Best of the Weekly Thread: can vitamin D3 decrease risk of dementia, the gut microbiome of the hunter gatherer, and do not concern yourself with what you cannot control

Does Vitamin D supplementation decrease risk of dementia?

A prospective cohort study that examined the association between vitamin D supplementation and incident dementia in 12,388 dementia-free adults from the National Alzheimer's Coordinating Center titled, Vitamin D supplementation and incident dementia: Effects of sex, APOE, and baseline cognitive status, and published fairly recently in March, 2023. 

Vitamin D is a nutrient that is essential for many bodily functions, including bone health, immune function, and cognitive function. In recent years, there has been growing interest in the potential role of vitamin D in dementia prevention, and this study aimed to see if there was a correlation between actual vitam D supplementation and incidence of dementia. 

In short, the study found and stated that “vitamin D exposure was associated with significantly longer dementia-free survival and lower dementia incidence rate than no exposure”. 

SIGNIFICANTLY longer dementia-free survival and lower dementia incidence.

Here are some key highlights from the findings of this study:

  • Vitamin D exposure was associated with 40% lower dementia incidence versus no exposure.
  • Vitamin D effects were significantly greater in females versus males and in normal cognition versus mild cognitive impairment.
  • Vitamin D effects were significantly greater in apolipoprotein E ε4 non-carriers versus carriers.

Let’s unpack these findings a bit more. 

Overall, the occurrence of vitamin D supplementation showed a 40% lower incidence of dementia, which I would definitely agree, is quite significant, especially considering this is just a single, very inexpensive preventive intervention with a host of other researched potential benefits such as improved immune function, and reduced risk of other disease. 

That said, the study found that women (who also comprise 65-70% of the total population afflicted with Alzheimer’s) were even more significantly affected by vitamin D supplementation.

It also found that those who exhibit no signs of dementia, and had normal cognitive function were also more significantly affected by vitamin D supplementation. Which means, prevention here with vitamin D supplementation (and natural sunlight exposure, which is the natural way to supplement with vitamin D3) is key, as supplementation BEFORE any signs of dementia actually shows a greater impact on helping to keep you free of dementia. 

Finally, non-carriers of APOE e4, a common genetic risk factor for Alzheimer’s, were found to also have a more significant impact on reducing incidence of dementia with vitamin D supplementation. (You can find this out with a basic genetic test), 

Final Thoughts

The study's findings are consistent with some previous research, which has suggested that vitamin D deficiency may be a risk factor for dementia. The difference with this study was that it was attempting to see if there was a correlation between actual vitamin D supplementation and incidence of dementia, which was found, and found to be significant at that. 

One limiting factor of the study was that it was observational and based on existing data sets, and was unable to determine a therapeutic, researched dose of vitamin D supplementation to reduce risk of incidence of dementia. 

Vitamin D supplementation needs can vary based on the individual, so it always helps to get your levels checked with some blood work. That said, there are some general rules I tend to follow that I think are pretty reliable. 

During the warmer spring and summer months, where sunlight is far more direct, and thus, effective at helping the body to naturally produce vitamin D3 (as well as making it more enjoyable to be outside gaining that natural exposure) I try to get as much natural light exposure as possible, and then supplement with probably 10,000-15,000iu of vitamin D3 per week. 

During the colder, drearier winter months, where sunlight is also far less direct, and far less effective at helping to produce D3 naturally, I will supplement with upwards of 50,000iu per week. 

I also recommend supplementing with extra vitamin K2 either through a high quality multivitamin, or a separate vitamin K2 supplement, with a vitamin D3 supplement. 

Vitamin D3 when taken in higher, what would be known as “therapeutic doses”, helps with calcium absorption, which is great for your bones, however, it can also lead to calcium buildup in your bloodstream, which you don’t want, and vitamin K2 helps mitigate that, along with having its own therapeutic benefits. 

This is a relatively minor downside to vitamin D3 supplementation, which can easily be offset by supplementing with extra vitamin K2, and I would say the tremendous, multi-faceted health benefits of supplementing with vitamin D3 far outweigh this minor downside. 

Vitamin D3 supplementation is probably the most inexpensive supplement you can buy, making it a cost effective, easy thing to implement on your quest for greater longevity. 

A research paper originally published in the journal Nature, titled “Hunter gatherer lifestyle fosters thriving gut microbiome” studied the gut microbiome of the Hadza, a hunter-gatherer tribe in Tanzania, and drew correlations to their rate of disease and overall health. 

NOTE: You do need to subscribe to Nature to view the full article, but I’m here to unpack it for you, and even expand upon its findings. 


The study compared the gut microbiomes of Hadza hunter-gatherers in Tanzania with those of people living in industrialized societies such as the United States. 

The Hadza have a much more diverse gut microbiome than people in industrialized societies, and their gut microbes contain fewer genes associated with responding to oxidative damage. The researchers believe that the Hadza's healthy gut microbiome is due to their traditional hunter-gatherer lifestyle, which includes a diet high in fiber, animal protein, and low in processed foods.

The study also found that the Hadza's gut microbiome is more similar to the gut microbiomes of our ancient ancestors than the gut microbiomes of people living in industrialized societies. This suggests that our modern diet and lifestyle may be contributing to the decline in gut microbial diversity.

The researchers hope that their findings will help to improve our understanding of the role of the gut microbiome in human health. They believe that studying the gut microbiomes of non-Western populations, such as the Hadza, could help us to identify microbes that are beneficial for human health and to develop interventions that can restore gut microbial diversity in people living in industrialized societies.

