Vitamin D

By Suzanne Fenske, MD, FACOG, ABOIM, MSCP

Why Women Need Optimal Vitamin D

Vitamin D is a critical nutrient for women’s health, and the benefits go well beyond bones. Women with health concerns, including pregnancy, PCOS, and perimenopause, all benefit from optimizing vitamin D levels. However, there is a lot of confusion about how much vitamin D you need, what optimal blood levels are, and if food alone is enough to get the benefits.

We’ll cover all these topics, and more, in today’s article. You’ll leave with a sense of how to optimize individual vitamin D levels through diet, lifestyle, and supplementation. Keep reading as we explore:

• What is vitamin D?
• Vitamin D food sources and sunlight exposure
• How much vitamin D do you need?
• Optimal vs. deficient blood levels
• Vitamin D supplementation for women’s health
• How to optimize vitamin D levels

What is Vitamin D?

Vitamin D is a fat-soluble vitamin. It’s essential, meaning required for life. However, unlike other vitamins and essential nutrients, vitamin D doesn’t only come from food. The body also makes vitamin D from cholesterol in the presence of ultraviolet (UVB) rays. Historically and traditionally, humans have gotten most of their vitamin D from the sun.

Vitamin D plays many vital roles in the body, and in some ways, acts more like a hormone than a vitamin. Vitamin D is required for:

• Calcium absorption, maintaining calcium blood levels, bone growth, and remodeling
• Immune system health, anti-inflammatory properties
• Metabolic health, including glucose metabolism and lipid balance
• Genetic expression, cell growth
• Ovulation, pregnancy, healthy aging, and other women’s health benefits we’ll discuss more below

Vitamin D Sources

There aren’t many foods that naturally provide high levels of vitamin D. Animal foods contain vitamin D3, which is the form that raises blood levels in humans. Plant foods don’t typically contain any vitamin D, except for sunlight-exposed mushrooms, which contain vitamin D2.

Food sources of vitamin D include:

• Fatty fish
• Cod liver oil
• Liver
• Egg yolks
• Cheese and butter, especially from grass-fed cows
• Fortified cow’s milk, fortified plant milks, and other fortified foods

As mentioned, the body also makes vitamin D in the presence of sunlight. However, the amount synthesized depends on several factors, including

• Skin color (dark skin blocks more UV rays)
• Time of day (10 am to 4 pm is best)
• Length of exposure (30 minutes or more, depending on other factors)
• Location (higher latitudes have fewer UVB rays)
• Time of year (many places don’t get UVB rays in the winter)

Living in northern climates and modern, indoor lifestyles make vitamin D synthesis challenging. Additionally, sunscreen also blocks UVB rays, which many people use for sun protection and to prevent skin cancer.

Combining the limited dietary sources with the challenges of making your own, vitamin D is one nutrient where supplementation is often required.

How Much Vitamin D?

The RDA (U.S. Recommended Dietary Allowance) for women is 600 IU of vitamin D per day. However, there is much debate around this recommendation being too low. A European consensus suggests 800 to 2000 IU per day may be more beneficial. Still, the average daily intake from food is well below this target, with women getting just 168 IU per day.

The better question may be how much vitamin D you need to maintain optimal blood levels of vitamin D? The answer may be different for everyone based on diet, sun exposure conditions, genetics, response to supplementation, and other factors.

Vitamin D Testing and Optimal Levels

The most helpful screening test is the 25-hydroxy vitamin D blood test, a simple test available through your doctor. Most labs will flag levels below 30 ng/mL as low and above 30 ng/mL as sufficient, but there is considerable debate about the optimal vitamin D levels in the blood.

Michael Holik, a researcher and leading expert on vitamin D, suggests a preferred vitamin D range of 40 to 60 ng/mL, with other studies suggesting optimal levels above 50 ng/mL. There may also be specific populations who benefit from even higher levels. It’s important to note that you can go too high; the upper range is typically 100 ng/mL. It can be challenging to meet and maintain optimal levels without supplementation.

Vitamin D Deficiency

Vitamin D deficiency affects bone health and overall health in children and adults. Deficiency in children presents as rickets, and deficiency in adults presents as osteomalacia (bone softening), along with other health conditions and risks.

