Fitness is a 360 lifestyle and we’re here to help educate you about all aspects of maintaining optimum health and wellness. This week’s Supplement Spotlight is on vitamin D. This supplement controls the expression of over 1,000 genes in the human body. Please read below to learn more about why everyone should be supplementing with vitamin D.
Why is vitamin D so important?
Nearly every tissue and cell in our body has a vitamin D receptor. Without enough activated vitamin D in the body, dietary calcium cannot be absorbed. Calcium is essential for signaling between brain cells, development of bone, and tooth formation. Let’s be honest, nobody likes rickets.
Studies also reveal that low vitamin D levels in the body are associated with:
- Increased loss of muscle strength and mass as we age
- Increased risk of cancers
- Lower levels of immunity
- Higher blood pressure
- The development of neurological disorders
- The development of diabetes
Alright, so we just spend more time in the sun or pop some supplements. Not so fast.
Despite the importance of vitamin D, it’s estimated that anywhere from 30% to 80% of the U.S. population is vitamin D deficient. It’s likely worse among people with darker skin living in northern zones, as their skin pigmentation screens out the relatively limited sunlight more effectively.
Vitamin D levels can also be affected by age and body fat levels. As we age, our ability to make vitamin D is reduced by 75%. Furthermore, vitamin D can get trapped in body fat, leading to a 55% reduction in blood levels for those who are over-fat.
What you should know about vitamin D
Vitamin D is a fat soluble vitamin that exists in various forms. The animal form is vitamin D3 (cholecalciferol) and the plant form is vitamin D2 (ergocalciferol). Vitamin D2 and D3 are not biologically active; they must be modified in the body to have any effect.
The active form of vitamin D is indeed a hormone and is known as 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] or calcitriol. (Feel free to use that as a conversation starter the next time you’re picking up a hot date.) Both vitamin D2 and D3 have been commercially synthesized and both forms seem to be effective at maintaining blood levels of vitamin D in the body.
Vitamin D isn’t really a “true” vitamin, as we don’t need food to attain it. Natural sunlight allows our body to create vitamin D and even destroys excessive amounts. How does that happen?
Step #1: We convert cholesterol to 7-dehydrocholesterol, which is a precursor of vitamin D3.
Step #2: When we are exposed to UVB radiation, 7-dehydrocholesterol in the skin is converted to vitamin D3.
Step #3: Vitamin D3 must then be hydroxylated in the liver and the kidneys to become active. At this point, it can exert its endocrine effect.
Think you’re soaking up vitamin D through office/car windows? Wrong. Glass blocks virtually all UVB, preventing vitamin D from being made.
And sunscreen is similar. Applying sunscreen with an SPF of 15 will decrease the amount of vitamin D made in the body by about 99%. Hooray for basal cell carcinoma prevention. But bummer for vitamin D production.
Activated vitamin D has a serum half life of 2-3 weeks and its production in the skin is limited to 10,000-20,000 IU each day. Spending 20 minutes riding your bike outside in the summer sun produces 100 times more vitamin D than government agencies say you need. And once serum levels reach 150 nmol/L, any excess is inactivated. Thanks be to Mother Nature.
Vitamin D production via the sun can change throughout the year depending on where you live. If you live north of Atlanta, GA, you will make zero vitamin D from the sunlight between November and March. If you live below Atlanta, GA, you’ll be all right. It is possible to build some reserves of vitamin D, but these reserves won’t last longer than a few weeks.
Vitamin D is extremely rare in foods. It’s found in fish, cod liver oil, mushrooms, liver and eggs – but usually not in substantial amounts (except in cod liver oil).
Farmed varieties of fish contain very little vitamin D compared to the wild varieties. The only reason we even get vitamin D from foods like milk and cereal is because these foods are fortified with it — it doesn’t naturally occur.
Breast milk contains low amounts, with about 25 IU per liter.
Thus, getting enough vitamin D from whole foods is virtually impossible; it truly is the sunlight vitamin.
Fortification studies in adults show that consuming 100 – 1000 IU of vitamin D each day results in increased blood concentrations by 15 to 40 nmol/L. Other data with supplements indicate that for every 100 IU of vitamin D we ingest, we raise our blood levels by 2.5 nmol/L.
What intake is optimal?
An intake of greater than or equal to about 1000 IU may be needed for most of the population. For postmenopausal women and older men, 25(OH)D concentrations of less than 30 to 80 nmol/L are associated with negative health outcomes.
For infants at northern latitudes, studies suggest that 200 IU vitamin D2 per day may not be enough to prevent vitamin D deficiency. A meta-analysis in adults suggested that an increased intake of vitamin D3 of 100 IU per day was associated with an increase in circulating concentration of 25(OH)D of 1 to 2 nmol/L. A recent study on women in Maine found that 800 IU of vitamin D per day was enough to reach and maintain adequate blood levels during the winter (for most of the women).
Thorne’s D-5,000 is NSF Certified for Sport®. Vitamin D protects a number of important functions in the body.
Most often, vitamin D is made available in pre-mixed dilutions that frequently contain potentially detrimental ingredients such as lactose, as well as preservatives such as BHT, BHA, sodium benzoate, and sorbic acid. Thorne’s vitamin D is formulated for individuals who are sensitive to those ingredients.
D-5,000 is available for purchase at Forte Fitness: $14.00 for 60 capsules (two month supply). One of the most inexpensive yet important supplements you should be taking.
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