The Benefits of Vitamin D

Dr. Jolene BrightenPublished: Last Reviewed: Wellbeing Leave a Comment

It’s been estimated that 41% of U.S. residents have a vitamin D deficiency. Vitamin D benefits are huge in women's health, which is why this article is going to get you in the know on how to improve your levels.

We’re often told to soak up some sun to get vitamin D—but what does vitamin D actually do? And what are the benefits of vitamin D for women’s health?

Fertility, period cramps, bone density, autoimmunity, and even fibroids may see improvement by getting your vitamin D in check!

In this article, I’ll break down exactly what vitamin D is (spoiler alert: It’s actually a hormone!), why we need it, how vitamin D deficiency can impact our health, and how to increase our intake of this nutrient. 

What is Vitamin D?

Interestingly, vitamin D is actually a hormone produced by the kidneys! Vitamin D is a vital component for good health and vitality. It’s important for maintaining strong bones  (it’s a key player in calcium and phosphorus absorption), good immune health, endocrine (hormone) function, cardiovascular health, and can regulate hundreds of genes via the vitamin D receptor (VDR). Additionally, vitamin D may have some anti-inflammatory properties. 

Vitamin D deficiency can cause and exacerbate multiple health issues (e.g. autoimmune conditions and cardiovascular disease). It’s therefore important to maintain optimal vitamin D levels. 

Vitamin D Metabolism

Want to get nerdy with me? Sure you do! Ok, if you don’t then just scroll down to the benefits and how to get vitamin D info.

Before we jump in, let me explain that there isn’t a single form of vitamin D. The active form of vitamin D is the 1α, 25-dihydroxyvitamin D or vitamin D3 (calcitriol). You may have seen it on a lab test as 1,25(OH) Vitamin D. Cholecalciferol and ergocalciferol (D2) are inactive precursors that the body uses to make active vitamin D. This activation takes place in the liver and kidneys. 

Ok, so now you're in the know that when I say vitamin D here, I am talking about D3 or 1,25(OH) vitamin D.

How does Vitamin D help the body?

Vitamin D is important for many reasons (yeah, we're gonna get into a lot here). Without sufficient amounts, we cannot effectively absorb calcium, and our immune systems are more vulnerable. In addition, our periods can be painful, our fertility may suffer (men too), our skin can become dry and dull (potentially causing rashes), and our hair may even fall out when vitamin D levels in the body drop.

Can vitamin D affect my period?

Longer cycles? Be sure to check your vitamin D. Studies have shown that insufficient vitamin D levels (20-30 ng/ml) are associated with two times the increased likelihood a woman will have longer cycles compared to women who have a vitamin D level above 40 ng/ml. Additionally, there is a 30% increased chance your menstrual cycle length will be longer with every 10 ng/ml decrease of circulating vitamin D levels.

If you're experiencing long cycles (days between one period to another) then you'll want to keep reading to understand what levels are ideal on lab tests and how to increase vitamin D levels naturally.

Does vitamin D help with period cramps?

There are studies that have shown a significant reduction in period cramps after 8 weeks of supplementing at 50,000 IU daily in women who are deficient in vitamin D. These women saw a rise in their vitamin D blood levels that on average rose above 50 ng/ml. As you'll read below, this is a level considered sufficient by the Vitamin D Council.

While there are trials using doses of 50,000 IU, this isn't what we typically use in clinical practice. As a naturopathic physician who supports women's hormones and helps them troubleshoot the worst of period problems, I typically use a dose of 5,000-10,000 IU depending on what lab work shows. In addition, we retest after three months of therapy to determine how the individual is responding.

In my clinical practice we use a liquid Vitamin D3/K2 because it is easier to modify the dose to meet the individual's needs. Keep reading because I'm going to share with you what you blood levels should be at, different dosing considerations for supplements and how to acquire vitamin D through diet and lifestyle therapies.

Vitamin D fertility

Vitamin D has been shown to be beneficial to women's hormones and fertility.

Polycystic ovarian syndrome (PCOS) is one of the leading causes of infertility. In one study, it was found that supplementation with vitamin D showed improvement in overall vitamin D status, “leading to an improvement in the quality of embryos and a significantly higher clinical pregnancy rate.”

