Table of Contents[Hide][Show]
- Vitamin D in Mushrooms?
- Nothing Against Mushrooms, but Don't Rely on Them for Vitamin D!
- Food Sources of Vitamin D3 (Hint: It's not Mushrooms!)
- Dangers of Vitamin D2 (Viosterol) for Pregnant Women
- Are You Vitamin D Deficient?
- How are Vitamin D2 and Vitamin D3 Different?
- Dangers of Relying on Vitamin D2 Instead of D3 During Pregnancy
The majority of the US population today, anywhere from 30% to 80%, are suffering from a wide variety of symptoms related to vitamin D deficiency (1).
This is concerning because scientists have found that not only is it necessary for calcium absorption in order to build strong bones, but vitamin D plays a major role in many body processes such as brain development and plasticity, immunity and autoimmunity.
Vitamin D deficiency is strongly related to the development of diabetes, autism, psoriasis, tuberculosis, osteoporosis, multiple sclerosis, Alzheimer’s, Parkinson’s Disease and cancer, even hypertension and psoriasis.
In addition, vitamin D helps to make cathelicidin which kills pathogens like tuberculosis in the body, herpes in the brain, and many others. In the research, colon cancer development is strongly linked to D3 deficiency (2).
Vitamin D has become a superhero.
Why the epidemic of vitamin D deficiency?
For starters, the best way for humans to get vitamin D is from the sun and most Americans today are sun-phobic with Helicopter Moms everywhere slathering up their children with sunscreen even before spending just a few minutes in the sun.
Traditionally sun bathing was considered optimum for health but in the last 50 years the sun has become the enemy.
Most sunscreens, themselves loaded with toxins such as parabens, titanium and other substances considered carcinogenic, are slathered on the body liberally with children most susceptible (3).
The medical establishment has warned about the dreaded skin cancer melanoma from too much exposure and accordingly most humans have cut themselves off the free and natural source of vitamin D that comes with sensible sunning.
Cod liver oil, which was long known to prevent D3 deficiency has been forgotten and shunned by some who say it contains too much vitamin A although cod liver oil was used for decades to cure and protect children from rickets, a potentially crippling disease (4).
During the winter, ultraviolet rays from the sun are not available in many places in the world, and it is difficult for many with their busy lives and those whose dietary choices preclude using fish and other animal sources, to get enough sun. Because vitamin D is so crucial to health, researchers are looking for other ways to supply vitamin D to a public literally starved for lack of this critical nutrient.
Vitamin D in Mushrooms?
In the past few years many blogs have expounded on the “glorious” vitamin D properties of mushrooms.
“Mushrooms are not only wonderful sources of vitamin D, but they offer us many opportunities for maintaining and improving health,” says mycologist Paul Stamets (5).
But that wonderful source he’s talking about is vitamin D2, which is otherwise made artificially from radiating ergot and yeasts. Just recently experiments showed that Vitamin D2 can also be produced from irradiation of some mushrooms or by growing them in the sun (6). While this is an improvement over D2 supplementation which has been associated with adverse effects due to contamination (7), it still doesn’t hold a candle to Vitamin D3 obtained from animal foods.
Nothing Against Mushrooms, but Don’t Rely on Them for Vitamin D!
Mushrooms are great. I love to cook with them and to gather them in the forest.
For me, it’s an ethnic inheritance: my Slovenian father gathered them every Fall and my Mother’s Polish brothers did the same. Mother told me stories about long hours cleaning and drying mushrooms as a child but reaping the rewards later with tasty mushroom soup when the snow was falling. But we didn’t eat mushrooms for their nutritional properties back then but for their taste.
Now for the rest of the story.
The natural form of vitamin D that is active in humans is vitamin D3, also called cholecalciferol, which is much more efficient in raising and sustaining blood levels of Vitamin D.
Humans who get sun exposure between the hours of 10 AM to 3 PM in the late spring, summer, and early fall store vitamin D in their body fat which is released throughout the winter months, allowing them to be vitamin D sufficient throughout the year.
The body controls levels of vitamin D so no matter how much sun you get, levels will not rise too high to become toxic (8). Still, sensible sunning should always be the rule!
Food Sources of Vitamin D3 (Hint: It’s not Mushrooms!)
Vitamin D3 occurs naturally in cod liver oil, fish oil and wild fish such as salmon, sardines, herring and cod which are the best sources, and is metabolized from them in the same pathway as is the D3 derived from sunlight (9).
