Si ragiona meglio con la Vitamina D al top

Più alte concentrazioni di vitamina D3 sono state associate con minore frequenza di demenza o danno cognitivo leggero valutati nell’ultima visita. La 25(OH)D_{3 (vitamina D3) è stata} misurata, con biopsia dopo la morte, in tutte le regioni del cervello. Nessuna specifica patologia cerebrale è stata significativamente associata ai livelli di vitamina, in particolare “la demenza è una malattia multifattoriale ed i meccanismi che la determina non sono sufficientemente ancora noti” ha detto Sarah Booth, uno dei principali autori dello studio.

Le vitamine D2 (ergocalciferolo) e D3 (colecalciferolo) sono biologicamente inattive e devono essere elaborate dall’organismo per acquisire attività biologica. E’ pertanto necessario un duplice passaggio: prima epatico e poi renale.

1) Nel fegato, la vitamina D viene convertita in 25 OH Vitamina D (calcidiolo), che rappresenta la principale forma circolante e di immagazzinamento

2) Nei reni, la 25 OH Vitamina D viene convertita in calcitriolo (1,25-diidrossi vitamina D [1,25(OH)2D]), che rappresenta la forma biologicamente attiva della vitamina D

Principali fonti di Vitamina D3

• pesce azzurro e olio di pesce, fegato, tuorlo d’uovo, burro, sintesi cutanea, integratori alimentari, farmaci

Principali fonti di Vitamina D2:

• funghi (coltivati ​alla luce UV), alimenti fortificati, integratori alimentari, farmaci

Lo studio è stato pubblicato su Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association

The brains of people with cognitive decline fare better with higher levels of vitamin D, research finds. “This research reinforces the importance of studying how food and nutrients create resilience to protect the aging brain against diseases such as Alzheimer’s disease and other related dementias,” says senior and corresponding author Sarah Booth, director of the Jean Mayer USDA Human Nutrition Research Center on Aging (HNRCA) at Tufts and lead scientist of the HNRCA’s Vitamin K Team. Vitamin D supports many functions in the body, including immune responses and maintaining healthy bones. Dietary sources include fatty fish and fortified beverages (such as milk or orange juice); brief exposure to sunlight also provides a dose of vitamin D. “Many studies have implicated dietary or nutritional factors in cognitive performance or function in older adults, including many studies of vitamin D, but all of them are based on either dietary intakes or blood measures of vitamin D,” says lead author Kyla Shea, a scientist on the Vitamin K Team and an associate professor at the Friedman School of Nutrition Science and Policy at Tufts. “We wanted to know if vitamin D is even present in the brain, and if it is, how those concentrations are linked to cognitive decline.”

Booth, Shea, and their team examined samples of brain tissue from 209 participants in the Rush Memory and Aging Project, a long-term study of Alzheimer’s disease that began in 1997. Researchers at Rush University assessed the cognitive function of the participants, older people with no signs of cognitive impairment, as they aged, and analyzed irregularities in their brain tissue after death. In the study, researchers looked for vitamin D in four regions of the brain—two associated with changes linked to Alzheimer’s disease, one associated with forms of dementia linked to blood flow, and one region without any known associations with cognitive decline related to Alzheimer’s disease or vascular disease. They found that vitamin D was indeed present in brain tissue, and high vitamin D levels in all four regions of the brain correlated with better cognitive function. However, the levels of vitamin D in the brain didn’t associate with any of the physiological markers associated with Alzheimer’s disease in the brain studied, including amyloid plaque buildup, Lewy body disease, or evidence of chronic or microscopic strokes. This means it’s still unclear exactly how vitamin D might affect brain function.

“Dementia is multifactorial, and lots of the pathological mechanisms underlying it have not been well characterized,” Shea says. “Vitamin D could be related to outcomes that we didn’t look at yet, but plan to study in the future.”

Vitamin D is also known to vary between racial and ethnic populations, and most of the participants in the original Rush cohort were white. The researchers are planning follow-up studies using a more diverse group of subjects to look at other brain changes associated with cognitive decline. They hope their work leads to a better understanding of the role vitamin D may play in staving off dementia. However, experts caution people not to use large doses of vitamin D supplements as a preventive measure. The recommended dose of vitamin D is 600 IU for people 1-70 years old, and 800 IU for those older—excessive amounts can cause harm and have been linked to the risk of falling. “We now know that vitamin D is present in reasonable amounts in human brains, and it seems to be correlated with less decline in cognitive function,” Shea says. “But we need to do more research to identify the neuropathology that vitamin D is linked to in the brain before we start designing future interventions.”