Part
hormone and part nutrient, vitamin D is essential for health. Here’s how to
tell if you’re deficient, and what to do about it.
Vitamin
D is critical for everything from bone health and immunity to hormone balance
and mental wellness. Unfortunately, it’s also pretty common to be deficient in
this key nutrient.
Most
vitamin D comes from sitting out in the sun, without sunscreen. Even if
everyone made sure to get outside enough, most of the planet doesn’t get enough
year-round direct rays to raise blood levels.
What is
Vitamin D?
Vitamin
D is technically a prohormone, which means it is a nutrient with hormone-like
properties in the body. It can be manufactured by the body in response to
direct sun exposure by interacting with cholesterol. (1) It is also known as a fat-soluble vitamin
because it is stored in the body’s fat cells and it absorbs best when taken or
eaten with fatty foods.
All
cells have receptors to bind with vitamin D – it’s that crucial of a nutrient.
Yet more than 1 billion people across the world have inadequate levels. (2) In the U.S. alone, more than 40 percent of
all adults are deficient. (3)
There
are several groups of people that are at higher risk of deficiency. They
include:
·
The elderly
·
Those pregnant or breastfeeding
·
Infants
·
Overweight or obese people
·
People who spend little time outdoors, or wear sunscreen
constantly
·
Those who don’t eat enough dairy or fish
What
Are Normal Levels?
The
recommended daily intake of vitamin D is set between 400 to 800 IU, but most
experts agree that this amount is too low to prevent true deficiency.
Depending
on where you live, you may not be able to get vitamin D from the sun very
often, as many locations get strong ultraviolet rays for less than half of the
year. Plus, aging reduces the body’s ability to synthesize vitamin D, so even
with adequate sun exposure, your levels could still be suppressed. (4)
How To
Understand Your Lab Tests
In
order to assess your vitamin D levels, doctors can run a lab test known as
25-vitamin D hydroxy or 25(OH)D. If you take vitamin D supplements, do not take
them on the day of testing until after your blood has been drawn.
There
is a very wide range that is considered “optimal” for vitamin D, and much will
depend on who you ask and how healthy you are. Overall, research supports
levels higher than 30 ng/mL for bone health, longevity, immune health, and
more. According to Mayo Medical Laboratories, vitamin D levels are classed as
such: (5)
·
<10 – Severe deficiency
·
10-24 – Mild to moderate deficiency
·
25-80 – Optimal
·
>80 – Possible toxicity
Signs
and Symptoms of Vitamin D Deficiency
You
might not know that you’re dealing with a vitamin D deficiency right away. Low
levels might persist for months or years before there are signs. Once you reach
that point, these are the most common giveaways that your vitamin D level might
be too low.
1.
Fatigue
There
are many causes of fatigue, and
vitamin D deficiency is one of them. (6) One case study identified severe vitamin D
deficiency as the cause of “heavy daytime tiredness and pervasive fatigue”,
which improved after the patient supplemented with dose-appropriate vitamin D.
(7)
Other
research confirms that vitamin D deficiency causes fatigue, with one study
showing that women with levels lower than 30 ng/mL were more likely to be
fatigued than those with levels higher than 30 ng/mL. (8)
2. Low
Immunity
The immune system relies heavily on vitamin D
to fight off bacterial infections and viral illnesses. When vitamin D levels
are low, the immune system is ill-equipped to fully fight off invaders. (9)
Research
finds a direct link between low levels of vitamin D and more frequent
infections with colds, pneumonia, and bronchitis. (10, 11, 12) Fortunately, vitamin D supplements can
help reduce that risk.
3. Bone
and Muscle Pain
Pain in
your bones or muscles can be indicative of low vitamin D levels. (13, 14) Research found that those deficient in
vitamin D were almost twice as likely to experience pain in the legs, ribs, or
joints compared to people whose vitamin D levels were considered normal. (15)
While
it’s not always easy to pinpoint the cause of muscle pain, research finds that
71 percent of people experiencing chronic pain are low in vitamin D. (16, 17)
4.
Depression
Vitamin
D is closely associated with mental health, particularly warding off
depression, and the risk gets higher as you age. (18) Because vitamin D has hormone-like
properties, it can exert a powerful influence over neurotransmitters.
Since depression also has ties to
inflammation, it’s thought that vitamin D can cool the internal
flame of an overactive immune system.
Research
shows that supplementing with vitamin D during cold months and even in cases of
seasonal affective disorder can improve symptoms of depression. (19)
5. Bone
Loss and Osteoporosis
Aging
impacts vitamin D stores and the body’s ability to synthesize vitamin D from
sun exposure, but it also wreaks havoc on bone density and mineral stores.
Still, excess calcium supplementation won’t fix all bone deficits. Vitamin D
helps the body use calcium and when levels are low, it can demonstrate signs of
deficiency.
Research
shows a direct link between low bone density and low vitamin D levels. It’s not
just calcium that your bones need, but adequate levels of vitamin D, too. (20)
How to
Correct Vitamin D Deficiency
Very few
foods have enough vitamin D in them to efficiently raise blood levels. Sun
exposure is the best natural way to get vitamin D, but mushrooms, egg yolks,
and fatty fish like salmon and mackerel are all good sources. (21)
If
you’re very low in vitamin D, many doctors will recommend taking 50,000 IU of
vitamin D once per week for a few weeks or a few months, depending on the
severity of deficiency. For those without severely low levels, improvements can
be made by supplementing with far lower doses, usually in the 2,000 to 4,000
range. (22)
Experts
also recommend 10 to 20 minutes of sun exposure daily, without sunscreen, and
with most of the trunk, arms, and legs bare. The more skin directly exposed to
direct sunlight, the more likely your body will trigger the proper rise in
blood levels. Individuals with darker skin tones may require more time in the
sun for this synthesis to take place.
It’s
important to talk to your doctor about your individual needs. If you’ve been
cautioned against sun exposure for skin cancer or other reasons, ask about
other ways you can maintain healthy vitamin D levels.
Bottom
Line
Vitamin
D is a multifaceted nutrient that also acts as a hormone. Many adults are low
in this critical nutrient, so it’s important to speak with your doctor if
you’re experiencing any of the above symptoms. Direct sun exposure is the best
way to get vitamin D but you can also supplement, as well as eat plenty of
fatty fish, mushrooms, and egg yolks.