Tired? Fatigued? Nervous, anxious, depressed? Are trips to a counselor burning a hole in your pocket to no avail? Maybe the answer lies not in your mind, but in your body. You could, like millions of Americans, be suffering a vitamin D shortage.

Symptoms of a vitamin D shortage can be tricky to pin down because they may sound like symptoms of other problems. Common complaints with this deficiency are tiredness, muscle fatigue, mood problems, and general fogginess of the brain. Some people begin to have muscle pains and bone pains as the deficit worsens. Others may suffer from an increase in weight. Beyond these symptoms, there are many medical conditions that are now becoming correlated with a shortage of this important vitamin. Asthma, diabetes, major depression, schizophrenia, and some cancers along with cardiovascular and metabolic problems are all being found to be associated with low levels of this vitamin.

Vitamin D is usually called the “sunshine vitamin” because our bodies manufacture it in response to exposure to sunlight. (There are two major forms of vitamin D: D2 and D3. For this article we are mostly referring to D3, the type more optimal for our bodies.) It plays a vital role in our physiology.

Vitamin D affects our neurochemistry, meaning our moods and thinking. It was recently discovered that the brain itself has receptors for vitamin D. It is vital to the proper operation of our muscles. For example, since it affects the body’s access to calcium, which is an important part of what makes muscles contract properly, too little leads to a general feeling of fatigue in the muscles. And of course, vitamin D is well-known for its role in the maintenance of strong bones and teeth.  It was deemed so important that the government started fortifying milk with vitamin D in the 1930s, making rickets (a disease causing pain and deformity of the bones) virtually disappear.

Why did Americans need this extra supplementation? Because our northern latitude means there are many days per year where we simply cannot get strong enough sun to trigger the production of vitamin D no matter how long our sun exposure. Interestingly, the fortification of foods with D is closely regulated in food because it has the possibility of being toxic if consumed at too high doses for a long period.

Numbers on the estimated amount of people suffering from this shortage vary, but it is generally agreed that it affects a substantial portion of the population. So how did we come to the point where we are suffering such a tremendous deficiency? Simple, with the modern lifestyle we have started spending so much time indoors that we don’t get enough sun exposure to manufacture sufficient D on a daily basis. Add to that the fact that when we go outdoors we tend to slather on the sunscreen, blocking the rays needed to trigger our cells to make D. And while it is true that we can ingest some from foods in our diet, the sources are limited and difficult to consume in great enough daily quantity (fatty fishes like mackerel, salmon and tuna, fortified milk and cereals, and liver). And let’s face it, most of us don’t think about it at all.

To find out for sure if you have a vitamin D shortage, go to a doctor and have a simple blood test done. Be sure to get a regimen prescribed if possible; a deficiency can require much higher initial doses than you would take once the insufficiency is corrected. Also, dosing can vary widely from person to person. This is further complicated by disagreement on what maintenance dose is effective- a number of studies and doctors suggest much higher doses may be needed than what the RDA currently is.

The safe upper dose is also debated. The U.S. Institute of Medicine recommends 4,000 IU  as the safe upper limit but the human body will manufacture up to 20,000 IU under ideal circumstances, and the Mayo Clinic provides information on dosing much higher than 4,000 IU per day for numerous ailments.  However, it is important to exercise caution with this vitamin due to the aforementioned potential for toxicity. A significant symptom of too much vitamin D is hypercalcemia. This means there is too much calcium in your bloodstream, which can be quite uncomfortable and lead to complications if unchecked. If you are a self-medicator, the sudden painful cramping in major muscle groups from too much blood calcium can be a noticeable indication that you’ve overdosed on D. Back off to a lower dose and the problem should resolve.

So if you’ve been struggling to find an answer to a decrease in the quality of your life, consider investigating your vitamin D levels with the help of your doctor. Nothing is more frustrating than feeling bad for “no reason” and getting to the bottom of such a problem can be life-transforming. Maybe the sunshine vitamin can help you sparkle a bit brighter, too.