Farmed fish are fed GMO (genetically modified) corn and soybeans and do not develop sufficient levels of vitamin D3 (10).
Natural D3 is also contained in blood sausage, some organ meats, butter and raw milk from cows on pasture, and eggs from pastured hens. Pasteurized milk contains a synthetic form of vitamin D3. Unfortunately fortified foods with synthetic vitamin D provide most of the vitamin D in the American diet.
Vitamin D3 supplements are made from irradiating lanolin from sheep skins (11).
Dangers of Vitamin D2 (Viosterol) for Pregnant Women
Shortly after its discovery in the early 1920’s, Vitamin D2 was patented and licensed to pharmaceutical companies. Dr. Weston Price wrote about synthetic D2, called Viosterol at that time, in his major work, Nutrition and Physical Degeneration in 1938, now in its 8th printing.
Dr. Price wondered if Vitamin D2 was indeed toxic based on the work of Dr. Wayne Brehm who published an article in the Ohio State Medical Journal about babies born to a group of women who took Viosterol D2 during pregnancy versus those moms who took only cod liver oil.
The mothers who consumed Vitamin D2 showed “moderate to marked placenta calcification,” and the skulls of their babies, “moderate closure of the fontanels,” a sign of abnormal calcification. Those who received Vitamin D2 plus calcium had “extensive calcification in the placenta and marked closure of the fontanels, with marked calcification in the kidneys“ showing extremely abnormal results (12). The Vitamin D2 was directing calcium into soft tissues and into the bones of the babies’ skulls which need to remain flexible during birthing and to accommodate further brain growth.
Are You Vitamin D Deficient?
How to determine if you are vitamin D deficient?
Doctors and laboratories judge deficiency by testing the levels of the vitamin D intermediate, 25 hydroxyvitamin D3, also called 25 (OH) D3, which is made from vitamin D in the liver and circulates in the blood.
If levels are:
- 10-20 ng/ml: Rickets and osteomalacia, the classical diseases of vitamin D deficiency, occur between these levels.
- 21–29 ng/ml and 20-40 ng/ml: Subclinical vitamin D deficiency or ‘vitamin D insufficiency, These levels may contribute to the burden of chronic diseases, particularly osteomalacia, osteoporosis, and possibly cancer, cardiovascular disease, type 2 diabetes, and infectious and autoimmune disorders.
- 40-64 ng/ml: Proposed optimal range for D3 by some researchers.
- 100 ng/ml and above: Can lead to toxicity in the general population (13-14).
Symptoms of vitamin D deficiency (rickets in children and osteomalacia in adults) include bone pain and tenderness, dental deformities, muscle cramps, short stature (in adults), skeletal deformities (bowlegs, bumps in the ribcage, scoliosis).
The most common physical symptoms in children include bulges at the wrist, and banana shaped bowed arms and legs (15).
Vitamin D deficiency does not only show up in physical affects but neurological effects as well. Low levels of vitamin D have been linked to schizophrenia and autism (16).
Rickets was almost eradicated in the 1940’s when cod liver oil was commonly given to children but doctors report that it has returned “with hundreds of children developing the condition every year.” The signs are most obvious during periods of rapid growth and between the ages 6-24 months. Experts have connected this resurgence to the increased amount of time spent indoors at school instead of outside at recess, and at the computer or watching TV instead of playing outdoors out of the sun. British authorities blame the comeback on the popularity of vegan and macrobiotic diets, and avoidance of meat and dairy products (17).
After ingesting foods rich in vitamin D3 or after sun exposure, the provitamin D binds to a protein in the blood which takes it to the liver where it is transformed (hydroxylated) into 25(OH)D3, then carried to the kidneys where it is made into the active form, calcitriol, or 1,25-hydroxyvitamin D3 (18).
The major health effects from vitamin D come through calcitriol’s interaction with the vitamin D receptor (VDR) and the VDR’s interaction with the RXR receptor (the vitamin A receptor). Calcitriol is also made in cells in the breast, prostate, lung, skin, colon, pancreas, and brain which too have vitamin D receptors (VDR). VDRs are also present in the central nervous system and affect neurotransmitters and neurotrophic factors relevant for mental disorders. “Approximately 2776 genomic positions are occupied by a VDR and 229 genes show significant changes in expression in response to vitamin D3″ (19).
