Did You Know These Facts about Vitamin D?
Crucial for optimal health
Vitamin D is crucial for skeletal processes, sleep, proper brain function, and mood regulation.
Production decreases with age
The elderly are prone to deficiency: a 20 year old physically produces four times as much vitamin D as a 70 year old.
Sunscreen blocks Vitamin D
Sunscreen is great at preventing premature skin aging and it also blocks the skin’s ability to produce vitamin D.
Shoot for 40 – 60 ng/mL
Studies show that people with 40 – 60 ng/mL blood serum D3 levels have the best long term health outcomes.
Take it with food (that has fat)
Take your vitamin D with food that contains fat for better absorption by your body.
Most have low levels
More than 70% of the US population has insufficient amounts of vitamin D in their body.
Many have clinical deficiency
It is estimated that 42% of US population is clinically deficient in vitamin D (blood serum level below 20 ng/mL).
Some foods are fortified
Deficiency is rampant despite the fortification of common foods like cereals, yogurts, milk, juice, and others.
Vitamin D Supplementation Overview
Every cell in the human body needs sufficient vitamin D to survive and thrive. This key nutrient has been shown to prevent osteoporosis and cancer, increase immunity, improve symptoms of depression, and studies have demonstrated its supporting role in the prevention of type I diabetes. Adequate vitamin D is also crucial for proper calcium absorption and processing by the body which impacts cellular metabolic processes and neuromuscular functions.
Vitamin D deficiency is shockingly common due to inadequate sun exposure and lack of foods rich in vitamin D in the Western Diet. Research shows that more than 70% of US adults may have insufficient Vitamin D levels for optimal health.
Vitamin D comes in two main forms, D2 and D3. When considering food sources and possible supplementation, D3 is the important form to focus on, as it is the biologically active form that is most easily absorbed and assimilated by the body.
It is almost impossible to reach optimal levels of vitamin D with food alone and experts are mixed in their recommendations of using sun exposure due to potential for skin damage. The food source highest in vitamin D is fatty fish, as well as beef liver and egg yolk. Supplementing daily with a high quality vitamin D3 supplement can be highly effective at reversing deficiency and maintaining optimal vitamin D levels.
Recommended Dosage for Supplementation
Most doctors and health professionals recommend regular supplementation with vitamin D. Scientific studies show that for optimal health and wellness, supplementation between 1,000-6,000 IU per day is recommended, and this might well be higher for someone with a compromised immune system, a known deficiency or insufficiency, or a pregnant woman.[1, 4, 31]
Methodology and Brand Recommendations
Supplements are not regulated by the FDA (Federal Drug Administration) and it can be hard to tease out quality brands of supplements from those that use the wrong form or cut corners. We took a scientific approach to evaluating supplement options and present our top choices after rigorous analysis and application of our methodology.
A Closer Look at Vitamin D
Why Vitamin D is Crucial for Health
Vitamin D, in comparison to other vitamins, is actually a steroidal hormone. Here are some of the key benefits provided by this essential substance:
- Prevention of osteoporosis, bone fractures, and sprains: A commonly overlooked but crucial reason to ensure proper vitamin D levels is that the body cannot adequately absorb calcium without sufficient levels of Vitamin D. When the body cannot absorb enough calcium, it begins drawing on existing bone stores, which can lead to weakened bone structure, fractures and disease.
- Proper processing of calcium: Optimum calcium levels are very important for general health, and crucial for reasons other than bone health. Calcium is an essential intracellular component for the maintenance of cell membranes. It plays a key role in proper muscle contraction, enzyme actions, hormone regulation, nerve cell function, and bone mineralization.
- Cancer prevention: Optimal vitamin D levels are important for cell growth regulation and possibly for preventing the development of unregulated cancer cells. There is also evidence through studies that indicates that increased vitamin D intake decreases the incidence of colon cancer.
- Increased immune health: Vitamin D has been proven to boost immune cells’ production of microbe-fighting proteins and helps modulate the immune system.
- Increased mood and help with depression: Large sample studies have demonstrated a strong correlation between vitamin D serum levels and incidence of depressive disorders and depression-related personality traits, such as openness and extraversion. Scientists suggest treatment with vitamin D supplementation for subgroups of depressed individuals, especially patients who many be susceptible to seasonal affective disorder (SAD), lower activity levels, and those in older age groups.
- Prevention of type I diabetes, multiple sclerosis, rheumatoid arthritis and Crohn’s disease: In animal studies, scientists have demonstrated that vitamin D supplementation has a mitigating or preventative effect on the onset of type 1 diabetes mellitus, multiple sclerosis, rheumatoid arthritis and Crohn’s disease.[9, 10] Other studies have indicated a link with schizophrenia and increased risk of many common cancers as a result of vitamin D deficiency. 
Internal Processing of Vitamin D
Vitamin D is a fat soluble vitamin, which means that it is dissolved and absorbed in the presence of fat and stored for long periods of time (along with vitamins A, K and E). The two main forms this vitamin takes are vitamin D2 (ergocalciferol) and D3 (cholecalciferol). Vitamin D3 is the more active and easily absorbed form, and is the primary target when aiming to increase blood levels of vitamin D in the body. As vitamins and minerals work in conjunction with each other, many health professionals recognize the importance of sufficient vitamin K2 levels as having synergistic effects with vitamin D.