Implantation rates have also been shown to be higher among women with sufficient vitamin D undergoing IVF. In my practice, I run a vitamin D (among other labs) prior to referring to a reproductive endocrinologist (RE) so we can ensure a woman has the best nutritional status to make the RE's job easier and the IVF outcomes more successful.

Vitamin D during pregnancy

Women with adequate vitamin D status have been shown to have lower risk of pregnancy complications like preeclampsia and postpartum bleeding.

In a recent Cochrane Review on vitamin D supplementation during pregnancy it was stated: “Supplementing pregnant women with vitamin D alone probably reduces the risk of pre-eclampsia, gestational diabetes, low birthweight and the risk of severe postpartum hemorrhage.” They went on to say that randomized controlled trials are needed to evaluate the risks and benefits of vitamin D supplementation in pregnancy.

Vitamin D Uterine Fibroids

Supplementing with vitamin D has been found to reduce the size of uterine fibroids. In an animal study funded by the National Institutes of Health it was found that vitamin D may be a beneficial, non-surgical approach to shrinking fibroids.

Interestingly, African American women have been shown to experience fibroids at 2-3 times the risk of white women. As you'll read below, darker pigmented skin is associated with a higher risk of vitamin D deficiency.

Vitamin D and Diabetes

Animal studies have shown that vitamin D3 plays a role in insulin secretion from the pancreas. Interestingly, studies have suggested that vitamin D insufficiency or deficiency negatively impacts blood sugar regulation. 

If you are struggling with symptoms of hormone imbalance then this is a vitamin you want to get tested. Blood sugar dysregulation can be the underlying issue that is driving your symptoms and poor vitamin D status may be playing a role. The good news is that your doctor can easily test this important nutrient. 

vitamin d fertility

Promotes bone growth 

Vitamin D is very important for calcium and phosphorus absorption. It is required in order for us to effectively absorb calcium from the gut. And what are calcium and phosphate important for? Bone health!

Adequate levels of these nutrients are important for building strong bones with normal mineralization. 

Without adequate vitamin D (and, by extension, calcium), bones may become thin, brittle, and misshapen. 

This can lead to osteopenia (reduced bone mass) and osteoporosis (brittle or thin bones). And before you start thinking, “wait, isn’t that something that only happens to older women,” I want you to know that osteoporosis starts now and then presents later. Or in other words, you have to take care of your bones today to ensure you don’t develop the disease later. Optimal vitamin D and healthy hormones can help! 

Bones Influence Your Mood

New studies are also pointing to bones being involved in the “fight or flight response.” Yes, forevs we’ve thought that it’s only been the role of the adrenal hormones, epinephrine and norepinephrine, to activate this response. But as it turns out, your bones are also producing a hormone that may be involved with stress. We’re early in our understanding, but this supports the idea that your bones, muscle, and fat cells are also endocrine organs. 

Fight disease

According to research, vitamin D deficiency has been associated with higher risk of cancer, heart disease, MS, arthritis, and type 1 diabetes. 

One reason for this is possibly that vitamin D helps regulate the immune system. It also acts as an anti-inflammatory, so optimal amounts are really important. 

Additionally, research has shown that vitamin D supplementation can help protect you against the flu and respiratory tract infections. So too little vitamin D can render you more likely to contract these illnesses. 

Autoimmune Disease

I want to spend a little more time here because the highest risk population for the majority of autoimmune diseases are women.

What’s important to understand about autoimmune diseases like lupus, multiple sclerosis, Hashimoto’s thyroiditis, type 1 diabetes, psoriasis, and rheumatoid arthritis is that they are mediated by immune cells called T cells. Vitamin D3 has been found to modulate these T cells in such a way that the autoimmune attack on the body is diminished. Good stuff, right!?!?! 

The other interesting connection between autoimmunity and vitamin D is that the further people live from the equator (less sun exposure), the more people we see with autoimmune disease with multiple sclerosis being the most notable.

And it isn’t just specific for adults. In fact, there have been several prospective studies that suggest that for children adequate vitamin D in pregnancy through adolescence may decrease the risk of autoimmunity.

