Dr. Michael Holick is one of the world’s leading authorities on vitamin D and bone health. His research in this area indicates that the deficiency in Vitamin D and calcium create a cascade of problems in your skeleton that most people, and even many doctors, don’t fully understand.
This post identifies two major bone health problems caused by Vitamin D deficiency. The first problem is osteopenia which could eventually lead to osteoporosis. The second problem (which is frequently overlooked) is osteomalacia. We discuss these issues in detail and identify what you can do to address these problems.
Summary: Vitamin D and Bone Health
This article explores how vitamin D deficiency creates two distinct but serious bone health problems, based on research by Dr. Michael Holick, a leading vitamin D expert.
The Two Bone Health Problems:
1. Osteopenia and Osteoporosis: When you’re vitamin D deficient, your body can’t absorb calcium effectively. To maintain critical blood calcium levels, your parathyroid glands release PTH hormone, which triggers a chain reaction that breaks down bone to release stored calcium. This continuous bone resorption leads to osteopenia (low bone mass) and eventually osteoporosis (brittle bones prone to fractures). This process is silent and painless.
2. Osteomalacia (Soft Bones): The same high PTH levels cause your kidneys to waste phosphate while saving calcium. Without adequate phosphate, your body cannot properly harden new bone matrix. This unhardened matrix swells like jello beneath the bone’s sensitive covering, causing deep, throbbing bone pain. This condition is frequently misdiagnosed as fibromyalgia, chronic fatigue syndrome, or depression.
Key Takeaways:
- Many people with chronic pain and fatigue may actually be suffering from undiagnosed vitamin D deficiency
- Get tested (25-hydroxyvitamin D blood test) to establish your baseline
- Most people require supplementation, especially in winter months
- Prevention is critical—by the time symptoms appear, significant damage has occurred
- Magnesium and adequate calcium intake are also important for bone health
Common Myths Debunked:
- You don’t need to take vitamin D with fatty foods (it absorbs well on its own)
- Showering after sun exposure doesn’t wash away vitamin D (it’s made in living skin cells)
- Magnesium doesn’t help absorb vitamin D, but it does support bone health in other ways
The bottom line: Vitamin D deficiency is preventable and treatable, but addressing it proactively is essential for lifelong bone health and quality of life.
Vitamin D, Calcium and Osteoporosis
Let’s begin with the relationship between vitamin D, calcium, osteopenia, and osteoporosis. When you’re vitamin D deficient, your body simply can’t absorb calcium efficiently from your food.
This triggers a critical problem, because your body prioritizes your blood calcium level above almost anything else. This level must be kept in a very tight range, as it controls everything from your nerve and muscle function to your basic metabolism.
Vitamin D Deficiency: Osteopenia and Osteoporosis
Here is happens when your vitamin D is low and your blood calcium level starts to dip:
- Your parathyroid glands, which have a built-in calcium sensor, detect this slight drop. They immediately increase the production of parathyroid hormone (PTH).
- Parathyroid hormone’s main job is to get blood calcium back to normal as fast as possible. It goes to your kidneys and tells them to activate more vitamin D, but this step doesn’t work well if you’re deficient to begin with.
- PTH’s other target is your skeleton, which acts as your body’s calcium bank. But PTH doesn’t awaken the bone-destroying cells directly. Instead, it triggers an indirect chain reaction.
PTH Stimulates Osteoblast Production
First, it interacts with your osteoblasts. These are the cells that normally build new bone.
However, the PTH stimulates these osteoblasts to produce a protein called RANK ligand. This protein then acts as a key, binding to immature cells (monocytes) in your bone marrow. This binding signal “induces” these small cells to fuse, forming a new, giant cell known as the osteoclast.
This newly formed osteoclast releases hydrochloric acid and enzymes to literally destroy your bone matrix. This process bores a small hole in your bone, releasing the calcium stored inside into your bloodstream.
Calcium Removal Reduces Bone Mineral Density
This action successfully brings your blood calcium back to normal. But the results can be dangerous: when you are vitamin D deficient, this bone resorption is happening constantly. You are gradually removing calcium and the very structure of your skeleton, day after day.
This slow, silent loss of bone mineral density is what leads first to osteopenia (low bone mass) and ultimately to full-blown osteoporosis, where bones become dangerously brittle potentially leading to hip or vertebral compression fractures.
Essentially, a vitamin D deficiency forces your body into a terrible trade-off: it sacrifices the long-term strength of your skeleton to keep your blood calcium stable for its critical moment-to-moment jobs.