Vitamin D has several ways to enter the body. People ingest vitamin D3, the more effective form of the vitamin, through a supplement or through food. Also, when the sun’s ultraviolet B (UVB) rays react with the 7-dehydrocholesterol (7-DHC) present in the skin, the body creates D3 in the skin. D3 from supplementation, food, or the skin, is then transported to the liver where it combines with extra oxygen and hydrogen molecules to result in the production of 25-hydroxyvitamin D, or 25(OH)D. This is the storage form of vitamin D called calcidiol and is also what labs measure through blood test to determine vitamin D levels in the body. When necessary, calcidiol travels to the kidneys where it adds another pair of oxygen and hydrogen molecules to become 1,25 dihydroxyvitamin D, otherwise known as 1,25(OH)2D, or calcitriol, which is the biologically active form. This hormone is then escorted around the entire body and absorbed by vitamin D receptors, which are found on almost all cells. Once vitamin D3 enters the cells through the VDR (vitamin D receptor), studies have shown that it actually affects gene expression (turns genes on or off), particularly pathways linked to autoimmune disease, cardiovascular disease and cancer. This means that gene expression can be positively impacted if vitamin D levels are where they should be, and negatively impacted if they are not.
Signs of Deficiency
Vitamin D deficiency, and especially insufficiency, is surprisingly common, even in sunny parts of the world where the population could easily be getting enough from sunlight alone. In many tropical cultures it is culturally common to purposefully avoid the sun, and in parts of the globe further from the equator, there is simply not enough sunlight throughout the year to maintain proper levels. According to the latest measurements, more than 70% of the US population has insufficient vitamin D for optimal health, with over 40% of the population estimated to have a clinical deficiency of the vitamin. When narrowed down to ethnicity, these numbers rise to 82% of black people and almost 70% of Hispanics. Deficiency is defined as having a 25(OH)D level below 20 ng/mL. Insufficiency is defined as having a level lower than 30 ng/mL.
Deficiency symptoms can manifest in the following ways:
- Rickets, a bone disease common amongst children in developing countries
- Increased risk of cardiovascular disease
- Bone pain and muscle weakness
- Poor immune health
Deficient and insufficient vitamin D levels in the body may also result in what doctors describe as “non-specific symptoms” such as occasional digestive upset, low energy, mood swings, headaches, brittle nails, brain fog, poor sleep and others. Also, studies indicate that deficiency and insufficiency in vitamin D may lead to increased risk of cancer, cardiovascular disease, depression, poor immune function, weak bones, and a host of other problems and be asymptomatic until disease manifests.
Getting to Optimal Vitamin D Levels
Experts offer mixed views on recommending sun exposure as a long term way of getting sufficient vitamin D. Some say that the benefits of getting vitamin D in the system far outweigh the risks to skin. Others cite new studies that indicate that all sun exposure may be harmful to the skin. Furthermore, the body can produce only a limited amount of vitamin D from UVB at a time. After reaching the production limit, further exposure to the sun proceeds to destroy the vitamin D that was previously created. Prolonged exposure to UV radiation from the sun not only has the potential to increase risks of skin cancers but is also linked to immune system suppression, photo-aging (skin aging), and increased risks of eye damage such as cataracts.
Sunscreen use is also a contentious topic. Sunscreen is useful for protecting the skin from photo-aging and for reducing the risk of certain types of skin cancers. However, it also blocks the body’s ability to produce vitamin D. Also, research has shown that use of sunscreen has no effect on prevention of basal cell carcinoma when the skin is exposed to sunlight. Additionally, some research indicates that sunscreen coupled with sun exposure actually increases the risk of getting melanoma. A host of health professionals are also concerned about toxic chemicals being absorbed into the bloodstream through the skin as a result of using the chemical sunscreens that are widely available. Current research seems to indicate that mineral sunscreens (active ingredient: zinc oxide) may be safer for long term use  than chemical ones containing oxybenzone, avobenzone, octisalate, octocrylene, homosalate and octinoxate. However, many experts believe that even using a chemical sunscreen is better than unprotected prolonged sun exposure.
There are other considerations when thinking about getting vitamin D through sunshine. An individual’s need for sunlight, how many minutes and times per week, hugely varies by personal characteristics such as skin color, geography, and time of year, and is very difficult to determine. Skin also gets less and less efficient with producing vitamin D in the skin from sun exposure with increasing age. Research shows that individuals older than age 70 have 75% less vitamin D production capability through sun-exposed skin.[10, 30]
A big reason that such a large percentage of the population is deficient in vitamin D is due to the fact that it is extremely difficult to get sufficient amounts through food and sun alone. While it is important to be aware of vitamin D rich foods as they are definitely beneficial in assisting with maintenance of healthy levels, most experts agree that food sources generally do not provide close to the recommended daily vitamin D levels.
