Vitamin D Review: 49 Critical Facts You Don’t Know

Update 4/8/20. At least 50% of the people reading these words have a vitamin D deficiency. That's even true if you live in Florida! Given the benefits of vitamin D, it's a pretty good idea you know what your levels are because lots of research is showing not only are most people deficient but lack of vitamin D increases our risk of several diseases. Because it's a critical nutrient, here are 49 BIG vitamin D facts, you probably don't know. After this list, you will be an expert on this very important nutrient.

1 It's More Hormone Than Vitamin

If you look at the chemical structure of vitamin D, it looks more like a hormone than a vitamin. It also acts more like a hormone than a vitamin too, having a variety of effects in the body. Because of this, if it were discovered today, I'd bet it would be called hormone D.

2 Every Cell Has Vitamin D Receptors

Most don't know every cell in your body has receptors for vitamin D. This fact goes to how important this vitamin is and how far-reaching it's effects are in the human body.

3 Your Liver And Kidneys Activate It

Whether we make it from the sun or take it as a supplement, our liver and kidneys are critical for turning vitamin D into its active form – “s 1,25-dihydroxyvitamin D.” While this is true, many other cells can activate vitamin D also. This includes cells in the brain, prostate, breast and lungs to name a few.

4 You Can Take It An Empty Stomach

We've all heard vitamin D is fat-soluble, but it turns out we don't need fat to absorb it. This surprising revelation came up as I was reading the Vitamin D Solution book, by Dr. Michael Holick. Dr. Holick is one of America's experts on this topic.

5 Overweight? More Vitamin D

Because it's fat-soluble, the vitamin is stored in fat cells. As such, overweight people have a greater ability to lock in vitamin D, preventing it from getting into the blood where it can help us. Some estimate those who are overweight with a BMI over 30 may need twice as much as a more normal weight person.

6 Bone Pain May Mean Deficiency

Osteomalacia – or soft bones – is basically the childhood disease, rickets in adults. One sign of osteomalacia is constant pain the bones. The pain gets worse when you press on the bone. The pain can be anywhere such as legs, arms, chest or even spinal pain. If not taken care of, osteomalacia can lead to osteoporosis.

7 It May Lower Blood Pressure

The vitamin causes blood vessels to relax and open up. This results in a drop in blood pressure. Conversely, lack of this nutrient may cause calcium to build up in blood vessels, promoting them to stiffen up. This can raise blood pressure and contribute to heart disease and stroke.

8 Deficiency May Make You Hungry

Being deficient may lead to problems with the appetite-reducing hormone leptin. Leptin is made in our fat cells. As leptin levels rise, we don’t feel hungry. As leptin levels fall, we get hungry.

By preventing a rise in leptin, a lack of vitamin D may cause increased hunger and weight gain. Is it a coincidence that vitamin D levels fall while weight increases during the winter months?

9 Most Foods Don't Have It

Unless it's fortified, most foods don't contain vitamin D. Those which do include fish like tuna and salmon, mushrooms and fortified foods like milk, orange juice, and some breakfast cereals.

10 D2 and D3 Are Equally Effective

There are two forms – D2 (ergocalciferol) and D3 (cholecalciferol). What's the difference?

• D3 is what we make when we go out in the sun
• D2 comes from yeast

While many assume D3 is more potent, this is debatable. I believe they are equally effective. See the next fact for proof.

11 Vitamin D Reduces Falls

One of the sexiest things about vitamin D is that it appears to help reduce falls in older adults significantly. One study showed as much as a 22% decrease in falls. In another study, a 72% reduction in falls was seen. Many anti-fall studies use 800 IU per day.

I'm rather proud I was one of the first in the US to call attention to this research in my book on supplements. Many studies have used D2 to reduce falls.

12 Taking 1000 to 2000 Is Usually Fine

For most people, getting 1000 IU to 2000 IU through food and supplements is usually enough to get most of the benefits of this vitamin although those who are deficient will need more to bring their blood levels up into the normal range.

13 Fish Is a Good Source

A typical 3 oz serving of Salmon can provide 600-1000 IU. Because it's not in many foods, it's difficult to get enough with diet alone. That’s why vitamins are often used.

14 The Sun Last Longer

When we make this nutrient from the sun, it remains in the body for about 4-8 weeks. When taken as a supplement, it's only around 2-4 weeks.

15 It Can Help Psoriasis

Some research suggests the vitamin can help cells with psoriasis to their normal.

16 Only UV B Rays Work

Sunlight is often divided into UVA and UVB rays. It's only the UVB rays the skin uses to convert cholesterol into this nutrient.

17 D's Other Names

Three other names for vitamin D are cholecalciferol, ergocalciferol and calcidiol.

18 Ask For This Blood Test

Ask your doctor to do a “Serum 25 (OH) D” Test. This is also called the 25-Hydroxy vitamin D test or “25 Vitamin D test.” That is the test you should get.

Here are at-home test kits too

19 The Type Used In Fortification

Fortified foods contain vitamin D2. D2 and D3 are equally effective.

20 These Groups May Be Vitamin D Deficient

Muslims, astronauts on long space voyages, submariners and those confined to nursing homes may also be low in this vitamin.

21 Vegans Should Take This Form

Vegans should look for vitamin D2 as this does not come from animal sources.

22 How Much Do My Levels Go Up?

As a rule, every 1000 IU of D will raise blood levels by 10 nanograms per milliliter of blood. So if the blood test said your level was 20 ng/ml, then taking 1000 IU would bring you up to 30 ng/ml.

23 It's Hard To Get Too Much

In his book, Dr. Hollick states people could take 10,000 IU for 6 months before they’d have to start wondering if they are taking too much.

