5 Things You’re Getting Wrong about Vitamin D

May 17, 2020

by Cathe Friedrich

Vitamin D plays a critical role in the human body. We think of it as being the bone health vitamin, but the sunshine vitamin behaves more like a hormone and plays other roles in human health. For example, vitamin D is active in regulating immune function and that’s important for all aspects of health. However, there are at least five things you’re probably getting wrong about vitamin D and that could impact your health.

You Depend on Diet to Get Enough Vitamin D

Most foods in their natural state aren’t good sources of vitamin D and many don’t contain any D at all. Among the scant natural food sources of vitamin D, fatty fish, such as salmon, mushrooms exposed to UV light, and some dairy foods contain modest quantities. Other foods are fortified with vitamin D. These include some plant-based milk, cereals, orange juice, and yogurt.

So, it’s hard to meet your body’s vitamin D requirements through diet alone. For example, you’d have to drink at least 6 glasses of vitamin D fortified milk each day to meet the minimum recommendation for daily intake. A glass of fortified milk contains around 100 international units and you need a minimum of 600 international units daily.

The best natural source of vitamin D is sunlight. When you expose your skin to sunlight, UVB rays activate a precursor on your skin that your liver and kidneys convert to active vitamin D. So unless you drink a lot of milk and eat fatty fish every day, you need sun exposure to maintain a healthy vitamin D level. That’s why people who live in Northern latitudes are more often deficient in vitamin D compared to those who live in the tropics.

Not Taking Vitamin D Supplements with a Meal

If you take a vitamin D supplement, you won’t absorb it well unless you take it with a meal that contains fat. However, the amount of fat matters. You don’t want to take your vitamin D supplement with a big dollop of fat. Studies show you absorb it best with a lower to moderate amount of dietary fat. In other words, taking it with 10 grams of fat is better for absorption than taking it with a high-fat meal that contains 40 grams of fat. However, a fat-free diet won’t cut it either. One study found that people absorbed 32% more vitamin D when they took a vitamin D supplement with 30 grams of fat as opposed to a meal free of fat.

Assuming a Multivitamin Will Supply Your Vitamin D Needs

The quantity of vitamin D in multivitamins is variable. A study published in BMJ Journals found that most multivitamins supply less than 400 IU of vitamin D and adults need at least 600 IU daily before the age of 70 and 800 IU afterward. If you’re already deficient in vitamin D, you may need much more to raise your level. You can get some of this from sunlight, but the sun isn’t a reliable source if you live in certain parts of the world. Plus, you need more sun exposure to raise vitamin D if you have dark skin, are obese, are over the age of 70, or have certain medical problems. Sunscreen also blocks your skin’s ability to make vitamin D. The best way to find out where you stand and how much vitamin D you need is to check a blood level via a test called a 25-hydroxy-vitamin D level. Based on the results, your doctor can recommend the amount that will best optimize your level.

Assuming Vitamin D Will Protect Your Bones

You need vitamin D to help your body absorb calcium and you need calcium to build new bone tissue. However, a well-conducted, meta-analysis in the journal Lancet showed that vitamin D doesn’t significantly improve bone density. On a more positive note, some studies show it helps older people with balance and lowers the risk of falling. So, it may help older individuals avoid bone fractures in an indirect manner. So, vitamin D may have some benefit for preventing bone fractures in older people, but don’t count on it, alone, to boost your bone density.

Assuming Vitamin D Can Lower Your Risk of Health Problems

It’s clear that a deficiency of vitamin D has health repercussions, but vitamin D supplementation has become popular as a means of lowering the risk of certain diseases. However, when the Agency for Healthcare Research and Quality looked at the results of 250 studies, it wasn’t clear whether vitamin D reduces the risk of health problems such as cardiovascular disease, diabetes, or cancer, as some people claim. However, it does play a role in immune health. Some studies show that having a high normal vitamin D level may lower the risk of respiratory infections and may also be beneficial for people with autoimmune diseases, especially multiple sclerosis.

The Bottom Line

Now, you know why you need vitamin D but also some myths and misconceptions about this vitamin. There’s still a lot we don’t know about the elusive D vitamin. There’s likely a “sweet spot” for vitamin D in the human body. You don’t want to be too low and you don’t want to have a vitamin D level that falls outside the normal range. Hopefully, one day we’ll know what the ideal vitamin D level is. Until then, make sure you’re getting some sun exposure every day and know your risk factors for vitamin D deficiency. They include:

Having darkly pigmented skin
Being obese or overweight
Eating a vegan diet
Living at a Northern latitude with little direct sunlight year-round
Being over the age of 60
Slathering on the sunscreen before going out

If you fall into a high-risk group, consider getting a blood test to check your 25 hydroxyvitamin D level, the best test for determining vitamin D status.

References:

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The Lancet. VOLUME 383, ISSUE 9912, P146-155, JANUARY 11, 2014.
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Minn Med. 2005 Nov;88(11):38-41.
BMJ Journals. Vitamin D supplementation: are multivitamins sufficient? Rebecca J Moon1,2, Elizabeth M Curtis1, Cyrus Cooper1,3,4, Justin H Davies2, Nicholas C Harvey1,3
National Institutes of Health. “Vitamin D”
Clin Rev Allergy Immunol. 2013 Oct; 45(2): 217–226. doi: 10.1007/s12016-013-8361-3.
MD Edge Dermatology. “Vitamin D – Myths or Truths?”
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