Surprising Vitamin D Myths and Facts

Weird, but true! While it’s common knowledge that we get vitamins and minerals from the food we eat, our skin actually converts sunlight into fat-soluble vitamin D.

There has been a lot of conflicting information in the media about this essential vitamin, so with summer upon us (and more time spent outdoors), let’s play a game of myth or fact to learn more about the sunshine vitamin.

You Can Get Vitamin D From Sun, Food and Supplements

Fact! When the skin is exposed to sunlight, it starts a cascade of chemical reactions that convert cholesterol found in the skin into vitamin D. Interestingly, your skin regulates how much vitamin D it makes from the sun, so there is no chance of vitamin D toxicity from sun exposure.

When it comes to food sources, the sunshine vitamin (measured in international units, or IU) is found naturally in only a few things including:

• Wild caught salmon: 450-900 IU in a 3.5 ounce serving (wild caught has significantly more than farmed);
• Cod liver oil: 450 IU per teaspoon;
• Mushrooms that are exposed to UV light as they grow: 400 IU per cup;
• Canned tuna: 269 IU in a 3.5 ounce serving;
• Egg yolks: 37 IU per yolk.

The recommended daily allowance (RDA) is 600 IU per day for healthy adults under 69, and 800 IU per day for those 70 and older. As you can see, that’s not easy to reach with the average diet, so many foods are fortified with vitamin D, including some cow’s milk (115 IU per cup), plant-based milks, orange juice (100 IU per cup), cereals and oatmeal (~100 IU per serving).

Finally, you can get vitamin D through a dietary supplement. There is a lot of research about how much people should take and whether a supplement even works—and the jury is still out. Currently, the recommendation for the average healthy adult is to try to consume 600-800 IU daily, be it through food, supplements or a combination of both.

There is a definite benefit to supplementation for those who are vitamin D deficient, but for those with normal blood levels, there is not as much evidence that a supplement is beneficial to long-term health.

Related: Trending: Vitamin D Is in High Demand

Vitamin D Is Good for Strong Bones

Fact! Many of us probably learned at a young age that calcium builds strong bones, which is true, but calcium needs vitamin D for the body to absorb it. Think of vitamin D as a taxi that brings calcium from the intestines into the blood.

So, less vitamin D means less calcium in the body, which can lead to weak bones. But that’s not all! Here are some other ways scientists believe vitamin D supports long-term health:

• May improve immunity;
• May prevent cognitive decline;
• May reduce the risk of stroke and heart disease;
• May reduce the risk of diabetes;
• May improve survival if one develops cancer.

Exposing Skin to Daily Sunlight Is the Best Way to Get Vitamin D

Myth! It makes sense to think that if our bodies are built to make vitamin D from the sun, it’s best to get it the way nature intended. However, the research to date states—and most skin care pros adamantly agree—that the risks of exposing the skin to UV rays far outweigh the risks of vitamin D deficiency, especially when we have other, safer ways to get adequate amounts.

Furthermore, the amount of vitamin D that our skin can make is directly related to the time of year and latitude of where we live. For example, if you live in the northern U.S., above 37˚ latitude, your skin probably won’t be able to produce enough vitamin D, especially during winter. That line cuts around the northern state line of North Carolina and then straight west across the country.

For those who have darker skin tones, it’s even harder to produce enough vitamin D from sunlight alone. So, for at least half of the country, we couldn’t get enough of the sunshine vitamin from the sun even if we wanted to!

More Is Better

Myth, sort of. The optimal daily dose of vitamin D is a hot area of research right now, with some studies looking at doses up to 5,000-10,000 IU. Remember, the RDA is currently set at 600 IU for healthy adults and the safe upper limit (UL) is 4,000 IU unless otherwise prescribed by a doctor.

Vitamin D is a fat-soluble vitamin. Unlike water-soluble vitamins, which are not stored in the body and need to be replenished daily, fat-soluble vitamins are stored in the body’s fat tissue.

This means that a high daily intake of vitamin D can lead to excess stores in our fat, potentially leading to toxicity that may include nausea, vomiting, muscle weakness, confusion, pain, excessive urination and thirst, and kidney stones. Extremely high levels of vitamin D can lead to kidney failure, irregular heartbeat and even death.

Toxic levels of vitamin D are almost always caused by taking too much vitamin D from supplements. Study after study has shown that supplementation can help if you are deficient, but if you are not deficient, the supplement does not improve outcomes or long term health.

When Choosing a Supplement, Cost Is the Most Important Factor

Myth! Just because a supplement is expensive does not make it better or safer. Supplements are not regulated as tightly as drugs in the U.S. Dietary supplement manufacturers do not have to prove that what they say is in their supplement is truly there, or in the amounts that they claim.

Therefore, it is best to buy supplements from manufacturers that pay third-party labs to test, evaluate and confirm supplement quality and quantity. Consumer Lab, National Sanitation Foundation (NSF) and U.S. Pharmacopeia (USP) are several reputable third-party testing labs, and you will find their seals on supplement bottles or on the manufacturer’s website.

Everyone Should Get Their Vitamin D Level Checked

Myth! If someone is doing their due diligence of staying safe in the sun and perhaps not eating a lot of foods that are fortified or naturally contain vitamin D, chances are they may be deficient. You don’t need a test to tell you that.

In those cases, the individual can skip straight to the treatment: getting more vitamin D foods into their diet or adding a third-party tested supplement of 600-800 IU to their daily regimen. Ultimately, this will end up being a personal conversation between the person and their physician, who will take into account lifestyle, food choices and medical history.

If you feel that all of that information was confusing and wishy washy, welcome to the world of nutrition research! There is so much we have yet to learn about vitamin D and how it impacts overall health. While we wait for more research to shed light on the sunshine vitamin, you and your clients should keep wearing your sunscreen, consuming foods that contain vitamin D (either fortified or naturally) and check in with your doctor if you’re concerned about potential deficiency.

Leigh-Anne Wooten, MS, RDN/LDN, FAND, is the founder and chief nutrition officer of Behind the Label, LLC (www.behindthelabel.biz). She has a master’s degree in nutrition science and is a Fellow of the Academy of Nutrition and Dietetics.