I’m a Korean American 1st generation dude/medical doctor/academic whose dad inspired him to find a better way to treat cancer. The views expressed on this blog are 100% my own.
I say this, because I simply wrote “70.3% of Americans are Vitamin D deficient” (with source) and that this line was deleted as a last minute editorial change in an ASCO chapter I wrote for education purposes in June 2025. My later statement “It should be reasonable standard of care to screen for a vitamin D25 before starting conventional therapy” (particularly in patients presenting with fatigue before starting treatment) was deleted and substituted with the above ASCO party line. I can understand the latter decision. But why does ASCO not want clinicians to know the prevalence of vitamin D deficiency in this country when that is arguably the best reason to do screening?
I joined a for-profit hospital system called Cancer Treatment Centers of America 2014-2024 after a start in academia, because I wanted to learn what works in a for-profit integrative oncology practice. I have now joined academia again to help share the data that is already sitting in front of them, that says very powerfully that we should be checking serum D25 levels before starting conventional therapy. Yet I find myself opposed by ASCO (American Society of Clinical Oncology) who maintains it should be standard of care to check a vitamin D25 only when about to start a bone-weakening agent for cancer care without any RCT (randomized controlled trials) evidence to justify the safety of waiting that long.
Here is my argument for future scientific discourse of why it should be standard of care with the available evidence. Vitamin D deficiency particularly <20 ng/ml is associated with significant fatigue symptoms which can improve by 65% on fatigue scores within days of vitamin D3 replacement (placebo usually only works 20-30% on fatigue). Fatigue affects 40% of patients who present with cancer at cancer centers, and now the research is saying we want them to get up and exercise during or after chemotherapy to improve survival without addressing their baseline fatigue? Fatigue predicts lack of willingness to engage with healthier lifestyle behaviors, and people embrace unhealthy lifestyles to cope with fatigue. Targeted vitamin D replacement is what we call one of the easiest wins in integrative oncology, and this has become an unfortunate “blind spot” for academia. It’s why patients would leave NCI designated cancer centers to get second opinions and stay at CTCA during its prime. It was part of the business model, improving quality of life in the first three days of the visit by optimizing human biology first.
Knowing this will likely not be published by a major medical publishing company unfiltered, I am making it available for free here, so we can finally drive knowledge into action in 2025.
The above and below photo belongs to Jean Makanna and is of the Salar de Uyuni in Bolivia, one of the most beautiful geographic areas to explore in such a small region. Her husband does amazing photography of classic airplanes in flight: https://ghosts.com/pages/about-us.
The third degree sunburns we took care of that day…Definitely could be called melanoma lake.
Planting bulbs and seeds to let my kids know there is always unconditional love to be found the more you play with the Earth and help them understand the intelligent medicines implicit in the natural foods we all can grow.
Above is an integrative oncology cancer center, figuratively (“Yellow” by Coldplay live in Sao Paulo Brazil).
Below, is a Gemini AI-generated image symbolic of a typical NCI-designated academic cancer center. The characters in blue are those who are vitamin D deficient (and most likely do not realize it), and those in yellow are those who are vitamin D adequate in the United States (only 29.7%). >95% of these patients in blue are about to start anti-cancer therapy without having their vitamin D checked and replaced if low. Screening for this deficiency is NOT standard of care at academic cancer centers. Yet the research suggests neutral-to-positive effects on cancer mortality (despite being of “amateur hour” intervention quality) and large effect sizes on quality of life, particularly fatigue when dosed correctly. Improving fatigue is important to even consider engagement with healthier lifestyles. Baseline fatigue is a well known major risk factor to not be capable of it.
A vitamin D deficiency is one of the easiest causes of fatigue to treat, but most conventional doctors do not know how to do it correctly in 2025. With sufficient doses, 65% improvement of fatigue can be expected within a week of treatment (caution: this is probably useless for those already above 30 ng/ml so please check your blood D25 test before guessing correct dose). Technically, people can do this for themselves without a doctor using over-the-counter D3 supplements (USP certified preferred), but let’s spread the word about vitamin D so physicians can help people do this safely.
Please like or share with colleagues and loved ones if you agree this should be standard of care at all cancer centers. I know some of you might have consequences from engaging with this post, so nothing personal to me if you don’t engage with it. The main thing is to start the clinical “practice” of doing it, and see the evidence in the patients you take care of, or even better for yourself if you are low.
