Vitamin D: The “Sunshine Vitamin” Most of Us Are Low In

Vitamin D has been in the news a lot lately because it’s so critical for immune function. Recent studies have shown that Vitamin D levels are lower in patients with SARS-CoV-2 (PMID: 32397511) and that supplementation with Vitamin D can reduce the risk of COVID-19 infections and deaths (PMID: 32252338). We’ve been talking about this incredible “vitamin” in functional medicine for years because of it’s profound effect on the immune system and pretty much every other body system.

What is Vitamin D?

We call it a vitamin but really it’s a pro-hormone synthesized from cholesterol in our skin in response to UVB radiation. We can also get it from certain foods.

Essential for:

– Bone strength

– Cardiovascular health

– Fighting infection

– Reducing inflammation

– Preventing cancer and autoimmunity

– Hormone production

– Mood balance

– Weight loss

– Cognitive function

– Healthy pregnancy and fertility

What does it do?

Vitamin D has a lot of important functions in the body. It helps balance calcium and phosphorus in the blood and keep your bones strong. It balances your immune system, helping kill bacteria, viruses, and fungi, and fighting inflammation, autoimmunity, and even cancer! (PMID: 31405892)

Vitamin D has been shown to help regulate adrenaline (epinephrine), noradrenaline (norepinephrine), and dopamine production in the brain, as well as help protect from serotonin depletion. This is why Vitamin D deficiency has increases your risk of depression.

Vitamin D plays a strong role in sex hormone production and is associated with improving fertility. It can reduce insulin resistance in women with PCOS and plays a role in preventing and treating fibroids and endometriosis. It promotes healthy follicle formation, and in studies of women undergoing IVF, women with higher vitamin D levels have not only pregnancy rates 35% higher, but higher quality embryos compared to those who are deficient (PMID: 25469131). It also appears to prevent preterm labor, pre-eclampsia, and gestational diabetes (PMID: 30322097)


There’s a great risk of deficiency in:

– Breastfed infants

– Older adults

– People with limited sun exposure

– People with darker pigmented skin

– People with inflammatory bowel disease or other fat malabsorption

– People with a BMI>30 or who have had bypass surgery

But I see suboptimal Vitamin D levels in at least 95% of my patients!

How to test

Blood test for 25-hydroxyvitamin D

Optimal level: 60-80 ng/mL

The “normal” reference range of 30-100 is too broad for optimal health

Sources of Vitamin D


10-15 minutes of unfiltered sunlight 3-4 days/week should be sufficient, but factors like air pollution, time of day, time of year, and sunscreen can limit exposure.

Food sources

– Cod liver oil

– Salmon

– Sardines

– Mackerel

– Tuna

– Egg yolk

– Shiitake mushrooms

– Fortified foods


D3 is the best-absorbed form and I prefer liquid for optimal absorption and easy dosing.

Maintenance dosing:

– Children <12 m. 400 IU daily

– Children >12 m. 600-1000 IU daily

– Adults 2,000-5,000 IU daily*

– Nursing moms 5,000-6,000 IU daily*

*Ideally you’d dose based on your Vitamin D level

*Supplementation greater than 5,000 IU should be monitored with routine blood testing

*Doses up to 10,000 IU daily are safe in adults for rapid correction of deficiency for short periods of time

Tip: Boost absorption and effects by taking D3 with fat-containing food and Vitamin K2

My favorite brands:

  • For infants and kids, I like Carlson Labs Super Daily D3 and Nordic Naturals Infant Vitamin D3.
  • For adults, Ortho Molecular Products has a great liquid D3 with or without K2, 5,000 IU capsules with or without K2, and 50,000 IU blister pack for weekly supplementation, so they’re my go-to. Thorne also has a liquid D3 and D3/K2.

For 10% off all professional-grade supplements, visit my Fullscript dispensary.

For specific guidance on the best supplementation for you or your child, schedule your free discovery call with me today and learn how you can benefit from becoming a patient.

You May Also Like…


Submit a Comment

Your email address will not be published. Required fields are marked *