We love reader questions! This week two questions about foods rich in vitamin D landed in our inbox. We’re not surprised that you’re thinking about vitamin D because deficiency is most common in the winter.
Why does vitamin D deficiency become more of a problem in the winter months? Because the best source of vitamin D is not food, but sunlight. Unlike most vitamins that you have to get through diet, your body can make its own vitamin D under the right conditions.
So how DOES your body make vitamin D? On the surface of your skin are vitamin D precursors, compounds that are activated by sunlight. Once activated, these precursors travel to your kidneys and liver where they undergo further modification to become active vitamin D.
The problem is you need sunlight to start this process and you don’t get as much sun exposure during the winter, especially if you live in Northern areas of the country. How much sun exposure do you need to meet your vitamin D requirements? It varies per person based on a number of factors.
Are You at High Risk for Vitamin D Deficiency?
Certain people need more sun exposure than others to make enough vitamin D. If you have a dark skin tone, the melanin in your skin blocks some of the ultraviolet rays required to make vitamin D. As a result, you have to stay in the sun twice as long to get enough vitamin D to meet your body’s requirements.
The amount of sun exposure you need depends on where you live too. Some areas of the country don’t get much direct sunlight, so you have to stay outside longer. If you have fair skin and go outside on a bright, sunny day, you can meet your vitamin D requirements with as little as 3 to 5 minutes of unprotected sun exposure daily. If you have dark skin and live in an area like Boston, Massachusetts (all that snow, oh my!), you’ll have to spend considerably more time in the sun.
One concern about unprotected sun exposure is the risk of skin cancer. Having encountered people with malignant melanoma, a potentially fatal form of skin cancer, we’re wary of unprotected sun exposure. Unfortunately, going outside with a sunscreen on won’t work. Sunscreens block most of the UV rays your skin needs to activate those all-important vitamin D precursors.
Standing in front of a sunny window with your skin exposed is ineffective too. Windows block almost all UVB rays, the type your skin needs for vitamin D synthesis.
Can You Meet Your Vitamin D Requirements Through Diet?
Don’t underestimate the importance of eating a healthy diet, but doing so probably won’t greatly affect your vitamin D levels. Most foods are pitifully low in vitamin D. Considering you need at least 600 I.U. of vitamin D daily if you’re an adult age 70 and under and 800 IU. if you’re over age 70, diet doesn’t have a major impact on vitamin D.
Also, keep in mind most experts believe the current vitamin D recommendations are too low. We believe you should be getting no less than 1,000 IU to 2,000 IU daily assuming you’re not at high risk for deficiency. By the way, IU stands for international units.
Here are some of the best food sources of vitamin D:
- Salmon, 3 ounces 447 IU
- Canned tuna, 3 ounces 154 IU
- Orange juice fortified with vitamin D, 1 cup 137 IU
- Milk fortified with vitamin D, 1 cup 120 IU
- Yogurt fortified with vitamin D, 6 ounces 80 IU
- Sardines, 2 sardines 46 IU
- Egg, 1 large 41 IU
- Breakfast cereal fortified with vitamin D 40 IU
Unless you’re eating salmon most days and drinking fortified milk or orange juice, it’s hard to get enough vitamin D exclusively through diet. That’s one reason vitamin D deficiency is so common.
Here’s a secret for you. A surprisingly good source of vitamin D is mushrooms grown in direct sunlight. (Most mushrooms are grown in the shade and aren’t high in vitamin D) If you’re lucky, you can find Dole’s Portobello Mushrooms in your area. These mushrooms grown in direct sunlight have 400 IU of vitamin D per 3 –ounce serving. Pretty impressive!
Why Should You Be Concerned about Vitamin D Anyway?
Research published in Mayo Clinical Proceedings, showed only about 30% of adults are getting optimal amounts of vitamin D. That means 70% of the population isn’t! Here are some factors that put you at greater risk for vitamin D deficiency:
- Dark skin coloration
- Being over the age of 70 (produce 75% less vitamin D from sun exposure)
- Having intestinal issues that reduce absorption – Crohn’s, Celiac disease etc.
- Having kidney or liver disease
- Getting little exposure to direct sunlight or wearing a sunscreen all the time
- Living at a latitude that doesn’t get direct sunlight year round.
So, why is there so much concern about vitamin D? Preliminary research suggests vitamin D is important for regulating immune function and deficiency may raise the risk for a number of health problems.
Dr. A checks vitamin D levels at times when people come into the office and complain of feeling weak, tired or achy. He finds a high percentage have low levels of vitamin D. This isn’t surprising when you consider these kinds of vague symptoms are common in people who are vitamin D deficient.
Other symptoms of vitamin D deficiency include generalized fatigue or achiness, unexplained feelings of sadness and frequent colds or respiratory infections. You simply don’t feel your best when you have low levels of vitamin D.
If you suffer with fibromyalgia, chronic fatigue or depression, it’s even more important that you ask your doctor to check a vitamin D level. People with these health issues often feel better when their vitamin D level is in the optimal range.
It’s one thing to get enough vitamin D to avoid a deficiency, not getting enough may also increase your risk for certain diseases. Be aware that research looking at vitamin D and its role in preventing health problems is still in its early stages. The evidence that vitamin D definitively lowers the risk of health problems isn’t there yet but there is suggestive evidence.