Since their discovery at the beginning of the 20th century, D2 and D3 have been used interchangeably and called collectively “vitamin D.” Pharmacy references have officially regarded these two forms as equivalent and interchangeable, yet this presumption of equivalence is based on studies of rickets prevention in infants conducted 70 years ago.
Vitamin D2 and Vitamin D3 are Not the Same Thing (but you can make a lot of money if you are a Vitamin D researcher and pretend they are)
In 1930 researchers already questioned the equivalence of Vitamin D2 and Vitamin D3 while working with cod liver oil verses Viosterol (D2). In 1949 the World Health Organization declared that the two were equivalent. But in the 1950’s preparations made with Vitamin D3 were found to be around 4 times more potent per unit as D2 (20).
Back to Paul Stamets, the founder of Fungi Perfecti and author of several articles on the web who is actively pushing mushrooms as a prime source of vitamin D.
Mr. Stamets is a mycologist, not a nutritionist or biochemist. He studies, sells and promotes mushrooms. In his articles, he incorrectly bases his claims on the premise that D2 and D3 are equal and equivalent which has been debunked by many studies in the past few years, but just recently rekindled by Dr. Michael Holick, one of the most famous vitamin D researchers in the world (21).
A 2008 study of Holick’s seems to give some credence to Stamets claims. Holick found that D2 is as effective as D3 in elevating blood levels of 25(OH)D (if you remember, the form of vitamin D that doctors and laboratories test to gauge vitamin D deficiency). But it seems that Dr. Holick has become a “flip-flopper” on his stance on vitamin D2. Just a year before, in 2007, he stated that “vitamin D2 is approximately 30% as effective as D3 in maintaining 25(OH)D levels, and up to three times as much vitamin D2 may be required to maintain sufficient levels (22)”.
And in an interview Holick insists: “Yes. I identified 25-hydroxyvitamin D3, which is the major circulating form used by physicians to measure vitamin D status in patients worldwide and the active form of vitamin D3 (calcitriol) back in the 1960’s (23)”.
Oh, how the profit motive can change things! Holick says that he believes that D2 is effective “because of the early literature that proved it was effective in preventing rickets” (1930s), and he hopes that the food industry will eventually fortify foods with vitamin D and it will be D2 versus D3 because D2 is much cheaper to produce (21). Interestingly, Europe does not allow food fortification with vitamin D2, folic acid or other synthetic vitamins.
Measurement is also an issue. Values for 25(OH)D2 in the Holick study were obtained by subtracting 25(OH) D3 from the total 25(OH)D. Levels of 25 (OH)D2 weren’t actually measured in and of themselves but determined from D3 levels (21).
It is well known that major U.S. food companies fortify their products with synthetic D2. This same study was funded by The Beverage Institute for Health and Wellness, a division of The Coca Cola Company. Futhermore, Dr. Holick is a paid speaker for the drug companies Merck, Eli Lilly, and the food giant, Proctor and Gamble, as well as a consultant for Amgen, Novartis, and Quest Diagnostics, the company that ran the laboratory work in this study. One of his fellow researchers named on the study is the Medical Director of Quest Diagnostics (21). Holick has conducted other studies on D2 in mushrooms funded by the National Mushroom Council (24) and on UV light funded by the UV Light Association.
In the same article the title itself is a bit deceptive: “vitamin D2 is as effective as vitamin D3 in maintaining circulating concentrations of 25-Hydroxvitamin D.” In reality, D2 forms 25(OH)D2 , and D3 forms 25(OH)D3 in the liver, two totally different substances with different pathways and pharmacokinetics (how they are handled in the body).
Vitamin D2 and Vitamin D3 don’t merge or metabolize in the same way at all (19,21)!
How are Vitamin D2 and Vitamin D3 Different?
Here are a few of the most glaring dissimilarities between Vitamin D2 and Vitamin D3.
- Their pathways are different.
- Their structure is different
- The half- life (how long half of the substance still remains in the system) of 25(OH)D3 is 3-6 weeks while the half- life of 25(OH)D2 is one week which means D2 isn’t around very long.
- D3 forms the active component calcitriol,(1,25-dihydroxyvitamin D3) while D2 forms 1,25 dihydroxy vitamin D2, which is NOT calcitriol.
- D2 dosent bind as well with the vitamin D binding protein (DBP) that carries vitamin D around the blood stream.
