Vitamin D is an essential fat-soluble vitamin. It’s sometimes called the “sunshine vitamin” because our skin makes it when exposed to the sun.
It’s also the most common nutrient deficiency! Especially here in Canada!
Like most vitamins, vitamin D has many functions in the body. It’s mostly known for its ability to help build strong bones. But, vitamin D is also important for a healthy immune system, digestive system, heart and mental health, blood sugar regulation, fertility, and resistance to cancer.
FUN FACT: Vitamin D is the vitamin with more scientific articles published since 2000 than any other vitamin.
Let’s talk about the many roles vitamin D has in promoting good health. We’ll also go over the different forms of vitamin D and what exactly is a deficiency. Finally, I’ll give you three sources of this critical nutrient and how much we should get.
Make sure you’re getting enough!
Vitamin D in the body
Vitamin D (calciferol) isn’t “active” in our bodies. To do its wonders, it first needs to be converted into the active form. This is a two-step process. First the liver converts it into 25(OH)D (calcidiol). Then, that is converted into 1,25(OH)D (calcitriol) in the kidneys. It’s this third, calcitriol, form that’s active in the body.
Vitamin D acts like a hormone! That means it’s produced in one part of the body (e.g. the skin), and travels through to act on another part (e.g. the bones).
Because vitamin D is fat-soluble, when you have more than enough, it gets stored in the liver, and isn’t flushed out in the urine like excesses of many other vitamins are.
FUN FACT: Fish liver oil contains vitamin D, but not fish oil – it’s the liver that stores vitamin D.
Vitamin D for bones
Vitamin D is most known for its importance for bone health. Bones are alive and are constantly remodeling themselves. This means they, as all tissues, need a constant supply of nutrients.
How does vitamin D help your bones?
Vitamin D helps the body absorb calcium more efficiently. And the mineral calcium is one of the major players to “mineralize” and strengthen our bones.
FUN FACT: New research shows it’s not just the kidneys that activate 25(OH)D into 1,25(OH)D – Bone cells can do this too!
Vitamin D works with other hormones to ensure optimal levels of calcium in the blood. When it comes to calcium, the body always prioritizes the blood over the bones. This is because the blood transports calcium around the body for critical functions like contractions of the heart and muscles.
When there is enough calcium in the blood, any excess is stored in the bones. This is when the bones are mineralized and strengthened. When there isn’t enough calcium in the blood two things happen to raise this level. First, vitamin D stored in the liver is activated to help absorb more calcium from food. Second, the body removes calcium stored in the bones to raise levels in the blood.
When we don’t get enough vitamin D (and calcium) regularly, bones can become weak and brittle. In children, severe vitamin D deficiency can cause rickets, and in adults it can cause osteomalacia, and over time osteoporosis can develop.
Having enough 25(OH)D in the blood is associated with higher bone density. Studies show that supplementing with vitamin D may reduce the risk of bone fractures.
Vitamin D, the immune system, and inflammation
Several studies have shown a link between low levels of vitamin D and immune-related conditions like atopic dermatitis and rheumatoid arthritis. In the lab, vitamin D seems to have “anti-inflammatory” and “antioxidant” properties.
FUN FACT: Inflammation is mostly caused by the response of our immune system to protect us against infections, irritants, and damage.
Vitamin D can reduce immune response and inflammatory markers. Some studies in people with immune conditions (e.g. cystic fibrosis, multiple sclerosis, & obesity), show that supplementing with vitamin D reduces some inflammatory markers in the blood.
Some researchers think vitamin D, due to its effects on the immune system, may also help with serious food allergies. A few small studies show that children with low vitamin D levels have an increased risk for food allergies.
Vitamin D and digestive diseases
Since vitamin D is fat-soluble, it’s absorbed along with fat in the diet. So, people who don’t eat or absorb enough fat are at risk of lower vitamin D levels. This can include people with many digestive issues such as celiac disease, inflammatory bowel diseases (IBD) like Crohn’s & colitis, as well as people who have had gastric bypass surgery. People who’ve had their gallbladders removed are also at a higher rick for low vitamin D levels.
Also, a healthy vitamin D status seems to go hand-in-hand with a healthy gut. For example, there is a link between sub-optimal vitamin D, gut microbiome status, gut inflammation, and diseases of the gut like IBD and colon cancer.
