The importance of Vitamin D in the Covid-19 pandemic: reports from Israel
It has been known for more than 40 years that vitamin D is of vital importance in the escalation of defensive immunity at the time of infection. It is also well-established that people with defective immunity are very susceptible to infection, with a high risk of death, and this has been illustrated well by the experience of AIDS. It has also been established on numerous occasions in many countries that vitamin D deficiency is very common, leading to sub-optimal immunity in many people.
In life in general, people are not aware of their vitamin D deficiency and the problems that result from it. Health issues such as respiratory infections, post-operative infections and recovery from surgery, problems in pregnancy, the development of diabetes, certain cancers, and multiple sclerosis are accepted as bad luck, even though they are known to have an increased incidence in people with vitamin D deficiency.
But when faced with a pandemic of Covid-19, a virus against which we have no learned immunity, the rapid time-scale brought disadvantages of vitamin D deficiency and impaired immunity into sharp focus. It was soon after the onset of the pandemic that we learned of the high susceptibility of those with low blood levels of vitamin D to critical and fatal Covid-19. It was obvious that a public health imperative to minimise ICU admissions and deaths, would be to correct vitamin D deficiency as soon as possible. But it was not to be.
Susceptibility of particular population groups
It became clear that the great majority of Covid-19 deaths occurred in the elderly, but we were told that they were just old, the official and unquestioned narrative that had no scientific foundation. Vitamin D is produced by the action of UV from the sun on 7-dehydrocholesterol (7-DHC) that is synthesised in the skin. It has been known for forty years that the thin dry skin of the elderly does not synthesise adequate amounts of 7-DHC and so vitamin D deficiency is inevitable, no matter how much time is spent in the sun.
It was also clear that people of Black African and South Asian ethnicity were particularly susceptible to critical and fatal Covid-19. The official narrative is that this has been the result of socio-economic disadvantage and racism. My reporting of the fact that of 26 working doctors in the UK who died from Covid-19, 25 (96%) were of Black African and South Asian ethnicity went officially unacknowledged even though it was the paradox that invalidated the socio-economic proposal. Well-known vitamin D deficiency in these ethnic groups was the obvious and scientifically established explanation, not officialy acknowledged.
In a previous Blog post I reported that the group of people in the UK hit hardest of all by the pandemic of Covid-19 have been Haredi Jews, those who are most orthodox. I pointed out that they have sun-avoiding behaviour, not by intent but as a result of clothing and other traditions that result in virtually no exposure of the skin to the sun.
VItamin D in Israel in 2001
Research in Israel 20 years ago investigated vitamin D status in Jewish new mothers in Israel, identifying as to whether they were orthodox (Haredi) or non-orthodox. Blood testing for vitamin D was undertaken after delivery. It was found that in the orthodox mothers the average mean blood level of vitamin D was 13.5ng/ml (34nmol/L) compared to 18.6ng/ml (46.5nmol/L) in non-orthodox mothers.
We can see in Figure 1 that extremely low blood levels of less than 5ng/ml, 12.5nmol/L, were found in 5.7% of orthodox mothers and in 2.7% of non-orthodox. Less than 10ng/ml (25nmol/L) was found in 32.7% of orthodox mothers and in 13% of non-orthodox. We will see from a later study how extremely low are these blood levels.
A very small vitamin D supplement of 400 units per day was given to some women during pregnancy and it had a small effect. As a result of this supplement, 2.2% of orthodox mothers had a blood level less than 5ng/ml, 12.5nmol/L, but none of the non-orthodox mothers. 13% of the orthodox mothers receiving the small vitamin D supplement had a blood level less than 10ng/ml, 25nmol/L, compared to 8% in non-orthodox.
|Figure 1. Jewish mothers in Israel – vitamin D status|
The messages from this study are that:
- vitamin D deficiency is very common in Israel, despite a sunny environment
- it is more common in orthodox mothers
- vitamin D supplement of 400 units per day is of little benefit
- blood levels of vitamin D are higher in the summer in non-orthodox mothers
- in orthodox mothers, blood levels of vitamin D do not increase in the summer.
Mukamel MN, Weisman Y, Somech R, et al. Vitamin D deficiency and insufficiency in orthodox and non-orthodox Jewish mothers in Israel. Isr Med Assoc 2001; 3: 419-421.
