Wellness in the winter months: part 2

Last week we dipped our toes into the frosty waters of the “winter blues” and the relationship between cooler temperatures and cognitive functioning; from benefits like increasing alertness (think ice baths) to the perils of Seasonal Affective Disorder. 

This week, we’re continuing in the same vein with a further look into how sunlight affects our brains. We've all heard about the importance of Vitamin D for strong bones, but did you know this "sunshine vitamin" also plays a critical role in brain health?

Recent research has shed light (pun intended) on the potential link between Vitamin D and cognitive function, particularly in relation to Alzheimer's disease. Keep reading for more on why Vitamin D is essential for our brains and how we can ensure we're getting enough of this vital nutrient!

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There are two main ways our bodies obtain Vitamin D:

1. Vitamin D3: This is the easiest form to obtain, produced when UVB rays from sunlight hit our skin and convert a compound known as a sterol into Vitamin D3. Around 80% of our Vitamin D is obtained this way.

2. Vitamin D2: This form comes from fungi and yeast and is often found in Vitamin D-fortified foods. It’s more difficult to obtain the total amount of Vitamin D required by your body for optimal functioning, but it is still a good option in making up the remainder of your requirements.

Once in our bodies, Vitamin D helps absorb and retain calcium and phosphorus, which are critical for building strong bones. But its benefits don't stop there - Vitamin D also bolsters the immune system and reduces inflammation by influencing the production of inflammatory compounds and suppressing pro-inflammatory cells. 

Our bodies can keep a store of vitamin D in the liver and fat cells for future use, which means you don't necessarily need a daily dose, as your vitamin D reserves can last for 10-12 weeks. However, this is only true if you have sufficient levels to begin with.

Despite being known as the "Sunburnt Country," did you know that more than 1 in 3 Australians have a mild-to-severe Vitamin D deficiency? (Healthdirect). 

This surprising statistic is due (in part) to the success of public health campaigns such as 'Slip, Slop, Slap,' which aimed to reduce skin cancer risks from excessive sun exposure. While these campaigns have been incredibly successful in promoting sun safety and reducing rates of skin cancer, they've had an unintended consequence on our Vitamin D levels. 

For most people, 5-30 minutes of sunlight without a UVB-blocking SPF will safely give you all the Vitamin D you need. However, those with a higher risk of skin cancer (e.g. people with fair skin, immuno-compromising conditions, or a family history of skin cancer) should check with their doctor to weigh up the risks and benefits.

Recent studies have linked low vitamin D levels with increased risk of Alzheimer's disease.

• A 2014 study found that participants deficient in vitamin D had a greater risk of dementia and Alzheimer's compared to those with adequate levels (Neurology).

• Another 2023 study found that vitamin D exposure was associated with living longer without dementia and a 40% lower overall dementia incidence (Alzheimer’s and Dementia). The study also identified certain groups who may benefit the most from vitamin D in terms of Alzheimer's risk, including women, people with standard cognition (as opposed to a cognitive impairment), and people without a specific known risk factor gene for Alzheimer's. This research is ongoing, so stay tuned.

• One study also found that participants with deficient Vitamin D had lower verbal fluency, which is your brain’s ability to retrieve information from memory. This is important as verbal fluency tasks are widely used as a way to identify early signs of dementia (Psychology Research and Behaviour Management).

It's worth noting that many large-scale studies (American Journal of Therapeutics, Journal of the American Geriatric Society) that assessed existing research found Vitamin D supplements don't seem to help most people's thinking and memory skills. This might mean that it's actually being out in the sunshine, rather than just the Vitamin D itself, that's good for our brains. While the relationship isn’t entirely clear, some researchers hypothesise that changes in brain structure which happen when we are exposed to sunlight may be the connection between natural sunlight and cognition. Further research is needed to confirm this hypothesis (Nature).

Still, it's not quite that simple - there are other things to consider too.

For example, people with darker skin naturally make less Vitamin D from sunlight because of higher levels of melanin in their skin. In America, Black people also have higher rates of Alzheimer's disease, but this is likely due to a mix of reasons, and not just Vitamin D levels. In these cases, some benefits of D3 supplementation have been shown (Source: Nature). Other factors like gender, genetics and a person's general health can play a role. 

So while Vitamin D is important, it's just one piece of a much bigger puzzle when it comes to brain health. It's always best to talk to a qualified and trusted doctor about your specific needs and situation.

So you’ve spoken to a doctor and you want to boost your Vitamin D levels? Here’s how to start:

1. Sunlight: 5-30 minutes of sun exposure most days can be sufficient, but this varies based on factors like season, cloud cover, and skin melanin content.

2. Diet: Include Vitamin D-rich foods such as fatty fish (salmon, trout, mackerel), egg yolks, beef liver, and mushrooms. Many foods are also fortified with Vitamin D, including milk, some yoghurts, and certain breakfast cereals, however evidence on their benefit is unclear. 

3. Supplements: For those who can't get enough Vitamin D through sunlight and diet, supplements may be necessary. As mentioned above, the benefits of Vitamin D supplementation are mixed, and it’s important to talk to your doctor before adding any supplements to your routine.

That’s all we’ve got ;

for this edition of MelonMag.

To us, it seems as though the jury is still out on whether taking Vitamin D supplements can directly prevent Alzheimer's disease. However, maintaining adequate levels of this crucial nutrient by getting outdoors (even in the winter cold!) appears to be important for overall brain health.

As we continue to unravel the many mysteries of cognitive health, a few things seem to be a constant: a balanced diet, regular exercise, and safe sun exposure are key components of a brain-healthy lifestyle. So get yourself out into some sunshine (safely, of course) and let the cognitive benefits roll in!

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💙 The MM Team

REFERENCES

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• Du, Y., Liang, F., Zhang, L., Liu, J., & Dou, H. (2020). Vitamin D Supplement for Prevention of Alzheimer’s Disease: A Systematic Review and Meta-Analysis. American Journal of Therapeutics, 28(6), e638–e648. https://doi.org/10.1097/mjt.0000000000001302

• Ghahremani, M., Smith, E. E., Chen, H., Creese, B., Goodarzi, Z., & Ismail, Z. (2023). Vitamin D supplementation and incident dementia: Effects of sex, APOE, and baseline cognitive status. Alzheimer’s & Dementia. Diagnosis, Assessment & Disease Monitoring, 15(1). https://doi.org/10.1002/dad2.12404

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