Since the Grassroots Health web-based calculator works internally according to a ratios of bodyweight - albeit with an upper limit to the supplemental amount - and since it is created and maintained by a long-standing nutrition advocacy organisation who employ and are lead by the world's foremost vitamin D researchers and MDs, it is of interest regarding my proposed guidelines.
Here is an account of its behavior in early October 2020.
The Grassroots Health Vitamin
D* calculator has a mode for people with no knowledge
of their current 25OHD levels:
The following is a compacted representation of what the form
looks like:
I set the calculator to aim for 50ng/ml and recorded all its outputs for body weights 1 to 159kg. I call the two figures it produces the base and upper recommended intakes. These are the same terms that I use for my two ratios, but the intended meanings of the GRH values and the amounts resulting from my suggested ratios are not the same
The base intake does not guarantee perfect health - it predicts half the population with this body weight (with no account of morphology - such as being overweight or obese) will, in the long term, attain the targeted 25OHD level.
The upper intake doesn't imply that taking more than this is dangerous. The 25OHD levels at which toxicity might become a problem are above 150ng/ml and you can see from this Ekwaru et al. graph adaptation from https://aminotheory.com/cv19/d3/ that the self-regulatory degradation of 25OHD to water soluble 24,25OHD, which is broken down and excreted, makes it very difficult to attain such high levels which are nearly twice as high as the top of this chart.
The Importance of Body Weight for the Dose Response Relationship of Oral Vitamin D Supplementation and Serum 25-Hydroxyvitamin D in Healthy Volunteers
John Paul Ekwaru et al. PLoS One 2014
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0111265
The GRH calculator rounds the internally-calculated value up or down to the nearest 0.025mg (1000IU), so the results span a wider range of D3 to body weight ratios than the internal calculations generate.
It is also clear that the upper intake is clipped at 0.25mg
(10,000IU) rather than rising above this as the Ekwaru et al.
curve for Obesity above indicates it should. This graph doesn't
represent body weight. There are problems with the BMI formula
being more likely to classify tall people as obese, when their
morphology is not as overly heavy as a shorter person with the
same BMI figure.
Still, anyone who weighs 150kg is surely obese, rather than just tall and well-built, or overweight. So when the imaginary horizontal line at the 50ng/ml level in the above graphs intersects, to the right of the bright green dot, with greater degrees of obesity, and with greater required D3 intake to attain the 50ng/ml, I see from this that the required intake goes well beyond 0.25mg (10,000IU) limit of the upper intake produced by the GRH calculator.
The calculator page cites 26 research articles, by way of a
clickable References link near the bottom. These seem to be
research articles, rather than documents which recommend particular
supplemental intakes. I did not pursue any of these cited
articles.
Below is the table of results as displayed, with my calculated D3 mg/kg body weight ratios.
After averaging out the 1000IU quantization, the base intake seems to be a ratio of 1.35ug/kg.
Before the upper intake's 10,000IU clipping kicks in at 73kg, I
think the upper intake ratio is about 3.6ug/kg = 2.7 times
the base ratio. This upper intake (before the clipping starts) is
intended to ensure 90% of the people attain the target 50ng/ml
25OHD level rather than the 50% of the base intake. There is a
lot of scatter in all the studies relating 25OHD levels to D3
intake. The clear curves of the Ekwaru et al. graph are averages
based on a large sample, but we must remember that half the people
for any given body morphology class and any given D3 intake have
25OHD levels below the line.
The columns below are:
- kg body weight.
- Base recommended intake, thousands of IU.
- Base D3 intake as a ratio of body weight
- Upper recommended intake, thousands of IU.
