Updated: Sep 28
Vitamin D in ADHD: Could it improve your focus?
In an age where attention has become the new currency, a growing segment of parents and young adults find themselves wrestling with focus-related challenges. In their quest for alternatives to medication, many are gravitating towards natural remedies. Among these, Vitamin D stands out, attracting significant interest from researchers and the media.
Could Vitamin D be the overlooked champion individuals with ADHD desperately need yet remain unaware of? Have we been so preoccupied with finding the ideal nootropic that we've neglected a crucial piece of the puzzle?
What is Vitamin D?
Vitamin D is a nutrient that can be made in the body or assimilated from food. Our own production requires direct sunlight to come in contact with our skin. This triggers a series of chemical reactions in the skin, liver and kidneys, leading to endogenous (our own) production of a molecule called calcitriol (active Vitamin D). Alternatively, when we consume Vitamin-D-enriched food such as fish or egg yolks, our bodies can extract Vitamin D3 and assimilate it for our own use.
Vitamin D plays an important role in our immune system and bone health; however, its role in brain health and attention deficit is less understood. It is not a common clinical practice for a doctor to test Vitamin D in a child or an adult with ADHD.
But the question is, should it be?
In this article, we will take a look at the current state of research and assess if Vitamin D can be of benefit to kids, adolescents and adults with ADHD. We will start this journey in the earliest days during pregnancy.
The Bottom Line: Vitamin D is an essential nutrient that our bodies can extract from food or a supplement and convert to active Vitamin D3. We can also synthesise it when our skin comes in direct contact with the sunlight.
Is low vitamin D during pregnancy a risk factor for ADHD in children?
Several studies have delved into the relationship between maternal vitamin D levels during pregnancy and the risk of ADHD in newborns. A recent comprehensive review  examining 28 published studies focusing on various psychiatric outcomes, including ADHD, in babies.
While some of these studies did reveal a link between low maternal vitamin D levels—generally defined as below 20-50nmol/L—and an increased likelihood of ADHD, the results were not conclusive across the board.
Interestingly, studies taking the measurements from maternal blood compared to the umbilical cord tended to show different results. Whether one is better than the other for testing & assessing Vitamin D status in the developing baby
Intriguingly, the way vitamin D levels were measured influenced the study outcomes. Research using maternal blood samples was more likely to identify a positive relationship than those relying on umbilical cord blood. While cordocentesis (testing through the umbilical cord) is often used to detect foetal issues and blood abnormalities during pregnancy, it's unclear whether this method is more accurate than testing the mother's blood.
Another point of confusion lies in the classification of vitamin D deficiency. The cut-off used in these studies was 50nmol/L, which some experts may argue is too generous. Medically, levels below 25nmol/L in children are categorised as deficient.  Consequently, setting the bar at 50nmol/L could potentially skew the results by including cases that aren't "truly" deficient.
Would the outcomes differ if the focus were narrowed to only those newborns with severe deficiencies—levels below 25nmol/L? It's a valid question, but as of now, we lack the large-scale data needed for a definitive answer.
Until we have those, it remains unclear whether vitamin D insufficiency during pregnancy constitutes a significant risk factor for ADHD.
The Bottom Line: Recent research offers mixed results on the link between maternal vitamin D levels during pregnancy and newborn ADHD risk, although there is a trend towards benefits. The criteria for vitamin D insufficiency may be too generous, calling for more focused studies for clarity in future research.
Does Vitamin D supplementation improve ADHD in children, adolescents and adults?
A review  of randomised controlled trials tried to answer this question. “Can we improve people’s ADHD by giving them Vitamin D? They pooled together results from 4 studies with a total of 256 participants. Most were children and a few adolescents, all aged < 18. Researchers gave half of them vitamin D supplements while giving a placebo to the other half, without changing anything else or telling the parents who had what. All of them were also taking a medication called methylphenidate, commonly prescribed for ADHD.
After 6-12 weeks, parents & teachers reported a small improvement in behaviour and attention. These improvements were not major, but they were sufficient enough to be clinically meaningful.
From the bird’s eye view, the findings in this study are compelling. It would indeed appear that giving kids and young adults Vitamin D helps improve symptoms. However, there are a few limitations we need to be aware of:
All study participants were already on ADHD medication, making it difficult to isolate the effects of Vitamin D supplementation alone.
The average Vitamin D levels among participants were above 25nmol/L, which is not considered deficient in the UK medical guidelines.
The studies often did not measure post-supplementation Vitamin D levels, leaving questions about the optimal levels for symptom improvement.
The age range for participants was under 18, so the applicability of these findings to younger children or older adults remains uncertain.