Osteomalacia and Vitamin D
But there’s a second, less-known consequence of this process, and it explains the deep, aching pain that many vitamin D deficient people feel.
Remember that flood of parathyroid hormone (PTH)? It doesn’t just go to your bones. It also goes to your kidneys with two very different instructions:
PTH tells the kidneys to reabsorb any calcium about to be lost in the urine and put it back into the blood. This makes perfect sense; it’s another way to prop up those critical blood calcium levels.
At the exact same time, PTH tells the kidneys to waste phosphate, flushing this critical mineral out of your body.
Why is this problematic? Everyone focuses on calcium, but mineralizing bone is like making concrete. To get strong cement, you can’t just have cement; you need the right ratio of sand and water, too.
It’s the same for your skeleton. To build strong, hard bone, you need an adequate amount of both calcium and phosphate. This “calcium-phosphate product” is what allows your body to harden the new collagen matrix of your skeleton.
Vitamin D, Osteomalacia, PTH, Calcium and Phosphates
When you are vitamin D deficient and your PTH is constantly high (a condition called secondary hyperparathyroidism), you create a new problem. Your body is successfully saving your blood calcium, but it’s dumping your phosphate.
Now, you have an “inadequate calcium-phosphate product.” You can’t mineralize the new bone matrix your body is trying to build.
This unhardened matrix is like jello. It absorbs water and begins to swell, expanding underneath the periosteum, the highly sensitive, skin-like covering of your bone. This condition is called osteomalacia, or “soft bones.”
That hydrated, swelling “jello” under your bone’s covering starts to throb. Patients complain of a deep, persistent, aching bone pain. It’s a pain they feel when they sit down, when they lie down, and it’s often mistaken for muscle pain.
The Osteomalacia Misdiagnosis Problem
Dr. Holick has observed that osteomalacia is frequently misdiagnosed. Patients presenting with chronic bone and muscle pain are often told they have one or all of the following by their physician:
- Fibromyalgia
- Chronic fatigue syndrome
- Depression
- Or that they’re “doctor seeking”
In reality, many of these patients are suffering from vitamin D deficiency. When treated with adequate vitamin D supplementation, they often experience dramatic improvements in energy levels and significant reduction in the achiness and pain they’ve been experiencing.
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Osteomalacia, Osteoporosis and Osteopenia: Key Differences
The primary difference between osteomalacia, osteoporosis and osteopenia lies in what is wrong with the bone and whether it causes pain.
Osteomalacia vs. Osteoporosis
Think of osteoporosis as a problem of quantity and quality. High PTH levels create osteoclasts that remove bone and decrease its mineral density. This process is silent.
Osteomalacia, on the other hand, is a “mineralization defect” caused by the same high PTH, but this time by its effect of wasting phosphate. Without enough phosphate to combine with calcium, your body cannot harden its new collagen matrix.
This unhardened matrix becomes like “jello,” which swells under the bone’s sensitive covering. Unlike the silent osteoporosis, this swelling causes “throbbing, aching bone pain” even without a fracture, and is often misdiagnosed as fibromyalgia.
Osteomalacia vs. Osteopenia
Osteopenia is simply the first step on the road to osteoporosis. It is the initial stage of “low bone mass” caused by the same silent process of osteoclasts removing bone. Like osteoporosis, it is a problem of quantity and quality.
Osteomalacia, as mentioned earlier, is a completely different mechanism. It’s not a loss of bone mass, but a failure to harden the bone you have, leading to “soft bones.”
The key distinction is the symptoms: osteopenia is silent, while osteomalacia is characterized by the chronic, throbbing bone and muscle aches from that “hydrated jello” expanding under the periosteum.
Osteomalacia vs Osteoporosis
Both osteoporosis and osteomalacia significantly increase fracture risk, but through different mechanisms:
- Osteoporosis creates a porous, weakened bone structure prone to breaking under stress or impact.
- Osteomalacia creates poorly mineralized, “soft” bones that lack the structural integrity to withstand normal forces.
Combined, these conditions create a perfect storm for fractures, particularly in the hip, spine, and wrist, which are the most common osteoporotic fracture sites.
Role of Vitamin D Across the Lifespan
Dr. Holick emphasizes that vitamin D is “critically important from birth until death.” Here’s why each life stage matters:
Pregnancy and Infancy
Pregnant women are often vitamin D deficient, and this has consequences that extend to their babies. Studies have shown that vitamin D status in utero directly affects bone health at birth.
