October 23, 2019
For individuals who cannot or prefer not to take oral capsules, the same increase in vitamin D levels in the blood can be achieved with a sublingual spray, suggest the results of a small UK randomized controlled trial.
Nutritionist Claire E. Williams, PhD, of the University of Sheffield, United Kingdom, and colleagues examined the ability of a daily sublingual spray to raise serum vitamin D concentrations in 75 healthy volunteers.
Working in collaboration with BetterYou Ltd, which manufactured the spray, they showed that it not only markedly and significantly increased 25(OH)D levels in comparison placebo, but the effect achieved with the spray matched that seen with a standard capsule.
Interestingly, the study results, published online last month in the European Journal of Clinical Nutrition, indicate that the participants had a slight preference for the sublingual spray.
"This research is the opportunity to highlight the importance of this essential vitamin in supporting overall health and in providing a valuable alternative source for those who may struggle to, or prefer not to, take tablets," said senior investigator Bernard M. Corfe, PhD, of the Department of Molecular Gastroenterology at the University of Sheffield.
"Often, people can forget or don't want to take a daily supplement, especially those who take multiple medications," he noted in a press release from his institution.
Also, "Children and people who have trouble swallowing due to medical conditions ... can also have difficulty taking tablets, so to find that a spray is just as effective at raising people's vitamin D levels provides a real alternative for those whose vitamin D levels are low."
An Exciting New Method of Offering Vitamin D, but Sun Exposure Best
The trial looks "rigorous" and the analysis is "appropriate," said Robyn Lucas, MD, PhD, of the Australian National University, Canberra.
"This is an exciting new method of offering vitamin D supplementation, particularly to people with malabsorption problems, as the paper points out," she told Medscape Medical News.
Lucas nevertheless noted that, "As there is evidence of non–vitamin D benefits of sun exposure, the best way to get sufficient vitamin D level is to get modest doses of sun exposure."
Indeed, previous studies have shown that for people with white skin, 9 minutes a day during summer "is sufficient to ensure [vitamin D] levels stay above 25 nmol/L throughout the year.
"And it is these very low levels where there is the best evidence for effects on health," she added.
"However, this new sublingual spray seems to be a good new option for people who for some reason can't or prefer not to get some sun exposure, or to bump levels up during the winter," she said.
Capsules and Spray Upped Vitamin D Equally
The authors note that vitamin deficiency is a worldwide problem and that vitamin D is "increasingly associated" with gastrointestinal, immunologic, and psychological disorders.
Moreover, "African Americans may require a higher dose of vitamin D supplementation to reach optimal serum 25(OH)D concentrations" in comparison with their white counterparts, they write.
Although the pharmacokinetics of supplementation with capsules has been widely explored, the authors highlight that there are few data on the impact of sublingual sprays and resulting circulating levels of serum 25(OH)D.
They therefore conducted a 6-week, double-blind, placebo-controlled, three-arm, parallel-design study in which 75 healthy individuals were recruited at Sheffield University and were randomly assigned to one of the following interventions:
- active capsules and placebo spray (n = 25),
- active spray and placebo capsules (n = 25), or
- double placebo (n = 25).
Both the active capsules and the spray contained a dose of 3000 IU (75 μg) of vitamin D3. Participants were instructed to use the assigned therapy daily for 6 weeks.
The study required that participants not be about to go on vacation or not to have recently gone on vacation. It was also a requirement that participants have no history of gastrointestinal disease or diabetes or a body mass index (BMI) >30 kg/m2.
At baseline, anthropometric measurements were taken and skin tone was assessed. Serum 25(OH)D concentrations were assessed at days 0, 3, 7, 14, 21, and 42 of supplementation.
The mean age of the participants was 22.4 years, and 52% were women. The mean BMI was 23.4 kg/m2.
The mean serum vitamin D concentration at baseline was 50.5 nmol/L; 14.9% of the participants were deemed to have deficiency (<30 nmol/L), 44.6% insufficiency (31–46 nmol/L), and 40.5% sufficient levels (>50 nmol/L).
There were no significant baseline differences between the treatment groups.
Analysis of blood samples at study exit indicated that both the group that had received capsules and the group that had used the spray showed marked increases in serum vitamin D levels. At the end of the study, levels averaged 91.35 nmol/L and 95.78 nmol/L, respectively, vs 55.62 nmol/L for those who received placebo (P = .001 overall).
The average rate of change in serum vitamin D levels was 2 nmol/day. Ranges were similar for the group that received capsules (0.69 – 3.93 nmol/L) and the group that received the spray (0.64 – 3.34 nmol/L).
Plateau Effect in Both Groups; 60% of Participants Preferred the Spray
Circulating concentrations of 25(OH)D "started to level off towards the end of the of the intervention... The mechanistic basis of this is unclear, and it is notable that both delivery platforms exhibit this effect, implying control in both enteric and transbuccal absorption," the team writes.
Corfe told Medscape Medical News that they were "pleasantly surprised" to see the plateau effect with both the capsule and spray formulations, inasmuch as there are concerns over potential toxic effects at high circulating levels of vitamin D.
"We're fascinated as to how that regulation might occur, but I think, if that holds true in larger studies, there's a lot of reassurance about overdosing, at least at these doses that we're using in this type of study," Corfe said.
When participants were asked at their exit from the study about their preference as to the delivery method, 60% preferred the spray, 24% the capsules, and 16% did not express a preference.
Corfe said, "If you are a reasonably healthy person and just worried about your vitamin D levels and looking to supplement across winter, for example," the study suggests that the choice over capsules or spray "boils down to personal preference."
One limitation of the study was that the population was homogeneous, Corfe noted. He said they would next like to study the spray in older adults, as well as in persons of ethnic minorities "who might have different challenges with vitamin D supplements."