The Sunshine Vitamin: D3 Benefits, Sources, and Dosage

Vitamin D, the sunshine vitamin, is important for a healthy immune system, bones, and nerves. Besides playing crucial roles in your physical health, it is also vital to your mental health.

Low levels have been linked to anxiety, depression, fatigue, and even brain fog.

This post explores how vitamin D3 supports your emotional and physical well-being, ways to safely get it from sun and supplements, ideal dosage ranges, and what to watch out for when optimizing your levels. It also links out to more detailed articles on topics such as getting vitamin D from sunlight, food sources, and vitamin D deficiency, so you can explore those topics too if interested.

What You’ll Learn in This Vitamin D Guide

• Key benefits for body and mind: How vitamin D supports physical and mental health, and emotional well-being
• D2 vs D3: Why the form of vitamin D matters for your body
• Natural sources: What to know about sunlight and food
• Supplements and safety: How much you need, plus practical guidance for safe use

Notes: The contents of this post are not intended to be medical advice. It is always advisable to consult with your personal medical professionals for individualized recommendations. I may receive a small commission on sales made from links in this post. 

16 Vitamin D Benefits: Why the Sunshine Vitamin Matters for Your Body and Brain

Research shows that healthy levels of vitamin D may:

1. Promote healthy bones and teeth
2. Strengthen muscles
3. Reduce inflammation 
4. Boost the immune system
5. Inhibit some cancers (i.e., colon, breast, ovarian, and prostate)
6. Assist your body's use of glucose (sugar)
7. Improve heart health 
8. Lower blood pressure
9. Slow cellular aging
10. Reduce risk of developing multiple sclerosis
11. Improve mood
12. Relieve anxiety
13. Reduce risk of Alzheimer's Disease
14. Relieve ADHD symptoms
15. Improve autism-related symptoms
16. Reduce risk for schizophrenia

Vitamin D Deficiency

Vitamin D deficiency is surprisingly common, especially among people with limited sun exposure, darker skin, digestive disorders, obesity, older age, or those taking GLP-1 medications.

🟢➜  I provide more details in this post: Vitamin D Deficiency: Causes, Symptoms & Research-Based Effects

How Vitamin D Benefits Mental Health

Vitamin D is a powerful antioxidant and anti-inflammatory nutrient — both of which have been shown to help mental health.

I have seen people have a 180-degree change from anxiety to calm when they raised their vitamin D up from unhealthy low levels.

Vitamin D is involved in many anxiety-related physical functions, including (See references 1-2):

• Movement of neurotransmitters
• Production of the calming neurotransmitter serotonin
• Use of calming neurotransmitter GABA
  
• Optimum health of nerve cells (this is where vitamin D's antioxidant and anti-inflammatory qualities come in)

D2 vs. D3: Which Form of Vitamin D Do You Need?

There are 2 forms of vitamin D: D2 (ergocalciferol) and D3 (cholecalciferol).

D2 is less stable and less effective than D3 at giving your body what it needs for biochemical reactions.

Natural Sources of Vitamin D: Sunlight and Foods

Where can you get vitamin D?

The best source of vitamin D3 is sunlight.

🟢➜  For more on this source of vitamin D, check out this post: Tips for How to Get Vitamin D from the Sun.

A few foods contain vitamin D naturally, but they get tricky because animal sources give you D3 while plant sources, such as mushrooms, offer only D2. How much UV light exposure an animal or plant gets will greatly impact how much vitamin D it contains.

Some countries mandate the addition of vitamin D to certain foods. 

🟢➜  For more on vitamin D food sources, check out this post: What Foods Have Vitamin D? (And Why Food Alone Isn’t Enough)

How Much Vitamin D Do You Need? RDA and Optimal Levels

Recommended Dietary Allowances for vitamin D are given in two ways: IU (International Units) and μg (micrograms). Each number is given in amounts recommended per day to maintain a healthy level. 

A Tolerable Upper Intake Level (UL) of 4000 IU/day or 100 μg/day has also been established for vitamin D. This upper limit only pertains to supplements because your body won’t over-make vitamin D from the sun. The US Food and Nutrition Board suggests staying under the limit unless supervised by a doctor. (Doctors will often prescribe supplement levels that go way over this limit for a short period of time if your blood tests show a low result for vitamin D.)

If cloudy weather or other conditions get in the way of you achieving enough sun exposure, you may benefit from supplementing with vitamin D3 because food sources of the vitamin are not thought to be adequate to get you to optimal levels. (3)

Your need to supplement may change throughout the year as your sun exposure changes. 

Top Vitamin D3 Supplement Options: What to Look For

Vitamin D supplements are available in two forms: D2 and D3. Remember that D3 is more usable by your body and, therefore, what we're looking for in supplements. (4-5)

More on specific supplements in a minute, but first, we need to talk about the potential of taking too much vitamin D.

