Most people are at least vaguely aware of Vitamin D’s importance in overall health.  But understanding its role when trying to get pregnant is essential in improving your fertility as you get older.  

So how does vitamin D improve fertility?  Studies have shown decreased vitamin D levels in women with low AMH, PCOS, uterine fibroids, and in men with poor sperm quality as compared to women and men without these health issues.

Far beyond vitamin D’s importance in absorbing calcium and promoting bone growth, vitamin D has very specific actions critical for optimal fertility health.  Whether you’re trying to conceive naturally or with medicated fertility treatments like in vitro fertilization (IVF), knowing your vitamin D level may be critical to your success in getting and staying pregnant.

Why is Vitamin D Important When Trying to Get Pregnant?

Adequate levels of vitamin D during pre-conception are required to ensure a healthy pregnancy.

One of its most important roles in fertility is during the implantation process and to protect the embryo so that the mother’s body doesn’t attack what is essentially a foreign body.  This is proven by the high concentrations of vitamin D in the uterine lining during the 1st trimester.

A study using egg donors further showed vitamin D’s influence on the uterine lining.  The results were a 31% live-birth rate in vitamin D-deficient recipients, compared with 59% among vitamin D-sufficient recipients.

What is known about Vitamin D’s importance to fertility includes its impact on: (study)

• AMH – Vitamin D stimulates anti-Müllerian hormone (AMH) production, which is a measure of ovarian reserve.  Vitamin D deficiency is associated with lower ovarian reserve.
• PCOS – Vitamin D supplementation improves insulin resistance and the effects of infertility treatment.  Obesity, vitamin D storage in fat tissue, and sun avoidance results in 65%–87% rate of Vitamin D deficiency in PCOS patients.
• Uterine fibroids – A common cause of infertility, fibroids appears more frequently in women with Vitamin D deficiency.  African Americans are 2-3 three times more likely to have fibroids than Caucasions, correlating with the observation that the average vitamin D levels are lower by almost 50% in African Americans as compared to Caucasians.
• Sperm quality – Low sperm count, motility, and morphology have been linked to low vitamin D levels.
• IVF – In one study, women with high initial vitamin D levels had a four time better chance for successful IVF procedure compared to the group with low levels.

What is the Best Source of Vit D?

Sunlight

We are solar-powered beings and require the sun for many of our biological functions.  However, being indoors for the vast majority of the day contributes to the epidemic of vitamin D insufficiency found in the majority of Americans.

Because 80% of the vitamin D your body makes is from sunlight and the remaining 20% comes from diet and supplements, the best way to increase vitamin D levels is to be in the sun.  

Spend 15-30 minutes daily, or about half the time it takes your skin to turn pink, in direct sunlight with NO sunscreen.

The goal is to get adequate sun and not burn.  Peak times are between 10am-3pm.

For light skinned people this may be only 15-30 minutes, but darker skinned people may need two hours or more in the winter.

Best Natural Food Sources of Vitamin D 

Vitamin D exists in two forms: vitamin D₂ (calciferol or ergocalciferol) and D₃ (cholecalciferol).

In animals, ultraviolet B radiation (UVB) converts cholesterol in the skin to D_3…thus the root “chole” in its scientific name, cholecalciferol.

D₂ is made in fungi (notably mushrooms) and yeast.

Vitamin D intake from foods is of minor significance compared to the sun because very few foods contain vitamin D naturally.

Although getting enough vitamin D from natural food sources alone is difficult, below are some of the best:

• fatty fishes like wild salmon, mackerel, sardines, herring, wild cod
• pasture-raised eggs
• grass-fed beef liver

Farmed fish and conventionally raised chicken and cows are fed GMO (genetically modified) corn and soybeans so do not develop sufficient levels of vitamin D.

Vegetarian Food Source of Vit D 

The only vegetarian source of natural vitamin D is mushrooms.

However, the form found in mushrooms, vitamin D₂, is not the same as that found in animal sources (vitamin D₃).

In fact, vitamin D₂ is not made in the human body at all and is less effective than the D₃ form that we make ourselves – no surprise there.

One study shows D₃

• Is 87% better at raising and maintaining vitamin D levels
• Produces 2-3 times more storage of the vitamin than D₂

Therefore, mushrooms should NOT be relied on as a natural food source of vitamin D.

Fortified Food Sources of Vitamin D

Most Americans get the majority of their vitamin D from fortified foods like milk, cereals, orange juice, and yogurt.

However, your body does not use vitamin D added to foods the same way as getting it from the sun or from foods that have vitamin D naturally in them.  This is because when you absorb the sun or eat real food, the synergistic effect of other vitamins, minerals, co-factors and enzymes in that food allow for optimal use by the body.