If you want to know all the evidence to support the above statements, check out my 3 new blogs posted over the past week here on my wordpress website. The very first blog includes a link to a free chapter (.pdf) I wrote for any institution or university to offer students, clinical trainees, residents as an essential tool for personal wellness (as you’re about to institutionalize them for a decade and those at highest risk for severe deficiency are people aged 10-30 years old, exactly those who are about to be exposed to Epstein-Barr (no not those two) virus, with 5 review questions at the end to make sure the essential knowledge is understood. Vitamin D3 is a weight based drug. It hasn’t been studied like one. D3 metabolite 1,25D is an essential hormone for wellness for all sentient beings on this planet.
The BLOGS (in summary for those reading this first and want quickie notes):
First, I propose ASCO (and NCCN) lead the charge. It should be standard of care for all cancer centers to screen for a vitamin D deficiency before starting conventional treatment. I share in that blog, the link to my free downloadable chapter about vitamin D essentials for clinicians and patients. It covers what it does and how effective it can be for symptoms like fatigue, insomnia, and foggy brain in those who are deficient. The chapter also explains how to measure and address it, so we all have the freedom to treat it ourselves.
The second blog is about how the randomized-controlled trials (RCTs docs call them) of D3 therapy of the past are heavily flawed and over-interpreted as to their clinical meaning in a patient with a known deficiency, and how no one should take them seriously for personalized vitamin D3 replacement therapy. The only thing these RCTs have proven is that indiscriminate low dose supplementation of general populations suck. None of these RCT’s offered scientific doses based on baseline D25 and patient weight, which is the gold standard until proven otherwise for individualized vitamin D replacement therapy. This led to low doses that would not help those with a lot of weight or very low D25 levels, the very ones who would stand to benefit the most.
Third and latest blog is about how integrative oncologists know vitamin D effects on fatigue are not placebo effects including reviewing a positive double-blinded (the gold standard for RCT quality) randomized controlled study and taking a deeper dive into EViDiF (Roy 2014) study to illustrate how high D3 doses you might have to give to be accurate/scientific at vitamin D replacement therapy (spoiler: as high as 20,000 to 25,000 IU/d) to really see the clinical benefit in your practice, and THIS is why it has become until now, a major “blind spot” for amazing and incredibly brilliant (more than me) talent in academia.
I am an academic breast oncologist providing cutting edge integrative breast cancer care in the Chicago-land area. Thanks for your support! Spread the word in the communities. Less important than the likes is that we get everyone yellow and prevent disease, cancer and unnecessary fatigue so we can all live our best life possible.
So just like Coldplay sings to the world – Time to #getyellow folks! And with no irony, it is an Asian American telling you this.
A glacier cave in Mendenhall Alaska. It’s big, beautiful and blue, but be yellow.
In my 1st blog, and free chapter release on why vitamin D should be looked at as a vitality sign for patients with cancer and addressed before starting conventional therapy, I highlighted the most obvious reason we should screen and treat a vitamin D deficiency, to help the ethnic minorities and obese patients who are the most likely to be vitamin D deficient and who stand the most to gain both in terms of baseline fatigue, insomnia and foggy brain (quality of life) and better cancer outcomes. This is absolutely a health equity issue, and perhaps the most fixable and impactful one America can focus on.
While vitamin D has been heavily studied for its potential impact on disease prevention and treatment, not as much so for quality of life in ‘healthy individuals’. Studies querying whether vitamin D is effective for fatigue in a healthy population is limited to one randomized placebo controlled trial and a single prospective cohort(Roy 2014), which isn’t a great look on the hierarchy of evidence, but as physicians promising to do no harm, it’s a far worse look to say we still need more randomized controlled trials (RCTs) to justify replacing an essential hormone deficiency that supports life of all sentient animals on this planet.
Let’s dive more into the EViDiF study(Roy 2014) where “healthy” individuals aged 18-75 years old who presented to a clinic with fatigue and no other acute medical issues. 77.2% were identified as having low D25 (<30ng/ml) even though 51.5% of the patients were on D supplementation (please dwell on what this says about our current ineffective practices). Among those who underwent vitamin D replacement therapy, 95.7% achieved normal D25 >30 ng/ml with a pretreatment mean of 19.71 ng/ml improved to 52.29 (p<0.001). Frankly, this is an amazing performance for rapid D3 replacement therapy and will be tough to replicate with individualized weight based dosing. At CTCA, we were only successful 60% of the time in the first year; this study did it 95% in 5 weeks. No toxicity and the mean fatigue score dropped from 31.5 to 11 p<0.001 (a 40 point fatigue score) or by 65% showing that the intervention was especially meaningful given placebo effects for fatigue in cancer patients is typically in the 20-30% range. These effect sizes are absolutely consistent with clinical experience when one starts to treat these deficiencies effectively.
