Veel mensen hebben te weinig Vitamine D tegen hart- en vaatziektes*
Uit een studie blijkt dat lage bloedwaarden vitamine D de kans op een metaboolsyndroom, hoge bloeddruk en hoge bloedsuikerwaarden flink doet
toenemen, en dat slechts 23% van de Amerikanen goede bloedwaarden vitamine D
heeft. 3577 tieners in de leeftijd van 12 tot 19 jaar werden 4 jaar gevolgd. Zij met een duidelijk vitamine D tekort (< 15 ng/ml) hadden 236% meer kans op hoge bloeddruk, 254% meer kans op hoge bloedsuikerwaarden en bijna 400% meer kans op een metaboolsyndroom als zij met voldoende bloedwaarden vitamine D. Het metaboolsyndroom is het voorstadium van ouderdomsdiabetes en hart- en vaatziekten. Mensen hebben deze ziekten dan nog niet maar dragen wel al risicofactoren, overgewicht, relatief hoge omtrek van de taille, hoge bloeddruk, en hoge concentraties van glucose, vetten en cholesterol in het bloed bij zich.
Uit een ander onderzoek blijkt dat het met de bloedwaarden vitamine D in ruim tien jaar tijd in Amerika duidelijk bergafwaarts gegaan is. Waren er 15 jaar geleden nog slechts 2,6% van de mensen met een duidelijk tekort (<11 ng/ml), dertien jaar later was dat percentage 9,2. Het aantal mensen met een matig tekort (< 20 ng/ml) liep op van 28% naar 40%. Nog slechts 23% van alle mensen heeft goede bloedwaarden vitamine D (> 30 ng/ml) en dat was
dertien jaar geleden nog 45%.
Low Vitamin-D Levels in Adolescents Predict CVD Risk Factors
In a large study of adolescents, low serum levels of 25-dihydroxyvitamin D (25[OH]D) strongly predicted prevalence of hypertension, hyperglycemia, and metabolic syndrome [1]. The findings were reported at the AHA 49th Annual Conference on Cardiovascular Disease Epidemiology and Prevention.
Adolescents with vitamin-D levels in the lowest quartile were almost four times more likely to have metabolic syndrome than those with vitamin-D levels in the highest quartile. "I think that is quite alarming," lead author Dr Jared P Reis (Johns Hopkins Medical Institutions, Baltimore, MD) said in an AHA podcast issued to the media.
However, it is too early to recommend vitamin-D supplementation, he added. "Additional studies are probably necessary--especially large sets of clinical trials--to determine whether or not vitamin-D supplementation is actually associated with a reduced risk of developing CVD risk factors, especially among adolescents."
Increasing evidence suggests that vitamin-D deficiency in adults may increase the risk for hypertension, diabetes, and CVD, but little is known about the link between vitamin-D levels and CVD risk factors in adolescents.
To investigate this relationship, the researchers analyzed data from 3577 adolescents 12 to 19 years old (51% boys) who participated in the 20012004 National Health and Nutrition Examination Survey (NHANES 20012004).
The adolescents had a mean serum 25(OH)D level of 24.8 ng/mL; those with vitamin-D levels in the lowest quartile (<15 ng/mL) were much more likely to have metabolic syndrome, hyperglycemia, or hypertension than those with vitamin-D levels in the highest quartile (>26 ng/mL).
Odds of CVD Risk Factors, Lowest vs Highest Vitamin-D Quartile
Risk factor Odds ratio (95% CI)*
Hypertension 2.36 (1.334.19)
Hyperglycemia 2.54 (1.016.40)
Metabolic syndrome 3.99 (1.2113.20)
*Adjusted for age, sex, race/ethnicity, body-mass index, socioeconomic status, and physical activity
Mean vitamin-D levels were lowest in African Americans (15.5 ng/mL), intermediate in Mexican Americans (21.5 ng/mL), and highest in whites (28.0 ng/mL). "This is thought to be due to the fact that African Americans have much more melanin in their skin, and this blocks UVB light and blocks the ability to produce vitamin D in the skin, so African Americans are at much higher risk of being vitamin-D deficient," said Reis.
Low vitamin-D levels were also strongly associated with being overweight and having abdominal obesity (p for trend <0.001 for both). This is likely because vitamin D is taken up within fat tissue, not because low vitamin-D levels lead to obesity, according to Reis.
Raises Important Questions
The study confirms that low vitamin D is linked with CVD risk factors in adolescents as well as adults, Dr Robert H Eckel ((University of Colorado, Denver, AHA past president), who was not involved in the study, told heartwire.
"I think there are more questions than answers, but I think this is an important finding, and an important trend that needs to have a more drilled-down, scientific approach to understand mechanisms," he said.
Further research is needed to determine whether low levels of vitamin D in adolescents are due to poor diet, lack of sunlight, both factors, or even to an increase in obesity, and whether they predict adverse health events in 20 to 30 years, he added.
Vitamin-D Deficiency Increasing
According to other research presented at the meeting, prevalence of vitamin-D deficiency in adults and adolescents in the US has risen sharply over the past 20 years [2].
Dr Sandy Saintonge (New York Hospital Queens, NY) and colleagues analyzed NHANES data and reported that prevalence of vitamin-D deficiency--defined conservatively as serum 25(OH)D below 11 ng/mL--rose from 2.6% in 19881994 to 9.2% in 20052006.
This is an "impressive" increase over a short interval, said Eckel.
Prevalence of vitamin-D deficiency during 20012006 was 28% to 40% if a less conservative cutoff of 20 ng/mL was used and was 70% to 80% if a cutoff of 30 ng/mL was used.
Further study is needed to determine optimal vitamin-D levels, according to the researchers. While the American Academy of Pediatrics now recommends a daily intake of 400 IU vitamin D--which can come from consuming milk, oily fish, or fortified foods or spending 10 to 15 minutes in the sun--other experts suggest that at least 1000 IU per day are needed.
The authors disclosed having no conflicts of interest.
1. Reis JP, von Muhlen D, Miller III ER, et al. Vitamin D status and cardiovascular disease risk factors in the us adolescent population. AHA 49th Annual Conference on Cardiovascular Disease Epidemiology and Prevention; March 11, 2009; Palm Harbor, FL. Poster P54.
2. Saintonge S, Bang H, Vogiatzi MG, et al. Is the relevance of vitamin D deficiency increasing? Data from the National Health and Nutrition Examination Survey: 1988-1994 and 2001-2006. AHA 49th Annual Conference on Cardiovascular Disease Epidemiology and Prevention; March 11, 2009; Palm Harbor, FL. Abstract 9. (Maart
2009)
Er zijn nauwelijks redenen te bedenken dat er duidelijk verschil zal zijn in het percentage van mensen in Amerika en hier in Belgi๋ en Nederland met een tekort aan vitamine D.