Without these complementary compounds, synthetic nutrients aren’t used in the same way as their natural forms

Furthermore, fortified foods are processed foods.

The focus of any fertility-enhancing diet is to eat more naturally nutrient-rich whole foods.

Decode Your DNA to Know If You are at an Increased Risk of Vitamin D Deficiency

Your DNA will give you an indication of your overall vitamin D status. 

On a practical level as you’re trying to get pregnant, this information will indicate how high your vitamin D supplement dosage should be to raise it more quickly.

Sequencing your DNA is easy with a service like 23andMe or Ancestry.com that provides your raw DNA data file.

In your raw genetic data file, search for “rs2282679” on Chromosome 4.

Because you get one copy of this gene from your mom and another from your dad, the gene you have is identified by a 2 letter combination.

If you have at least 1 copy of the G variant of rs2282679, you have a higher risk of lower vitamin D levels.  By knowing how well your body transports vitamin D to the target tissues like the uterine lining, you can adjust your supplement intake accordingly to raise your vitamin D levels more quickly.

Three possible genetic combinations exist:

• TT – normal vitamin D level
• GT – increased risk of vitamin D deficiency.
• GG – highest risk of vitamin D deficiency.

Supplementing with 1,000 IU of vitamin D₃ per day generally raises vitamin D levels by around 5-10 ng/ml.

For GT and GG people, they may require higher vitamin D supplementation doses to achieve the same levels as TT individuals.  Carrying at least 1 G variant can result in a 49% increased risk for vitamin D deficiency of <20 ng/mL. (study)

Is vitamin D your magic bullet to better fertility?  No, it’s not the only factor but it’s impactful enough to make sure you have adequate levels.

Action Steps to Getting Optimal Vitamin D Levels

1. Have your vitamin D level tested.  Ask your doctor to check your 25-Hydroxy Vitamin D status.  Alternatively, you can order it yourself here if you do not have health insurance or want to get it done more quickly.
2. Target an optimal level of at least 40 ng/mL.
3. If your level is below 40 ng/mL, start with 5000 IU per day, taken in the morning.  study Buy vitamin D as cholecalciferol in extra virgin olive oil, coconut oil, or flaxseed oil.
4. Get at least 15 minutes of direct sun without sunblock every day.  More time is needed if you are darker skinned.
5. Recheck your vitamin D levels every month.

Related Questions

How are vitamin D supplements made?

Animal-sourced vitamin D supplements in the form of vitamin D₃ (cholecalciferol) are made from the fat of lambs’ wool.  D₃ is what your body makes from sunlight.  

Plant-sourced vitamin D supplements in the form of vitamin D₂ (calciferol or ergocalciferol) is made from fungus or yeast.

Because D₃ is the form naturally made by your body, not D₂, use the D₃ form if you’re not vegetarian or vegan.

I don’t like to be in the sun.  Can I just take vitamin D supplements?

No.  The supplements are meant to bridge gaps from your nutrition and lifestyle.  The most efficient way your body produces vitamin D is with direct sun.

The sun is an underutilized free therapeutic tool.  In addition to making vitamin D, it is also essential to setting your circadian rhythm so your hormone levels are regulated and balanced optimally.  You’re getting a whole range of other fertility-boosting effects from being in the sun wisely.

Soy Ginger Salmon

Packed with protein, omega 3 fatty acids, vitamins, minerals, antioxidants, and, of course, vitamin D, salmon is one of the best foods to improve fertility quickly.

Enjoy salmon 3-4 times a week when trying to get pregnant.

Ingredients:

• 3 tbsp coconut aminos (soy sauce substitute)
• 1 tbsp toasted sesame oil
•  1 tbsp rice vinegar
•  2 cloves garlic — minced (about 2 teaspoons)
•  2 teaspoons grated fresh ginger
•  1/2 teaspoon garlic-chili paste or sriracha
•  1 pound wild salmon fillet, 1/2 inch thick
•  Optional: Chopped green onions, toasted sesame seeds, fresh orange

Directions:

1. Preheat oven to 400° F.
2. In a small bowl, mix the coconut aminos, sesame oil, rice vinegar, garlic, ginger, chili paste.
3. Place the salmon skin side down in an oven proof pan.  Brush sauce over salmon.  Reserve a few spoonfuls of the sauce for serving.
4. Bake for 8-10 minutes, or until cooked to desired doneness.  Don’t overcook or it will get really dry!
5. Serve immediately, topped with reserved glaze, chopped green onion, sesame seeds, and a squeeze of orange.

30-DAY SUN CHALLENGE

1. Make it a point to eat your lunch outside instead of in front of your computer.
2. After eating, walk with a co-worker until your lunch break is over.
3. Use sunscreen on your face and neck but keep your arms and legs (if possible) free of clothing and sunscreen.