Vitamin D in Israel in 2021
We now have the results of a new study from Israel. It looks at the outcome of Covid-19 related to pre-infection Vitamin D status, and "Guess What?" The outcome is far better in people with the highest (not toxic) blood levels of Vitamin D. Let us look at the details.
The study was of 1176 patients admitted to the Galilee Medical Centre on account of Covid-19. 253 of these had blood levels of Vitamin D measured prior to infection. For the purpose of analysis they were divided into four groups based on blood levels:
- less than 20ng/ml, 50nmol/L
- 20 to 29.9ng/ml, 50 to 75nmol/L
- 30 to 40ng/ml, 75 to 100nmol/L
- greater than 40ng/ml, 100nmol/L.
The analysis shows many interesting features, as displayed in the tables and figures.
|Figure 2. Blood levels of Vitamin D in advance of Covid-19|
Figure 2 shows the distribution of blood levels of Vitamin D. 52.5% of those admitted to hospital had a previous blood level less than 20ng/ml, 50nmol/L. This in itself identifies a serious public health problem that was identified in new mothers in 2001 and remains twenty years later. Only 15.8% had a level greater than 40ng/ml, 100nmol/L.
Table 1 shows the relationship between the blood levels of Vitamin D in advance of Covid-19 and the severity of illness when it happened. The Table shows the numbers in each group, and also the percentages of Vitamin D status in each illness category.
|Table 1. Relationship between severity of Covid-19 and pre-existing blood levels of Vitamin D|
Table 2 illustrates the dramatic effect of pre-existing blood levels of Vitamin D on death from Covid-19. A blood level of greater than 20ng/ml, 50nmol/L, makes death very unlikely. A blood level of less than this put an individual at considerable risk of death, an excess risk that can be eliminated by the public health action of correcting Vitamin D deficiency.
|Table 2. Deaths from Covid-19 and pre-existing blood levels of Vitamin D|
We can see in Figure 3 that most patients with mild illness have higher blood levels of Vitamin D, greater than 30ng/ml, 75nmol/L.
|Figure 3. Blood levels of Vitamin D in patients with mild Covid-19|
When we look at Figure 4 we find that in moderate illness the patients are predominantly those with low blood levels of Vitamin D
|Figure 4. Blood levels Vitamin D in patients with moderate Covid-19|
Figure 5, below, shows that severe Covid-19 occurs almost exclusively in those with low levels of Vitamin D, less than 20ng/ml, 50nmol/L.
|Figure 5. Blood levels Vitamin D in patients with severe Covid-19|
Figure 6 shows that critical Covid-19, patients, those who would have been admitted to intensive care, were almost exclusively those with the lowest blood levels of Vitamin D. On the other hand patients with blood levels greater than 30ng/ml, 75nmol/L, did not require intensive care unit support.
|Figure 6. Blood levels Vitamin D in patients with critical Covid-19|
We can look at this is another way. What is the pattern of illness that occurs with Covid-19 in people with the lowest blood levels of Vitamin D, less than 20ng/ml, 50nmol/L?
Figure 7 demonstrates that those with the lowest blood levels of Vitamin D are most likely to have severe or critical illness.
|Figure 7. Covid-19 in patients with the lowest blood levels of Vitamin D, <20ng/ml <50nmol/L|
When the blood level of Vitamin D is above the critical level of 20ng/ml, 50nmol/L, the threat of severe or critical illness is very much reduced, as shown in Figure 8.
|Figure 8. Covid-19 in patients with blood levels of Vitamin D|
When the blood level of Vitamin D is greater than 30ng/ml, 75nmol/L, Covid-19 is likely to be mild, shown in Figure 9.
|Figure 7. Covid-19 in patients with blood levels of Vitamin D|
Figure 10, below, shows that when the blood level of VItamin D is greater than 40ng/ml, 100nmol/L, severe and critical Covid-19 does not occur. 12 patients out of 13 had just mild illness, and one had just moderate illness.
|Figure 7. Covid-19 in patients with the highest blood levels of Vitamin D, >40ng/ml, >100nmol/L|
38 of the 253 patients died. Deaths, occurring in hospital, were almost entirely in patients with the lowest levels of Vitamin D, less than 20ng/ml, 50nmol/L. (Table 2, repeated)
|Table 2. Deaths from Covid-19 and pre-existing blood levels of Vitamin|
It appears that the three patients who died with blood vitamin D levels of 30ng/ml, 75nmol/L, they did so without going to the Intensive Care units, for reasons not explained.
