The Power of Vitamin D

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You’ve likely heard of Vitamin D.  You also probably know that us humans get our D from the sun, or things like fortified milk or orange juice.  Do you know why it’s so important? Are you getting enough?

Did you know that in a study published by the NIH, 41.6% of adults in the US were diagnosed with a vitamin D deficiency?! Even more for some groups!
Vitamin D deficiency has been linked to fatigue, depression, cardiovascular disease, kidney disease, chronically getting sick with every bug that goes around, muscle weakness, even psoriasis!
It’s so important to take a vitamin D supplement year round, but ESPECIALLY in the winter when there is less sunshine, we are more covered, and we spend less time outside.

What is Vitamin D?

Vitamin D is a fat-soluble vitamin that is naturally present in very few foods, added to others, and available as a dietary supplement. It is also produced endogenously when ultraviolet rays from sunlight strike the skin and trigger vitamin D synthesis.

Vitamin D promotes calcium absorption in the gut and maintains adequate serum calcium and phosphate concentrations to enable normal mineralization of bone. It is also needed for bone growth and bone remodeling. Without adequate vitamin D, bones can become thin, brittle, or misshapen. Vitamin D sufficiency prevents rickets in children and osteomalacia in adults.  Together with calcium, vitamin D also helps protect older adults from osteoporosis.

Vitamin D has other roles in the body, including cell growth, neuromuscular and immune function, and reduction of inflammation.

How Much Do I Need?

There is considerable discussion of the serum concentrations that is associated with deficiency (e.g., rickets), adequacy for bone health, and optimal overall health, and cut points have not been developed by a scientific consensus process. Based on its review of data of vitamin D needs, a committee of the Institute of Medicine concluded that persons are at risk of vitamin D deficiency at serum 25(OH)D concentrations <30 nmol/L (<12 ng/mL). Some are potentially at risk for inadequacy at levels ranging from 30–50 nmol/L (12–20 ng/mL). Practically all people are sufficient at levels ≥50 nmol/L (≥20 ng/mL); the committee stated that 50 nmol/L is the serum 25(OH)D level that covers the needs of 97.5% of the population. Serum concentrations >125 nmol/L (>50 ng/mL) are associated with potential adverse effects  (Table 1).

Table 1: Serum 25-Hydroxyvitamin D [25(OH)D] Concentrations and Health*
nmol/L** ng/mL* Health status
<30 <12 Associated with vitamin D deficiency, leading to rickets in infants and children and osteomalacia in adults
30–50 12–20 Generally considered inadequate for bone and overall health in healthy individuals
≥50 ≥20 Generally considered adequate for bone and overall health in healthy individuals
>125 >50 Emerging evidence links potential adverse effects to such high levels, particularly >150 nmol/L (>60 ng/mL)

* Serum concentrations of 25(OH)D are reported in both nanomoles per liter (nmol/L) and nanograms per milliliter (ng/mL).
** 1 nmol/L = 0.4 ng/mL

 

Do you know what your levels are?

 

Sources of Vitamin D

So where do you get Vitamin D?

Food
I’ve always preferred to get my nutrients primarily from food sources.  However, I have learned over the last few years that it is often very difficult to do so, ESPECIALLY when it comes to Vitamin D.  Very few foods in nature contain vitamin D. The flesh of fatty fish (such as salmon, tuna, and mackerel) and fish liver oils are among the best food sources. Small amounts of vitamin D are found in beef liver, cheese, and egg yolks. Vitamin D in these foods is primarily in the form of vitamin D3 and its metabolite 25(OH)D3 . Some mushrooms provide vitamin D2 in variable amounts.

Fortified foods provide most of the vitamin D in the American diet. For example, almost all of the U.S. milk supply is voluntarily fortified with 100 IU/cup. Other dairy products made from milk, such as cheese and ice cream, are generally not fortified. Ready-to-eat breakfast cereals often contain added vitamin D, as do some brands of orange juice, yogurt, margarine and other food products.