Vitamin D Supplements: Safety Concerns and Side Effects

Vitamin D is fat-soluble, so it can build up in your body.

Water-soluble vitamins like the Bs or C will get flushed out through your urine if you take too much, but the fat-soluble vitamins are retained if you overdo the supplements.

Too much vitamin D can have a negative impact on your body systems, including interfering with calcium getting laid down in your bones.

You can’t get too much D from the sun, as your body will just stop making it when you’ve hit ideal levels. You can, however, overdo intake from supplements.

Testing Your Vitamin D Levels: Why, When, and How

It can be particularly beneficial to do blood tests to check your baseline vitamin D amount before supplementing and then monitor levels with testing while you supplement, so you can hit ideal levels.

If your vitamin D levels are low, a doctor will typically prescribe short-term high doses above the UL to get your levels up to normal, but you should only megadose with a doctor’s supervision. (As I said in the previous section, vitamin D from supplements can build up in your body.)

There are at-home vitamin D tests such as this one by Everlywell. (I'm not attesting to the accuracy of this particular test kit. The exact test kit that I successfully used in the past is no longer available.)

Interactions Between Vitamin D and Medications: What to Know

Vitamin supplements can sometimes cause negative reactions when combined with pharmaceutical medications.

Vitamin D supplements may cause harm when used with some statins and diuretics, according to the NIH vitamin D factsheet. 

Talk to your physician before starting supplements if you are on medications. You can also do a check of medication/supplement interactions on sites dedicated to this function, such as Medscape's Drugchecker.

Vitamin D3 Dosage for Mental and Physical Health

Dr. Leslie Korn recommends the following supplementation dosage for adult men and women in her book Nutrition Essentials for Mental Health: A Complete Guide to the Food-Mood Connection: (6)

• 2000–4000 IU/day

I see that most vitamin D supplements come in 5000 IU doses. 

If you have vitamin D deficiency, a doctor will likely prescribe higher doses, but be very careful about taking large amounts on your own because of the possibility of overdosing that I mentioned above. 

High-Quality Vitamin D3 Supplement Examples 

Note: I may receive small commissions for purchases made through links on this site, but they don't impact your cost. I offer them for your convenience. 

Nordic Naturals is a high-quality supplement brand. They have vitamin D supplements in both 1000 IU/serving and 5000 IU/serving. 

More Diet and Supplements Help for Mental Health

Vitamin D is an important piece of the puzzle when it comes to both physical and mental health — but it’s only one part of a much bigger picture.

In Feed Your Calm: Anti-Anxiety Anti-Stress Diet and Supplement Tips for Stress Resilience, I take a broader, practical approach to this topic. The book looks at how nutrition and supplements work together, and how to apply that knowledge in real life without getting overwhelmed.

It includes:

• Key nutrients that influence anxiety, mood, and brain function
• Practical ways to improve your diet in manageable steps
• Guidance on using supplements thoughtfully and effectively

If you’re looking to move beyond individual nutrients like vitamin D and build a more complete approach to supporting your mental and physical well-being, this is a helpful next step.

References

1. Rhonda P. Patrick and Bruce N. Ames, “Vitamin D and the Omega-3 Fatty Acids Control Serotonin Synthesis and Action, Part 2: Relevance for ADHD, Bipolar Disorder, Schizophrenia, and Impulsive Behavior,” FASEB Journal 29, no. 6 (2015): 2207–2222, https://doi.org/10.1096/fj.14-268342.

2. M. Wrzosek, J. Lukaszkiewicz, and A. Jakubczyk, “Vitamin D and the Central Nervous System,” Pharmacology Reports 65 (2013): 271–8.

3. Ulrike Lehmann et al., “Efficacy of Fish Intake on Vitamin D Status: A Meta-Analysis of Randomized Controlled Trials,” American Journal of Clinical Nutrition 102, no. 4 (2015): 837–847, https://doi.org/10.3945/ajcn.114.105395.

4. Laura Tripkovic et al., “Comparison of Vitamin D2 and Vitamin D3 Supplementation in Raising Serum 25-Hydroxyvitamin D Status: A Systematic Review and Meta-Analysis,” American Journal of Clinical Nutrition 95, no. 6 (2012): 1357–1364, https://doi.org/10.3945/ajcn.111.031070.

5. Victoria F. Logan et al., “Long-Term Vitamin D3 Supplementation Is More Effective Than Vitamin D2 in Maintaining Serum 25-Hydroxyvitamin D Status over the Winter Months,” British Journal of Nutrition 109, no. 06 (2012): 1082–1088, https://doi.org/10.1017/s0007114512002851.

6. Leslie E. Korn, Nutrition Essentials for Mental Health: A Complete Guide to the Food-Mood Connection (New York: W. W. Norton, 2016), 267.

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