Does that mean just taking vitamin D will eliminate autoimmunity? Unlikely. Autoimmune disease, in my clinical experience, is multifactorial. But vitamin D undeniably plays a role.

While we don’t quite have enough evidence to state that vitamin D will prevent an autoimmune disease, there is a lot of evidence to suggest that both correcting insufficient or deficient levels, along with maintaining sufficient levels in the body may help decrease the risk of autoimmune disease. 

Eczema and Vitamin D

Eczema or atopic dermatitis tends to flare in the winter. In one study, as little as 1,000 IU/day for a month was shown to improve winter related eczema. There have been several randomized control trials showing that vitamin D therapy reduced severity and extent of the eczema rashes. Even a pharmaceutical version of Vitamin D called Calcipotriol in a cream applied to hand eczema has shown promise.

Vitamin D and Breast Cancer

Vitamin D is involved in the regulation of many genes via the vitamin D receptor (VDR), including the growth and differentiation of cells. Low vitamin D status has been associated with an increased risk of developing breast and colorectal cancer in observational studies. 

In ecological studies, it’s been observed that the higher latitude or further from the equator an individual resides the higher the mortality rate is with breast cancer. Other studies have shown no difference in risk of breast cancer. Conversely, in a meta-analysis of five prospective cohort studies and one retrospective, higher vitamin D in the blood was associated with a 33% reduction in risk of death.

Reduce depression

In the United States, it’s estimated that 14.8 million people have depression. Worldwide, depression is considered the leading cause of disability, affecting a whopping 121 million people. 

In a study examining the relationship between vitamin D and seasonal affective disorder (SAD), it was found that light therapy significantly improved mood. What this means is, for people who may experience depression seasonally (e.g. in winter), exposure to light might help. 

In winter, it’s darker longer, and we stay indoors more because it’s freezing outside. This leads us to get very little sunlight, which affects our vitamin D levels. So, getting more sun and increasing vitamin D could really help with mood disorders. 

Boosts weight loss

The World Health Organization has named obesity an epidemic of the 21st century. Obesity also increases the risk of vitamin D deficiency. 

In a study of 50 overweight and obese women, in a group of whom received vitamin D supplementation while the other group did not, it was found that vitamin D helped with weight loss. 

Obesity is associated with lower vitamin D levels because vitamin D synthesized by the skin or taken via supplement or diet can be sequestered in the fat cells. And while increased adiposity (fat cells) is a risk for developing a vitamin D deficiency, it isn’t just a matter of supplementing at the same dose as an individual with less body fat. In fact, trials have shown that when people with higher body fat are given the same dose of vitamin D as leaner participants their levels of vitamin D do not improve as expected.

Vitamin D Deficiency Symptoms

Getting a blood test is best to determine your vitamin D status. If you’re having any of these signs of deficiency then it’s a good idea to make an appointment with your doctor and discuss if vitamin D testing is right for you.

Frequent sickness 

Vitamin D is essential for maintaining a healthy immune system that can effectively fight illness. If you find yourself getting sick often, especially with viruses, it’s possible that you have a vitamin D deficiency. 


In a study of women who complained of fatigue, it was found that they were either deficient in vitamin D, or just did not have high enough levels of vitamin D (i.e. insufficient vitamin D). 

In another study, a woman who suffered from fatigue found symptom resolution by supplementing with vitamin D. Vitamin D may deficiency may be the cause of low energy levels in some individuals.

Muscle pain and weakness

Low vitamin D can present as muscle pain and weakness in adults and children. It appears to be most pronounced when levels drop below 20ng/dL. In fact, one study showed that in 150 people referred for non-specific muscle pain, 93% had a vitamin D deficiency.

Hair Loss

We all lose some hair each day. A little shedding is normal. However, if you’re pulling out handfuls of hair when you brush it, or see loads of hair going down the drain every time you wash it, it’s possible that your hair loss is becoming more severe. 

One of the most severe forms of hair loss, alopecia areata, is associated with vitamin D deficiency. In a study of 23 patients with alopecia, one common thread was that they all had very low vitamin D levels. 


Low vitamin D levels have been associated with increased risk for depression. 