24 Vitamin D Helps Strengthen Bones

When people don’t get enough D, they don’t absorb as much calcium to keep their bones strong. Normal bone loss is about 0.3 to 0.5 % per year. At the start of menopause, women can lose 3%-4% of bone mass per year. After menopause, it drops to about 2% per year.

25 Vitamin D And Prostate Cancer

Low D levels in the blood appear to increase the odds of getting prostate cancer. Higher D levels reduce the odds of prostate cancer.

26 The Colon Cancer Connection

One study noted elevated D levels appear to increase the odds of surviving colon cancer by 48%.

27 Can Vitamin D Help Diabetes?

Studies tend to show when we are deficient in D, insulin resistance – one of the hallmarks of metabolic syndrome (pre-diabetes) goes up. Increasing vitamin D may decrease metabolic syndrome and diabetes risk.

28 It May Help Autoimmunity Diseases

Autoimmune diseases are those where our immune system attacks us by mistake. Evidence suggests the nutrient may help keep the immune system healthy and reduce autoimmune diseases.  Autoimmune diseases are less likely in areas that get a lot of sunlight.

29 Vitamin D And MS

Multiple Sclerosis is an autoimmune disease where the immune system attacks the fatty covering  (myelin) surrounding nerves. It’s more likely to occur in areas where people get less sunlight.  Lack of the nutrient during younger years puts us at greater risk of getting MS in the future.

30 Makes Older Adults Stronger

Studies show D supplements increase strength in older adults. Who knew?

31 Vitamin D Helps Rheumatoid Arthritis

People with rheumatoid arthritis (RA) tend to be low in D and have more pain than those with higher levels.

32 It May Reduce Cavities

People with more cavities tend to have lower levels of D.

33 Vitamin D Alters Gut Bacteria

With all the talk these days about how to have a happy gut, add D to the list. Some research suggests it can alter the composition of the microbiome – bacteria inside of us.

34 It May Help Depression

Well done studies suggest a link between low D levels and depression and improvement of depression when the vitamin is supplemented. One review stated improvement in depression was significant when people took at least 800 IU per day.

35 Vitamin D May Help with Asthma

While research is needed there seems to be a  link between asthma and low D levels. Some research finds the vitamin as effective as medications. It’s a bit controversial so stay tuned.

36 Clinically Deficient In Vitamin D When…

When your blood levels are 20 ng/ml or less you are classified as “deficient.” I’ve known people whose levels were only 12 ng/ml.

37 Optimal Vitamin D Levels Not Known

Most experts agree people should be somewhere between 30 ng/mg and 100 ng/ml. Some advocate 40ng/ml – 50 ng/ml. The optimal amount would likely differ between medical issues and is best discussed with your doctor.

38 The Highest Risk Of Deficiencies Are…

One review of 4,495 people noted that overall, 42% of people were deficient. The highest rates of deficiencies were in blacks (82.1%) and Hispanics (69.2%).

39 Factors Related to Low Vitamin D Include

The following tend to be associated with deficiency:

• no college education
• being overweight/obese
• being in poor health
• having high blood pressure
• not consuming milk
• having low HDL (good) cholesterol levels

Mind you, this doesn't necessarily mean they are related. They might just be a coincidence.

40 Remember the Different UV Rays

UVA rays  “age” and cause wrinkles (A for aging), while UVB rays cause sunburn (B for burn) Vitamin D is only made from UVB rays.

41 Look for Broad Spectrum Sunscreen

Sunscreens that block both UVA and UVB rays are “broad spectrum.” If your sunscreen doesn’t say it's a broad spectrum, it probably only blocks UVB rays.

42 Vitamin D Drug Interactions

Talk to a pharmacist about your intake if you take medications. Possible interactions include cholesterol-lowering statin meds, ulcer meds, and high-blood pressure meds.

43 Does Window Light Count?

Generally, windows will filter out UVB rays, which are the rays that make this vitamin.  Windows don't filter out UVA rays which cause wrinkles and premature aging.

44 Do Lightbulbs Produce Vitamin D?

The light bulbs in your home do not produce vitamin D. You can purchase special sun lamps that will do this. Some light bulbs may list they produce UVB rays. Investigate those claims before you buy them.

45 Can We Absorb D In Orange Juice?

Orange juice has no fat but it turns out we can still absorb it in orange juice.

46 What's The Best Brand Of Vitamin D?

All quality-made vitamin D supplements would be expected to be the same. A supplement from company A and company B should be identical if they contain the same amount (say 1000 IU, for example).

More expensive brands are not better. While it's often recommended to look for the “USP” ( United States Pharmacopeia) label as a way to check for quality, I believe brands that have been around a long time- Walmart, Costco, Vitamin Shoppe or GNC brands – should be just fine to use.

47 Can Vitamin D Become Toxic?

It's unlikely that most people take a typical 1000 to 2000 IU supplement daily to develop toxicity. Even taking 10,000 IU daily would take months of daily use before it becomes toxic. A blood test would show elevated calcium (hypercalcemia). This can lead to kidney stones. Other vague signs of vitamin D overdose include:

1. constipation
2. increased thirst
3. confusion
4. depression

The best way to know for sure is to get a blood test.

48 Fish vs. Fish Oil Supplements?

Fish like salmon will have some of the vitamins, but fish oil supplements generally have none.

49 Why Is Vitamin D Measured In IU?

Because it's the convention used. It’s a measure of biological potency. IU stands for international units. It’s the convention used for things like vitamin A and D. 1 IU of vitamin D = 0.025 micrograms (mcg). So, if you take 1000 IU, this equals 25 micrograms. If you take 2000 IU, this equals 50 micrograms.

I hope this helped open your eyes to the importance of this vitamin.

Here's The Best Book I've Seen About It

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