Vitamin D is a fat-soluble vitamin that is critical to the body’s ability to absorb calcium and phosphorus. Often referred to as “the sunshine vitamin,” vitamin D is produced in the body when exposed to adequate sunlight and is also available exogenously from a variety of food sources, including fatty fish such as salmon, trout, mackerel, and tuna; beef liver, egg yolks, fortified cereal; and most notably fortified whole milk. Vitamin D is essential for healthy bones and teeth, and is important to the body’s overall immune function.
Unfortunately, nearly 40% of the world’s population is vitamin D deficient and most of them are asymptomatic and unaware of it. It is difficult to get enough vitamin D from sunshine and food alone, so fortification of foods and supplementation can help to bridge the gap. Fortification of foods (milk, orange juice, cereal) began in the 1930s as a means to eradicate deficiencies in vitamin D. When supplementing with vitamin D, it is important to monitor your level, as toxicity is possible when supplementing for long periods of time without medical guidance and periodic blood work.
This review of the effects of vitamin D on mood and sleep in a healthy population found that vitamin D plays a role in serotonin (neurotransmitter) production, which is associated with elevated mood and feelings of well-being, and with melatonin production, which is associated with healthy sleep habits and can also contribute to elevating moods. They suggested that further research is required.
This study of vitamin D3 analog stimulation of hair growth in nude mice provided strong evidence that vitamin D3 analogs can stimulate the growth of hair in nude mice that do not normally have visible hair. More research is called for.
In this study, the role of vitamin D in hair disorders and hair follicle cycling was explored. Researchers concluded that the vitamin D receptor also plays a role in the anagen phase of the hair growth cycle, but additional research is still needed to fully understand the relationship and to get consistent results.
At this point, there is low potential for vitamin D to have any significant impact on weight management, though sufficient levels of D are needed for optimal health.
Researchers in this study investigated the effect of vitamin D on weight loss and both traditional and nontraditional cardiovascular lab markers in healthy overweight subjects. Participants supplemented with 83 mcg of vitamin D, but there was no significant weight loss noted when compared to the placebo.
This systematic review and meta-analysis found that there was an inverse relationship between the percentage of body fat mass and vitamin D levels. More research is needed to determine the impact, if any, of vitamin D on weight management.
There is increasing evidence indicating that vitamin D can have an effect on muscle strength and durability.
This systems-based investigation into vitamin D and skeletal muscle repair, regeneration, and hypertrophy indicated the potential for vitamin D promoting muscle restoration in those who had insufficient levels of vitamin D.
This systematic review with meta-analysis of the effect of vitamin D on upper and lower body muscle strength levels in healthy individuals found that vitamin D supplementation increases both upper and lower limb strength, though further research should focus on its effect on muscle power, endurance, and strength.
This randomized controlled trial evaluated the effect of vitamin D supplementation on healthy, overweight men undergoing a weight reduction program. The results confirmed that vitamin D supplementation may support testosterone levels in men, but additional research is needed to draw significant conclusions.
Though approximately 40% of the world’s population is vitamin D deficient, most people are asymptomatic. There are particular groups of people, however, who are more vulnerable to potential vitamin D deficiency than others. Those who have digestive issues that might make absorption more difficult are inclined to be vitamin D deficient. People who spend most of their time indoors or in areas of high pollution, which can be barriers to getting vitamin D from the sun, are also more inclined to be deficient. The more melanin there is in a person’s skin makes absorption of vitamin D from the sun more difficult and could lead to deficiency. The use of sunscreen, while extremely important, has also created a challenge to getting enough vitamin D from the sun.
Symptoms of vitamin D deficiency include fatigue, muscle weakness, bone issues, pale skin, hair loss, loss of appetite, and changes in sleep patterns. While fatigue is frequently a symptom of vitamin D deficiency, it is not exclusively associated with it. It is important to talk to your doctor about any concerns around low energy and fatigue.
This study of the effect of correction of low vitamin D found that normalization of participants’ levels significantly improved the severity of their fatigue symptoms.
This study of the effect of vitamin D supplementation on people with self-perceived fatigue found that vitamin D significantly improved fatigue in otherwise healthy persons with vitamin D deficiency.
According to this abstract, vitamin D deficiency can have a serious negative impact on the dental and oral health of both adults and children. Its authors contend that vitamin D levels should be considered to promote good oral health, and that vitamin D deficiency might hamper oral development and play a significant role in certain oral conditions.
Vitamin D is essential for bone health, and this abstract notes that studies have demonstrated that vitamin D supplementation can promote muscle strength which contributes to a decrease in issues with bone health.
The recommended Dietary Allowance (RDA) for vitamin D intake sufficient to maintain bone health and normal calcium metabolism in healthy people is 10-20 mcg (400-800 IU) for all persons depending upon age, and 15 mcg (600 IU) during pregnancy and lactation. Due to the decreasing ability to absorb vitamin D that comes with age, older adults may require more vitamin D (>70 mcg).
When supplementing with vitamin D, it is important to measure your levels with a routine blood test on a regular basis to ensure that you are falling within normal range. Any deviation should be discussed with your physician in order to determine its cause and possible solutions.
The best sources of vitamin D, the “sunshine vitamin,” are sunlight and foods that are naturally high in vitamin D. Fatty fish like salmon, trout, canned tuna, swordfish, cod liver oil, mushrooms, and eggs are all excellent food sources of vitamin D. And since the 1930s, a number of foods have become fortified with vitamin D. All processed milks (whole, almond, soy, oat), tofu, orange juice, yogurt, and cereals are all excellent fortified sources of vitamin D, though it’s important to note the serving size in terms of its relation to the recommended dietary allowance (RDA).
A 30-minute walk in the sun may also provide the necessary D when you need it.
If you are choosing to supplement, look for a premium brand like Care/of’s vitamin D and vegan vitamin D. And always consult your physician or healthcare provider when changing your supplement regimen.