Is there a connection between vegan eating and Hikikomori (Japanese social withdrawal syndrome)?

A slightly weird case report by Suzuki et al. has just been published in the slightly unusual journal Heliyon. The article describes a 33-year old Japanese woman who seems to have been following (and seems to still follow) a vegan diet and at the same time seems to have lived almost (or entirely?) indoors for a large number of years. This resulted in severe vitamin D deficiency which in turn lead to associated health problems.

What's weird about this case report?

Now, what I find weird is that neither does the article describe this woman's vegan diet (was it even completely vegan?), nor is there any (!) mention of any (!) supplements she was taking at any (!) point in time - just no information on diet and dietary supplements AT ALL.
Similarly (and similarly weird): the woman's "Hikikomori" lifestyle is not described in detail ... and, sort of like with vegan diets, there seems to be considerable variation from one person living a "Hikikomori" lifestyle to the next person.

In addition, what I find weird is that the article is titled "Repeated hypocalcemia in a patient with "Hikikomori" following veganism". Now, I'm not surprised anymore when non-vegan nutritionists or medical doctors use the term "veganism" to describe a vegan diet. If they have to, let them. But in the "Discussion" section of their own article the authors seem to (it seems to me) contradict their own assumption that this case has all that much to do with "veganism".

What is Hikikomori?

Hikikomori is a relatively common occurrence in Japan and describes complete social withdrawal - people just living inside their rooms and never going out - BUT just how "complete" and whether these individuals really "never" go out seems to vary a lot.  

Teo and Gaw in 2010 described "Hikikomori" as a "form of severe social withdrawal [...] characterized by adolescents and young adults who become recluses in their parents' homes, unable to work or go to school for months or years." They also indicate that not all people with a "Hikikomori" lifestyle can be described as having a psychiatric disorder. Rather they suggest that "Hikikomori" be described as "a Japanese culture-bound syndrome of social withdrawal".

The authors of the case report discussed here, Suzuki et al. (2022), describe "Hikikomori" as a "[p]athological social withdrawal", with "more than million people in Japan" living such a "Hikikomori" lifestyle. The authors state that "Hikikomori" includes "marked [continuous] social isolation in one's home" for at least 6 months. The social isolation in these cases is associated with "significant functional impairment or distress".

Back to the case of the vegan woman with Hikikomori

What do we know about her from this article?

Where did she live?

The authors are all affiliated with institutions in Tokyo, which might indicate that this woman lived in or near Tokyo, Japan.

When did she become vegan? And why was she vegan?

This isn't explained very well: The authors state that ...
  • ... the woman "followed a vegan diet" and ...
  • ...  "At the age of 10, following a death in the family, she became unable to eat animal products." 
Side note: This is more than a little reminiscent of the Korean "anti-vegetarian" novel "The Vegetarian", in which vegetarianism is made to appear like a trauma-related mental illness.

When did she start living a "Hikikomori" lifestyle?

  • "A 33-year-old woman who had been withdrawing from society (Hikikomori) for more than 15 years" ... that would mean since she was about 18 years old.
  • "At the age of 18, she developed the habit of over-eating and vomiting. From that time onwards, she spent most of the day inside her room with the curtains closed. After that, she neither worked nor went outside."
This description seems to indicate that this woman NEVER went outside for about 15 years - but there must have been at least some exceptions such as for the hospital visits mentioned. The description also indicates that the woman had bulimia - which makes it hard to absorb the nutrients in the food the person eats because the food that is vomited back up doesn't reach the intestine where nutrients are mostly absorbed.

What symptoms did she have?