- D2 interacts less with the enzyme in the liver which converts it to the intermediate form.
- The enzymes in the mitochondria (the powerhouses of the body) convert D3 five times as fast as they convert D2.
- Calcitriol from D3 binds to the vitamin receptor (VDR) up to 40% more than D2, and is able to potentially generate significant biological activity.
- D3 can cross the blood-brain-barrier to interact with the many VDRs in most parts of the brain which indicates the presence and need for D3 in building the brain.
- D3 has proven effective in clinical trials in preventing falls whereas no clinical trials have shown D2 effective. Studies have shown the effectiveness of D3 in preserving bone density in older adults and reducing fracture. No studies of D2 have shown that it prevents fractures.
- D2 is less effective in raising blood levels in older men than in younger men (7,19,21,25,26).
These are just a few ways in which D2 and D3 are different from one another so it really doesn’t matter if mushrooms contain a lot of D2 and D2 raises 25(OH) D2 levels just as much as D3 raises 25(OH)D3 levels — they just aren’t the same thing.
Even if D2 is active with the VDR receptor at a much lower capacity (affinity) than D3, with excessive intake it may reduce the number of binding sites available for D3 at that receptor. A 2012 study using mushrooms treated with UV light and D2 supplements showed an increase in D2 levels but a decrease in D3 levels in subjects who ingested them (27). Another 2012 study showed 9 times the decline in D3 compared with placebo in subjects taking D2 supplements versus subjects taking D3 supplements (28).
Other studies from researchers have shown that:
- D3 is more effective in raising vitamin D levels in the blood than D2, up to 70% (1.7 times) greater (29); D3 is approximately 87 percent more potent in raising and maintaining vitamin D concentrations and produces 2- to 3-fold greater storage of vitamin D than does D2 (30).
- 250 ug (micrograms) of D2 was needed to raise the D levels the same as 100 ug of D3 (18).
- Over a period of 28 days, D2 and D3 concentrations rose to similar levels but D2 levels fell rapidly down to base values around 14 days, while D3 levels peaked at day 14 and remained above the base levels until 28 days (28).
Dangers of Relying on Vitamin D2 Instead of D3 During Pregnancy
At no other time in life is vitamin D status as important as in pregnancy. If Mom is deficient, baby will be as well. When a woman is pregnant her calcitriol levels (the active form of vitamin D) become extremely elevated, up to a 3-4 fold increase, dependent on the 25(OH)D levels made in the liver.
Pregnancy itself is the primary force behind this increased calcitriol and it is independent of calcium levels. Data has shown that a circulating level of at least 40 ng/ml to 100 ng/ml of 25(OH)D3 is needed to optimize calcitriol production during pregnancy.
There is strong evidence that a woman’s needs for vitamin D are not 400 IU as the government agencies recommend, but 4000 IU/day and 6400IU/day when breastfeeding. Studies have shown these levels of supplementation with D3 have been safe and effective, and infants had “superior vitamin D status.” (14)
Under these circumstances, who would want to trust the health of their baby to Vitamin D2 supplements or mushrooms?
The best advice to avoid dangerous Vitamin D deficiency is to get safe sun exposure often and to eat plenty of foods high in vitamin D3, as well as liberal amounts of a quality fermented cod liver oil.
*Vitamin D is the generic name of the vitamin which has several distinct forms, called vitamers. Vitamin D is classified into five different classes numbered from 2–6. D3 is the active form in humans (25). Any reference in this article to vitamin D refers to D3, unless so stated.
1 Lampe F and Snyder S. Michael Holick, PhD, MD: Vitamin D Pioneer. Altern Ther Health Med. 2008 May-Jun;14(3):65-75.
3 Plourde E. Sunscreens:Biohazard: Treat as Hazardous Waste. 2011. Irvine CA:New Voice Publications.
4 Mellanby E. An experimental investigation on rickets. Lancet 1919;1:407–412.
5 Stamets P. Place Mushrooms in Sunlight to Get Your Vitamin D: Part Two. The Blog. Huffpost Healthy Living, July 21, 2012;
http://www.huffingtonpost.com/paul-stamets/mushrooms-vitamin-d_b_1658690.html; and Stamets P. Place Mushrooms in Sunlight to Get Your Vitamin D: Part One. The Blog. Huffpost Healthy Living. Huffpost Healthy Living. 07-02-2012.
http://www.huffingtonpost.com/paul-stamets/mushrooms-vitamin-d_b_1635941.html. Stamets P. Place Mushrooms in Sunlight to Get Your Vitamin D. GreedMedInfo. July 10, 2014.