The Bottom Line: The 2019 review suggests that Vitamin D supplementation may offer modest improvements in ADHD symptoms for individuals under 18. However, limitations such as pre-existing medication and lack of adult data call for further research. It is currently unclear whether adults with ADHD who are low in Vitamin D would benefit from supplementation.
What are the ideal levels of Vitamin D for ADHD?
According to the National Institute for Health & Care Excellence (NICE) in the UK, the deficiency cut-off for adults currently sits at 25 nmol/L. This value is the same for children and adults. Although these numbers are based on musculoskeletal health rather than brain health, in the absence of wider guidelines, it is the best we have.
As you may now appreciate, these values are significantly lower than what was used in the ADHD studies above.
Naturally, two questions are coming up:
Is it possible that we are simply not working with the right populations? That the kids and moms in these studies are (for the lack of better terminology) “not deficient enough?”
And is it also possible that if we only included populations with strict < 25nmol/L levels, the results would have been (or wouldn’t have been) more definite?
We know from the research on cognitive health that extreme chronic vitamin D deficiency (< 10 ng/mL / 25nmol/L) might cause significant harm to brain health.
As indicated above, you want to make sure your levels are above 50 nmol/L (20ng/mL) and possibly even at 75nmol/L (30ng/mL) as seen in other studies in ADHD . Higher levels up to 90 nmol/L have been, in longitudinal studies, linked to better quality of long-term health and fewer cardiovascular-related incidents; however, that line of research is beyond the scope of this article.
For families planning pregnancy or currently expectant mothers, optimising vitamin D levels in cooperation with a licensed health professional might offer a benefit for the brain health of the newborn (and parents).
The Bottom Line: The UK's National Institute for Health & Care Excellence (NICE) sets the vitamin D deficiency threshold at 25 nmol/L for both adults and children. This threshold is higher in almost all ADHD studies, which begs the question: Are we really studying the appropriate populations? As an adult, you should strive for levels above 50nmol/L and getting them in the mid-80s and 90s might offer maximum protection for your long-term health. If you're planning a family or expecting, it's a good idea to chat with a healthcare professional about keeping your vitamin D levels in check—it could be a game-changer for your baby's brain health.
How do I check my vitamin D levels? Do I need to supplement?
Your doctor can run a simple blood test that will reveal your numbers. Depending on where you're located, your results might be displayed in either ng/mL or nmol/L. 1 ng/mL is equivalent to 2.5 nmol/L. If a medical route is not an option, you can order a private test from companies such as Medicheck or BetterYou, in the UK. Other companies across the world are available.
Regarding supplements, this is best discussed with your doctor or an alternative healthcare practitioner. The risk of unsupervised megadosing is that prolonged supplementation with high doses may lead to Vitamin D toxicity , a highly problematic situation.
Is vitamin D in food? How much per day do I need?
According to the NHS UK 
Babies up to the age of 1 year need 8.5-10 mcg / 340-400 IU (International Units) of vitamin D per day.
10 mcg (400 IU) per day is also recommended for adults
Sample Food Values
salmon 1 fillet - 1071 IU
mackerel 1 fillet - 402 IU
UV-irradiated mushrooms, ½ cup - 366 IU
sardine, 1 whole - 154 IU
whole milk, 1 cup - 124 IU
milk (2% fat), 1 cup - 119 IU
fortified plant milk, 1 cup - 60-120 IU (brand-dependant)
Aiming to enrich your daily diet with foods that are higher in vitamin D is a simple way to maintain healthy levels, especially over winter months when direct sun exposure tends to be a luxury.
Wait, what? Do mushrooms make Vitamin D?
That’s right! Mushrooms can indeed synthesise  their own vitamin D when exposed to UV radiation or natural sunlight. However, it's worth noting that UV-irradiated mushrooms primarily produce Vitamin D2 (Ergocalciferol), a less active form that requires conversion to Vitamin D3 in the liver.
Did you know? (the geeky bit)
When we talk about vitamin D, we usually think of D3 (Cholecalciferol), which we can get from certain foods, D3 supplements, or naturally from sunlight exposure. If you get your vitamin D levels tested by your doctor, they are most likely to measure the storage form, which is made by the liver from the Cholecalciferol form made in your skin (or consumed in supplements). This is known as Calcidiol or 25-OH-Vitamin D3. In the kidneys, the body can turn it into a hormonal form, which is not tested very often since it rarely fluctuates significantly in the body, even during winter months. This is known as Calcitriol (or 1,25-dihydroxycholecalciferol (1,25-OH2-D3)).
