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Fat Soluble Vitamins---Vitamin D---Part I

Posted Aug 26 2008 12:41pm

This is one of the most forgotten and most important of the vitamins I've been researching. Fair warning---this will end up being multiple posts. I have found too many things to share, to try and put it all in one post.

Vitamins A, D, E and K are all classified as fat soluble vitamins - since they are soluble in fat and are absorbed by the body from the intestinal tract. They follow the same path of absorption as fat and any condition interfering with the absorption of fats would result in poor absorption of these vitamins as well. This class of vitamin can be stored in the body to some extent, mostly in the liver, and because of this, short term deficiencies are less likely to manifest themselves slower than the water-soluble vitamins.

Vitamin D is another one of the many deficiencies seen after WLS. Many post-ops just take this supplement combined in their calcium. Is that enough? Or better yet, is it the correct type? In doing this research, I've found that most of these supplements come in varying forms. It DOES matter which form you take. I'm not talking about pills vs liquids here. I'm talking about the variety of different types of the same vitamin.

First I'll give the role of Vitamin D in the body. Then we'll see how it applies to WLS.

Vitamin D is a fat-soluble vitamin that is essential for maintaining normal calcium metabolism. Vitamin D 3 (cholecalciferol) can be synthesized by humans in the skin upon exposure to ultraviolet-B (UVB) radiation from sunlight, or it can be obtained from the diet. Plants synthesize vitamin D 2 (ergocalciferol), which also has vitamin D activity in humans. When exposure to UVB radiation is insufficient for the synthesis of adequate amounts of vitamin D 3 in the skin, adequate intake of vitamin D from the diet is essential for health.

Vitamin D has many functions in the body, Calcium Balance, Cell Differentiation, Immunity, Insulin Secretion, and Blood Pressure Regulation. It has to ACTIVATED first to do anything.

Vitamin D itself is biologically inactive, and it must be metabolized to its biologically active forms. After it is consumed in the diet or synthesized in the skin, vitamin D enters the circulation and is transported to the liver. In the liver, vitamin D is hydroxylated to form 25-hydroxyvitamin D [25(OH)D], the major circulating form of vitamin D. Increased exposure to sunlight or increased intake of vitamin D increases serum levels of 25(OH)D, making the serum 25(OH)D concentration a useful indicator of vitamin D nutritional status. In the kidney and other tissues, the 25(OH)D 3 -1-hydroxylase enzyme catalyzes a second hydroxylation of 25(OH)D, resulting in the formation of 1alpha,25-dihydroxyvitamin D [1,25(OH)2D]—the most potent form of vitamin D. Most of the physiological effects of vitamin D in the body are related to the activity of 1,25(OH)2D.

Your doc can check your levels. Be specific---you need (25-OH-vitamin D3) level done. While I'm at it---Vitamin D is not really a vitamin---it is a steroid hormone precursor. I found this info in an article on The Heart Scan Blog . John Cannell on Vitamin D

The active form of vitamin D is a steroid (actually a seco-steroid) in the same way that testosterone is a steroid and vitamin D is a hormone in the same way that growth hormone is a hormone. Steroid hormones are substances made from cholesterol, which circulate in the body, and work at distant sites by "setting in motion" genetic protein transcription. That is, both vitamin D and testosterone regulate your genome, the stuff of life. While testosterone is a sex steroid hormone, vitamin D is a pleomorphic (multiple function) steroid hormone.

Now that we have it activated in the body. What is the body gonna do with it? Why is it so important? Let's find out, shall we.

Calcium Balance

Maintenance of serum calcium levels within a narrow range is vital for normal functioning of the nervous system, as well as for bone growth, and maintenance of bone density. Vitamin D is essential for the efficient utilization of calcium by the body (1) . The parathyroid glands sense serum calcium levels, and secrete parathyroid hormone (PTH) if calcium levels drop too low. Elevations in PTH increase the activity of 25(OH)D 3 -1-hydroxylase enzyme in the kidney, resulting in increased production of 1,25(OH)2D. Increasing 1,25(OH)2D production results in changes in gene expression that normalize serum calcium by 1) increasing the intestinal absorption of dietary calcium, 2) increasing the reabsorption of calcium filtered by the kidneys and 3) mobilizing calcium from bone when there is insufficient dietary calcium to maintain normal serum calcium levels. Parathyroid hormone and 1,25(OH)2D are required for the latter two effects

Now we know as post op WLSers, calcium absorption is a real biggy. It is SOP(standard operating procedure) for anyone having WLS to be on a calcium supplement twice a day for the rest of your our lives. Period. Not just any form of calcium either---it must be calcium citrate only, as I pointed out in this post here .