For the purpose of death analysis, there are just two groups, those with vitamin D less than 20ng/ml, 50nmol/L (34 patients), and those with higher levels (4 patients).
If you were to develop Covid-19, what blood level of Vitamin D would you choose?
|Figure 11. Deaths from Covid-19 and pre-existing blood levels of Vitamin|
The study did not distinguish between orthodox and non-orthodox Jews, but we have seen that in the UK orthodox Haredi Jews have had an exceptionally high mortality rate from Covid-19. The two main ethnic groups in Israel are Jews and Arabs, but there are several minority ethnic religious groups within Arab people. For the purpose of analysis, the study divided its sample into Arab and non-Arab.
The Vitamin D status of the two groups is shown in Figure 12.
|Figure 12. Blood levels of Vitamin D in Israel|
The frequency of very low blood levels of vitamin D less than 20ng/ml, 40nmol/L, is almost twice as high in the Arab group as in the non-Arab. The reason is not investigated directly, but is most likely to be the result of sun-avoiding behaviour, with very little exposure of the skin to the sun in Muslim people.
There is no mention of illness category or mortality related to ethnicity, but we can assume that the large proportion of Arab people with very low blood levels of Vitamin D would lead to a high incidence of serious and fatal disease. It is likely that, as in the UK, this will also be the case in the most orthodox Jews.
The age categories for analysis are:
- less than 50 years
- 50 to 65
- 65 and older
The relationship between age and vitamin D status is shown in Figure 13.
|Figure 13. Blood levels of Vitamin D related to age|
The result is not surprising. Older people have on average lower blood levels of vitamin D. In this study, of the patients with Covid-19 aged 65 or older (grey bars), 59.4% had blood vitamin D levels less than 20ng/ml, 50nmol/L, compared to just 13.5% of those aged less that 50 years.
We have seen above that older people progressively fail to synthesise adequate amounts of 7-dehydrocholesterol, and as a result UV from the sun is unable to produce sufficient vitamin D to enable optimal immunity.
Vitamin D levels in co-morbidities
The 2021 study from Israel provides additional data of considerable importance, an analysis of co-morbidities.
It has been recognised in the UK and other European countries that Black African and South Asian ethnicities, and increasing age were major factors in the risk of serious, critical, and fatal Covid-19. But certain pre-existing illnesses, co-morbidities, were also recognised as increasing such risk. These are not surprising to those who are aware of clinical practice. The co-morbidities recognised in the study from Israel are as follows:
- COPD, chronic obstructive pulmonary disease
- CHD, coronary heart disease
- CKD, chronic kidney disease
- Obesity, BMI >30
The relationship of these to blood levels of Vitamin D are shown in Table 3.
|Table 3. Covid-19, co-morbidities, and pre-existing blood levels of Vitamin D|
Absolute numbers in each group are shown in Table 3, and it is obvious that all these co-morbidities are strongly associated with the lowest blood levels of vitamin D, less than 20ng/ml, 50nmol/L.
A study performed in the UK in early 2021 demonstrated the same thing and I have reviewed it previously. It demonstrated very similar findings to this table, but the findings were interpreted in an absurd way. If there was a high Covid-19 death rate from CHD, age, or ethnicity, then these were the stated reasons and Vitamin D deficiency was regarded as incidental. In other words the interpretation was that there was no evidence that Vitamin D deficiency was of any importance. The vitamin D deficiency of ethnic minorities was left untreated, with countless deaths resulting. The paper completely failed to follow the scientific process of finding the common factor (in this case Vitamin D), a vital step in understanding as described by William of Ockham.
The conclusion of this well-publicised but extremely poor UK study was ultimately withdrawn, but this was not reported in the national press.
The Israel study accepts that the totality of the data indicate a pivotal role of pre-existing blood levels of Vitamin D in predicting the outcome of Covid-19.
The conclusions and implications of the two studies from Israel are perfectly clear and irrefutable. The blood level of Vitamin D is the major determinant of outcome from symptomatic Covid-19. The target blood level must be 40ng/ml, 100nmol/L, so as to optimise immunity against severe and critical Covid-19. Had this approach been instituted as a public health initiative at the onset of the Covid-19 pandemic, there would have been many fewer deaths and very much reduced pressure on hospitals and intensive care units.
