The researchers, led by Markus Juonala from the University of Turku, measured vitamin D levels of children and young people at baseline and then measured for carotid intima-thickness (IMT) – an indicator of structural atherosclerosis – as adults.
Atherosclerosis is a chronic disease caused by accumulation of cholesterol in the artery leading to inflammation and atheroma (blocked arteries). It is sub-clinical - meaning asymptomatic – and can therefore go undetected and untreated for decades.
The scientists studied 2,148 young Finnish people, measuring vitamin D levels at age 3-18 years using stored serum. The subjects were then re-examined 27 years later at age 30-45 years, with measurements of IMT taken from the posterior wall of the left carotid artery using ultrasound.
The scientists also took into account other conventional cardiovascular risk factors, such as diet, physical activity and smoking, measured using detailed questionnaires and confidential medical histories at both childhood and adulthood.
The scientists found that subjects with 25-OH vitamin D levels in the lowest quartile in childhood (_ 40 nmol/L) were at significantly higher risk of IMT as adults (21.9% vs 12.7%, P _ .001).
Vitamin levels below 43 nmol/L were associated with an increased IMT risk. Current US guidelines suggest that the optimal level in childhood is 50nmol/L.
"The association was independent of conventional cardiovascular risk factors including serum lipids, blood pressure, smoking, diet, physical activity, obesity indices and socioeconomic status," said Markus Juonala of the University of Turku Finland, one of the study’s authors.
“Conversely, low levels of adult vitamin D were not associated with subclinical atherosclerosis. This suggests that the effects of vitamin D on cardiovascular risk may operate earlier in the life-course.”
An argument for fortification?
"More research is needed to investigate whether low vitamin D levels have a causal role in the development increased carotid artery thickness. Nevertheless, our observations highlight the importance of providing children with a diet that includes sufficient vitamin," Juonala said.
The study identified children at high risk of developing vitamin D deficiency as those whose diet is poor in sources of vitamin D (either through natural sources or fortified foods), those who do not regularly take food supplements or children who do not have adequate sunlight exposure.
Since the baseline measurements of the study were taken, legislation regarding food fortification in Finland and other Scandinavian countries has been relaxed and most milks, margarines and yoghurts are now fortified with vitamin D, leading to “higher serum vitamin D levels in children and adolescents.”
Mannfred Eggersdorfer of vitamin D supplier DSM told NutraIngredients: “Food fortification is an effective tool to improve the vitamin D status in the whole population as is demonstrated in countries like the US and Canada; food fortification is “cheap”, effective and has a high return on investment.”
“In my view the Nordic countries are the 'front runners' in communicating the risk of vitamin D inadequacy for the general population as well as in putting fortification with vitamin D in place. The other countries in Europe are lagging behind however (…) and we do not see progress in fortification of food items like dairy products.”
In 2014 the European Food Safety Authority (EFSA) found vitamin D-enriched UV-treated baker’s yeast was safe for use in foods.
Source: Journal of Clinical Endocrinology & Metabolism
Published Online: February 10, 2015, doi 10.1210/jc.2014-3944.
Title: "Childhood 25-OH Vitamin D Levels and Carotid Intima-media Thickness in Adulthood: The Cardiovascular Risk in Young Finns Study"
Authors: M. Juonala, A.Voipio, K.Pahkala et al.