I'll discuss later how calcium and Vitamin D play such an important role in WLS.

Cell Differentiation

Cells that are dividing rapidly are said to be proliferating. Differentiation results in the specialization of cells for specific functions. In general, differentiation of cells leads to a decrease in proliferation. While cellular proliferation is essential for growth and wound healing, uncontrolled proliferation of cells with certain mutations may lead to diseases like cancer. The active form of vitamin D, 1,25(OH)2D, inhibits proliferation and stimulates the differentiation of cells.
In layman's terms it can help put a stop to cancer.


Vitamin D in the form of 1,25(OH)2D is a potent immune system modulator. The VDR is expressed by most cells of the immune system, including T cells and antigen-presenting cells, such as dendritic cells and macrophages (6) . Macrophages also produce the 25(OH)D 3 -1-hydroxylase enzyme that converts 25(OH)D to 1,25(OH)2D (7) . There is considerable scientific evidence that 1,25(OH)2D has a variety of effects on immune system function that may enhance innate immunity and inhibit the development of autoimmunity.
Here we have another example of a vitamin helping with the immune system. How many of you out there in WLSland stay sick about half the time? Are you getting enough of your vitamins???

Insulin Secretion

The VDR is expressed by insulin secreting cells of the pancreas , and the results of animal studies suggest that 1,25(OH)2D plays a role in insulin secretion under conditions of increased insulin demand (9) . Limited data in humans suggests that insufficient vitamin D levels may have an adverse effect on insulin secretion and glucose tolerance in type 2 diabetes (noninsulin-dependent diabetes mellitus; NIDDM).
I don't worry too much about this from my personal standpoint. The low carb/ketogenic diet I follow helps me with my insulin resistance.

Blood Pressure Regulation

The renin-angiotensin system plays an important role in the regulation of blood pressure (13) . Renin is an enzyme that catalyzes the cleavage (splitting) of a small peptide (Angiotensin I) from a larger protein (angiotensinogen) produced in the liver. Angiotensin converting enzyme (ACE) catalyzes the cleavage of angiotensin I to form angiotensin II, a peptide that can increase blood pressure by inducing the constriction of small arteries and increasing sodium and water retention. The rate of angiotensin II synthesis is dependent on renin (14) . Recent research in mice lacking the gene encoding the VDR, indicates that 1,25(OH)2D decreases the expression of the gene encoding renin through its interaction with the VDR (15) . Since inappropriate activation of the renin-angiotensin system is thought to play a role in some forms of human hypertension , adequate vitamin D levels may be important for decreasing the risk of high blood pressure.
In short, Vitamin D plays a round about role in helping keep your blood pressure under control. To quote Martha "it's a good thing".

To answer the questions I posed at the beginning of this post,no we probably don't get enough. Hey it's a fat soluble vitamin--we never get enough. Most people don't.

One Billion People Don't Get Enough Vitamin D

In the July 19 issue of the New England Journal of Medicine, Michael Holick, director of the General Clinical Research Center at Boston University School of Medicine and director of the Bone Healthcare Clinic at Boston Medical Center, published an overview of his work on vitamin D.

According to Holick, it has been estimated that one billion people in the world are vitamin D deficient or insufficient...

~ Washington Post

Also most of you just take your calcium/Vitamin D combo. First off most of these forms are the wrong type of calcium--calcium carbonate. Secondly, it is the wrong type of Vitamin D. Vitamin D Must Be Oil Based form. Tablets do not work. You can get Vitamin D from sunlight also.

Vitamin D, Sunshine, and Your Health

  • If you totally avoid the sun, recent research indicates you need about 4,000 units of vitamin D a day! Which means you can't get enough vitamin D from milk (unless you drink 40 glasses a day) or from a multivitamin (unless you take about 10 tablets a day), neither of which is recommended.
  • Most of us make about 20,000 units of vitamin D after about 20 minutes of summer sun. This is about 100 times more vitamin D than the government says you need every day.
  • The only way to be sure you have adequate levels of vitamin D in your blood is to regularly go into the sun, use a sun bed (avoiding sunburn), or have your physician administer a 25‑hydroxyvitamin D test . Optimal levels are around 50 ng/mL (125 nM/L ).
  • If you don't get vitamin D the way Mother Nature intended, from sunshine, you need to take supplemental vitamin D3 cholecalciferol. Since most of us get a lot more vitamin D from sunshine than we realize, most of us need about 2,000 units a day extra.

Well that does it for today. There is still alot of info to go on Vitamin D alone---so stay tuned.
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