  • The woman developed extreme vitamin D deficiency. Her vitamin D blood levels were extremely low (25-OH-D was <4 ng/mL [<10 nmol/L], i.e. below the limit of detection of the test used).
  • Here blood calcium levels were extremely low (called "hypocalcemia") ... vitamin D is needed to properly absorb calcium in the intestine. She had already "experienced repeated episodes of hypocalcemia" before and had been treated with "intravenous calcium infusion". Had the hospital never checked her vitamin D levels before? (seems like it) ... Her severely low blood calcium levels lead to "numbness and stiffness in her limbs".
  •  She was also severely underweight (body height: 153 cm; body weight: 32 kg; body mass index: <14 kg/m2 [!]).
  • Her skin was pale
  • The authors state that her vitamin B12 levels were fine. But the value they give [plasma/serum B12: 268 pg/mL, i.e. 198 pmol/L] , seems to indicate that she was at least borderline B12 deficient. Homocysteine or methylmalonic acid (MMA) were not tested, it seems.
  • She did not seem to have any other deficiencies: "No decrease in trace elements was observed." 
  • There was also a "pressure ulcer on the patient's back near the buttocks." [PICTURE]

How was she treated?

  • She "was prescribed active vitamin D and calcium supplementation [...] and her symptoms gradually improved."
  • "She was diagnosed with an eating disorder and obsessive-compulsive disorder by a psychiatrist." and "inpatient treatment was [...] refused. The patient returned home, but she self-interrupted her outpatient visits."
  • There is a mention of "her oral medication" which she had already received during the previous years - but no mention of what this means exactly. As previously she seems to not have been given vitamin D supplements and calcium was given by infusion in the hospital, this may (seems to) refer to actual medication (not dietary supplements) - but it's not mentioned what this was. The oral medication might have been antidepressants (selective serotonin reuptake inhibitors), as described in the article: "Patients with obsessive-compulsive disorder should be treated with cognitive-behavioral therapy, a selective serotonin reuptake inhibitor (SSRI) medication, or both. In this case, the patient refused to be hospitalized; therefore, her obsessive-compulsive disorder could not be addressed, resulting in self-interruption of treatment. In the future, the patient might be at a risk of being transported with arrhythmia or other fatal disease, so it might have been better to continue hospitalization and treatment."

Was this case of severe vitamin D deficiency really related to a vegan diet?

The title of this case report is "Repeated hypocalcemia in a patient with "Hikikomori" following veganism", suggesting that "veganism" (a vegan diet) may be the cause of the hypocalcemia. Now, this may very well be, because a vegan diet without vitamin D supplements and without vitamin D-fortified foods and without any direct sunlight over many years will likely result in severe vitamin D deficiency. However, these are four factors together, not just a vegan diet.

In addition, the authors themselves list a number of reasons that the woman's vegan diet was only one factor among quite a few:
The woman ...
  • ... was vegan
  • ... had "Hikikomori" and avoided ALL sunshine (it appears - but the latter isn't stated)
  • ... did not take vitamin D supplements (it appears - but this isn't stated)
  • ... did not consume vitamin D-fortified foods (it appears - but this isn't stated)
  • ... did not consume any other vegan sources of vitamin D (such as sun/UV light-exposed mushrooms; it appears - but this isn't stated)
  • ... had bulimia and was extremely underweight

