegetarians and 52 were
vegans.
The research team looked at the children's nutrient
intakes, body composition and cardiovascular risk how likely they are
to have heart disease or a stroke in the future.
The study
was observational, so researchers didn't make any changes to the
children's diets. They recruited children who were already eating these
diets.
Specifically, it was a type of observational study
called a cross-sectional study. They looked back at the children's
diets, growth and cardiovascular risk factors at a given time point.
The
research team ensured the children in the vegan and vegetarian group
were similar to children in the omnivore group, in factors that impact
growth and cardiovascular risk factors. These include sex, age, parental
smoking, parental education, clinical characteristics of their mother's
pregnancy and, importantly, their parents' height.
What did the researchers find?
The
researchers found that compared to children on omnivore diets, children
on vegan diets had a healthier cardiovascular risk profile, with 25 per
cent lower levels of low-density lipoprotein (LDL, or unhealthy
cholesterol).
However the vegan children had an increased risk of
nutritional deficiencies. They were more likely to have lower levels of
vitamin B12, calcium, vitamin D and iron in their diet.
Children
on vegan diets had about 5 per cent lower bone mineral content and were
on average 3cm shorter in height. This is important, as the higher the
bone mineral content, the higher the bone mineral density.
This
5 per cent difference is concerning, as people have a limited period of
time at this age in which they can optimise their bone mineral density;
95% of bone mass is attained by about 20 years of age. Lower bone
densities are linked to higher rates of fractures in later life.
Vegetarians
showed less pronounced nutritional deficiencies but, unexpectedly, a
less favourable cardiovascular risk profile compared to both meat-eaters
and vegans. The authors attributed this to a lower-quality diet, with
these children consuming more processed foods.
Are there any problems with the study?
Observational
studies are only able to tell us if something is linked, not if one
thing caused another. This study only tells us there is a link between
these diets and the outcomes they looked at.
But in this study, there are plausible biological links between bone development and growth in children.
Calcium,
vitamin D and protein are critical for bone development and growth.
These nutrients may be lower in vegan diets, as they come mainly from
animal products:
-calcium is found in dairy products
-vitamin D, which we normally get from exposure to sunlight on our skin, is also found in animal foods but in smaller amounts
-protein from plant foods is considered of lower biological value than animal sources.
One
single plant source of protein won't provide you with all the essential
amino acids (the protein building blocks your body is unable to make
for itself) that are needed. Vegans need to make sure they eat a variety
of plants so they get a good mix of all the essential amino acids.
So, why didn't the researchers carry out an intervention study and change the diets of the children?
First, it would be difficult to find children and their families who are willing to change their diets for a long period.
Second, it would be unethical to put children on a diet potentially affecting their growth and cardiovascular risk factors.
This study, conducted in Poland, is the only one to look at growth and cardiovascular outcomes in vegan and vegetarian children.
One
small study in children aged five to ten years isn't enough for the
scientific community to say these results are valid and we must act on
them.
But it does give us clues about potential problems and what we can look out for.
As the researchers indicated, more observational studies are needed, and in different countries.
So what does it mean for children on vegan and vegetarian diets?
This
doesn't mean every child who follows these diets is going to have these
nutritional and health benefits or problems. And we also can't say
whether these problems will persist into adulthood.
But it
does highlight potential risks which health practitioners and parents
need to be aware of. And it's a reminder to either find suitable
replacements that align with the family's diet philosophy, or prescribe
supplements if a deficiency is diagnosed through a blood test.
In
particular, parents and caregivers need to be careful their children
are maintaining a good intake of protein from a variety of vegan sources
(beans, lentils, nuts) and calcium (from calcium supplemented plant
milks).
Whether you're following a vegan, vegetarian or
meat-eating diet, you still need to make sure the diet is balanced
across all food groups.
The study is also a reminder to
minimise your family's intake of processed foods which are high in salt,
sugar and saturated fat, which are risk factors for heart disease and
stroke.
If you're concerned about your children's diet, talk
to your GP or an accredited practising dietitian, who can assess their
growth and diet. Evangeline Mantzioris.
Blind peer review
The reviewer has provided an accurate assessment of the research paper.
The
study highlights the importance of meal planning to optimise food and
nutrient intakes of children whose usual dietary pattern is vegan or
vegetarian and the need for regular use of fortified foods and/or
dietary supplementation with vitamin B12 and vitamin D and potentially
calcium and iron, particularly for vegans.
However, the
results of the study may be a best case scenario, given most families
participating were highly educated and hence likely to be more invested
in planning family meals. It is possible other families might have less
healthy dietary patterns, and therefore greater nutritional deficits.
Together
with the results highlighted by the reviewer about bone mineral content
and height, as well as iron and cholesterol levels, this study confirms
both the potential risks and benefits associated with vegan and
vegetarian diets in children.
A key message is that families
following plant-based diets need more advice and support to optimise
their food and nutrient intakes, and their children's diet-related
health and well-being. Clare Collins. (The Conversation)