Back pain

Do you suffer from chronic back pain, specifically lower back pain? Inadequate vitamin D could be the cause. This pain could be a symptom of osteomalacia, a type of bone weakening

Since we know that vitamin D is very tightly connected to bone health, it stands to reason that being deficient in vitamin D could cause bone pain. These are often mistaken for muscle pains, because we typically don’t expect our bones to hurt!

Osteoporosis and risk of fracture

Bone loss is multifactorial with nutrition status, weight bearing exercise and hormones all being important factors. Vitamin D deficiency has been found to be associated with increased risk of hip fracture and bone loss. This is in part due to the fact that if vitamin D is low then intestinal calcium absorption will also be low.


This is where vitamin D deficiency is quite extreme and the bones do not solidify in children. As a result, the weight bearing bones begin to bow.

Vitamin D Risk Factors

For some groups (despite spending safe amounts of time in the sun, and eating foods containing vitamin D), vitamin D deficiency is more likely. 

Dark skin 

People with naturally dark skin have a higher likelihood of being vitamin D deficient than those with light skin. This is because melanin (the pigment in our skin) doesn’t absorb as much UV radiation, making it more difficult for the body to synthesize vitamin D.

Being elderly

People as young as 50 have an increased risk of being vitamin D deficient. As we age, we become less effective at synthesizing vitamin D from sunlight. Additionally, the older we get, the more likely we are to stay indoors—and less time outdoors = less sunlight = less vitamin D.  

Celiac Disease

Diseases that impact your body’s ability to absorb nutrients can have long-lasting detrimental impacts especially as certain key nutrients become depleted. Vitamin D is often found to be low in those with Celiac disease.


Obesity is a worldwide health problem, especially in developed nations. Studies have shown a correlation between a high BMI and lower level of serum 25-hydroxy vitamin D. It has also been found that obese men and women are less likely to get vitamin D from dietary sources. Lastly, it’s possible that obese individuals expose less skin to the sun than their non-obese counterparts. 

Diets low in fish and dairy

Unfortunately, it’s very difficult to get enough vitamin D from diet alone. Fatty fish like salmon and mackerel (as well as fish liver oils) are probably the best dietary sources of vitamin D. It is also found to a lesser degree in beef liver, cheese, and egg yolks. 

Vitamin D deficiency is more common for those with milk allergies, lactose intolerance, and for those who follow a vegan diet. If you do not tolerate milk, then I wouldn’t advise introducing it into your diet as the only means to raise vitamin D status.

Even with the best diet and sunlight exposure, you may need supplementation so getting tested is best.

Countries with little sun

Because we need sunlight to get our vitamin D synthesis on, people in countries with little sunlight are vulnerable to vitamin D deficiency. In addition to getting some vitamin D from food (like fish and cheese), we need exposure to sunlight to ensure our vitamin D levels are optimal. 

However, even those in super sunny countries aren’t off the hook! Think about it: It’s summer. The sun is blazing. It’s humid. What’s the last thing you want to do? Go outside! So even though you may live in an area that gets plenty of sunshine, it might just be too uncomfortable to go outdoors. Or, it’s so hot that it really isn’t safe to be outside. This could very easily lead to vitamin D deficiency.

Spending too much time indoors

Today, the world is literally at our fingertips. We can buy clothes, food, toiletries, and other necessities online. We can text and call our friends. We can have takeout delivered to our door. We work from home or in office buildings. What’s the common thread here? Being inside. 

For many of us, there is just no real need to go outside. And by not spending time in nature and soaking up a few minutes of safe, healthy sunshine, we could very well be causing a vitamin D deficiency. 

No Gallbladder

If you’ve had your gallbladder removed, you’re more likely to have trouble absorbing fat-soluble nutrients. The gallbladder stores up bile that’s made by your liver and released when you eat to help fats be absorbed. Without your gallbladder, bile is released as it’s made which means there’s not typically enough around when you eat.

If your Vitamin D is still low despite supplementation and you no longer have your gallbladder, you may need additional digestive support to make sure fats including Vitamin D are properly absorbed.

Vitamin D Test

The best way to determine your vitamin D needs is to have lab testing. You can meet with your doctor to discuss testing or you can order vitamin D testing direct to discuss with your doctor.

