Vitamin D is Crucial to Overall Health

Are you getting enough vitamin D? It is vital you do! This super vitamin, which the skin produces in response to ultraviolet (UV) rays from the sun, is not only important for strong healthy bones, it is also necessary for your overall health. It’s an essential factor in making sure your muscles, heart, lungs and brain work well, and it helps your body fight cancer.

Low levels of vitamin D have been found to be very common in the United States and Canada, resulting in significant health problems.¹  Vitamin D insufficiency is now recognized as a pandemic, affecting 30-50 percent of the population.^1,2  Vitamin D insufficiency is a key contributor to many human diseases including several cancers, diabetes, cardiovascular disease, depression, cognitive decline, and autoimmune diseases.^{1, 3}

It is estimated that over 50 million adults in the United States either have, or are at risk of developing, osteoporosis.⁴  Osteoporosis is a condition where you lose too much bone or don’t make enough bone to replace the bone that you normally lose. If you lose too much bone, your bones become less dense and are more likely to break. People with osteoporosis have low bone density. Maintaining vitamin D sufficiency is crucial for bone health, and a key feature in a strategy to prevent osteoporosis.

Vitamin D’s role in bone health

Vitanin D functions as a hormone because it sends a message to the intestines to increase the absorption of calcium and phosphorus. By promoting calcium absorption, vitamin D helps to form and maintain strong bones.Vitamin D also stimulates osteoblastic (bone-building cells) activity. Vitamin D deficiency results in diminished calcium absorption, and has been linked to a higher incidence of osteoporosis-related bone fractures seen in postmenopausal women and older Americans.^{3, 5} 

There have been claims that vitamin D supplementation is unnecessary for bone health. A 2015 analysis pooled many studies and stated the conclusion that vitamin D supplementation does not reduce the risk of falls or other negative outcomes by 15 percent or more.⁶

However, there are details to be considered. This analysis did not take  into account D2 vs. D3, and also did not group studies by the dose of vitamin D. A previous pooled analysis, which analyzed studies based on the dose of vitamin D, established that dose matters. This analysis  considered the actual intake of vitamin D, not just whether or not the person had been assigned to the supplement group. In this analysis, there was a 30 percent reduction in hip fracture rate at the highest level of vitamin D intake (792-2000 IU) in the supplement groups compared to the control groups. ^{7, 8}

An earlier meta-analysis supports this idea, recommending 800 IU as the minimum effective dose.⁹ However, another meta-analysis in 2018 disagreed; the authors did not find a reduction in risk even when examining only trials that used 800 IU/day or more.^{10, 11}

We don’t know exactly why the results of these analyses have not been consistent. There are many factors that affect bone health, including weight-bearing physical activity. A combination of nutrients work together to keep bones strong, including vitamin D, calcium, magnesium, phosphorus, vitamin K, and polyphenols.

In many supplementation studies, the baseline blood vitamin D levels of the patients are not taken into account. Vitamin D is probably most effective when it moves someone from a level of deficiency or insufficiency to sufficiency. If the dose is too small to achieve that, or if many of the participants are already sufficient, we may not see an effect.

Regardless, vitamin D is an essential nutrient, and it is imperative to get adequate amounts to perform all of its vital functions in the body. For many people, supplementation is necessary to be vitamin D sufficient.

Vitamin D  fights  multiple diseases, including cancer  

Vitamin D is known to have protective effects on bone health, and, in addition, vitamin D has several other critical functions.

Scientists have found that vitamin D has biological actions in almost every cell and tissue in the human body. Keeping vitamin D levels in the favorable range is associated with a longer life. In the elderly and in middle-aged adults, in a variety of different populations from different countries, sufficient vitamin D levels were linked to a lower risk of death from cancer, cardiovascular disease, or all causes. ^12-15 Vitamin D regulates several genes and cellular processes related to cancer progression. Some of the most groundbreaking findings in nutrition science in recent years have been evidence of the powerful protection provided by vitamin D against common cancers:

• Breast cancer: Higher blood vitamin D levels are associated with a lower risk of being diagnosed with breast cancer and a higher rate of survival among women who have already been diagnosed.¹⁶
• Colorectal cancer: A 2015 review of 15 studies found that sufficient vitamin D levels were consistently associated with reduced risk of colorectal cancer. ¹⁷ Even after diagnosis with colorectal cancer, higher vitamin D levels are associated with reduced mortality.¹⁸  
• Cancers of the prostate, pancreas, lung, and endometrium are also associated with vitamin D insufficiency. ^{1, 19}

Vitamin D has growth-inhibitory effects on cells derived from breast, colon, prostate, and skin cancers, and a 2014 meta-analysis concluded that supplementation with vitamin D3 was associated with a 12 percent lower risk of death from cancer. ²⁰ D3 is the natural form of the vitamin, made by the body in response to sunlight. Because it is absorbed better and  is more effective, less D3 is needed than D2 ^21-25  In a review of 56 trials of vitamin D supplementation, vitamin D3 was found to decrease mortality risk, however D2 was not. ^20 26 For comparison, the tolerable upper limit (the maximum recommended daily dose) is currently 4000 IU.

Large doses of hundreds of thousands of IUs may be problematic even when using vitamin D3. For example, a study testing a dose of 500,000 IU vitamin D3 in elderly women found an increased the rate of falls, and a trend toward an increase in fracture risk compared to placebo.²⁷

One possible explanation of these negative effects is that the excessively large dose of vitamin D could have stimulated rapid bone turnover, resulting in the breakdown of existing bone.²⁸ Not all studies on high dose vitamin D showed negative effects. ²⁹

However, a recent meta-analysis pooled all the conflicting data, and concluded that high dose vitamin D supplementation had no effect on fracture risk but slightly increased the risk of falls. ³⁰

A moderate, consistent daily dose of D3 is a safe and conservative method to keep vitamin D levels in a healthy range, not too high and not too low.
There is significant scientific agreement that a blood level of 25(OH)D (twenty-five-hydroxyvitamin D) should be at least 30 ng/ml for several aspects of health.^{14, 31, 32} It is reasonable, therefore, to supplement if one’s levels fall below this optimal range.

But again, more is not always better; the research suggests that increasing one’s 25(OH)D above approximately 45 ng/ml confers no further benefit and may even be detrimental.^{14, 33-36}

Getting the right amount of vitamin D
For most people, the principal source of vitamin D is  produced by the skin in response to sunlight. Very few foods naturally contain vitamin D, and achieving adequate vitamin D levels via sunlight can be difficult depending on your geographical location, skin color, and opportunities for sun exposure, especially in the winter months.

Also, sun exposure to assure optimal Vitamin D status may damage and age the skin increasing wrinkling, mottling and the risk of skin cancer. A smart option is a moderate daily dose of vitamin D3, not too much or too little.

We should aim for the sweet spot of blood 25(OH)D to be between 30 to 45 ng/ml, as suggested by the scientific evidence^{14, 32, 37} 

We should choose D3, the natural form of the vitamin, the form the body produces in response to sunlight. There is overwhelming evidence of benefit, and no risks noted in a reasonable dose. Ingest a moderate daily dose of supplemental vitamin D3 (approximately 50 mcg or 2000 IU/day) to reach the 30-45 ng/ml window. If you do not supplement, it makes sense to have your 25(OH)D levels tested and be proactive about your health because a long-standing deficiency can be harmful. If 25(OH)D is between 25 and 30 while taking 2000 IU (50 mcg), instead of increasing the dose, I recommend making sure the supplement is taken with a meal with fat (nuts and seeds) for better absorption. Only for those whose 25(OH)D is below 25 do I recommend moving the daily dose up to 3000 IU.