Now let’s go into the dosing schema (not discussed in the chapter) which was D2 50,000 IU three times weekly for 5 weeks (three times the dose usually given for vitamin D deficiency in clinical practice, or the equivalent of D2 21,429 IU/day. That’s the comfort level physicians will need to have regarding D2 or D3 dosing, to be effective in the treatment of a severe vitamin D deficiency especially in obese individuals (D2 or D3 is fine in my opinion, I just don’t like binding my patients to a prescription which is required for D2 50,000 IU week). Please note, this was a loading dose schema limited to 5 weeks for individuals with a pre-selected vitamin D deficiency, not for long term use and certainly would be toxic if taken long term for normal BMI patientsor patients with normal D25 levels already(which is why I didn’t put these details in the chapter). Know your D25 level and dose intelligently.
The only vitamin D randomized-placebo controlled study in healthy patients with a primary endpoint of fatigue was double-blinded and conducted by Nowak et al 2016. 120 healthy individuals (mean age 29) with severe deficiency (13-14 ng/ml for the D and placebo arm) and symptoms of fatigue were randomized to a one time dose of D3 100,000 IU (3571 IU/d) or placebo. The primary endpoint, change in the fatigue assessment scale (FAS) at 4 weeks, was significantly superior for vitamin D versus placebo (delta=2.5 points, p=0.01) but somewhat mild effect size. Of note, serum D25 did go up 14 ng/ml in the D group, but still left most patients under <30 ng/ml, and the increase in serum D25 significantly moderated the benefit on fatigue p=0.02, suggesting better replacement dosing would have been more effective.
How else do we know it’s not placebo? Clinical experience. The actual dose matters. For example, for me, I did not improve until I had a sufficient dose (started on 2000 IU/d and improved only when the dose went up to 5000 IU/d). When you treat patients, similarly, ineffective doses correlate with less likelihood of the patient having any symptom improvement. Second, if the patient forgets to take doses over time, recurrence of the fatigue eventually is assured (just like patients getting synthroid for hypothyroidism).
Any reasonable physician understands this as the clinical phenotype one would expect for an endogenous hormone that promotes wellness in a human being, not just a placebo effect. We would have stopped giving synthroid for subclinical hypothyroidism in the absence of any RCT to support it long ago, if we did not in fact see similar behavior in patients (clinical consequences for not treating it or staying on it). Since I would guess-timate at academic cancer centers at least in the U.S., <5% (this is generous as I suspect the number is 0%) probably routinely screen and replace correctly a vitamin D deficiency, it’s not surprising to me that a large community of brilliant academicians using the strictest quality of evidence to guide clinical care would have a natural blind spot to this correlation. No effective D3 dosing, no patients reporting fatigue improvement to raise the question. To be clear this is not a conspiracy, but a perfect example of what current FDA Director Marty Makary calls a blind spot in academic medicine.
Lastly, obviously not everyone with a low vitamin D25 has symptoms. I have talked to patients with <10ng/ml who claim to have no bothersome symptoms, and no improvement when replacing (more likely men than women in my experience). But we need to know this information more precisely to shape health care policy and quantify expected impact. So I am designing an investigator initiated study to look at rapid vitamin D replacement protocols for vitamin D deficient patients, with primary endpoints of looking at whether patients with fatigue at baseline have improvement before starting neoadjuvant chemotherapy with placebo crossover so that the group that does not get the rapid replacement before starting, still gets it during neoadjuvant treatment, and whether the target D25 achieved correlates to pCR rates. This avoids the ethical issues of placebo controlled D3 studies in the future. The secondary endpoint will be whether pCR rates correlate significantly to serum D25 level achieved and PFS if funded.
If you have any correlative or biological research questions on you wish to collaborate with me, please contact me at my @lumc.edu address.