The Vitamin D Council recommends maintaining serum levels of 50 ng/ml (equivalent to 125 nmol/L*), with the following reference ranges:

  • Deficient: 0-40 ng/ml (0-100 nmol/l)
  • Sufficient: 40-80 ng/ml (100-200 nmol/l)
  • High Normal: 80-100 ng/ml (200-250 nmol/l)
  • Undesirable: > 100 ng/ml (> 250 nmol/l)
  • Toxic: > 150 ng/ml (> 375 nmol/l)

How can you increase your vitamin D intake?

So maybe you’ve been reading and are getting a little freaked out because you’re checking a lot of those “risk factor” boxes. Don’t worry; I got you! 

I’ve got a few simple ways for you to increase your vitamin D intake. The same thing may not work for everyone, but I am sure you will find a method of increasing your vitamin D intake that works for you and your lifestyle. 


This is probably the easiest way to increase your vitamin D intake. Instead of drinking your morning cup of coffee inside, grab your mug and spend a few minutes outdoors. Reading a great book? Find a quiet, sunny spot at your local park (or in your garden, if you have one) and spend some time there. Instead of doing yoga in your living room, roll out your mat on the patio. 

It's important to note that your skin must be free of sunscreen and clothing to reap the most benefits from the sun. Additionally, you should try to be in the sun for a certain amount of time (e.g., 15 minutes) for optimal endogenous production.

These are all simple changes that can get you into the sun more. But always be aware of how hot it is and how strong the sun is. You never want to put yourself at risk for heatstroke or sunburn by spending hours in the midday sun. Find that balance, and try to get small amounts of sunshine. 

Let's have some real talk though, there have been studies to show that those who live in the sunniest of places, like Ecuador, still have vitamin D insufficiency/ deficiency. This is why it is best not to assume and instead, get tested!

You may find you need a supplement and there is no shame in that. Keep reading to learn about healthy supplementation.

Vitamin D Foods

If you cannot spend time in the sun for health reasons, live in an area that doesn’t get much sunshine, or just plain don’t like being out in the sun, eating foods containing vitamin D is a good alternative. 

Some foods that contain vitamin D include:

  • Fatty fish (e.g. salmon, mackerel, sardines)
  • Cod liver oil
  • Foods that have been fortified with vitamin D (e.g. milk, cheese, orange juice, cereal, and some non-dairy milk products)
  • Egg yolks
  • Beef liver

Vitamin D supplements

If you can’t get enough sun (e.g. you work in an office or live in a place with little sunlight), or your diet is low in vitamin D, supplements are a very useful option. In addition, if your lab testing reveals your are insufficient or deficient in vitamin D, your doctor will likely recommend supplementation.

It is important to select Vitamin D3 with K2 to increase your blood levels and prevent toxicity issues.

Dr. Brighten Vitamin D3/K2 is a naturally emulsified liquid vitamin D3 (and vitamins K1 and K2). It is highly bioavailable and concentrated, with 1ml offering 2,000 IU of vitamin D. 

A liquid supplement such as this is a good option because you can easily modify the dose that is best for you. 

The Vitamin D Council recommends the following maintenance dosages on days that you don’t sunbathe:

  • Children: 1,000 IU/ 25lbs of body weight, up to 125lbs (A 50lb child would need 2,000 IU)
  • Adults: 5,000 IU
  • Pregnant & Breastfeeding: 5,000 IU daily*

*Note that if mom is sufficient then it is unlikely baby also needs a vitamin D supplement.

Obese adults should consider a higher dose, not to exceed 10,000 IU. If you are taking a dose higher than 5,000 IU daily then it is wise to retest after 3 months of supplementation to monitor your levels and then every 6 months or as often as your doctor recommends.

If you struggle with absorption in your GI tract, another potential route is using topical Vitamin D, which might be helpful for those without a gallbladder, or who have high fat loss in the stool (also called steatorrhea).

Vitamin D Toxicity

There's no evidence to support the idea that vitamin D toxicity can develop from prolonged sun exposure. Vitamin D toxicity is often brought about by over supplementation (50,000 IU/day or more).

