This chart shows the relationship between vitamin D levels and peak flu season months. It displays data from the CDC on the average peak month of flu activity each year from 1982-1983 to 2017-2018, with most years peaking between December and March. It also shows average vitamin D levels by month, with the lowest levels (less than 15 ng/ml) occurring between January and March, and levels below 20 ng/ml spanning October through June. The chart suggests that vitamin D deficiency, as indicated by levels below 20 ng/ml, may be associated with increased flu activity and the typical winter peak of the flu season.

5. www.grassrootshealth.net
Chart Date 3/23/2020
©2020 GrassrootsHealth
CDC.gov, 2018. (Flu Season Peak Month)
Cannell et al., Epidemiol Infect, 2006. (Vitamin D Level by Month)
20
18
16
14
12
10
8
6
4
2
0
TimesMonthwasSeasonPeak
Month
Aug Sept Oct Nov Dec Jan Feb Mar Apr May June July Aug
PeakMonthofFluActivity1982-1983through2017-2018with
AverageVitaminDLevelperMonth
VitaminDLevel
(ng/ml)
35
30
25
20
15
10
(nmol/L)
87.5
75
62.5
50
37.5
25
VitaminDLevelbyMonth
FluSeasonPeakMonth
Jan-Marchaverages<15ng/ml,
verydeficient;Oct-Juneaverages
all<20ng/ml,stilldeficient