Blood level of Vitamin D less than 20ng/ml, 40nmol/L, should be regarded as critically low and requiring immediate correction. Testing the population for blood level of Vitamin D must become a public health policy. This is easily affordable.
More work is required to establish the dose of Vitamin D that is required to correct inadequate blood levels. The 2001 study from Israel indicated clearly that 400units per day given during pregnancy was hopelessly inadequate and did not eliminate serious Vitamin D deficiency. This is the dose that UK heath agencies advise, but they state that the more realistic dose of 4,000 units per day is safe. This is the dose that is regarded as appropriate by most medical scientists who study Vitamin D.
I have indicated previously that by definition and before the days of physical measurement, one unit of Vitamin D was defined as the daily requirement of a 10 gram immature mouse. We can scale up from that so that the daily requirement of a 60kg human would be 6,000 units, and for a 120kg obese human 12,000 units each day. To be cautious, perhaps half of these doses would be a reasonable starting point for determining the dose that would be appropriate in achieving the blood levels of 40ng/ml, 100nmol/L. This must be the target level, as the study from Israel indicates.
The important thing is that rather than just giving Vitamin D supplement, the achievement of target blood levels must be recorded. It is standard practice in the treatment of anaemia and diabetes, and similarly blood pressure in hypertension. This must be a public health priority.
Thanks for this. Important findings.ReplyDelete
Now will other governments listen and learn about the importance of vitamin D ?ReplyDelete
Sadly,it seems that no governments are listening about Vitamin D. They are all blindly following the W.H.O. narrative.Delete
No. There is no money for Pharma in vit D. So no campaign contributions.Delete
This comment has been removed by the author.ReplyDelete
Superb analysis David, I've tweeted itReplyDelete
David, the Andalucian government has for a year been recommending all the residents of municipal care homes to have their vitamin D status assessed, and to receive supplementation if necessary. More recently this has been adopted as a recommendation throughout SpainReplyDelete
Such a pity that our government fails to heed this simple and clearly effective advice.ReplyDelete
I requested my surprised GP to have my bloodtest include vD. TheReplyDelete
Result was a prescription for 5000iu per day.I take 1000iu per day as I was told by another GP that I am overdosing?
The first GP was right - the second GP was wrong. 5000iu daily is widely recommended as a dose sufficient to correct deficiency. Volunteers taking ten times this dose suffered no side effects whilst being monitored over a six month period.Delete
Michael (retired physician)
NOAEL (no observed adverse effects level) for vitamin D supplements is set by EFSA (European Food Safety Authority) to 250 µg/day (10.000 IU).Delete
The Endocrine Society recommends 10,000 IU of vitamin D as the upper safe limit for all and recommends 6,000 IU daily for eight weeks to ensure a blood level above 75 nmol/L or 30 ng/mL.
Vitamin D supplementation (cholecalciferol) is biochemically inactive and LD50 (lethal dose) for vitamin D supplementation is unknown.
It is unfortunate anyone is still of the opinion that 75nmol/l 30ng/ml is adequate or sufficient while covid is about.Delete
COVID-19 is, in the end, an endothelial disease
To successfully prevent a cytokine storm we require MAXIMUM inhibition of proinflammatory cytokines. We only start to enable the inhibition at 30ng/ml 75nmol/l and it's only maximized at 50ng/ml 125nmol/l or above.
See article https://www.sciencedaily.com/releases/2012/02/120223103920.htm
In order to stabilize the endothelium we need to maintain all forms of vitamin d3, cholecalciferol, calcidiol, calcitriol in serum.
In this image we see cholecalciferol is the form that best stabilizes the endothelium but it has a half-life in serum of just 24hrs, so it's necessary to take it daily and ensure 25(OH)D remains above 50ng/ml 125nmol/l.
This figure 2 from Hollis's paper mentioned in my previous post https://imgur.com/gallery/CWBxV4U
shows people with vit d levels at/below 30ng/ml 75nmol/l have little if any free cholecalciferol in serum while those with levels at/above 50ng/ml 125nmol/l have significant amounts of free available cholecalciferol to stabilize the endothelium and inhibit inflammation.
It is a pity to skimp on vitamin d daily supplementation when ischaemic heart disease is responsible for 16% of the world’s total deaths. Stroke and chronic obstructive pulmonary disease are the 2nd and 3rd leading causes of death and Lower respiratory infections remained the world’s most deadly communicable disease.