6 Urbain F et al. Bioavailability of vitamin D2 from UV-B-irradiated button mushrooms in healthy adults deficient in serum 25-hydroxyvitamin D: a randomized controlled trial Eur J Clin Nutr. 65, 965-971 (August 2011) doi:10.1038/ejcn.2011.53
7 Houghton LA, Vieth R. The case against ergocalciferol (vitamin D2) as a vitamin supplement. Am J Clin Nutr. 2006 Oct;84(4):694-7.
8 Lampe and Snyder
9 Holick MF. Vitamin D deficiency. N Engl J Med 2007;357:266-81. DOI: 10.1056/NEJMra070553
10 Lampe and Snyder
11 Calvo MS, Whiting SJ, Barton CN. Vitamin D fortification in the United States and Canada: current status and data needs. Am J Clin Nutr 2004;80:1710S-6S. [PubMed abstract].
12 Price WA. Nutrition and Physical Degeneration. La Mesa: Price Pottenger Nutrition Foundation. 2008. p453-454
13 Vasquez A, Manso G, Cannell J. The Clinical importance of vitamin D ) cholecalciferol): a paradigm shift with implication for all health care providers. Alt Ther. Sept/Oct 2004; 10(5): 28-36
14 Pludowski P et al. Vitamin D effects on musculoskeletal health, immunity, autoimmunity, cardiovascular disease, cancer, fertility, pregnancy, dementia and mortality-a review of recent evidence. Autoimmun Rev. 2013 Aug;12(10):976-89. doi: 10.1016/j.autrev.2013.02.004. p 985.
15 National Institutes of Health. MedlinePlus. Rickets. http://www.nlm.nih.gov/
medlineplus/ency/article/000344.htm. 6-18-2014Vitamin D.
16 Humble MB. Vitamin D, light and mental health. J Photochemistry Photobiology B: Biology. 2010 Nov; 101(2): 142-149. DOI: 10.1016/j.jphotobiol.2010.08.003
17 Yapp R. The Return of Rickets. Mail Online. Daily Mail. July 19, 2014.
18 Holick MF. Vitamin D deficiency. N Engl J Med 2007;357:266-81. DOI: 10.1056/NEJMra070553
19 DeLuca GC. Review: The role of vitamin D in nervous system health and disease. Neuropath Applied Neurobiol 2013. 39:458-484.
20 Houghton and Vieth, 2006
21 Holick MF et al. Vitamin D2 is as effective as vitamin D3 in maintaining circulating concentrations of 25-hydroxyvitamin D. J Clin Endocrinol Metab. 2008 Mar;93(3):677-81. Epub 2007 Dec 18. http://www.ncbi.nlm.nih.gov/pubmed/18089691
22 Holick, 2007, p.275.
23 Lampe and Snyder, 2008
24 Keegan RJH et al. Photobiologiy of vitamin D in mushrooms and its bioavailability in humans. Dermato-Endocrinology 5:1, 165–176; January/February/March 2013; © 2013 Landes Bioscience.
25 Jäpelt RB and Jakobsen J. Vitamin D in plants: a review of occurrence, analysis, and biosynthesis. Front Plant Sci. 2013; 4: 136.
26 Vieth R. Vitamin D supplementation, 25-hydroxyvitamin D concentrations, and safety. AmJClinNutr 1999; 69: 824-56.
27Stephensen CB et al. Ergocalciferol from Mushrooms or Supplements Consumed with a Standard Meal Increases 25-Hydroxyergocalciferol but Decreases 25-Hydroxycholecalciferol in the Serum of Healthy Adults. J. Nutr. July 1, 2012 jn.112.159764.
28 Logan VF et al. Long-term vitamin D3 supplementation is more effective than vitamin D2 in maintaining serum 25-hydroxyvitamin D status over the winter months. Br J Nutr. 2013 Mar 28;109(6):1082-8. doi: 10.1017/S0007114512002851; and Logan VF, Long-term vitamin D3 supplementation is more effective than vitamin D2 in maintaining serum 25-hydroxyvitamin D status over the winter months. Br J Nutr. 2012 Jul 11:1-7.