Wild salmon is the best source of vitamin D from food, containing 447 UI (11 mcg) per serving. Atlantic, farmed salmon has a lower vitamin D content. A serving of tuna provides 154 IU (4 mcg) and an egg yolk, 41 IU (1 mcg). There are several foods on the market now that are fortified with vitamin D, such as milk (120 IU) and orange juice (137 IU). For reference, most health professionals recommend daily vitamin D intake in the range of 1,000 to 6,000 IU.[1, 31]
The easiest way to ensure optimal vitamin D levels is through supplementation with D3. However, not all supplements are the same in quality and efficacy. Many lower quality supplements consist of a synthetic version of D2, instead of the biochemically active version, D3. Research indicates that D3 supplements are 87% more potent in raising blood serum levels that their synthetic D2 counterparts.[18, 19]
Some people choose to supplement with cod liver oil as a food-based source of vitamin D. 1 tablespoon of cod liver oil has 1360 IU of vitamin D and some people respond well to it. However, the source of the cod and quality of the processing of the oil is important when choosing this type of supplementation. However, it is also important to note that cod liver oil contains naturally occurring vitamin A along with the vitamin D. Taking too much vitamin A, especially as it tends to accumulate in the body, could lead to toxicity and is dangerous.
Vitamin D3 supplements are available in pill and liquid form. When taking the pill form, it is important to have some kind of food or drink containing fat alongside it to increase absorption. Liquid forms of the supplement usually include some fat to increase absorption and can be taken alone. It is also recommended that vitamin D supplements are taken in the morning or no later than the mid-afternoon as there is some evidence that indicates that the processing of vitamin D in the body could interfere with proper melatonin production which is necessary for quality sleep.
Proper Dosage and Contraindications
Doctors, healthcare practitioners, researchers and national guideline experts vary on the recommended amount of daily vitamin D intake. Based on research, interviewing practitioners, and looking at current scientific studies, it seems that a daily supplementation level of 1,000 to 6,000 IUs per day is optimal to reach and maintain healthy vitamin D levels. Individuals who find out that they have deficient or insufficient vitamin D levels are advised to take supplementation on the upper end of this range, and many people take 5,000 IUs per day for long periods of time with no adverse effects. It is also generally wise to potentially vary supplementation levels according to lifestyle and dietary choices. For example, a person living in Boston may want to take 5,000 IUs per day in the wintertime and a lower amount during the summer, provided he or she is not using sunscreen when getting sun exposure.
Before determining the appropriate amount of vitamin D to supplement with, many doctors and health practitioners rely on a blood test to get a closer look at the level of deficiency present in any given individual. Deficiency is defined as having levels below 20 ng/mL and anything less than 30 ng/mL is considered insufficient. Most labs and doctors will look for levels of 30 to 50 ng/mL as a normal level of vitamin D in the blood. However, current research studies demonstrate that this target level may be too low for optimal body function and that a level of 40 to 60 ng/mL of vitamin D in the blood is suggested for optimal health.[10, 21, 22, 23] Individuals being treated for cancer, heart disease, or those recovering from surgery may benefit from having vitamin D levels that are even higher.
It will likely take at least several weeks to get blood serum levels to increase, depending on the level of deficiency, and for the individual to feel the effects of the higher level. For an individual supplementing with 1,000 IU/day, it could take 5-6 weeks, but some effects might be felt sooner. Most healthcare practitioners recommend retesting vitamin D levels after 10-12 weeks. When discovering a deficiency through a blood test, some people choose to supplement with 50,000 IU once a week for 8 weeks and then retesting their levels and starting a lower daily or weekly maintenance dose.
Vitamin D toxicity is extremely rare. One could be at risk for reaching toxic levels after supplementation with 50,000 IU (10x the normal supplementation dose) or more every day for several months. Toxic levels are believed to be reached when the serum vitamin D concentration reaches 150 ng/mL and are typically from long-term, very high dose use of supplements. Toxic levels of vitamin D can raise blood calcium levels above the normal range which can lead to kidney damage, cardiovascular system damage and other health consequences.
Possible drug interactions that should be discussed with a doctor include cholesterol lowering statins, steroid medications such as prednisone, and seizure drugs dilantin and phenobarbital. Furthermore, if you have or might have hyperparathyroidism, lymphoma, kidney stones, kidney disease, or liver disease you should discuss the decision to supplement with vitamin D with a doctor. Certain medications may interfere with vitamin D absorption and should be discussed with a doctor.
Another important point to keep in mind is that, for some, absorption and assimilation of vitamin D from both foods and supplements could be compromised if gut health is poor, as Vitamin D is absorbed in the small intestines. According to Harvard Medical School, if an individual suffers from conditions such as Chrohn’s disease, leaky gut syndrome, celiac disease, chronic pancreatitis or cystic fibrosis, vitamin D levels in the body could be compromised.
Recommended Products and Methodology
The primary differences between the vitamin D supplements on the market are product concentrations, patient preferences and non-active ingredients – some brands include fillers, binders, potential allergens and preservatives which may be harmful with long-term use.
For example, many common vitamin D brands contain soy, cholesterol, and stearates. Furthermore, we found numerous examples of products containing corn oil and artificial colors and preservatives.
See our recommended Vitamin D products and read more about our methodology for selecting recommended products.