The sweet smell of a moonstone peony flower in early spring
In truth, vitamin D is both a supplement/drug that can be orally dosed, and an endogenous hormone that can go up and down based on UV exposure and additional dietary intake. The predominantly negative population based supplementation (regardless of baseline D25) RCTs done to date have hopefully proven that population based supplementation with conservative D3 dosing isn’t very effective. [RCTs= randomized controlled trials, ASCO= American Society of Clinical Oncology and is considered a standard-bearer (along with NCCN) for the best in clinical oncology care]
Clearly targeted supplementation is a superior approach from the patient perspective as it offers more precise dosing with D3 based on actual weight and change in D25 desired with the physician, followup options in cases of major lifestyle changes, and with a vitamin D25 test costing $48-58 for walk-in friendly professional labs like Labcorp or Quest (in the United States) it is one of the most cost-effective tests for quality of life in integrative oncology care.
No RCT exists to question the wisdom of targeted supplementation. And that’s where academic cancer centers have to recognize D25 is a vitality sign for cancer patients, and ignoring the severe levels of deficiency particularly in black, hispanic, asian, native american populations is particularly a health care policy that is putting all ethnic minority and obese patients at higher risk for fatigue, foggy brain and conventional therapy toxicity at minimum, and likely worse cancer mortality if they don’t end up getting bone weakening agents (apparently the only reason per ASCO to check a D25 at all).
The formula for vitamin D3 dosing is not a mystery that we have to use population based dosing algorithms to treat patients with a deficiency, which is the cognitive error of using IOM or Endocrine Society Guidelines (mostly informed by population-based supplementation RCTs) to replace a known deficiency. The formula for rapid replacement for patients ages 18-88 (https://pubmed.ncbi.nlm.nih.gov/20139241/) is Delta25D(in nmol/L not ng/ml) desired=0.025x(dose per kg body weight). An online calculator to skip the conversions is available here (which also provides maintenance doses).
On Reddit, the vitamin D community likes to use a U.S.-friendlier formula (Weight in kg X 100 IU/day) to calculate appropriate maintenance doses, which at least is concordant with observational cohorts and a more “clinically comfortable” approach for patients without deficiency symptoms, but the author prefers knowing D25 and using more rapid replacement protocols in the context of cancer care because there might be only one chance to help the patient feel the benefit and reinforce its importance throughout the continuum of their care.
One of the ironies of the vitamin D RCTs done to date is that their greatest weakness is complete ignorance of D3 “drug pharmacokinetics” (lipid solubility) which requires “massive” (relative to what most doctors are used to prescribing) dosing based on the BMI/weight. My greatest adjustment in the first few years of practicing vitamin D3 replacement for all deficient patients before starting conventional therapy when I worked at CTCA was being comfortable with 10,000 IU – 25,000 IU/d!
But for those following the hierarchy of evidence as bible and still believe the RCTs of population based supplementation as gospel of truth that treating a vitamin D deficiency is not worthwhile, consider this then. If you are a clinical research investigator like me and you receive a study protocol asking if you would be interested in studying Drug X which on phase I studies requires BMI adjusted dosing, but the phase II protocol only wants to test the drug at a fixed dose that a priori you already know is not going to work for over 75% of the population due to how low the dose is and the predominantly white Caucasian population tested (least at risk for vitamin D deficiency), you would question the sanity of the investigator, and never work with that company again. These are the “amateur hour” RCTs that are keeping you from understanding how important vitamin D replacement therapy is for those who are low.
So ironically, vitamin D which has always been “reframed” as a drug by the medical literature as a justification to ignore all the other evidence I reviewed in my last blog and free chapter, and therefore requires RCT evidence to justify replacing a deficiency before starting conventional therapy for cancer…has never been appropriately studied as a weight-based drug. There is no RCT that has actually looked at an a priori logical weight based replacement schedule to make sure those who need the D3 the most actually get the right amount. That is the study we need if we want to get the high quality evidence others are waiting for to best understand vitamin D as a drug AND endogenous hormone.
One criticism that is valid since there is not a lot of research on fatigue and vitamin D specifically: how do we know the fatigue studies with vitamin D wasn’t placebo effect? Including myself? I’ll address that question in the next blog. Thanks for reading!
How it feels to be vitamin D deficient
Four shots from Antelope Canyon, AZ – the beauty and yin yang of the life-sustaining and cell-damaging qualities of sunlight
First, I propose ASCO (and NCCN) lead the charge. It should be standard of care for all cancer centers to screen for a vitamin D deficiency before starting conventional treatment. I share in that blog, the link to my 