Vitamin D Deficiency

Nutrient deficiencies are usually the result of dietary inadequacy, impaired absorption and use, increased requirement, or increased excretion. A vitamin D deficiency can occur when usual intake is lower than recommended levels over time, exposure to sunlight is limited, the kidneys cannot convert 25(OH)D to its active form, or absorption of vitamin D from the digestive tract is inadequate.

Prolonged exclusive breastfeeding without the recommended vitamin D supplementation is a significant cause of rickets, particularly in dark-skinned infants breastfed by mothers who are not vitamin D replete. Additional causes of rickets include extensive use of sunscreens and placement of children in daycare programs, where they often have less outdoor activity and sun exposure.

In adults, vitamin D deficiency can lead to osteomalacia, resulting in weak bones. Symptoms of bone pain and muscle weakness can indicate inadequate vitamin D levels, but such symptoms can be subtle and go undetected in the initial stages.

Groups at Risk of Vitamin D Inadequacy

Obtaining sufficient vitamin D from natural food sources alone is difficult. For many people, consuming vitamin D-fortified foods and, arguably, being exposed to some sunlight are essential for maintaining a healthy vitamin D status. Most also require dietary supplements might be required to meet the daily need for vitamin D, and especially to reach levels for optimal health.

Breastfed infants
Vitamin D requirements cannot ordinarily be met by human milk alone, which provides <25 IU/L to 78 IU/L. (The vitamin D content of human milk is related to the mother’s vitamin D status, so mothers who supplement with high doses of vitamin D may have correspondingly high levels of this nutrient in their milk.)

Older adults
Older adults are at increased risk of developing vitamin D insufficiency in part because, as they age, skin cannot synthesize vitamin D as efficiently, they are likely to spend more time indoors, and they may have inadequate intakes of the vitamin. As many as half of older adults in the United States with hip fractures could have serum 25(OH)D levels <30 nmol/L (<12 ng/mL).

People with limited sun exposure
Home bound individuals, women who wear long robes and head coverings for religious reasons, and people with occupations that limit sun exposure are unlikely to obtain adequate vitamin D from sunlight.  Those that live in the Northern Hemisphere fall into this category as well.  Because the extent and frequency of use of sunscreen are unknown, the significance of the role that sunscreen may play in reducing vitamin D synthesis is unclear. Ingesting RDA levels of vitamin D from foods and/or supplements will provide these individuals with adequate amounts of this nutrient.

People with dark skin
Greater amounts of the pigment melanin in the epidermal layer result in darker skin and reduce the skin’s ability to produce vitamin D from sunlight. Various reports consistently show lower serum 25(OH)D levels in persons identified as black compared with those identified as white. It is not clear that lower levels of 25(OH)D for persons with dark skin have significant health consequences. Those of African American ancestry, for example, have reduced rates of fracture and osteoporosis compared with Caucasians. Ingesting RDA levels of vitamin D from foods and/or supplements will provide these individuals with adequate amounts of this nutrient.

People with inflammatory bowel disease and other conditions causing fat malabsorption
Because vitamin D is a fat-soluble vitamin, its absorption depends on the gut’s ability to absorb dietary fat. Individuals who have a reduced ability to absorb dietary fat might require vitamin D supplementation. Fat malabsorption is associated with a variety of medical conditions, including some forms of liver disease, cystic fibrosis, celiac disease, and Crohn’s disease, as well as ulcerative colitis when the terminal ileum is inflamed. In addition, people with some of these conditions might have lower intakes of certain foods, such as dairy products fortified with vitamin D.

