Vitamin D is an important vitamin with powerful effects on several systems throughout the body. Obtaining sufficient vitamin D whether from food sources, the sun or supplements, is important for everyone. But women especially will want to take note making sure their vitamin D status is adequate.
What is vitamin D?
Vitamin D is a fat-soluble vitamin that acts as a hormone. It is nicknamed the sunshine vitamin as it can be made in the skin with exposure to ultraviolet light. Because vitamin D can be made in the body, it is essential in the diet only when exposure to sunlight is limited or the body’s ability to synthesize it is reduced. Whether vitamin D is obtained from food sources or the sun, it is inactive until it is modified by biochemical reactions in the both the liver and the kidneys.
Vitamin D has many important functions in the body including:
- Mineralization of bones and teeth
- Absorption of calcium and phosphorus
- Cell differentiation
- Blood pressure regulation
Causes of vitamin D deficiency in women
Women appear to have lower vitamin D levels than men for several reasons:
- Women tend to have more body fat than men. Being obese or having more body fat is an important factor in lowering vitamin D levels because fat cells absorb vitamin D and keep it from circulating throughout the bloodstream.
- Women tend to spend less time outdoors than men with adequate exposure to the sun. Women may also be more likely to use sunscreen blocking UV light for making vitamin D in addition to wearing hats or clothing with long sleeves or pants.
- As we age, whether a woman or man, less vitamin D is absorbed from dietary sources and our bodies produce less vitamin D in our skin from the sun.
- If a woman lives above the 42nd parallel – from Chicago or Boston north – the months of November through February do not produce sufficient vitamin D even on a sunny day.
Testing for vitamin D status
Vitamin D status is checked with a blood test called a 25(OH)D blood test. This can be done at a doctor’s office and it will show whether a person is getting enough vitamin D or not and if they need to take a supplement or not.
Depending on what organization you trust more on the results of this test and what your physician recommends, the ranges of vitamin D status vary as to whether a person is considered deficient, insufficient or sufficient in their vitamin D status:
If you go by the Vitamin D Council, they recommend the following:
Deficient – 0-30 ng/ml
Insufficient – 31-39 ng/ml
Sufficient – 40-80 ng/ml
Toxic – >150 ng/ml
The Endocrine Society follows and recommends these ranges:
Deficient – 0-20 ng/ml
Insufficient – 21-29 ng/ml
Sufficient – 30-100 ng/ml
What does a vitamin D deficiency mean for a woman?
If a woman is deficient in vitamin D, it can affect her health in many ways:
- Breast cancer – Studies have shown women with sufficient vitamin D levels had a 45% decreased risk of breast cancer. Other studies have found that women diagnosed with breast cancer had, on average, lower blood levels of 25(OH)D.
- Ovarian cancer – The impact of vitamin D on ovarian cancer has not been as well studies but it is reported to have a protective effect. A recent study found that sufficient vitamin D status appears to delay progression of ovarian cancer.
- Cardiovascular disease – A growing number of studies point to vitamin D deficiency as a risk factor for heart attacks, congestive heart failure, peripheral arterial disease, and strokes. Even though more large scale studies are required, a recent 2016 study suggest that daily vitamin D supplementation may reduce cardiovascular risk factors.
- Depression – There have been studies suggesting that supplements of vitamin D may improve mild depression. At this point, treatment with high dose supplements of vitamin D for depressive symptoms is considered experimental and should only be used with medical supervision.
- Lupus – Lupus is a chronic autoimmune disease that can affect almost any organ system in the body with multiple symptoms. About 9 out of 10 adults with lupus are women ages 15 to 45. Vitamin D has been found to have effects on immune function and inflammation with studies suggesting a relationship of vitamin D to autoimmune conditions. This may suggest a possible connection of low vitamin D status and lupus.
- Osteoporosis – Postmenopausal women are at a higher risk of the brittle bone disease of In order for calcium to be absorbed and deposited into bone, there must be sufficient vitamin D for this to happen. Women who have had a low calcium intake over the years along with insufficient vitamin D, are more likely to develop osteoporosis as they age. Women obtaining adequate vitamin D along with calcium throughout their lifetime appear to have a reduced risk of osteoporosis.
- Fatigue and tiredness – An often overlooked potential cause of chronic tiredness is vitamin D deficiency. Several studies have shown a relationship between vitamin D and fatigue in women with blood levels under 20 ng/ml or 21-29 ng/ml compared to women with blood levels over 30 ng/cl.
Recommendations and sources of vitamin D
The current Institute of Medicine Guidelines for vitamin D are as follows:
- Infants 0-12 months – 400 IU (International Units)
- Children 1-13 years – 600 IU
- Adolescents 14-18 – 600 IU
- Adults 19-70 years – 600 IU
- Adults 71 or older – 800 IU
- Pregnancy – 600 IU
- Breastfeeding – 600 IU
Best sources of vitamin D include the following:
- Sunlight – Between 10-20 minutes of sun exposure on arms and legs or face 3 times weekly between 10 am to 3 pm.
- Food sources:
- Cod liver oil, 1 tablespoon – 1360 IU
- Cooked salmon, 3.5 ounces – 400 IU
- Sardines in oil, 1.75 ounces – 250 IU
- Tuna in oil, 3 ounces -200 IU
- Vitamin D fortified orange juice, 1 cup – 142 IU
- Vitamin D fortified milk, 1 cup – 98 IU
- Vitamin D fortified yogurt, 6 ounces – 80 IU
- Egg yolk, 1 -20 IU
- Vitamin D3 supplements – Best to consult with your physician on the amount to take. Most adults can safely take up to 2000 IU of vitamin D3 a day for maintenance.