There’s also a critical misconception about breastfeeding: while breast milk provides exceptional nutrition, it contains essentially no vitamin D. Infants who receive breast milk as their sole source of nutrition will become vitamin D deficient, and their bones will not develop optimally.
Research by Dr. Bruce Hollis and Dr. Carol Wagner demonstrated that lactating women need to take 6,400 IU of vitamin D daily to ensure their breast milk contains enough vitamin D to meet their infant’s requirements.
This high dose is necessary because, unlike our hunter-gatherer ancestors who were outside daily producing thousands of units of vitamin D naturally, modern mothers are predominantly indoors.
Young Adults: The Silent Bone Loss
Many young adults in their 20s and 30s have perfectly normal bone density tests. However, Dr. Holick warns that subtle bone loss is often occurring beneath the surface.
Young professionals who:
- Work indoors all day
- Have inadequate calcium intake
- Are vitamin D deficient
are constantly removing small amounts of calcium from their skeleton. While the loss may only be an eighth to a quarter of a percent annually, multiplied over 20-30 years, this represents significant bone loss that should never have occurred.
This cumulative loss means you’ll enter your later years with less bone mass than you should have, setting the stage for earlier onset of osteopenia and osteoporosis.
How Much Vitamin D Do You Need for Bone Health?
Dr. Holick chaired the Endocrine Society practice guidelines back in 2010, with cancer recommendations in 2011, and all the members of the committee were experts in the field of pediatric, adult and elderly vitamin D and bone-related issues.
After reviewing carefully the literature, we concluded that for maximum bone health with no evidence of osteomalacia, your blood level needed to be 30 nanograms per milliliter or higher, which translates into European numbers as 75 nanomoles per liter.
The Institute of Medicine and many other government agencies will use 50 nanomoles per liter or 20 nanograms per milliliter, but in Dr. Holick’s opinion, that will not completely prevent you from having an increase in parathyroid hormone removal of calcium and matrix from your skeleton as well as causing osteomalacia.
What is Enough Vitamin D for Bone Health?
These results are based on a study done in Germany. This pathologist had 675 healthy German adults ages 20 to 90 years of age. They died unexpectedly in an accident of some sort, so he obtained a piece of their bone and their blood and he then looked with what’s called histomorphometry, looking very carefully at the structural components of that bone biopsy to look for evidence of osteomalacia.
He related it to blood levels of 25-hydroxyvitamin D to see no evidence of osteomalacia in 675 healthy adults. Your blood level needed to be 75 nanomoles per liter (i.e., 30 nanograms per milliliter). And so it was based on that information and also PTH levels will continue to decrease as you improve your vitamin D status. And it begins to plateau at around 30 to 40 nanograms per milliliter.
So it’s for those reasons that the Endocrine Society considered that for maximum bone health, you should really be at least 75 nanomoles per liter (30 nanograms per milliliter), and probably because of the vagaries of the assays out there, 40 to 60 nanograms per milliliter (100 to 150 nanomoles per liter) we consider to be ideal for your bone health.
How Do You Determine Your Vitamin D Level?
Forty to sixty ng/mL is a blood level target, not a dosage. You can’t directly convert blood levels to daily IU intake because everyone absorbs and metabolizes vitamin D differently.
However, here’s the general relationship:
To achieve and maintain 40-60 ng/mL blood levels:
- Most adults need approximately 2,000-4,000 IU per day
- Obese individuals may need 4,000-6,000 IU per day or more
Rule of thumb:
- Every 1,000 IU of daily supplementation typically raises blood levels by about 10 ng/mL (25 nmol/L) on average
- But this varies significantly by individual factors like body weight, baseline levels, genetics, and sun exposure
Dr. Holick’s recommendations:
- Adults: 1,500-2,000 IU per day as a baseline
- Obese individuals: 2-3 times more (3,000-6,000 IU)
Best approach:
- Get your blood levels tested
- If you’re below 40 ng/mL, supplement with 2,000-4,000 IU daily
- Retest after 3 months to see if you need to adjust
- Once at optimal levels, maintain with appropriate dosing
The only way to know for certain what dose YOU need is to test your blood levels before and after supplementation.
Dr. Holick's Three-Pillar Approach to Bone Health
Based on his extensive research and clinical experience, Dr. Holick recommends a straightforward three-part strategy for maintaining bone density and reducing fracture risk:
1. Adequate Calcium Intake
Ensure you’re consuming enough dietary calcium or supplementing appropriately. Calcium is the building block, but it needs vitamin D to be absorbed efficiently.
