A low vitamin D intake in childhood is associated with a higher risk of a type of cardiovascular disease that can be diagnosed in in adulthood, researchers in Finland have found.
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.
Some findings show that women who don’t get enough vitamin E in their diets also appear to be more likely than others to show early signs of atherosclerosis, even before they experience any symptoms of the condition. They concluded that the highest risk of early atherosclerosis were those who took in the lowest amount of vitamin E in their diets.
Blood levels <20 ng/ml) are associated with nearly a 50 percent increase in the mortality rate in older adults. Although vitamin D can be obtained from limited dietary sources and directly from exposure to the sun during the spring and summer months, the combination of poor dietary intake and sun avoidance has created vitamin D deficiency or insufficiency in large proportions of many populations worldwide.
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 supplementation?
“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.”
“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,” however the quality of vitamin D may need to be improved to render it effective.
“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.”
Mae Chan holds degrees in both physiology and nutritional sciences. She is also blogger and and technology enthusiast with a passion for disseminating information about health.