Having optimal natural 25(OH)D levels at/above 50ng/ml 125nmol/l help reduce or prevent these conditions progressing.
Great science... Great courage to present a woke report of medical facts devoid of political and finacial influence by self interested powers that actually care note for the true well being of society.ReplyDelete
You are to be commended Doc David for standing up for life no matter what madness is being forced on the nieve population....!
Its sad though that so many of your peers are so silent and weak at the very time when society needs medical leadership to be strong.
There are other highly and more effective and cheap treatments which also need honest exposure like yours to society but are also not being spoken of truthfully.
WELL PRESENTED DOC....!
It is possible 40ng/ml 100nmol/l is a too conservative target in the current situation.ReplyDelete
Covid is in the end an Endothelial disease. https://pubmed.ncbi.nlm.nih.gov/32882706/
and if we are going to prevent a cytokine storm we need to be able to maximize the inhibition of proinflammatory cytokines.
We know How vitamin D inhibits inflammation https://www.sciencedaily.com/releases/2012/02/120223103920.htm
Cells incubated in 30 ng/ml vitamin D and above showed significantly reduced response to the LPS. The highest levels of inflammatory inhibition occurred at 50 ng/ml.
Not only does cholecalciferol enable the inhibition of proinflammatory cytokines but it also stabilizes endothelial function. However the half life in serum is just 24 hrs so daily dosing (or sun/uvb exposure) is required and to ensure significant measureable amounts of cholecalciferol remain freely available in serum 25(OH)D needs to be at/above 50ng/ml 125nmol/l.
Circulating Vitamin D3 and 25-hydroxyvitamin D in Humans: An Important Tool to Define Adequate Nutritional Vitamin D Status
If you look at figure 2 from this paper you can see that those with levels below 40ng/ml 100nmol/l will have less cholecalciferol in the form in serum than those with 50ng/ml 125nmol/l and above.
It costs very little more to maintain truely optimal vitamin d status.
Thanks Ted. A blood level of 40ng/ml appears to be OK for Covid-19, but I suspect that blood levels are going down following vaccinations. A higher reserve will therefore be necessary. With additional supplement my level is now about 70ng/ml, 170nmol/L.Delete
From a complete non medicReplyDelete
Many thanks for your very helpful article and comments on this subject
It is very concerning to realise the lack of action by Gov in using this data and probably to be expected in this day and age
Can you please tell me just how much in layman’s terms I should take of vitamins D supplement to match what you are suggesting please, and would I need a blood test before starting to determine my current level of vitamins D or is the rang so great that this would not be an issue
Many thanks for your courage to publish this information
Most UK adults in December have 25(OH)D levels around (or below 45nmol/l but dropping down toward 35nmol/l by FebruaryDelete
To reach 125nmol/l (50ng/ml) takes more than 8000iu daily vitamin d3 and to get above 40ng/ml 100nmol/l takes more than 5000iu/daily.
These amounts are from
They assume you are not overweight.
There are charts in the above pdf showing amount per lb (55 iu/d) or kg (116iu/d) of bodyweight for underweight or overweight people.
The safety of daily vitamin d3 dosing is such that for people who have not been using daily vitamin d3, 10,000iu daily is absolutely safe for 3 months to enable everyone to get over 50ng/ml 125nmol/l after which 5000iu should be sufficient daily throughout March to September next year to maintain a safe level.
COVID-19 mortality risk correlates inversely with vitamin D3 status, and a mortality rate close to zero could theoretically be achieved at 50 ng/ml (125nmol/l) 25(OH)D3:
Ps I should have added that I am 70 plus yearsReplyDelete
At an age greater than 70 a vitamin D supplement becomes more important. I am 78. I take 20,000 units once a week. This gives a good blood level of 40ng/ml, 100nmol/L. Blood test is good at some stage, but do not delay taking vitamin D. If you are to have a vaccination, take an additional 40,000 units as a single dose two weeks before.Delete
Dietary Vitamin D and Its Metabolites Non-Genomically Stabilize the EndotheliumDelete
I suspect you haven't read this paper or understood it's significance.
If it's true it's important to ensure cholecalciferol remains in serum in that basic form. That is why it's important to take vitamin d3 daily.
Circulating Vitamin D3 and 25-hydroxyvitamin D in Humans: An Important Tool to Define Adequate Nutritional Vitamin D Status
https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC1868557/?tool=pubmed Figure 2 shows cholecaliferol vitamin d3 in serum in relation to 25(OH)D.