People who are obese or who have undergone gastric bypass surgery
A body mass index ≥30 is associated with lower serum 25(OH)D levels compared with non-obese individuals; people who are obese may need larger than usual intakes of vitamin D to achieve 25(OH)D levels comparable to those of normal weight. Obesity does not affect skin’s capacity to synthesize vitamin D, but greater amounts of subcutaneous fat sequester more of the vitamin and alter its release into the circulation. Obese individuals who have undergone gastric bypass surgery may become vitamin D deficient over time without a sufficient intake of this nutrient from food or supplements, since part of the upper small intestine where vitamin D is absorbed is bypassed and vitamin D mobilized into the serum from fat stores may not compensate over time.

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Vitamin D and Health

Optimal serum concentrations of 25(OH)D for bone and general health have not been established; they are likely to vary at each stage of life, depending on the measures selected.

The FNB committee that established DRIs for vitamin D extensively reviewed a long list of potential health relationships on which recommendations for vitamin D intake might be based. These health relationships included resistance to chronic diseases (such as cancer and cardiovascular diseases), physiological parameters (such as immune response or levels of parathyroid hormone), and functional measures (such as skeletal health and physical performance and falls). With the exception of measures related to bone health, the health relationships examined were either not supported by adequate evidence to establish cause and effect, or the conflicting nature of the available evidence could not be used to link health benefits to particular levels of intake of vitamin D or serum measures of 25(OH)D with any level of confidence. This overall conclusion was confirmed by a more recent report on vitamin D and calcium from the Agency for Healthcare Research and Quality, which reviewed data from nearly 250 new studies published between 2009 and 2013. The report concluded that it is still not possible to specify a relationship between vitamin D and health outcomes other than bone health.

Depression
Some studies suggest an association between low vitamin D levels in the blood and various mood disorders, including depression, seasonal affective disorder (SAD), and premenstrual syndrome (PMS). Also vitamin D supplementation may improve symptoms of depression associated with SAD.

Osteoporosis
More than 40 million adults in the United States have or are at risk of developing osteoporosis, a disease characterized by low bone mass and structural deterioration of bone tissue that increases bone fragility and significantly increases the risk of bone fractures. Osteoporosis is most often associated with inadequate calcium intakes, but insufficient vitamin D contributes to osteoporosis by reducing calcium absorption. Although rickets and osteomalacia are extreme examples of the effects of vitamin D deficiency, osteoporosis is an example of a long-term effect of calcium and vitamin D insufficiency. Adequate storage levels of vitamin D maintain bone strength and might help prevent osteoporosis in older adults, non-ambulatory individuals who have difficulty exercising, postmenopausal women, and individuals on chronic steroid therapy .

Cancer
Laboratory and animal evidence as well as epidemiological data suggest that vitamin D status could affect cancer risk.

Vitamin D emerged as a protective factor in a prospective, cross-sectional study of 3,121 adults aged ≥50 years (96% men) who underwent a colonoscopy. The study found that 10% had at least one advanced cancerous lesion. Those with the highest vitamin D intakes (>645 IU/day) had a significantly lower risk of these lesions .

Other conditions
A growing body of research suggests that vitamin D might play some role in the prevention and treatment of type 1  and type 2 diabetes, hypertension, glucose intolerance, multiple sclerosis, and other medical conditions. However, most evidence for these roles comes from in vitro, animal, and epidemiological studies, not the randomized clinical trials considered to be more definitive. Until such trials are conducted, the implications of the available evidence for public health and patient care will be debated. One meta-analysis found use of vitamin D supplements to be associated with a statistically significant reduction in overall mortality from any cause, but a reanalysis of the data found no association. A systematic review of these and other health outcomes related to vitamin D and calcium intakes, both alone and in combination, was published in August 2009.

 

Vitamin D Supplementation

Since it is nearly impossible to get all of the vitamin D we need from our food, and certainly if we want to have optimal levels for health, supplementation is essential.  Just be mindful of the company you buy from! I get mine here.

I take a natural vitamin from a company with the highest quality standards.  In nearly 60 years, they have never had a recall! That’s unheard of! If you have any questions about vitamin D or supplementation, leave a comment or send me a message!

 

 

References

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