- Upper D3 intake as a ratio of body weight
Target 50ng/ml:
kg Base ,000IU ug/kg Upper ,000IU ug/kg
1
1
25.0
1 25.0
2
1
12.5
1 12.5
3kg
1
8.3
1 8.3
4
1
6.3
1 6.3
5
1
5.0
1 5.0
6
1
4.2
1 4.2
7
1
3.6
1 3.6
8
1
3.1
1 3.1
9
1
2.8
1 2.8
10kg
1
2.5
2 5.0
11
1
2.3
2 4.5
12
1
2.1
2 4.2
13
1
1.9
2 3.8
14
1
1.8
2 3.6
15
1
1.7
2 3.3
16
1
1.6
2 3.1
17
1
1.5
2 2.9
18
1
1.4
3 4.2
19
1
1.3
3 4.0
20kg
1
1.2
3 3.8
21
1
1.2
3 3.6
22
1
1.1
3 3.4
23
1
1.1
3 3.3
24
1
1.0
3 3.1
25
1
1.0
4 4.0
26
1
1.0
4 3.8
27
1
0.9
4 3.7
28
1
0.9
4 3.6
29
2
1.7
4 3.4
30kg
2
1.7
4 3.3
31
2
1.6
5 4.0
32
2
1.6
5 3.9
33
2
1.5
5 3.8
34
2
1.5
5 3.7
35
2
1.4
5 3.6
36
2
1.4
5 3.5
37
2
1.4
5 3.4
38
2
1.3
5 3.3
39
2
1.3
6 3.8
40kg
2
1.3
6 3.8
41
2
1.2
6 3.7
42
2
1.2
6 3.6
43
2
1.2
6 3.5
44
2
1.1
6 3.4
45
2
1.1
7 3.9
46
2
1.1
7 3.8
47
2
1.1
7 3.7
48
3
1.6
7 3.6
49
3
1.5
7 3.6
50kg
3
1.5
7 3.5
51
3
1.5
7 3.4
52
3
1.4
8 3.8
53
3
1.4
8 3.8
54
3
1.4
8 3.7
55
3
1.4
8 3.6
56
3
1.3
8 3.6
57
3
1.3
8 3.5
58
3
1.3
8 3.4
59
3
1.3
9 3.8
60kg
3
1.3
9 3.8
61
3
1.2
9 3.7
62
3
1.2
9 3.6
63
3
1.2
9 3.6
64
3
1.2
9 3.5
65
3
1.2
9 3.5
66
3
1.1
10 3.8
67
4
1.5
10 3.7
68
4
1.5
10 3.7
69
4
1.4
10 3.6
70kg
4
|
10 3.6
71
4
|
10 3.5
72
4
|
10 3.5
73
4
|
10 3.4
74
4
1.4
10 3.4
75
4
1.3
10 3.3
76
4
|
10 3.3
77
4
|
10 3.2
78
4
|
10 3.2
79
4
|
10 3.2
80kg
4
1.3
10 3.1
81
4
1.2
10 3.1
82
4
|
10 3.0
83
4
|
10 3.0
84
4
|
10 3.0
85
4
|
10 2.9
86
4
1.2
10 2.9
87
5
1.4
10 2.9
88
5
|
10 2.8
89
5
|
10 2.8
90kg
5
|
10 2.8
91
5
|
10 2.7
92
5
1.4
10 |
93
5
1.3
10 |
94
5
|
10 2.7
95
5
|
10 2.6
96
5
|
10 |
97
5
|
10 |
98
5
|
10 2.6
99
5
|
10 2.5
100kg
5
1.3
10 |
101
5
1.2
10 |
102
5
|
10 2.5
103
5
|
10 2.4
104
5
|
10 |
105
5
1.2
10 |
106
6
1.4
10 2.4
107
6
|
10 2.3
108
6
|
10 |
109
6
|
10 |
110kg
6
|
10 |
111
6
1.4
10 2.3
112
6
1.3
10 2.2
113
6
|
10 |
114
6
|
10 |
115
6
|
10 |
116
6
|
10 2.2
117
6
|
10 2.1
118
6
|
10 |
119
6
|
10 |
120kg
6
1.3
10 |
121
6
1.2
10 2.1
122
6
|
10 2.0
123
6
|
10 |
124
6
1.2
10 |
125
7
1.4
10 |
126
7
|
10 2.0
127
7
|
10 1.9
128
7
|
10 |
129
7
1.4
10 |
130kg
7
1.3
10 |
131
7
|
10 1.9
132
7
|
10 |
133
7
|
10 |
134
7
|
10 |
135
7
|
10 1.9
136
7
|
10 1.8
137
7
|
10 |
138
7
|
10 |
139
7
|
10 |
140kg
7
1.3
10 |
141
7
1.2
10 |
142
7
|
10 1.8
143
7
1.2
10 1.7
144
8
1.4
10 |
145
8
|
10 |
146
8
|
10 |
147
8
|
10 |
148
8
1.4
10 |
149
8
1.3
10 |
150kg
8
|
10
151
8
|
10 1.7
152
8
|
10 1.6
153
8
|
10 |
154
8
|
10 |
155
8
|
10 |
156
8
|
10 |
157
8
|
10 |
158
8
|
10 |
159
8
1.3
10 1.6
If there was no clipping of the upper intake, then for a 150kg
person, this would be about (150 * 3.6) = 0.54mg = 21,600IU, which
seems good to me - but I am not a doctor.
I was curious to see how weight increases from birth. This page
has charts for US girls and boys. This one is for the girls:
