Hi friends! Today we are chatting about Vitamin D, another common nutrient of concern for people on plant-based diets. Heck, this is a nutrient lots of people are concerned about, and the vitamin often comes up in the popular media. So what is Vitamin D? What is the “vitamin D controversy?” How do you know if you are vitamin D deficient? Read on for more vitamin D information!
Disclaimer: As always, this is general information intended for healthy adults. Your needs may vary based on medical status, lifestyle, or life-stage. Please never replace generalized health information you’ve read online with individualized clinical care.
What is vitamin D?
Vitamin D is a fat-soluble vitamin that is found naturally in a very small number of foods. Most people get their vitamin D from fortified foods, and/or the sun.
There are two main dietary forms of vitamin D: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol), which differ in their side-chain structure.
Vitamin D2 is manufactured by UV radiation of ergosterol in yeast, and D3 is manufactured via irradiation of 7-dehydrocholesterol from lanolin. Lanolin is a sheep product, and thus, some do not consider this form of vitamin D purely vegan*.
Both D2 and D3 are well-absorbed. It seems many believe that D3 is somehow superior; in reality, both are considered to be well-absorbed and effective at raising serum levels of vitamin D, with the only major difference being that at very high doses, D2 may be less potent than D3.
*This is why some people do not consider fortified cereals like Cheerios to be 100% vegan; If you are vegan and confused on what to think on the topic, as I am no moral authority on the topic, I encourage you to make the judgement that feels right to you.
What does vitamin D do?
Vitamin D has many functions in the body. It helps promote calcium absorption in the gut by up-regulating a transcription factor that leads to more calcium receptors to rise to the surface of the intestinal tract, and take in calcium. This helps the body maintain adequate blood levels of calcium and phosphate, which support normal mineralization of bones.
Vitamin D is also important for bone growth and remodeling, as well as cellular growth, immune and neuromuscular function. It can also help play a role in reducing inflammation, and many genes that encode proteins that regulate cell proliferation, differentiation and apoptosis are modulated in some capacity by vitamin D.
How much vitamin D do you need?
The RDA for vitamin D is listed in IU and mcg below. For reference, 40IU is equivalent to 1mcg.
- 0-12 months: 400IU (10mcg)
- 1-13 years: 600IU (15mcg)
- 14-70 years: 600IU (15mcg)
- >70 years: 800IU (20mcg)
- Pregnant/breastfeeding: 600IU(15mcg)
What foods contain vitamin D?
As mentioned above, very few foods naturally contain vitamin D. Some fatty fish (like tuna, salmon, and mackerel) contain good sources of vitamin D, and small amounts can be found in egg yolks and beef liver.
Some mushrooms contain vitamin D2, although the amounts they contain varies. Treating mushrooms with UV radiation has been shown to increase their vitamin D2 content.
Most Americans get the vitamin D in their diet from fortified foods. Milk, for example, is voluntarily fortified in the United States, and contains about 100IU/cup. Plant-milks are also often fortified with vitamin D; the exact amount varies brand to brand, so be sure to check labels.
Cereal is also often fortified with vitamin D, although organic and natural brands are typically not fortified. Again, read labels to check how much your favorite products have!
Here are some food sources of vitamin D:
- Salmon (3 ounces): [447IU/112% DV]
- Fortified orange juice (1 cup, check labels as fortification values vary): [137 IU/34% DV]
- Fortified milk (1 cup): [115-124IU/29-31%]
- Mushrooms (1 cup): [~2-17IU, depending on variety, 0.3-3%]
- Swiss cheese (1 ounce): [6IU/2%]
- Fortified cereal: Example – Cheerios (1 cup): [3.4ug/10%]
Vitamin D from Sun Exposure
That’s right, vitamin D, the “sunshine vitamin,” can absolutely be obtained from the sun. In fact, a lot of people meet at least some of their vitamin D needs via sun exposure.
Vitamin D is the only vitamin you can make endogenously (meaning on your own) in your skin, which makes it a pretty neat vitamin!
How? UVB radiation with a wavelength of 290-320 nanometers can penetrate uncovered skin and covert a compound known as 7-dehydrocholesterol to previtamin D3, which then becomes vitamin D3.
Cloud cover, the season, time of day, smog, sunscreen, and melanin content of the skin can all impact the amount of vitamin D synthesized in the skin. Complete cloud cover reduces your ability to make vitamin D from sunlight by 50%, and severe pollution can reduce this ability by up to 60%. Sunscreen with SPF of greater than 8 blocks vitamin D-producing UV rays.
Because of all of the variables involved in the body’s ability to create vitamin D from sunlight, it is difficult to give a general guideline for sun exposure to meet vitamin D needs, however, some suggest between “5–30 minutes of sun exposure between 10 AM and 3 PM at least twice a week to the face, arms, legs, or back without sunscreen” might be sufficient.
That said, exposing your skin to the sun without sunscreen carries its own set of risks, namely sunburn, photoaging (aka wrinkles), and skin cancer.
What happens if you don’t get enough vitamin D?
Inadequate vitamin D consumption is linked to higher risks of developing osteoporosis, because not getting enough vitamin D may limit the amount of calcium your body is able to absorb.
Vitamin D deficiency is also associated with rickets, a condition in which bones bow.
There is some evidence that not being vitamin D deficiency is associated with lower risks of certain cancers and type 2 diabetes, hypertension (high blood pressure), and MS; however, these conclusions have been drawn from studies are either epidemiological in nature, and/or done on animals, so for now, interpret these results with caution.
Who is at risk for not getting enough vitamin D?
People who do not consume fortified foods (like fortified milks, plant-milks, orange juices, and cereals), people who don’t eat much fatty fish, and/or those who have malabsorption issues (generalized, as well as fat-malabsorption issues) may be at risk for vitamin D deficiency.
Individuals who do not spend much time in the sun, and those who have more melanin in their skin, may also be at higher risk of vitamin D deficiency.
Also, breastfed infants should get a vitamin D supplement to meet their needs, as breastmilk is typically inadequate.
Am I Vitamin D deficient? What’s the controversy?
Have you ever heard of the vitamin D controversy? Yes? No? Maybe only if you’re weird like me and spend lots of time reading nutrition stuff? Anyways, long story short, the cutoffs for vitamin D deficiency were changed in 2011, and even today, different authorities have different opinions about what blood level of vitamin D is the right place to diagnose deficiency.
As a brief history, in 2010, the Institute of Medicine (IOM) estimated that blood levels vitamin D levels of >20ng/mL or higher were adequate, and that levels below that were considered deficient.
Then, in 2011, the Endocrine Society stated that the desired serum concentration of 25(Oh)D is >75 nmol/L or (>30 ng/ml).
To complicate matters further, a large review published by endocrinologists and epidemiologists in 2016 in the New England Journal of Medicine concluded that a more appropriate cutoff for vitamin D deficiency would be 12.5ng/mL, which is lower than both the OM and Endocrine Society recommendations.
This makes deciding if a person is vitamin D deficient complicated; the precise answer depends on who you ask.
Obviously, levels lower than 12.5ng/mL are considered deficient by all metrics, but there is some murky territory in the lower teens/20s levels of blood levels of vitamin D.
Until the science can reach a consensus, chat with your healthcare provider if you have concerns over your blood levels of vitamin D. There is no widely-agreed upon blood level of vitamin D for optimal health, and many experts believe that the desired amount may vary across ages and life stages.
If your vitamin D is low, increasing vitamin D intake can help increase blood levels of vitamin D, although the relationship is not linear for reasons scientists still don’t quite understand. Chat with your healthcare provider to find a plan that works for you.
Can you get too much vitamin D?
When it comes to dietary intake, you can absolutely get too much vitamin D. Because it is fat-soluble, it can be stored in fat in your body. If you consume too much vitamin D, it is possible to experience vitamin D toxicity, which leads to a variety of symptoms, including loss of appetite, weight loss, excessive urination, kidney stones, and heart arrhythmias.
It can also cause the level of calcium in your blood to rise, which can lead to tissue calcification, which may lead to damage to the heart, blood vessels, and kidneys.
The tolerable upper intake level (also known as ULs – the amount you should not go over per day) of vitamin D are:
- 1,000IU (25mcg) for infants: 0-6 months, and 1,500IU (38mcg) for infants 7-12 months
- 2,500IU (63mcg) for infants: 1-3 years
- 3,000IU (75mcg) for infants: 4-8 years
- Adults and children over 9 years: 4,000IU (100 mcg)
- Pregnant and lactating adults: 4,000IU (100 mcg)
Excessive sun exposure does not lead to vitamin D toxicity (although excessive sun exposure with no protection can lead to other issues).
Vitamin D and Depression
It is a popular belief that vitamin D deficiency can cause depression. The media ran wild with this idea after a 2012 report (which was a case-report series of 3 women) linked vitamin D deficiency to depression.
Ever since, there seems to be a widespread belief that vitamin D deficiency may cause, worsen, or trigger depression.
I am going to do a whole, in-depth blog post about this topic in the very near future, as I think it’s an extremely interesting topic worthy of its own post, but for now, suffice it to say that low vitamin D serum has been associated with mental distress such as depression, ADHD, and autism, but there is no real clear consensus that adding vitamin D to the diet is related to or beneficial to treating these disorders.
So, there might be some sort of link, but whether or not vitamin D deficiency is a partial risk factor for these disorders, and/or if it’s just an interesting association, more randomized clinical trials could be helpful to better understand any potential benefits of improving vitamin D intake among those with depression and other mood disorders.
Take Home: The Vitamin D Controversy: What is Vitamin D? And Am I Vitamin D Deficient?
Vitamin D is a fat-soluble vitamin found naturally in very few foods. It is added to some foods, like milk, plant-milks, OJ, and cereals, and is available in supplement form. Your skin can also make vitamin D using UV rays from the sun. The cutoffs to determine vitamin D deficiency are controversial. If you are concerned about your vitamin D intake, look for fortified foods and beverages, and speak with your healthcare provider about getting bloodwork done to explore if supplementation is appropriate.
That’s all for now! I hope you enjoyed. If you are looking to learn more about potential nutrients of concerns for people on plant-based diets, check out this post on nutrition for vegans. Leave questions and comments below, and/or reach out to me on Instagram, Twitter, or YouTube.
If you liked “The Vitamin D Controversy: What is Vitamin D? And Am I Vitamin D Deficient?” You may also like:
- Nutrition for Vegans: What You Need to Know If You’re on a Plant-Based Diet
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