Vitamin D blood levels below 20 ng/mL are most often the definition of deficiency; levels between 21 and 29 ng/mL represent insufficiency. Collectively, approximately one billion people worldwide have deficient or insufficient vitamin D levels, which increase the risk of mortality, infections (including Covid), and acute and chronic diseases.

Vitamin D for Women’s Health

Maintaining optimal vitamin D levels and using vitamin D supplements may offer specific benefits for women’s health. Let’s explore some of these benefits.

Bones

Vitamin D plays a critical role calcium metabolism and bone health. In postmenopausal women without osteoporosis, vitamin D supplementation improves bone remodeling. However, supplementation alone doesn’t reduce fracture risk, at least based on current data. Other factors certainly play a role, such as estrogen levels.

Pregnancy

Vitamin D is a vital nutrient for pregnancy and infant health. Vitamin C deficiency in pregnancy is associated with miscarriage and poor bone and teeth development. Supplementation during pregnancy, up to 4000 IU per day, may help mitigate these risks.

Cardiovascular Health

Heart disease remains the leading cause of death for women, with risks increasing substantially after menopause. Vitamin D plays a crucial role in cardiovascular health by reducing inflammation, regulating blood pressure, maintaining lipid balance, and promoting healthy arterial function. Still, some research suggests that vitamin D supplementation may not reduce cardiovascular risk and that other factors are also at play.

Metabolism

As cardiovascular changes occur during perimenopause and post-menopause, metabolic changes go hand-in-hand. With reduced estrogen levels comes decreased glucose sensitivity, altered lipid profiles, weight gain, and a general decline in metabolism. These metabolic changes are also associated with low vitamin D levels. Vitamin D supplementation may help maintain glucose sensitivity and prevent metabolic disorders in the future.

Body Composition

A new study (in preprint) suggests that vitamin D influences body composition and the utilization of energy stores. Vitamin D supplements may help direct excess calories toward muscle growth rather than fat storage. This research is great news for women, particularly those in perimenopause, and another reason why optimizing vitamin D levels may benefit overall health.

PCOS

Women with polycystic ovary syndrome (PCOS) may also benefit from higher vitamin D levels, not only in pregnancy, but before pregnancy as well. This systematic review suggests that vitamin D supplementation in women with PCOS results in higher ovulation and pregnancy rates, and lower androgen levels.

How to Increase Vitamin D

Vitamin D alone isn’t a magic cure-all pill, but may enhance how the body functions and promote overall health and wellness for women, along with some of the specific bone, immune, and other benefits outlined in this article.

Here are some ways to optimize your vitamin D levels:

• Get tested. At TārāMD, we always test and monitor vitamin D levels as part of your comprehensive care. We help determine what optimal blood levels look like for you and the supplemental doses required to reach and maintain these levels.

• Include vitamin D-rich foods. We always advocate a food-as-medicine nutrition approach, and eating vitamin D-rich foods is a helpful way to consume some vitamin D and other fat-soluble nutrients, provided these foods fit into your nutrition plan. However, it is challenging to obtain enough vitamin D from food alone, and supplementation may be necessary.

• Enjoy safe sun exposure. A starting point may be 30 minutes of peak sun exposure (when available) to arms and legs without sunscreen, but you may need more or less time based on what works for your body. Getting outdoors during the day also benefits sleep, the nervous system, and physical health.

• Supplement. Choose vitamin D3 supplements from a reputable source and consume them with food so they digest along with fat. Vitamin D doesn’t work alone, and you may also need to optimize vitamin K2, magnesium, and other nutrient levels. Don’t worry, you don’t have to figure it out on your own. We are here to help!

Vitamin D isn’t a straightforward nutrient, and there is a lot of nuance in what levels are best for you and how to achieve those levels through the available sources. When it comes to vitamin D, there isn’t a single recommendation for all women, which is where personalized, integrative care comes in. At TārāMD, we help you understand and integrate all of the pieces of your healthcare plan, including vitamin D, to help you reach your goals and live a long, thriving life.

References

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