Getting Vitamin D during the dead of winter

By John D Day MD

The noon-day sun is the number one source of our vitamin D. But in the dead of winter it's too cold to go outside, the sun is too low in the sky, and these inversions block out the sun's rays. As a heart rhythm specialist at the Intermountain Medical Center Heart Institute, here's why vitamin D matters, and how you can get it during the winter season.​​​​

EnoughVitaminD
Our winter this year in Salt Lake City has been particularly challenging thus far. With frigid temperatures, oppressive inversions and sunless skies, one cannot help asking, “am I getting enough vitamin D”?

Why should we even worry about the sunshine vitamin or vitamin D?  
Based on a study we presented at the annual scientific sessions of the American Heart Association in 2010, of 132,000 Utah residents, 85% of us are lacking in vitamin D (levels less than 40 ng/dL). Does it really matter if our bodies have inadequate levels of vitamin D?  The answer is a resounding “yes”. Having sufficient levels of vitamin D has been shown to help prevent osteoporosis, heart disease, cancer, Alzheimer’s Disease, strokes, high blood pressure, diabetes, and it may slow the aging process.

How do we get vitamin D?  
The best way to get vitamin D is naturally from the sun. However, if you live above the 37th parallel (37 degrees latitude), or anywhere north of Los Angeles, then you really can’t get much vitamin D from November to March when the sun is very low in the sky (all of Utah is above the 37th parallel). Thus, we have to rely on the vitamin D we were able to store up from the summer or the vitamin D we can take in through our diets and supplements.  Unfortunately, there just are few vitamin D food sources as our bodies really were designed to get the vitamin D we need from the sun.

Just how much time in the sun do we need?
Just 15 minutes of sun at mid-day in the summer is sufficient. Of course, this varies based on how much skin is exposed (darker skinned people may need more time), the time of the day (mid-day is best for vitamin D), altitude (the higher the altitude you are at the more vitamin D your body can make), cloud cover, etc. There are some great smart phone apps or websites that can allow you to calculate your exact dose from the sun. Just be sure not to be in the sun longer than 15 minutes without sunscreen or covering up to prevent increased risk of future skin cancer. In addition to the vitamin D we get from the sun, sunlight has been shown to have a profound beneficial effect on allowing us to feel better.

However, in our frigid winter smog filled inversions getting a sunburn is probably the furthest thing from our minds right now.

So what can we do? 
Good food sources of vitamin D include fatty fish such as salmon, especially the wild salmon, tuna, mackerel, mushrooms, eggs and vitamin D fortified foods such as milk (any milk will do--cow, soy, almond, or coconut milk are all fortified). My favorite way to get vitamin D in the winter is from salmon.  Just a small 4-ounce serving of salmon offers us 265% of our daily recommended allowance of this critically important vitamin. As vitamin D can be stored, just 2.5 servings of salmon each week would get us all of the vitamin D we need.

What if you just don’t like fish? 
This described me perfectly my entire life until just a few months ago. I remember vividly as a child not being able to leave the table until I ate my fish. However, as a middle-aged cardiologist very concerned about my health, I am learning to like fish. I must admit that it has not been easy but I am now faithfully doing it. I eat wild Alaskan salmon twice a week. I want to emphasize “wild” as the wild salmon has less contaminants or pollutants than fish grown in a farm. In addition to all of the wonderful vitamin D in salmon, it is also very high in omega 3s and vitamin B12 and also reduces cholesterol and decreases your risk of heart disease. I should point out here that the American Heart Association has recommended at least two servings of fish each week as part of a healthy diet.

What dose of Vitamin D should I take each day?
Given the popularity of supplements in our US culture, I should at least briefly touch on the subject of vitamin D supplements. Just today in clinic I was asked by a patient, “what dose of vitamin D should I take each day?” This is a difficult question to answer, as we don’t really know whether vitamin D supplements are actually healthy for us or not. There are several big ongoing vitamin D supplement trials currently going on that should be able to help answer this question. It is important to remember that there have now been many vitamins and supplements that have been shown to be potentially harmful. As with all nutrients, it is always much better if we can get them naturally rather than in a pill.

Can I end up taking too much Vitamin D?
Certainly, if your vitamin D levels are very low based on a simple blood test that your doctor can order for you, less than 40 ng/dL, getting more sun, eating fatty fish, or taking a supplement certainly makes sense.  The recommended daily allowance of vitamin D is 600 IU/day. For those who are vitamin D deficient, they may need higher amounts, up to 1,000 IU/day, until their vitamin D levels are in the normal range. However, especially with supplements, we need to ensure that we don’t get “toxic” on vitamin D.  Especially high levels of vitamin D have been shown to cause kidney stones and permanent kidney damage. Based on our study of 132,000 Utahns, which was presented at the American Heart Association meeting in 2010, we found that 2% of Utahns had potentially toxic levels of vitamin D (more than 100 ng/dL). In these patients, their risk of a serious heart condition called atrial fibrillation was increased 2.5 fold. Atrial fibrillation is very worrisome as it can lead to strokes, dementia, and heart failure.

So what can we do to make sure we get the right amount of vitamin D year-round? I would recommend the following three simple suggestions:
  1. Get 15 minutes of sun each day in the late spring, summer, and early fall. 
  2. Eat two servings of a fatty fish each week, like wild salmon, from November to March.
  3. For vegetarians or those who hate wild salmon, drink 3 cups of a vitamin D fortified milk (cow, almond, soy, etc.) each day from November to March (liquid vitamin D is better absorbed than the pill form).
If we can follow these two simple recommendations, we can enjoy all of the health benefits of vitamin D naturally and continue to stay young.