What in the world is Vitamin D? Vitamin D is a nutrient that has tremendous value and acts on many functions of the human body. I can bet that you probably didn’t know that about 42% of the American population is deficient in Vitamin D. The people who are more at risk of low Vitamin D levels are those who spend most of their days indoors, practice a vegetarian or vegan diet, or have darker skin. If you fall into any of these groups, listen up. Addressing Vitamin D deficiencies is crucial to overall health. Lets take a walk through identifying and addressing low Vitamin D. Before we discuss how to get more Vitamin D into your life, lets go through the incredible benefits of having healthy Vitamin D levels.
Bone and Teeth Strength
Vitamin D regulates the amount of calcium and phosphate in the body which is important in maintaining the health of bones and teeth. Since Vitamin D helps the body absorb calcium in the gut that we consume through our diets, it plays a vital role in strengthening our bones and teeth. Now it is important to note that Vitamin D is only effective when there are sufficient calcium levels in the body, so including calcium enriched foods such as dairy products and dark leafy greens into your diet would be beneficial. Increased absorption of calcium through mechanisms of vitamin D can decrease the likelihood of and even improve osteopenia and osteoporosis. A 2004 study looked at the relationship between vitamin D levels and its impact on falls and bone mass. It was found that sever vitamin D deficiency (<30 nmol/L) is common in hip fracture patients 
In a 1986 study that looked at biopsies performed on skeletal muscles of individuals who were Vitamin D deficient, atrophy of the Type II muscle fibers was found . Type II muscles fibers are the ones that known as fast twitch muscle fibers and are associated with quicker muscular movements. This is something to note when looking older adults where a misstep or loss of balance could result in a fall. In a randomized, controlled study, it was found that treatment of 48 elderly stroke survivors with 1000 IU of vitamin D2 daily saw significant increase in mean type II muscle fiber diameter and percentage of type II muscle fibers over a two-year period.
Immune System Boosting
The immune system defends the body against foreign, invading organisms by promoting protection while maintaining tolerance to self. The detriments of vitamin D deficiency on the immune system has become clearer in recent years and it has shown that having lower vitamin D can increase one’s susceptibility to infection and diathesis. Before modern day treatments, vitamin D was used to treat tuberculosis through exposure to the sun and foods such as cod liver oil. In a study from 1988 to 1994, nearly 19,000 subjects found that those with lower vitamin D levels (<30ng/ml) were more likely to self-report a recent upper respiratory tract infection than those with sufficient levels . This study also, saw that the number of infections were lower in the summer and higher in the winter due to the fluctuating amounts of sun exposure.
In another cross-sectional study of 800 military recruits in Finland, it was found that recruits with lower vitamin D levels lost significantly more days of active duty from upper respiratory infections than recruits with higher levels. There are a number of cross-sectional studies that have found correlations between vitamin D levels and rates of influenza  as well as other infections such as bacterial vaginosis  and HIV. All of these studies reported and association of lower vitamin D levels and increased rates of infection.
The most accurate way know your Vitamin D levels is to schedule a visit with your primary care provider and request blood work to be done. This will tell you if your Vitamin D levels are adequate or out of whack. If you do not wish to go into a doctor’s office, you can take effective at-home tests from companies such as Everlywell. Once you know, proper actions can be taken.
Where Can I Get the Natural “D”?
Vitamin D is also known as the “sunshine” vitamin, so the most natural source of getting the D is from the sun. Research has shown that at as little as 20-30 minutes of sun exposure (arms and leg exposed). There is even belief that it can be beneficial to go outdoors without sunglasses on due to the eyes’ capabilities to absorb Vitamin D. If your work keeps you inside for hours on end or you have darker skin, it may be beneficial to get outside more often or look to Vitamin D supplements to fill the gap.
Ok, the sun is cool, but what can I eat that has the D in it? Some of the highest density foods for Vitamin D are egg yokes, liver, red meat and fatty, oily fish such as salmon, sardines, herring and mackerel. There is a lot of meat full of Vitamin D, so if you partake in the vegetarian or vegan diet, it might be a good idea to spend a lot of time outside or supplement.
Things to consider
Though you cannot overdose on vitamin D with sun exposure, it is important to protect your skin to reduce the risk of skin damage and cancer. Supplementation of vitamin D is where people can get into a sticky situation. Too much calcium build-up (hypercalcaemia) can weaken bones and potentially cause damage to the heart and kidneys. So, be sure to get your blood work done by a licensed medical professional to know where your vitamin D levels before supplementing.
We are living in a time where our health is more important than ever before. Taking simple steps to improve your health is imperative to longevity. Exercising, eating nutritiously, getting good sleep and even taking vitamins can go long way in improving your overall health.
 Vitamin D status and bone turnover in women with acute hip fracture.
Nuti R, Martini G, Valenti R, Gambera D, Gennari L, Salvadori S, Avanzati A
Clin Orthop Relat Res. 2004 May; (422):208-13
 Role of vitamin D in skeletal muscle function. Boland R
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 Association between serum 25-hydroxyvitamin D level and upper respiratory tract infection in the Third National Health and Nutrition Examination Survey.
Ginde AA, Mansbach JM, Camargo CA Jr
Arch Intern Med. 2009 Feb 23; 169(4):384-90.
 Epidemic influenza and vitamin D.
Cannell JJ, Vieth R, Umhau JC, Holick MF, Grant WB, Madronich S, Garland CF, Giovannucci E
Epidemiol Infect. 2006 Dec; 134(6):1129-40.
 Maternal vitamin D deficiency is associated with bacterial vaginosis in the first trimester of pregnancy.
Bodnar LM, Krohn MA, Simhan HN
J Nutr. 2009 Jun; 139(6):1157-61.
 High frequency of vitamin D deficiency in ambulatory HIV-Positive patients.
Rodríguez M, Daniels B, Gunawardene S, Robbins GK
AIDS Res Hum Retroviruses. 2009 Jan; 25(1):9-14.