Vitamin D

Question 1

Define a dietary immunostimulant?

Answer 1

Food constituents or supplements that are claimed to boost immunity and reduce the risk of infection

Question 2

The problem linked to dietary immunostimulants in athletes?

Answer 2

The evidence for their efficacy in reducing infections (pathogens resistance) is limited

Question 3

What is the aim of pathogen resistance?

Answer 3

Increase immunity to restrict pathogen entry

Question 4

What is the aim of immune tolerance?

Answer 4

Reducing the duration and severity of symptoms

Question 5

What the problem with prescribing supplements to athletes?

Answer 5

Evidence is based on data from clinically suppressed populations, therefore, there is greater potential for nutritional supplementation to have a benefit on the immune function

Question 6

Common food sources of Vitamin D?

Answer 6

Oily fish
Red meat
Egg yolk
Liver
Fortified food - cereals, milk, and mushrooms

Question 7

As a general rule, what % of our Vitamin D comes from the diet?

Answer 7

10-20%

Question 8

How is Vitamin D synthesised?

Answer 8

7-Dehydrocholestrol reacts with UV rays -> Cholecalcifol (Vitamin D3) -> liver (location of dietary Vitamin D2 and 3) -> converted to 25-hydroxyvitamin D3 -> kidney -> 1,25-dihydroxyvitamin D3 -> maintain calcium balance in the body

Question 9

What is the active form of Vitamin D in the body?

Answer 9

1,25-dihydroxyvitamin D3

Question 10

What’s the association between Northen Latutides and Vitamin D?

Answer 10

Between the months of November to March, there are insufficient UV-B rays to produce vitamin D

Question 11

What is the role of Vitamin D in immunity?

Answer 11

Bone health
Muscle function
Direct effect on innate immune function
Reduces inflammation
Reduces overactive (auto)immunity

Question 12

How does Vitamin D directly affect innate immune function?

Answer 12

Increases monocyte oxidative burst activity
Increases antigen-presenting compounds function
Increases macrophage production of antimicrobial proteins

Question 13

What’s a dietary source of Vitamin D3?

Answer 13

Foods

Question 14

What’s a dietary source of Vitamin D2?

Answer 14

Supplements

Question 15

In Bellavia et al. 2016 what’s the role of 1,25-dihydroxyvitamin D3 on immunity - Macrophages and Monocytes?

Answer 15

Increase antimicrobial peptides
Increase phagocytosis in macrophages
Decrease IL-6 and IL-12

Question 16

In Bellavia et al. 2016 what’s the role of 1,25-dihydroxyvitamin D3 on immunity - Th17 cells?

Answer 16

Decreased differentiation in Th17 cells - promotes autoimmunity
Decrease IL-17a, IL-17F, TNF-a, and IL-21
Increase apoptosis

Question 17

In Bellavia et al. 2016 what’s the role of 1,25-dihydroxyvitamin D3 on immunity - Th1 cells?

Answer 17

Decreased differentiation in Th1 cells
Decrease TNF-a, IL-2, IL-9, IL-22
Increase apoptosis

Question 18

In Bellavia et al. 2016 what’s the role of 1,25-dihydroxyvitamin D3 on immunity - Dendritic cells?

Answer 18

Decreased expression of MHC class 2
Decreased presenting antigen cells
Decrease IL-2 and IL-23
Increase TGF-B and IL-10

Question 19

In Bellavia et al. 2016 what’s the role of 1,25-dihydroxyvitamin D3 on immunity - B-cells?

Answer 19

Decreased proliferation of B-cells
Decreased differentiation into plasma cells
Decreased secretion of immunoglobulins

Question 20

In Bellavia et al. 2016 what’s the role of 1,25-dihydroxyvitamin D3 on immunity - T-helper type-2 response?

Answer 20

Increased differentiation in Th2 cells

Increase IL-3, IL-4, IL-5, and IL-10

Question 21

In Bellavia et al. 2016 what’s the role of 1,25-dihydroxyvitamin D3 on immunity - Treg cells?