Here are some health problems that PRELIMINARY studies show vitamin D MAY lower the risk for:
- Type 2 Diabetes
- Autoimmune diseases, especially multiple sclerosis
Keep in mind that some of the recent studies looking at vitamin D for disease prevention have been disappointing. A large clinical (almost 26,000 people) trial looking at vitamin D supplements for prevention of heart disease and cancer is underway. The results should be available in early 2018.
Should You Take a Vitamin D Supplement?
At this point, there’s not enough evidence to support taking high doses of vitamin D for the prevention of any disease, BUT you still need to make sure you’re getting enough of it.
If you’re not at high risk for deficiency based on the risk factors discussed, you may be able to meet your vitamin D needs by taking a 1,000 IU per day supplement. If you manage to get enough sun exposure, about 30 minutes a week on bare skin, and eat foods fortified with vitamin D, you may get by without taking a supplement at all.
If you ARE at high risk for vitamin D deficiency or are already deficient, you’ll likely need more than 1,000 IU of vitamin D daily. We recommend asking your doctor to check your vitamin D level if you’re at high risk. (See risk factors above) By doing this, you’ll know how much you need to take to get to where you need to be.
Don’t take high doses of vitamin D in the belief that more is better. Vitamin D is a vitamin your body stores. As a result, very high doses can lead to toxicity. Plus, taking very high levels of vitamin D can increase calcium absorption. This calcium could potentially deposit in tissues.
In most cases, you would have to take more than 10,000 IU a day for a long period of time to develop toxicity. Dr. A and I both take 5,000 IU a day. We’ve checked our levels a few times and find this dose keeps our level in the ideal range. For you, it may be different.
Why Do We Take a Supplement When Vitamin D for Disease Prevention is Unproven?
Supplement with vitamin D or not? Good question. It’s pretty hard to get enough vitamin D unless you live in a bright, sunny climate year round. While we don’t recommend taking vitamin D solely for disease prevention, we believe it’s important to avoid a deficiency. With deficiency being so common and foods rich in vitamin D being so uncommon, it makes sense to supplement.
Through supplementation, Dr. A and I stay within the recommended range for vitamin D based on blood studies. If we didn’t take a supplement, we would probably drop too low. We wear a sunscreen when we go outside and don’t consume a lot of dairy or other fortified foods.
Forms of Vitamin D
If you read the label on vitamin D supplements, you’ll see it comes in two forms, vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). The D3 form comes from lanolin, a waxy substance produced by the sebaceous glands of sheep. Vitamin D2 is the form of vitamin D fungi produce naturally but is also produced synthetically and added to supplements.
It’s not clear whether vitamin D3 is superior to vitamin D2, but preliminary studies suggest vitamin D3 is more effective at raising vitamin D levels and maintaining them. For this reason, we recommend the vitamin D3 form, unless you’re a vegetarian or vegan. Even if you are vegetarian or vegan, you have options. Lichen produce vitamin D3, making it possible for companies to offer vegan vitamin D3.
The Bottom Line
Hope we’ve inspired you to think about your vitamin D status and whether you’re meeting your vitamin D requirements. If you have any of the risk factors for vitamin D deficiency we talked about, get your vitamin D level checked. Even if aren’t at high risk, you still may want to consider taking 1,000 IU of vitamin D daily. It’s a good idea to check with your doctor before doing this. For example, people who have a medical condition called sarcoidosis shouldn’t take supplemental vitamin D.
Choose a vitamin D supplement from a reputable manufacturer. Recently, we signed up to receive reports from a service that independently tests vitamins, minerals and supplements to make sure they contain what they say on the bottle. We’ll slowly be adding more supplements that pass independent testing on the “shop” portion of the website.
Like you, we like to get supplements as inexpensively as possible WITHOUT sacrificing quality. One of the least expensive and best values for a vitamin D3 supplement that passed independent testing is Source Naturals Vitamin D-3 Liquid Drops. With drops, it’s easy to adjust the dose.
If you prefer a gel cap, Country Life Vitamin D3 is one of the better values. Based on results from independent testing, price isn’t necessarily an indicator of quality. Some expensive brands don’t have the amount of vitamin D listed on the bottle – so choose wisely.
Take Action Points:
Keep track of how much vitamin D you take in through diet for a week or two.
Estimate your sun exposure. You need about 30 minutes of unprotected sun exposure weekly to meet your vitamin D requirements.
From the above, estimate how much vitamin D you’re taking in each week. If it’s less than 7,000 IU, you’re falling short. If so, think about taking a vitamin D3 supplement.
Look at the risk factors for vitamin D deficiency listed above. Are you in a high risk group? Consider getting your doctor to check your vitamin D level.
Hope we’ve given you “food for thought” and you have a better understanding of vitamin D. Do you know someone who could use this information? Feel free to share. 🙂
National Institutes of Health. “Vitamin D”
Mayo Clin Proc. 2010 Aug; 85(8): 752–758. doi: 10.4065/mcp.2010.0138.
Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysis. Am J Clin Nutr 2012.