Just another reason to make sure your gut flora is healthy!
Vitamin D and cancer
It’s not just colon cancer that’s associated with low levels of vitamin D. Higher levels of vitamin D are associated with lower risk for prostate, and breast cancers.
In the lab, cancer cells don’t seem to do as well when exposed to higher levels of vitamin D. They don’t divide or invade other tissues as well; and, they seem to die easier.
Vitamin D and heart health
Several studies have linked low levels of vitamin D in the blood with heart disease. Higher levels of vitamin D in the blood may reduce blood pressure and the risk of heart disease by a small amount. Supplementing with vitamin D may help lower blood pressure.
Vitamin D and blood sugar
Low vitamin D levels are associated with higher levels of insulin resistance in people without diabetes. It may also increase the risk of developing diabetes. Supplementing with vitamin D may help improve blood sugar management.
Vitamin D for mental and brain health
Cells in key areas of the brain have “receptors” for vitamin D. Vitamin D also has a role in circadian rhythms and sleep, affects growth of nerve cells, and impacts the developing brain.
There is growing evidence of the links between low blood levels of 25(OH)D and symptoms of depression. Some studies also show a link between low vitamin D levels and increased risk of Alzheimer’s and Parkinson’s diseases.
Vitamin D and fertility
Vitamin D seems to help improve the motility and survival of sperm cells.
It’s also important for maturity of the eggs, growth of the uterine lining, embryo implantation, as well as helping to organize immune cells in the uterus for protection against infections.
It also helps to avoid gestational hypertension and diabetes.
Forms of vitamin D
Many vitamins come in more than one form. With vitamin D, it comes in two different forms: D2 and D3. There are small differences in their chemical structure.
FUN FACT: Both forms are activated the same way: to 25(OH)D and then 1.25(OH)D.
Vitamin D2 (ergocalciferol) is the plant-based form, while vitamin D3 (cholecalciferol) is from animals. Both forms can help rickets. At higher doses, however, vitamin D2 is less potent than vitamin D3.
Sources of vitamin D
There are three main sources of vitamin D – sun exposure, foods, and supplements.
Sources of vitamin D – Sun exposure
Our skin contains “pre” vitamin D. When exposed to UV rays from the sun, this “previtamin” is converted into vitamin D (calciferol).
Especially here in Canada, vitamin D levels decline in people throughout the winter due to less sun exposure.
The problem with getting vitamin D via sun exposure is that too much UV radiation can contribute not only to skin cancer, but also to dryness and other cosmetic changes in the skin over time.
Let’s look at how to get enough vitamin D from foods and supplements.
Sources of vitamin D – Foods
Vitamin D is not naturally found in very many foods. The best sources include fatty fish and fish liver oils. Some is also found in beef liver, some cheeses, and egg yolks. Because these are animal sources, they are in the D3 form. Some is even already converted into 25(OH)D which is thought to be 5 times more potent than the regular D3 form.
Naturally occurring plant sources of vitamin D2 are some mushrooms that have been exposed to the sun. That’s about it.
Because it’s naturally found in so few foods, vitamin D is also added to certain foods. This is called “fortification.” In fact, fortified foods are the main source of dietary vitamin D in the US.
Fortification of food with vitamin D can improve vitamin D status of the food. Some of these vitamin D fortified foods include milk, some orange juices, breakfast cereals, and yogurt.
FUN FACT: Because vitamin D is a fat-soluble vitamin, absorption from foods, drinks, and supplements is improved when taken at the same time as a fat-containing meal.
Sources of vitamin D – Supplements
Vitamin D supplements come in both forms: D2 and D3. The plant-based D2 form is manufactured by exposing yeast to UV radiation. The animal-based D3 form is made from lanolin.
If you are at risk for vitamin D deficiency, your health care provider can test your blood for levels of 25(OH)D and recommend a course of action specific for you.
However, if you don’t have a professional recommendation for how much vitamin D to take, the safest way to supplement is to follow the instructions on the label. And never take more than 4,000IU/day (100 mcg/day), unless told to by your licensed health care provider.
