# Exploring Vitamin D Synthesis and Function in Cardiovascular Health: A Narrative Review
## 5 Impact of Dietary Vitamin D Fortification on Blood Vitamin D Levels and Cardiovascular Outcomes  
Fortification strategies, while jurisdictional in nature, demonstrate variable impacts on cardiovascular health across different states. Dairy products, bread, and breakfast cereals are the foods most commonly fortified with Vitamin D [79]. In countries where there is no mandatory fortification policy, data show that the fortification of foods with Vitamin D could counteract Vitamin D deficiency [80]. In Finland, for example, data modeling studies led to a policy of mandatory Vitamin D food fortification that increased 25(OH)D concentrations in the population by 18 nmol/L [81]. In vitro studies suggest that altering the lipid composition of fortified foods increases the absorption of Vitamin D3 [78]. Proposed fortification strategies may not be as effective because the matrix and composition of foods may alter Vitamin D absorption and bioavailability [82]. Supplements and fortified foods serve as additional sources of Vitamin D. Both Vitamin D2 and D3 can be synthetically produced for supplementation and fortification purposes [83]. The debate on the bioequivalence of Vitamin D2 and D3 in fortification and supplementation suggests that D3 may be superior, especially when administered in the form of supplements or injections. Despite numerous researches that have investigated Vitamin D2 and D3 additionally, there is a lack of research directly comparing the effect of Vitamin D2 and D3 from biofortified foods on 25(OH)D concentrations. The fortification of dairy products with Vitamin D is considered cost-effective and bioavailable, so much so that some countries have mandated fortification [84]. Studies show a significant increase in 25(OH)D levels following the consumption of fortified dairy products, although most research has focused on female participants [85]. The efficacy of fortified foods for males and various dietary preferences remains important [86]. In addition, non-dairy fortification strategies, including bars and juices, meet the needs of those who avoid dairy products. These studies emphasize the importance of selecting appropriate foods for fortification to accommodate different dietary habits and ensure widespread improvement in Vitamin D status [87; 88]. Although both D2 and D3 can be effective in increasing Vitamin D levels when added to foods, D3 generally shows superior bioavailability and efficacy in improving Vitamin D status [89]. The choice of foods to be fortified is critical in maximizing the benefits of Vitamin D fortification policies, particularly in meeting the nutritional needs of different population groups [90]. Fortifying bread with 11.3 \(\upmu\)g of Vitamin D/100 g could result in a daily Vitamin D intake of 23.7 \(\upmu\)g, raising the serum 25(OH)D concentration in the German population from 45 nmol/L to 75 nmol/L during winter as demonstrated by [PERSON] et al. [80]. Moreover, a 12-month study involving nursing home residents who consumed bread fortified with 125 \(\upmu\)g (5000 IU) Vitamin D3 daily observed an increase in serum 25(OH)D levels from 28.5 nmol/L to 125.6 nmol/L [91]. While these strategies have successfully elevated Vitamin D levels, the direct correlation between these increases, and a significant reduction in major cardiovascular events is not clearly established. Despite effectively increasing serum vitamin D levels, supplementation did not yield clear cardiovascular benefits in several studies, suggesting that the role of vitamin D in cardiovascular health might be more complex and not solely dependent on improving Vitamin D status. This underscores the potential limitations of fortification in addressing the multifactorial nature of cardiovascular diseases [75].