Picture: Vitamin D synthesis and metabolism
Source: Dominguez LJ, Farruggia M, Veronese N, Barbagallo M. Vitamin D Sources, Metabolism, and Deficiency: Available Compounds and Guidelines for Its Treatment. Metabolites. 2021 Apr 20;11(4):255. doi: 10.3390/metabo11040255. PMID: 33924215; PMCID: PMC8074587.
What About Store-Bought Mushrooms?
Most supermarket mushrooms aren't particularly high in vitamin D2. This is because they're often grown in the dark or receive minimal exposure to UV light. However, some companies go the extra mile by irradiating their mushrooms post-harvest to boost their vitamin D content; you'll find this information clearly labelled on the packaging—and usually reflected in the price.
The amount of vitamin D2 in commercially sold mushrooms exposed to UV radiation can differ significantly. Some studies have shown  that these can contain up to 400 IU of vitamin D per 100g of fresh weight. In some instances, when sliced mushrooms with a higher exposed surface area were exposed to natural daylight in midday, they generated nearly 800 IU. That’s as little as 5 button mushrooms. Smaller mushrooms only need about an hour to generate 400 IU, whereas larger ones take about twice as much time.
Conducting a home experiment where you expose store-bought mushrooms to direct sunlight for an hour or two is a fun experience if you are fortunate enough to have a balcony, garden or a large window. While you might not notice any immediate change in flavour, consistently doing this could contribute to maintaining healthy vitamin D levels. It also makes you feel more connected to the food you eat.
The Bottom Line According to NHS UK, adults and babies need 10 mcg (400 IU - International Units) of vitamin D per day. Foods like salmon, mackerel and dairy are high in vitamin D, and UV-irradiated mushrooms can even synthesise their own D2 form. Commercial mushrooms vary in vitamin D content depending on UV exposure, some may carry “High in Vitamin D” tags but will come at an extra cost. While both D2 and D3 from food require a complex chemical conversion inside our bodies to be turned into the active form called Calcitriol, regular intake from food can help protect and even optimise our levels further.
How much vitamin D can I get from sunshine?
Our bodies have the capability to synthesise Vitamin D naturally when exposed to sunlight.
This process is initiated by the Ultraviolet Radiation (UVR) emitted by the sunshine, particularly UV-B. The UVB rays start a chain reaction that begins in our skin and culminates in our kidneys, resulting in the production of Vitamin D. However, several factors  can influence this production, including skin tone, latitude, time of the day, season, applied sunscreen and individual genetic variabilities in vitamin D assimilation.
According to the British Skin Foundation “(quote) “for lighter skin types – daily sunlight exposure for 10-15 minutes between April and September provides sufficient year-round vitamin D while also minimising the risks of sunburn and skin cancer. For darker skin types, 25-40 minutes is recommended.”
Moderation and caution are required when exposing our bodies to prolonged sunshine. Of the 3 UVR types (UV-A, UV-B and UV-C), UVA is the most dangerous. It penetrates the deepest layers of our skin and has the potential to damage the DNA . Over time, this may increase the risk of melanoma (skin cancer).
For this reason, it is always essential to apply appropriate sunscreen with an appropriate SPF. More information can be found on the British Skin Foundation website.
At a Glance Summary: Our bodies can naturally produce Vitamin D through 10-15 minutes of daily sun exposure for lighter skin types and 25-40 minutes for darker skin types, according to the British Skin Foundation. However, factors like skin tone, time of day, and season can affect this process. Utilise adequate sunscreen protection to minimise the risk of sunburn complications such as melanoma.
Summary & Key Takeaway Points
The Vitamin D-ADHD Link
Lower levels of vitamin D during pregnancy may increase the likelihood of ADHD diagnosis in the baby.
Children with ADHD often tend to be on the lower side of the optimal levels.
The Role of Supplementation
Supplementing children and adolescents with ADHD, in a small study of 257, has shown benefits to inattention and behaviour.
There is no adult data on Vitamin D supplementation and ADHD - more research is needed.
Target Vitamin D Levels:
Maintain your levels above 50nmol/L and if possible, get into the upper 80s or mid 90s for maximal protection
Testing for Vitamin D and supplementation
Vitamin D levels can be tested by a doctor, through private testing company or by ordering a finger prick test.
Consult supplementation with a licensed professional to prevent overdose and subsequent Vitamin D toxicity - especially if pregnant or planning pregnancy
Dietary Sources of Vitamin D
Fatty fish, dairy, and fortified foods are excellent sources of vitamin D. Ensure regular addition of these in your diet
UV-irradiated mushrooms are a great alternative for vegans and vegetarians
12-40 minutes per day, depending on your skin tone is sufficient to protect your levels
Wear sunscreen with an appropriate factor if spending prolonged amount of time on direct sunlight
Do you feel lost in the maze of conflicting ADHD information?
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