Answer 21

Increased differentiation in T-regs

Increase IL-10 and TGF-B`

Question 22

Relationship between Vitamin D concentration and self-reported URT infection? (Ginde et al. 2009)

Answer 22

The higher your Vitamin D intake the less likely you are to report a URT infection
Well established relationship

Question 23

Vitamin D and seasonal variations in respiratory infection? (Berry et al. 2011)

Answer 23

Protocol
- controlled for adiposity, lifestyle, and socio-economic factors
Results
- vitamin D status mirrors respiratory infections
- each 10nmol/L increase in 25(OH)D as associated with 7% decrease in infection

Question 24

Which increase in 25(OH)D (nmol/L) is associated with 7% decrease in infection? (Berry et al. 2011)

Answer 24

10nmol/L

Question 25

Each 10nmol/L increase in 25(OH)D is associated with what % decrease in infection? (Berry et al. 2011)

Answer 25

7%

Question 26

Vitamin D status amount UK athletes in winter? (He et al. 2013)

Answer 26

Only 5% of athletes have optimal vitamin D status throughout the year During the winter vitamin D status is reduced Trend suggesting that higher levels of vitamin D are associated with lower levels of URI incidence Higher levels of vitamin D reduce symptom severity and improves vitamin D tolerance Higher levels of vitamin D reduce symptom duration A sub-optimal vitamin D status is associated with low saliva S-Iga secretion rate A sub-optimal vitamin D status is associated with low plasma cathelicidin

Question 27

What is plasma cathelicidin?

Answer 27

An antimicrobial protein made by macrophages and neutrophils

Question 28

What do you need to consider when assessing studies looking at vitamin D supplementation in athletes?

Answer 28

``` Duration Diet Dose Environment Method of supplementation Prior activity level Latitude Sample size Sample timing ```

Question 29

Vitamin D supplementation in sub-elite athletes? (He et al. 2016)

Answer 29

Protocol - 39 endurance athletes - latitude = 53 degrees north - 5000 IU (125ug) of vitamin D3 (tablet) vs placebo - 14wks during winter training Results - vitamin D status was increased with supplementation and decreased in the placebo (due to winter) - increase in SIgA secretion rate, cathelicidin levels in plasma and saliva over time with vitamin D3 supplementation after 7wks, however, a decrease after 14wks

Question 30

Why might SIgA secretion rate increase with supplementation after 7wks, yet decrease after 14wks? (He et al. 2016)

Answer 30

The effect of vitamin D supplementation might occur very quickly and disappear over time This might be due to higher exposure to infections during the winter

Question 31

Vitamin D oral spray and vitamin D levels in Gaelic footballers? (Todd et al. 2017)

Answer 31

Protocol - 43 Gaelic footballers - latitude = 55 degrees north - 3000 IU (75ug) of vitamin D3 (oral spray) vs placebo - 12wks during winter training Results - vitamin D status increased ith the vitamin D3 oral spray and remained low in the placebo group - no effect of vitamin D3 oral spray on plasma cathelicidin

Question 32

What could account for the differences between He et al. (2016) and Todd et al. (2017)?

Answer 32

Dose Post-intervention period levels of Vitamin D Sample timing

Question 33

Why might vitamin D3 dose affect results between He et al. (2016) and Todd et al. (2017)?

Answer 33

Might be a threshold value to elicit effects

Question 34

Why might post-intervention period levels of vitamin D3 affect results between He et al. (2016) and Todd et al. (2017)?

Answer 34

Todd et al. 2017 potentially didn't reach sufficient optimal levels to elicit effects, linked to dose

Question 35

Why might the sample timing of vitamin D3 effect results between He et al. (2016) and Todd et al. (2017)?

Answer 35

Differences have been seen at 7 wks (He et al. 2016), whereas Todd et al. 2017 only measures after 12wks

Question 36

Which is one potential reason He et al. (2016) and Todd et al. (2017) did not assess URS?

Answer 36

The number of participants was too small to meaningfully assess the association between vitamin D and URS

Question 37

Supplementation in vitamin D deficient Taekwondo athletes? (Jung et al. 2018)

Answer 37

Protocol - 25 athletes - latitude = 33 degrees north - 5000 IU (125ug) of vitamin D3 vs placebo - 4wks during winter training Results - vitamin D status increased with vitamin D3 supplementation and remained low in the placebo groups - URS symptom score was lower with vitamin D3 supplementation - no difference in SIgA concentration between the groups