2. Optimal Vitamin D Levels
Supplementation is often necessary, particularly for those who:
- Live in northern latitudes
- Spend most time indoors
- Have darker skin (which requires more sun exposure to produce vitamin D)
- Are pregnant or lactating
- Are elderly (skin becomes less efficient at producing vitamin D with age)
3. Weight-Bearing Exercise
Weight bearing exercise provides the mechanical stress that bones need to maintain density. The impact of your feet hitting the ground (during brisk walking, for example) translates force to your hips and spine, stimulating bone maintenance and remodeling.
Dr. Holick reports that in his elderly patients with osteoporosis, this three-pillar approach, adequate calcium, adequate vitamin D, and regular weight bearing exercise, was sufficient to maintain bone density.
Vitamin D Intake During Winter
Many people dismiss their increased achiness and fatigue during winter months as being due to cold weather, overwork, or seasonal affective disorder. While these factors may contribute, Dr. Holick points out that much of this discomfort may actually be due to worsening vitamin D deficiency.
During winter:
- Sunlight is less intense and available for fewer hours
- People spend even more time indoors
- Skin exposure is minimal due to clothing
- Vitamin D production plummets
The result? Worsening osteomalacia and the characteristic throbbing bone pain that patients often attribute to other causes.
Taking Action: What You Need to Know
Understanding the mechanisms behind vitamin D deficiency and bone health is the first step. Here’s what you should do:
- Get Tested: Ask your doctor to check your vitamin D levels (25-hydroxyvitamin D blood test). This establishes your baseline.
- Consider Supplementation: Many people require supplementation to maintain optimal levels, especially during winter months. Dosing should be personalized based on your levels, latitude, lifestyle, and health status.
- Don’t Wait for Symptoms: By the time you have symptoms of osteomalacia or receive a diagnosis of osteoporosis, significant bone loss has already occurred. Prevention is far more effective than treatment.
- Think Long-Term: The bone health choices you make today affect your fracture risk decades from now. Young adults who optimize their vitamin D and calcium status now are investing in their future mobility and independence.
- If You’re Pregnant or Breastfeeding: Talk to your healthcare provider about appropriate vitamin D supplementation for both you and your baby.
Magnesium, Vitamin D and Bone Health
Magnesium is a very important component. I mean it’s a minor component of your bone, but independently magnesium actually will have some effect on your parathyroid glands and on enzymes that may be activating vitamin D.
So we always recommend, especially since elders seem to be more prone to magnesium deficiency, a magnesium supplement is a reasonable choice along with a vitamin D supplement. And we haven’t really talked about this at all, but you also have to make sure you have adequate calcium intake.
FAQs: Vitamin D and Bone Health
Here are some frequently asked questions about Vitamin D. Dr. Holick kindly addressed each of these during our interview.
Vitamin D Production and Aging
As an adult, does vitamin D production change as you age? In your fifties, sixties, or seventies?
There’s a lot of confusion out there that aging decreases the efficiency of your ability to absorb vitamin D. We did the study and showed that’s not true.
However, what is true is that your skin begins to thin as you age, and so the efficiency of producing vitamin D in your skin is less efficient at 70 than it would be at 20 or 30 years of age.
Studies have been done—and we’ve done some of them—to show that if you take elderly people, put them outside on a veranda and expose their legs and arms to sunlight, you can raise their blood level of 25-hydroxy vitamin D.
But again, I always recommend vitamin supplementation because, as you noted, time of day, season, latitude, skin pigmentation—you really have to be a hunter-gatherer outside, basically half-naked every day, like a Maasai herder, for example, in order to be able to make enough vitamin D.
Showering After Sun Washes Away Vitamin D
If you take a shower after you’ve been in the sun, do those things wash away or prevent the process of vitamin D from occurring? Am I correct?
No. I’m glad that you asked the question. It’s ridiculous to suggest that you should not take a bath after being exposed to sunlight, and the reason is that you’re making vitamin D in your living cells. You’re not making it on the surface of your skin. You cannot wash vitamin D off your skin or from your cells when you’re exposed to sunlight. So that is a myth.
So just on the skin washing—my understanding was that it was the interaction of the soap and then the oil on your skin that interfered with the process. That’s not correct?
Thank you for asking. It doesn’t make any sense. What’s happening is that your epidermis has several layers, right? And it’s the basal layer right next to the dermal capillary bed where most of it’s made. We published that some 40 years ago. So you are making it in living cells right next to your blood system, and so you can’t possibly wash this off.
