In Vermont, the days are now short and winter is here. That means less sunlight. For those who like to get a natural dose of Vitamin D by heading outside, the options are limited and that’s a problem.
Your body needs Vitamin D for bone growth and health and other important body functions. But many of us are Vitamin D deficient. Vitamin D deficiency is linked to breast cancer, colon cancer, prostate cancer, heart disease, depression and weight gain.
Here to talk to us about Vitamin D and how to get more of it and why are Bridget Shea, RD, and Emily Clairmont, RD. Both are registered dieticians at the University of Vermont Medical Center.
Why do we need Vitamin D?
Shea: Vitamin D is most often associated with bone health and strength, because of its essential role in regulating calcium and phosphorous. Research suggests that sufficient levels of Vitamin D might slow bone loss as a part of the natural aging process, help prevent osteoporosis, and reduce bone fractures.
We also know that Vitamin D is active in many tissues and cells and even controls some genes, including those associated with cancers, autoimmune diseases and infections. Researchers demonstrate that Vitamin D can reduce cancer growth and plays a crucial role in our immune system and our ability to fight infections.
Through research we have found that many cells in a variety of tissues and organs in the body have Vitamin D receptors, which leads us to believe that there are functions of the vitamin we don’t yet know about. Vitamin D might have hormone-like qualities, meaning that the vitamin affects the activity of other parts of the body and acts as a messenger that controls activities throughout the body.
How much Vitamin D do we need?
Clairmont: The amount of Vitamin D recommended is currently in debate. Two main organizations and institutions, the Institute of Medicine and the Endocrine Society, have varying opinions and recommendations for how much Vitamin D we need and this ranges, depending on your age.
|Daily Vitamin D intake|
|Infants||1-18 years||19-70 years||71+ years|
|IOM||400 IU||600 IU||600 IU||800 IU|
|Endocrine Society||400-1000 IU||600-1000 IU||1500-2000 IU||1500-2000 IU|
Your body produces Vitamin D when your bare skin is exposed to direct sunlight. This form is called Vitamin D3. Some plants also have the ability to produce Vitamin D when exposed to sunlight. This form is called Vitamin D2. Both forms have the ability to be converted to the active form of the vitamin and used throughout the body. D3 lasts longer in the body than D2, and therefore could potentially have a longer-lasting effect on blood levels.
What foods contain Vitamin D?
Clairmont: Fortified foods are one of the main sources, meaning that it’s been added to a food that doesn’t naturally contain Vitamin D or contains it in small amounts. So, milk, yogurt, orange juice, cereals, margarine are fortified with Vitamin D2. We are also starting to see food products fortified with Vitamin D3.
Mushrooms can be an excellent source of the vitamin. Some mushrooms are exposed to UV light when they are grown, and being a plant, they have the ability to produce Vitamin D2 from that UV light exposure. This is something that you can replicate at home, even if you purchase dried mushrooms. If you expose them to direct sunlight, they have the ability to produce Vitamin D2. Egg yolks also contain Vitamin D3. Another good food source is cold water fish and fish liver oils. These are the most robust whole food source of Vitamin D, and these are all in the Vitamin D3 form.
Cod liver oil which is commonly found in grocery stores and has about 1300 international units (IUs) of Vitamin D3; whereas, a three-ounce cut of salmon has about 450 IUs of Vitamin D3. We can compare that to fortified milk, which has about 115 to 125 IUs of Vitamin D2 per 8 oz glass.
How do we know if we’re getting enough Vitamin D?
Shea: It’s estimated that as many as one billion people could be deficient in Vitamin D worldwide. That’s partially due to how we obtain the vitamin.
We get the vitamin mainly from direct sun exposure, as well as through food, but there is a limited amount of foods that have vitamin D, so most of it is coming from our skin’s ability to produce vitamin D. A lot of things will impact how much Vitamin D we can make: season, time of day, the length of day, how cloudy it is, the amount of smog, the amount of melanin in the person’s skin, clothing, and wearing sunscreen.
We all know that we should wear sunscreen when we’re exposed to the sun to prevent sunburn, but sunscreen over eight SPF will block the rays which produce vitamin D. You need at least 15 to 20 minutes of near full body sun exposure on most days in order to get enough Vitamin D. At our latitude in Vermont, we don’t produce any Vitamin D for most of the year, specifically from November to April, when the angle of the sun is such that there are reduced UVB rays. Anywhere in the US above 37 degrees north in latitude, which is the majority of the population of the US, we’re not producing any vitamin D through the sun, through the winter months.
For most people, a supplement is necessary during the winter, and sometimes even during the summer months.
Who is at risk for Vitamin D deficiency?
Shea: There are a lot of groups at risk for Vitamin D deficiency. Those include breastfed infants, if their mother is not getting enough Vitamin D. Older adults whose skin is less able to produce Vitamin D, maybe spend more time inside and are less likely to eat sources of Vitamin D. People with limited sun exposure, either due to their job, limited mobility, choice of clothing including wearing clothing that covers a lot of their skin. Those with darker skin, because more melanin reduces the skin’s ability to produce Vitamin D. People who have any chronic condition that affects their ability to absorb fat, because Vitamin D is a fat soluble vitamin, so fat is necessary to help our bodies absorb it.
Individuals who are either overweight or obese are more likely to be deficient in the vitamin. It’s thought that perhaps the subcutaneous fat could sequester the vitamin and limit the amount that’s circulating and that’s available. Then also people who are vegan or don’t consume fortified foods may be at increased risk.
Can you get a vitamin D test to find out where you stand?
Shea: You can get a Vitamin D test. It’s a simple blood test that your doctor could order. This blood test will test for levels of 25 hydroxy Vitamin D which is a precursor for the active vitamin. I think that anyone who meets the criteria for being at increased risk of Vitamin D deficiency should ask their doctor about getting a blood test. Also, if you’ve been supplementing with Vitamin D, it’s important to get a blood test to make sure that your levels are either not too high or not too low.
Clairmont: There is an upper limit for Vitamin D intake associated with Vitamin D supplementation and that is determined to be 4000 IUs for individuals who are nine years or older. Most studies that look at Vitamin D toxicity look at intakes between 10,000 and 40,000 IUs per day.
Does taking a Vitamin D supplement interact with other medications?
Clairmont: It does not appear that supplementing with Vitamin D will affect any medications. However, there are several medications known to interfere with Vitamin D metabolism. So, what we see is that some medications may affect Vitamin D levels in our bodies.
It’s best to ask your doctor if any of your medications are known to interfere with any vitamin or mineral, not just Vitamin D. Then, of course, it’s always an option to talk to your provider about a referral to a dietitian if you want to discuss possible drug nutrient interactions.