Now we know cholecaliferol is required in that form to stabilize endothelial function we need to be taking (or making) it daily. Hollis was anticipating this finding here.
The Role of the Parent Compound Vitamin D with Respect to Metabolism and Function: Why Clinical Dose Intervals Can Affect Clinical Outcomes here https://academic.oup.com/jcem/article/98/12/4619/2833974
Thanks Ted, for the lead to this paper, which I am about to read.Delete
Interesting article at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3487008/ regarding human cathelicidins -ReplyDelete
"Moreover, production of LL-37 in macrophages is stimulated by vitamin D released by sunlight through the skin. Probably the sun baths, recommended for years for overcoming tuberculosis, increase the ability of LL-37 to kill intracellular Mycobacterium tuberculosis . "
Is there no end to the talents of Vitamin D?
This comment has been removed by the author.Delete
Thanks for highlighting these Israeli studies.ReplyDelete
However, there appears to be something wrong with "Figure 13. Blood levels of Vitamin D related to age."
The 4 bars of any given colour should add up to 100%, representing all the patients in the corresponding age group. That looks roughly accurate for the green bars, but the grey bars look like they add up to something like 170%, and the blue bars fall somewhere in the middle.
The grey bars show blood levels for patients 65 and older, and indicate that almost 60% of those folks have blood levels of vitamin D that are in the bottom range. Or course, we already know that serious/fatal Covid outcomes are worse for the elderly. If the 60% number is correct, I'm not sure this study shows anything more than that vitamin D levels decline with age -- although I guess the comparison of orthodox and non-orthodox patients is suggestive.
FWIW, I take 5000 - 10,000 IU daily, so I wouldn't call myself a vitamin D skeptic.
Hi. The bars of any colour won't add up to 100%. Rather, each set of three colours for each D level range will add up to 100. The mistake is in the word 'releted'.Delete
If that's the case, then the following interpretation from the article is not correct:Delete
"In this study, of the patients with Covid-19 aged 65 or older (grey bars), 59.4% had blood vitamin D levels less than 20ng/ml, 50nmol/L, compared to just 13.5% of those aged less that 50 years."
If each set of 3 bars sum to 100%, then the proper interpretation of this graph would be:
"in the group of people with vitamin D blood levels less than 20ng/ml, 59.4% were aged 65+, and 13.5% were less than 50 years old."
It would be illuminating to know the age distribution of the patients in the study.
Yes, your corrected interpretation fits the chart and the original table from the paper.Delete
And I'm a 2000IU D3, 2 x cod liver oil, frequent salmon, Australian sunshine and doubly vaccinated betting man.
While there are benefits from sun exposure apart from vitamin d production people must accept for natural vitamin d production UVB has to reach ground level. So early morning and late afternoon, or any time shadow is longer than height will not generate any extra vitamin d. The reason sun exposure never causes vitamin d toxicity is UVA reaching ground level degrades cholecalciferol by converting it to Lumisterol and Tachysterol which although they have may have health benefitsthese are not vitamin d related and have only recently be suggested. People spending time in UVA only light, sitting behind glass windows, under fluorescent tubes will inevitably have lower vitamin d status than those in direct sunlight.ReplyDelete
There is a short video here https://dminder.ontometrics.com/about.html explaining the production of vitamin d3 from UVB from sunlight.
Thanks Ted – important up to date information. Papers just read (with difficulty)Delete
Osteoporosis is related with lacking calcium admission, however vitamin D assists with calcium ingestion. Long haul lack of vitamin D expands the gamble of osteoporosis2. https://slides.com/fortismedicalbilling206ReplyDelete
Unfortunately the link provided doesn't open for me.ReplyDelete
If we look at average vitamin d levels for adults in UK and USA we see they are below the optimal level for calcium absorption.
Heaney has a graph of Calcium absorption in relation to 25(OH)D level which you can see here https://academic.oup.com/ajcn/article/88/2/541S/4650022?login=false
Average USA adult vitamin d levels are around 20ng/ml 50nmol/l about half the level required for optimal calcium absorption.
If we raised the threshold for vitamin d insufficiency to 40ng/ml 100nmol/l we could ensure everyone was able to better absorb the calcium in food and water and not rely on calcium carbonate supplements that are known to cause problems.