Vitamin D Must Be Taken With Fatty Foods
Go on the internet and they say you have to have vitamin D supplement with fat, a fatty meal. Not true.
Vitamin D will be absorbed on its own on an empty stomach because it goes into the small intestine, and then chylomicrons are made. It’s absorbed into your lymphatic system, goes up into your superior vena cava, is dumped into your bloodstream, and then goes to your liver to get converted to 25-hydroxy vitamin D.
However, if you have Crohn’s disease, ulcerative colitis—we’ve done studies to show it markedly reduces your ability to absorb vitamin D. Celiac disease affects about 10% of the population who have celiac disease or gluten sensitivity, and they have a difficult time absorbing vitamin D. So typically when I see patients who are vitamin D deficient and I give them vitamin D and it didn’t rise very much, then I would work them up for celiac disease. And often that was the cause.
Just so that I could correct a mistake that I’ve been saying to everybody—make sure that you’re taking it with fatty foods. It doesn’t matter what they take it with?
Nope. Again, we did the study and we showed that in orange juice, on a piece of toast, or in corn oil didn’t make any difference at all.
Source of Vitamin D: Skim Milk vs. Whole Milk
But more importantly, what was interesting is that one of the reasons people thought that vitamin D is in milk is because of the fat, right? But the problem, of course, is that most people drink skim milk now that has no fat.
So we asked the question: What is your ability to absorb vitamin D from skim milk versus whole milk? And you’d be shocked at the answer, which is it’s better in skim milk than it is in whole fat milk.
And the reason is that when you are ingesting whole fat milk, you don’t absorb 100% of the fat. Some of it is lost and the vitamin D sticks with it. It’s a very small difference, but it was curious to me. Yeah, it’s a misconception out there. You don’t need fat in order to absorb vitamin D. Vitamin D is fat-soluble and is perfectly happy on its own.
Vitamin D from Sunlight vs. Oral Vitamin D Supplements
But also there’s an interesting other concept that we demonstrated, which is that when you take vitamin D orally, it rapidly goes up in your blood and then rapidly comes back down. But when you make it in your skin, it takes a while for it to be released into the bloodstream. So when you make vitamin D in your skin, it lasts two to three times longer in your body than it does if you take an oral dose.
Magnesium Is Important for Absorbing Vitamin D
And another myth out there is that magnesium is important for absorbing vitamin D, and that’s nonsense.
Does magnesium play a role though for osteoporosis if people are trying to increase their calcium?
So magnesium is a very important component, I mean, it’s a minor component of your bone, but independently magnesium actually will have some effect on your parathyroid glands and on enzymes that may be activating vitamin D.
We always recommend, especially for elders who seem to be more prone to magnesium deficiency, that a magnesium supplement is a reasonable choice along with a vitamin D supplement. And we haven’t really talked about this at all, but you also have to make sure you have adequate calcium intake.
Conclusion
Vitamin D deficiency isn’t just about weak bones, it’s about a complex cascade of hormonal and metabolic changes that simultaneously weaken bone structure and cause inadequate mineralization. The result is increased fracture risk and often debilitating bone pain.
The good news? This is preventable and treatable. With adequate vitamin D, calcium, and regular weight-bearing exercise, you can protect your bones and maintain your quality of life from young adulthood through your senior years.
As Dr. Holick’s research has shown time and again, vitamin D truly is critical “from birth until death.” The question isn’t whether you need it, it’s whether you’re getting enough.
About Dr. Michael Holick
Dr. Michael Holick established how numerous factors such as seasons, times of the day, skin pigmentation, sunscreen use, and latitude can influence how much vitamin D we can get from the sun.
He is the author of four books, including The Vitamin D Solution. Dr. Holick is an endocrinologist and professor of medicine, physiology and biophysics. He’s also the director of the Vitamin D Skin and Bone Research Laboratory, the director of the Helio Therapy Light and Skin Research Center, and the director of the Ehlers-Danlos Clinic Research Program at Boston University of Medicine.
Among his many accomplishments, he identified not only the primary circulating form of vitamin D in the blood, but other forms of vitamin D and their importance on health. Along with others, he helped develop the first clinical assays to measure different forms of vitamin D, guidelines on determining vitamin D deficiency and how to treat it, as well as sensible recommendations for sun exposure. It is a privilege to introduce you to one of the world’s leading authorities on vitamin D for your health from birth until death.
Margaret Martin
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