Updated: June 15th, 2025
- Vitamin D deficiency can impact myriad health issues, including inhibiting your ability to lose weight.
- Vitamin D is the building block of the powerful steroid hormone calcitriol.
- Vitamin D helps maintain hormonal balance and a healthy immune system.
- Daily vitamin D recommendations are drastically lower than most people need, and can safely take.
- Some ways to avoid vitamin D deficiency include limited exposure to sun without sunscreen, eating whole foods high in vitamin D, high quality supplements, and testing levels to know exactly where you stand.
“You really think that my problems could stem from a lack of Vitamin D?” Mary had come to me after several frustrating months of doctor visits with no answers. She was exhausted, depressed, having stomach problems, couldn’t sleep, and she couldn’t lose weight no matter what she tried.
Vitamin D has been a hot topic for several years due to the number of health concerns vitamin D deficiency impacts, including: osteoporosis, depression, heart disease and stroke, cancer, diabetes, parathyroid problems, immune function, and even weight loss. But many health care professionals still don’t consider it when patients present with a range of symptoms that can be related to so many other conditions as well.
Many of today’s conventional clinicians received little to no training in medical school for this problem. They may not be in the habit of testing for vitamin D deficiency; even if they test, they aren’t familiar with effective treatment. But practitioners from both sides of the aisle are seeing more cases of vitamin D deficiency, so awareness is rising. A colleague reported that 85–90% of his patients don’t get enough D. And that’s consistent with what I see in my practice.
For more information, read our article, “Vitamin D Testing and Treatment – What You Need To Know.”
How can this be happening? And what should you do about it for you and your family? The answer isn’t as simple as drinking more fortified milk.
I’ve been testing and treating patients for vitamin D deficiencies for many years, and I know there are effective, natural strategies that work in most cases. Diagnosis is easy, and treatment with supplementation is easy, safe, affordable, and can bring wonderful results. Let’s explore the role of vitamin D in your health, and what you can do about it if you aren’t getting enough.
What does vitamin D do for the body?
Although this essential nutrient is called a vitamin, dietary vitamin D is actually a precursor hormone — the building block of a powerful steroid hormone in your body called calcitriol. It’s old news that vitamin D is critical to the health of our bones and teeth; deeper insight into the wider role vitamin D plays in our health is much more recent.
Vitamin D works in concert with other nutrients and hormones in your body to support healthy bone renewal — an ongoing process of mineralization and demineralization which, when awry, shows up as rickets in children and osteomalacia (“soft bones”) or osteoporosis (“porous bones”) in adults.
Researchers are discovering that D also promotes normal cell growth and differentiation throughout the body, working as a key factor in maintaining hormonal balance and a healthy immune system. It appears that calcitriol actually becomes part of the physical composition of cells, assisting in the buildup and breakdown of healthy tissue — in other words, regulating the processes that keep you well.
What’s more, evidence from studies tracking the prevalence of disease by geography and nationality shows clear links between vitamin D deficiency and obesity, insulin resistance, heart disease, certain cancers, and depression. Since most of these problems take many years to manifest, vitamin D deficiency has been overlooked by many providers for a very long time.
Your body can’t create vitamin D on its own. Instead, it’s designed to make it through sun exposure. In theory, you can make an ample supply of vitamin D with as little as a couple of hours per week in the sun — provided the UVB rays are strong enough. You can also ingest D through food, especially fatty fish like wild–harvested salmon. Plus, lots of foods are fortified nowadays, so vitamin D deficiency should be an easy problem to solve, right? But the truth is, we’re just not getting enough; and so many of us aren’t even close.
For more information, read our article, “Vitamin D — The New Giant For Bone Health And Overall Disease Prevention.”
Major vitamin D functions
- Supports key mineral absorption and metabolism (especially calcium and phosphorus in the blood and bones)
- Regulates normal cell differentiation and proliferation (e.g., prevention of cancer)
- Promotes insulin sensitivity and blood sugar regulation (insulin secretion)
- Regulates over 200 genes through binding to vitamin D receptors throughout the body
Vitamin D requirements
Though the daily recommended intake (DRIs) values have grown in recent years – to 600 International Units (IU) for ages 14-70 and 800 IU for those over 70 – they’re still woefully inadequate, especially for people who get limited sun exposure.
Some studies have shown that adults need 3000–5000 IU per day, and others indicate healthy adults can readily metabolize up to 10,000 IU of vitamin D per day without harmful side effects. Both the European Union’s Scientific Committee on Food and the US Food and Nutrition board list 4000 IU per day as the upper limit. But the latest science strongly suggests most adults should be taking more. What gives? I agree that testing and monitoring is necessary if you are taking more than that upper limit; my point is that vitamin D at doses far higher than today’s daily intake values appear to be safe – to promote optimal health, reduce the risk of many serious diseases, and even speed healing for serious health concerns.
Symptoms of Vitamin D deficiency
Vitamin D deficiency may be characterized by muscle pain, weak bones and fractures, low energy and fatigue, lowered immunity, depression and mood swings, and sleep irregularities. Women with renal problems or intestinal concerns (such as IBS or Crohn’s disease) may be vitamin D deficient because they can neither absorb nor adequately convert the nutrient.
The impact of vitamin D on health
Most people are aware that vitamin D has an impact on bone health and osteoporosis, particularly in postmenopausal women. But there are many other conditions impacted by vitamin D as well.