The authors write: 
  • "Hypocalcemia can occur in people with a low exposure to ultraviolet light, especially in those with a diet that is deficient in vitamins" [vitamin D specifically].
  • "our data revealed that her repeated hypocalcemia was due to vitamin D deficiency, mainly caused by a lack of sunlight exposure." - That is, it was mainly NOT DUE TO HER VEGAN DIET.
  • "Vegan foods are considered healthy; however, a lack of food diversity and supplementation can result in nutrient deficiencies". -- not an incorrect statement
  • "Vegan diets can provide vitamins and minerals if proper supplements are consumed." -- correct
  • "vegans do not usually experience nutritional deficiencies." -- I wish this was correct, but it seems a little "understated".
  • "In our case, there were no deficiencies in trace elements or other vitamins." -- Well, firstly, they surely didn't test every vitamin and mineral, and second, her B12 levels appear have been a little low.
  • "Good sources of calcium can be obtained by increasing the intake of calcium-rich foods from plant sources". -- Yes, or mineral sources.
  • "no diet can provide adequate amounts of active [?] vitamin D, exposure to sunlight is essential" --- which again confirms that her vegan diet was NOT THE MAIN FACTOR. 
  • "Miyakoshi reported that “Hikikomori” causes calcium and vitamin D deficiency due to a lack of sunlight exposure" -- which again confirms the same. 
  • "lack of sunlight, which causes vitamin D deficiency, is thought to occur only in severe “Hikikomori” who spend most of their day inside the house." -- This seems to have been the case with this woman, but it is not clearly explained.
Despite all of this, the authors go on (well, you have to write something in the Discussion section, true) to speculate that vegan diets may be a "risk factor" for developing "orthorexia nervosa" (for which there isn't any good evidence) -- however, the authors do mention that this is just suspected by some, and the authors do nicely describe "orthorexia" as "the disease concept of orthorexia nervosa [...], described as a pathological obsession with healthy eating". And the authors furthermore speculate that "[a]lthough we do not know the direct causal relationship between veganism and “Hikikomori”, it has been suggested that vegans might have a risk of psychiatric disorders in this way and may be associated with “Hikikomori” as well." In other words, they suggest that vegan diets may be a causal factor for "Hikikomori" -- which, if we want to be very precise, is not unthinkable, IF the vegan diet is severely deficient in vitamin B12 and/or in vitamin D (with no sunshine), which in turn can easily happen vegan diets without supplements or fortified foods or sunshine (for vitamin D).

The authors conclude: "Taking active vitamin D and calcium supplementation should be considered to prevent repeated hypocalcemia in patients with “Hikikomori” following a vegan diet, who are thought to have low calcium intake and sunlight exposure. Psychiatric intervention is essential, but treatment can be difficult." But no one should take "active vitamin D" (i.e. 1,25-OH-D, calcitriol) without medical supervision because an overdose can be very dangerous.

Take home messages for vegans:

  • It seems that her vegan diet was one factor in her developing severe vitamin D deficiency. However, this happened under very extreme circumstances, including practically never leaving the house (see all the factors listed in the bullet points under "the woman's vegan diet was only one factor among quite a few").
  • Vegans should make sure they have a reliable source of vitamin B12 (see number 1 here).
  • Vegans should also make sure they get enough sunshine and/or take a vitamin D supplement (see number 3 here). 
  • Given the high number of people with a "Hikikomori" lifestyle in Japan (far more than one million people), maybe the "vegan movement" in Japan should put together a vegan task force to help vegans with Hikikomori. For someone without much of an understanding of Japanese culture, I'm not in a place to suggest promising strategies to address "Hikikomori".

Moral of the story:

Help those who want to be vegan stay safe and (if they want to) be healthy.


  • Keisuke Suzuki, Kazuyuki Miyamoto, Shutaro Ozawa, Raichi Kawakami, Motoyasu Nakamura, Gen Inoue, Akihito Kato, Yoko Tarumi, Masaharu Yagi, Kenji Dohi: Repeated hypocalcemia in a patient with "Hikikomori" following veganism. Heliyon. 2022 Jun 7;8(6):e09563. doi: 10.1016/j.heliyon.2022.e09563. eCollection 2022 Jun.
  • Keisuke Suzuki, Kazuyuki Miyamoto, Shutaro Ozawa, Raichi Kawakami, Motoyasu Nakamura, Gen Inoue, Akihito Kato, Yoko Tarumi, Masaharu Yagi, Kenji Dohi: Corrigendum to "Repeated hypocalcemia in a patient with "Hikikomori" following veganism" [Heliyon 8 (6), (July 2022), Article e09563]. 2022 Jul 19;8(8):e10020. doi: 10.1016/j.heliyon.2022.e10020. eCollection 2022 Aug. -- You can see here that a corrigendum was published about one month after publication of the article. However, the corrigendum only states: "In the original published version of this article the abstract was omitted, having been uploaded as a cover letter rather than in the manuscript. This has now been corrected and the abstract has been included in the publication. The authors apologize for the error. Both the HTML and PDF versions of the article have been updated to correct the errors." -- So, they are saying that neither the editor of the journal nor the peer reviewers noticed that there was no abstract. Also: no abstract has been added in PubMed Central (PMC) [as of 17 March 2024]