It's generally regarded that healthy adults taking less than 10,000 IU/ day of vitamin D will not develop vitamin D toxicity, although monitoring via blood work is best to understand what is true for you.

In adults who supplement with high dose vitamin D for long periods of time, they are at risk for kidney stones and calcification of their heart and kidneys.


For strong bones, a healthy immune system, and better moods, vitamin D is an incredible tool for your health toolkit. 

By getting plenty of sunshine (with common-sense precautions), consuming foods rich in vitamin D, and supplementing if necessary, you can help support optimal levels of vitamin D for your body.

Additional References

Kulie T, Groff A, Redmer J, Hounshell J, Schrager S. Vitamin D: An Evidence-Based Review. The Journal of the American Board of Family Medicine. 2009;22(6):698-706. doi:10.3122/jabfm.2009.06.090037.

Vitamin D Fact Sheet – National Institutes of Health

Holick MF. Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease. The American Journal of Clinical Nutrition. 2004;80(6). doi:10.1093/ajcn/80.6.1678s.

Wang H, Chen W, Li D, et al. Vitamin D and Chronic Diseases. Aging and disease. 2017;8(3):346. doi:10.14336/ad.2016.1021.

Penckofer S, Kouba J, Byrn M, Ferrans CE. Vitamin D and Depression: Where is all the Sunshine? Issues in Mental Health Nursing. 2010;31(6):385-393. doi:10.3109/01612840903437657.

Entezari M, Khosravi Z, Kafeshani M, Tavasoli P, Zadeh A. Effect of Vitamin D supplementation on weight loss, glycemic indices, and lipid profile in obese and overweight women: A clinical trial study. International Journal of Preventive Medicine. 2018;9(1):63. doi:10.4103/ijpvm.ijpvm_329_15.

Urashima M, Segawa T, Okazaki M, Kurihara M, Wada Y, Ida H. Randomized trial of vitamin D supplementation to prevent seasonal influenza A in schoolchildren. The American Journal of Clinical Nutrition. 2010;91(5):1255-1260. doi:10.3945/ajcn.2009.29094.

Ecemis GC, Atmaca A. Quality of life is impaired not only in vitamin D deficient but also in vitamin D-insufficient pre-menopausal women. Journal of Endocrinological Investigation. 2013 Sep;36(8):622-7. doi: 10.3275/8898.

Mahamid M, Abu-Elhija O, Samamra M, Mahamid A, Nseir W. Association between vitamin D levels and alopecia areata. The Israel Medical Association Journal. 2014 Jun;16(6):367-70.

Vitamin D for Pain – Pain Science

How much sun is enough? – SunSmart

Vitamin D Deficiency: A Common Risk Factor for Seniors – Parent Giving

Vanlint S. Vitamin D and Obesity. Nutrients. 2013 Mar; 5(3): 949–956. doi: 10.3390/nu5030949

Cortese M, Riise T, Bjørnevik K, et al. Timing of use of cod liver oil, a vitamin D source, and multiple sclerosis risk: The EnvIMS study. Multiple Sclerosis Journal. 2015;21(14):1856-1864. doi:10.1177/1352458515578770.

Juntongjin, P., & Pongprasert, R. (2019). Calcipotriol ointment shows comparable efficacy to topical steroids in chronic hand eczema. Dermatologic Therapy. doi:10.1111/dth.12956

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About The Author

Dr. Jolene Brighten

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Dr. Jolene Brighten, NMD, is a women’s hormone expert and prominent leader in women’s medicine. As a licensed naturopathic physician who is board certified in naturopathic endocrinology, she takes an integrative approach in her clinical practice. A fierce patient advocate and completely dedicated to uncovering the root cause of hormonal imbalances, Dr. Brighten empowers women worldwide to take control of their health and their hormones. She is the best selling author of Beyond the Pill and Healing Your Body Naturally After Childbirth. Dr. Brighten is an international speaker, clinical educator, medical advisor within the tech community, and considered a leading authority on women’s health. She is a member of the MindBodyGreen Collective and a faculty member for the American Academy of Anti Aging Medicine. Her work has been featured in the New York Post, Forbes, Cosmopolitan, Huffington Post, Bustle, The Guardian, Sports Illustrated, Elle, and ABC News. Read more about me here.