Evidence is mounting that vitamin D may protect against some cancers, particularly breast cancer, prostate cancer, and colorectal cancers. In fact, over 60 years of research have shown vitamin D supplementation or sunlight-induced vitamin D conversion to be associated with lower incidence of cancers.
Another area of vitamin D research is its relationship to depression. Seasonal affective disorder, or SAD, is a situational mood disorder brought on by decreasing daylight in the winter months. High doses of vitamin D during these months have proven to be a very effective natural remedy for SAD, leading most practitioners to believe that normal neurotransmitter function depends in part on adequate vitamin D synthesis.
Vitamin D levels are inversely related to those of melatonin, another mood-regulating hormone. Melatonin helps modulate your circadian rhythms, with darkness triggering melatonin secretion by the pineal gland within your brain, bringing you down gently at night for sleep. Insomnia, mood swings and food cravings are influenced by melatonin. Sunlight shuts melatonin production off, while triggering release of vitamin D — that’s why doctors recommend getting outdoors as a remedy for jet lag.
Vitamin D also plays a role in the way your body can regulate weight. In the past 20 years multiple studies have shown a correlation between higher blood levels of vitamin D and leaner body mass.
I think a critical piece to understand is the vitamin D connection with insulin resistance. Vitamin D deficiency may contribute to the wide set of disorders associated with metabolic syndrome (syndrome X), as well as to Polycystic Ovarian Syndrome (PCOS).
In a study published in 2004, the authors saw a 60% improvement in insulin sensitivity in healthy, vitamin D replete adults — and concluded vitamin D was more potent than two prescription medications commonly used to treat type 2 diabetes! But the cadres of drug reps spread out across America are not likely to be reminding your healthcare practitioner about this study. They are not likely to have heard about it!
For more information, refer to our extensive article list in our Insulin Resistance section.
What you can do to prevent vitamin D deficiency
Vitamin D deficiency may be a pervasive problem, but the best way to protect yourself from any deficiency is to build your health from the bottom up and let your body balance itself. I acknowledge the controversy over whether our primary source of vitamin D should be the sun, diet, or supplements. Which combination is best for you depends on many variables, including your age, nutritional status, and geographic location. In a world where so many of us are at risk of vitamin D deficiency, I recognize each of these sources as valuable. With this in mind I recommend the following steps to prevent vitamin D deficiency:
Allow yourself limited, unprotected sun exposure.
Head outside in the early morning and late afternoon (no more than 15 minutes for light-skinned individuals, 40 minutes for darker skin) — particularly between May and September if you live anywhere higher than about 35–40° latitude. (See the World Atlas to check out your latitude!). Pay careful attention – if you start to see redness on your skin, it’s time to cover up or head inside.
Not only will this help your body manufacture vitamin D, but you’ll also get some mood-boosting benefits. Most of us can sense the positive influence of sunlight in our own lives by the immediate lift we get from taking a walk outdoors on a beautiful sunny day. Soaking in the warmth of the sun is one of the most relaxing activities we share with all living creatures — just watch a cat dozing in a beam of sunlight.
Eat a diet rich in whole foods.
Nutrient-dense, fatty fish like mackerel and sardines are good sources of vitamin D. Egg yolks, fortified organic milk and other dairy products, and some organ meats (like liver) are also reasonably good natural sources of D. Because vitamin D is still somewhat of a mystery, we’re not sure which cofactors are important for its absorption, but we can surmise they are most fully present in wholesome food.
Take a top-quality multivitamin every day.
This will help fill in any nutritional gaps. For the biggest benefits, choose one that includes fish oil.
Check with your healthcare professional about vitamin D testing.
If you think you may be suffering from vitamin D deficiency, get a blood test and ask for the results. Although many conventional practitioners think a value of 20-60 ng/ml is normal, I like to see an optimal value of 50–70 ng/ml. Please see our article on testing and treatment for guidelines and precautions.
Discuss adding a vitamin D supplement to your diet with your healthcare provider.
If you don’t get out in the sun every day for 15 minutes in the early morning and late afternoon, consider supplementing with 1000–2000 IU of vitamin D3 per day — at least during the winter months! You may need higher levels to reap all the long-term health benefits vitamin D has to offer you, so talk it over with your healthcare provider. This is important for women of all ages — especially those over 50. If you do take higher levels, be sure to get follow-up testing to monitor your response.
Note that for a long time, vitamin D2 was prescribed for vitamin D therapy. I believe this form has more potential for toxicity and is much less effective than natural vitamin D3. Nowadays vitamin D3 supplements are widely recognized as the superior, more bio-ready form for use in the body.
MarcellePick.com has a range of high-quality, pharmaceutical grade supplements to enhance your health.
Remember to look at the whole picture
Keep in mind that in the end, optimal health is never about just one thing. Vitamin D is just one component of an ever-changing picture — your health is a work in progress that needs your consistent attention and support.
It may turn out that vitamin D is the key everyone’s been looking for, but more likely it is an important part of a far greater whole-health picture. What matters most is how you feel and what works for you. Remember Mary? I tested her, and sure enough, she was very low in vitamin D. Through a targeted treatment plan, we got her levels where they needed to be, and the issues that had been haunting her for months disappeared. I encourage you to investigate your personal vitamin D level with your medical practitioner as part of a comprehensive approach to your whole health.