Rate of Disease in the Hadza

The rate of disease is lower in the Hadza than in Western, industrialized societies. This is likely due to a number of factors, including their traditional hunter-gatherer lifestyle.

The study published in Nature found that the Hadza have a much lower prevalence of chronic diseases such as heart disease, stroke, type 2 diabetes, and cancer than people living in industrialized societies. The study also found that the Hadza have a much lower incidence of infectious diseases such as malaria, tuberculosis, and HIV/AIDS.

Noteworthy about all of the above is the complete lack of any traditional medical care in Hadza society, including pharmaceutical drug interventions. 

It’s all in the Microbiome Biodiversity

The average gut microbiome biodiversity is significantly lower in Western industrialized nations than in non-Western hunter-gatherer societies, meaning tribal societies like the Hadza have a wider range of total species of healthy bacteria in their gut. 

The above study found that the Hadza have a gut microbiome that is 44% more diverse than the gut microbiomes of people living in industrialized societies.

The researchers believe that this difference in gut microbiome diversity is due to a number of factors, including diet, lifestyle, and exposure to environmental factors. 

One could easily draw a correlation between the greater biodiversity in gut microbiome of the Hadza, and their diet rich in whole, “living” foods, and the absence of an overtly sterilized environment, leading to more exposure to beneficial bacteria, as cleaning and sterilizing not only kills bad bacteria, but also kills good bacteria, and there’s far more beneficial bacteria worth being exposed to, than there are pathogenic bacteria. 

The lower gut microbiome diversity in Western industrialized nations is associated with an increased risk of chronic diseases such as obesity, type 2 diabetes, and heart disease. In fact, the #1 correlation researchers can draw between the higher incidence of chronic disease in Western societies is the lower gut microbiome diversity. 

Gut Microbiome and Gene Expression

Did you know 90% of serotonin, your body’s “feel good” neurotransmitter, is produced in the gut!?

Your gut microbiome functions like a second brain, and different bacteria strains control different processes in the body, release anti-inflammatory and anti-aging enzymes, and control your gene expression. This all could be why greater gut microbiome diversity correlates to less disease and better overall health. Plain and simple, if you have a greater diversity in specific strains of bacteria, you have more bacteria that do more of these beneficial things. 

Gene expression is the process by which the information encoded in genes is converted into a functional product, such as a protein. This process is essential for all life, as it allows cells to synthesize the proteins they need to function.


The percentage of gene expression that comes from the gut microbiome is not yet fully understood. However, studies have shown that the gut microbiome can influence the expression of genes involved in a variety of functions, including metabolism, immunity, and neurological development.

One study found that the gut microbiome could account for up to 15% of the variation in gene expression in the liver. Another study found that the gut microbiome could influence the expression of genes involved in obesity and insulin resistance.

It is thought that the gut microbiome can influence gene expression through a variety of mechanisms, including the production of metabolites, the modulation of the immune system, and the production of signaling molecules.

Okay, okay, you get it, your gut bacteria does all kinds of amazing things to keep you healthy and maintain homeostasis (and remember, if the body maintains homeostasis, it doesn’t develop disease), and improving biodiversity in your gut is critical to this, but the fact of the matter is, we live in a Westernized society, so what do we do?

Tips to improve Gut Microbiome Diversity

  1. Get outside and be willing to get dirty. The soil in the ground contains 10x more bacteria than the air does. Furthermore, getting outside in different environments will also expose you to new strains of bacteria. In short, go to new places outside and at minimum, get those bare feet in the grass.
  2. Eat whole, organic, unprocessed foods. Food that is sprayed with pesticides, herbicides, and fungicides (which are all getting stronger and stronger as well) kill the beneficial bacteria found naturally on our food from the air and soil. Then, when you process food, you sterilize it, thus removing any remaining “living” nature to it.
  3. Avoid antibacterial soaps and cleaning products. “Antibacterial” means all bacteria good and bad. “Kills 99.9% of germs” is not a good thing, as most of said “germs” are beneficial. Remember, the Hadza have a much lower rate of infectious disease as well because they have more gut microbiome diversity, which naturally staves off pathogenic infection. Opt for cleaning and personal care products using natural oils and ingredients
  4. Eat/drink fermented foods. Fermented foods produce much higher rates of probiotics as they form naturally in the fermentation process. Work foods and drinks into your diet like kombucha, kefir, kimchi, yogurt, and sauerkraut. Choose the ones you like best, and make sure they’re still “living” foods as we tend to process fermented foods as well like yogurt, sauerkraut, and kimchi. 
  5. Supplement with probiotics. This is a very easy way to get the benefits of beneficial bacteria in your gut. I recommend this probiotic from Just Thrive, as it’s a combination of probiotic spores, which will actually “re-seed” your gut and increase biodiversity.
  6. Avoid over the counter synthetic medicines that destroy your gut microbiome like NSAIDs (ibuprofen, advil, aleve), antacids, among others. 

“The more we value things outside our control, the less control we have.”
-Marcus Aurelius

Life has a way of coming at you in ways you can’t expect or imagine. 

People and occurrences will bump into you, get in the way of your desired path. 

All too often, much of this is out of your control. 

What is, however, in your control, is how you respond. 

You cannot control what you cannot control, but you can control how you respond to life and how it comes at you, regardless of how it comes at you. 

Concerning yourself with things that are out of your control, (which if we’re being honest and objective with ourselves, is most of life) is not productive. 

Always remember that you are powerful, that no matter what comes your way, you can choose how you respond to it, choose to be positive.

And for all else that you can’t control, do not concern yourself with that.