29 Trang HM. Evidence that vitamin D3 increases serum 25-hydroxyvitamin D more efficiently than does vitamin D2. Am J Clin Nutr. 1998 Oct;68(4):854-8.
30 Heany RP et al. Vitamin D3 Is More Potent Than Vitamin D2 in Humans. JCEM. 2011 DOI: 10.1210/jc.2010-2230
Some of this debunking was clear and the author rightfully gave thought to biases.. This article was far from thorough, however, and therefore, inconclusive. Neither the author nor the studies cited make any distinction between D2 produced synthetically, D2 produced from various types of mushrooms grown or dried in the sun, and D2 produced by irradiating Button mushrooms. Until these distinctions are made, and we are shown which forms of D2 are used in the studies, the jury is still out.
This author rightfully points out the difference between wild caught vs farm raised salmon. If that distinction had been neglected, and only Farm Raised Salmon had been used, then the fact that salmon has D3 could have been debunked.
While D3 does seem to be superior, based on everything I’ve read thus far, we should also consider, when one consumes sun dried mushrooms, they are getting much more than just D2. They are also getting everything the mushroom uses in synergy with the D2. Just as the author showed how fish oil or wild caught salmon also contain vitamin A, which increases the efficacy of the D3.
Mark J Kaylor
You might find this paper on mushrooms and vitamin D of interest. They state: “Therefore, mushrooms are a rich source of vitamin D2 that when consumed can increase and maintain blood levels of 25-hydroxyvitamin D in a healthy range. Ingestion of mushrooms may also provide the consumer with a source of vitamin D3 and vitamin D4.” Here is a link to the full paper: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3897585/
Jan Patenaude, RD, CLT
Regarding organic coconut. . . it’s not true that they are all organic. I live in Hawaii. Coconut palms can be treated topically and systemically. And, although they mostly don’t make it to the water, I don’t know about the coconut. But, surely they could be found in the sap, from which coconut syrup, sugar and coconut aminos are made. quora.com/Are-pesticides-used-in-growing-coconuts-What-are-they-and-are-they-harmful
I was pleased to find an intelligent article about this latest misleading claim, which I didn’t believe in the first place, but I thought I may have missed something.
Recently (April 2019 in England) I bought a pack of mushrooms (these were the only suitable kind available at the Aldi store): “Nature’s Pick” [another intentionally misleading name], “British Vitamin D Chestnut Mushrooms”. It says on the label: “UV-treated mushrooms … Controlled light treatment was used to increase vitamin D levels.”
I have known that UV irradiation raises D2 levels in mushrooms, but it is not the same as the more crucial D3 kind (though, it is said D2 is also effective in preventing rickets). Still, I couldn’t believe that you can sun mushrooms and get the most important kind of vitamin D (D3) that is produced in the human body during basking.
So, although partly true, I was basically right in my scepticism, but it is nice to be backed up by an intelligent article like this.
This is one example of the cynical way various companies exploit ignorant shoppers with health claims to sell their stuff for more.
Just as another example of this dishonest method: you can get “organic coconuts” and “organic pine nuts” as well. The “organic pine nuts” cost here £4 a pack, but you can get non-organic pine nuts too (though the pack says nothing about that), which cost £3 a pack.
Sadly, most people don’t seem to know that coconut palms or “pine nut” bearing pines are never treated with any chemicals anyhow, so they are all “organic”. In other words, you are paying extra for the word “organic”, which is true, but since there is no non-organic variety of these, it is to fool the shopper into paying out more for the fad. And the examples could go on.
Excellent article. Thank you.
In all honesty, there seems to be a disagreement about D2 and D3 in the medical community. There are plenty of people who disagree with the author about the differences or lack thereof between D2 and D3 in use.
The fact they have different pathways and work differently does not mean that one is better than the other. The problem is that the author has started with the premise that D3 is the “good” version and that D2 is the bad version because it has a different pathway.
The emotive language used “Absurd” “Debunking” is indicative of an preconception by the author.
Yes D2 and D3 are different.
But this article is about mushrooms as a source of vitamin D2, not about the value of D2 over D3. It is absolutely clear that Mushrooms exposed to uv light do produce significant amounts of Vitamin D2 which do help fulfil the bodies vitamin requirement.
This is not absurd and it has not been debunked.
This is just a rant by someone who has the opinion that D2 is not as good as D3.