That’s because too much vitamin D can become toxic. One effect of too much vitamin D is that blood levels of calcium can get too high. This can lead to “calcification” which can damage blood vessels, the heart, and kidneys. Getting too much vitamin D is mostly a risk when taking supplements; not so much from sun exposure or food intake
And don’t forget to check with your doctor and/or pharmacist if you’re taking medications because vitamin D supplements can interact with some of them.
In infants, since formulas must have vitamin D added to them, breastfed infants are often recommended vitamin D drops. Speak with your licensed healthcare professional for recommendations.
My preference is the D-Mulsion from Genestra because the vitamin D has been emulsified in a base of extra-virgin olive oil making the bioavailability much better.
Vitamin D deficiency
Studies show that between 30-80% of people simply don’t get enough vitamin D. This deficiency is so common that some researchers have called it a “public health concern” and a “global problem.”
Vitamin D deficiency is when someone has less than 30 nmol/L of 25(OH)D in the blood. Ideally you want at least 50 nmol/L (20 ng/L).
- <50 nmol/L = deficient
- 50-120 nmol/L = sufficient
- 120-150 nmol/L = optimal
- 375+ nmol/L = toxic
To reach toxic levels of vitamin D, heavy dosing for long periods of time are needed. This is very rare.
Vitamin D deficiencies can happen when, over time, people are not getting enough safe sun exposure, or are not eating enough foods containing vitamin D. It can also happen if the vitamin D is not being absorbed very well, or if the kidneys have trouble converting the “previtamin” D into the active form 1,25(OH)D.
People who are more likely to be deficient in vitamin D include:
- Pregnant and lactating women, and breastfed infants;
- Older adults;
- People with limited sun exposure (living in Canada for example!);
- People with darker skin;
- People with digestion issues that prevent proper absorption (e.g. inflammatory bowel disease, celiac disease, etc.);
- People with obesity; and,
- People who have undergone gastric bypass surgery.
How much vitamin D do we need?
For adequate blood levels of 25(OH)D, how much vitamin D do we need to get every day?
To get enough vitamin D from the sun, a general rule is to get about 5–30 minutes of sun between 10:00 a.m. & 3:00 p.m. at least twice a week to the face, arms, legs, or back without sunscreen.
When it comes to vitamin D from foods and supplements, in Canada and the US the Institute of Medicine (IOM) has set target daily amounts called the “Recommended Dietary Allowance” (RDA). Although on the lower end of optimal, they ensure that at least 97% of people get sufficient vitamin D every day. Those recommendations are:
- 10 mcg (400 IU) per day for infants under the age of one.
- 15 mcg (600 IU) per day for everyone aged 1-70 years old, including pregnant and lactating women.
- 20 mcg (800 IU) per day for everyone over the age of 70.
Vitamin D in foods and supplements may be measured in both mcg (micrograms) and/or IU (international units). The conversion factor is 40 IU = 1 mcg.
Depending on your lab scores, higher values are often needed. In the winter months here in Canada I usually recommend 3-4,000IU a day and 1-2,000IU in the summer months.
Vitamin D has many health-promoting roles in the body. Most of the evidence is for bone health, but it’s also associated with a healthy immune system, digestive system, heart and mental health, blood sugar regulation, fertility, and resistance to cancer.
Vitamin D is also the most common deficiency.
We can get vitamin D from sun exposure, some foods, and supplements.
The best way to know how much vitamin D you need is to have your blood tested if you’re at risk. If you don’t have a test or professional recommendation, following the label directions on your vitamin D supplements can be a safe way to get enough.
These are the most common signs of vitamin D deficiency:
- Getting Sick or Infected Often
- Fatigue and Tiredness
- Bone and Back Pain
- Impaired Wound Healing
- Bone Loss
- Hair Loss
- Muscle Pain
If you’re experiencing some of these symptoms or are unsure if you should supplement with vitamin D, the first step would be to ask your Doctor to run a 25(OH)D blood test to find out where your levels are at.
If you have more questions, not sure if you’re deficient in vitamin D or how much you should take, or if you have any other vitamin or mineral deficiencies, email me to discuss: firstname.lastname@example.org.
Are you struggling with one of the topics discussed today affected by vitamin D such as digestive issues, fertility, and mental health? Sign up for my free 30 min consultation and receive your Whole Body Health Profile and find out where your main imbalances are if the BIE Process can help you reach your health goals!
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