Vitamin D3: Not Just for Strong Bones Anymore

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By Benjamin V. Treadwell, Ph.D.

vitamin-d3Depending on who you talk to, you may hear different opinions on taking vitamins. However, recent research indicates at least some of us, especially as we get older, may need more nutrition than our diet is providing. Certain vitamins may also help protect us from health concerns associated with aging. Take vitamin D3, for example, and its potential benefits related to type 2 diabetes.

What’s in a Name?
Vitamin D3 is actually a steroid-like hormone that was miss-classified. By definition, a vitamin is a micronutrient our cells cannot produce in sufficient quantities for optimal health. In fact, the body is able to manufacture enough of this substance under the right conditions – exposing the skin to sunlight.

“Vitamin D3 is actually a steroid-like hormone that was miss-classified.”

Early researchers didn’t make this connection. Instead, they observed that rickets (malformed bones related to vitamin D deficiency) didn’t occur in people on fish-rich diets. Since the nutrient was supplied by fish oil, not the body, it was considered a vitamin. What the scientists didn’t realize was that the fish oil “vitamin” was in the sun-activated form (D3). (See Juvenon Health Journal Volume 2, Number 6, “Vitamin D – A Vitamin in Need of Revision.”)

Vitamin D Developments
In recent years, we’ve learned a lot more about vitamin D3. It binds to specific receptors on cells to elicit its response. Contrary to earlier theories, these receptors are found on many other cells in addition to those associated with calcium transport for bone formation. Scientists have discovered them on liver, brain, pancreas and fat cells to name a few.

“Type 2 diabetes may be affected by vitamin D deficiency.”

The list of health concerns that may be associated with vitamin D deficiency has expanded dramatically, too. Along with abnormal bone formation, they may now include obesity, depression, immune system imbalances, type 2 diabetes…even cancer. However, to establish definite connections, there’s a lot more research to be done. (See Juvenon Health Journals Volume 5, Number 4, “Vitamin D – Recent Provocative Discoveries” and Volume 5, Number 3, “Vitamin D – A Hormone with New Health Benefits.”)

Current Research
In a very recent clinical trial at Tufts University, a research team set out to determine the effects of supplementing with vitamin D3 on a specific population: people at high-risk of developing type 2 diabetes or already in the early stages of the condition. Potential participants were carefully screened for experimental consistency.

“The results of the Tufts University vitamin D3 clinical trial were encouraging.”

Before starting the 16-week protocol, the 92 subjects underwent a series of tests to establish various baseline levels for comparison at the end of the study. They included blood sugar before and after injection of intravenous glucose and plasma blood hemoglobin protein, HbA1c, (elevated in diabetic patients).

Participants were randomly assigned to one of three groups. Group one took 2,000 IU of vitamin D3 only each day. Group two also took 2,000 IU of vitamin D3 daily, but combined with 800 mg of calcium. Group three took a placebo capsule that contained neither vitamin D3 nor calcium.

Promising Indications
The results were encouraging. The vitamin D3 group, compared to the placebo group, showed a significant increase in secretion of insulin in response to intravenous injection of glucose. This improvement in pancreatic function means the body is better able to metabolize glucose, preventing potential damage.

“The vitamin D3 group showed an improvement un pancreatic function.”

Consistent with this finding, the rate of increase of HbA1c trended lower with those taking vitamin D3. Although this data was not statistically significant, the investigators felt it was meaningful, particularly in such a short-term study. (Side note: adding calcium didn’t produce any effect, positive or negative.)

Vitamin D3, You and Me
Because participants in the Tufts University trial were borderline type 2 diabetics (pre or early stage), the results can really only be theoretically extrapolated to this segment of the population. The authors comment that it will take longer-term trials to support vitamin D3’s effectiveness in reducing the probability of diabetes for individuals already at high risk. They never suggest their results apply to everyone, or imply that we all should take 2,000 IU of vitamin D per day to improve glucose metabolism and slow the onset of type 2 diabetes.

“Could vitamin D3 help regulate pancreatic insulin secretion and glucose metabolism?”

However, many vitamin experts do feel the optimal intake of D3 is significantly greater than the RDA of 600 mg. Many also believe the older we are, the higher the dosage should be. Aging skin seems to be less able to absorb the sunlight needed for the body to activate enough of this micronutrient.

The upper safe limit for vitamin D was recently raised to 2,000 IU per day. Although this is still controversial (Many experts feel it should also be much higher.), the vitamin appears to be far less toxic than previously thought, even at very high doses. In any case, more and larger trials are definitely called for. Research needs to corroborate these preliminary indications that vitamin D3 could be key to regulating insulin secretion by the pancreas, as well as glucose metabolism.

Ask Ben Dr. Treadwell
answers your questions.

question:  I have read about the potential benefits from taking vitamin D. I was wondering whether there is a danger in taking too much vitamin D, as some suggest taking as much as 5,000-10,000 IU per day. — D

answer: Vitamin D is actually a hormone synthesized by the body, although often not in sufficient amounts for optimal health (hence, the “vitamin” label). How much vitamin D the body makes depends on skin tone, age (less for those of us over 50), whether your diet is high in fat and sunlight exposure.

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The potential benefits of Vitamin D supplements have received a lot of attention in recent years. But scientists are still debating how much the body needs to prevent or attenuate health conditions that may be associated with deficiency. Many feel we need a lot more than the current RDA of 400-600 IU. 2,000 IU is generally accepted as the safe upper limit.

Because of all the variables, I recommend consulting your health professional on the best dosage. I suggest staying below 2,000 IU until more research is done. You’ll also want to select a good quality D3 supplement. Vitamin D3 is ready to be modified by the liver, kidney and various body tissues for a range of biological activities.

Dr. Benjamin V. Treadwell is a former Harvard Medical School professor.

Research Update
With the growing popularity of processed foods that are high in sugar, type 2 diabetes is becoming more common. A group of
Boston-area investigators set out to determine whether supplementing with vitamin D3 would positively affect this health concern.

The team – from Tufts Medical Center, the USDA Human Nutrition Research Center on Aging at Tufts University, the Departments of Nutrition and Epidemiology at the Harvard School of Public Health, and the Channing Laboratory research division of Brigham and Women’s Hospital and Harvard Medical School – recently published their findings inThe American Journal of Clinical Nutrition.

Early observational studies on a possible association between low levels of plasma vitamin D and a higher risk of type 2 diabetes prompted the group’s interest. Theirs would be the first clinical trial to study the effects of supplemental vitamin D3 in humans.

The research involved 92 participants, prescreened for higher risk of developing type 2 diabetes. All the subjects were examined before the start of the trial to establish baseline levels for glucose tolerance, HbA1c (marker for blood glucose level/glycemia), insulin secretion and insulin sensitivity. These tests confirmed that 93% were at high risk and 7% were in the early stages of the condition.

The population was divided into three groups. The participants received either 2,000 IU of vitamin D3 alone, 2,000 IU of D3 plus 800 mg of calcium, or a placebo daily. After 16 weeks, the investigators repeated the pre-trial tests.

The results? A statistically significant improvement in insulin release (pancreatic function as measured by the glucose tolerance test) for the D3 groups, as compared to the placebo group. There was, however, no change in insulin sensitivity for either D3 group. (Adding calcium had no effect within the parameters of this trial.) Although the rate of HbAc1 formation (glycemia) trended lower in the D3 groups, as compared to placebo, this result was not statistically significant.

The research team noted their trial suggests that supplementing with vitamin D may help improve glycemia and slow the progression to clinical type 2 diabetes in adults at high risk. However, they also cautioned that, because their study lasted only 16 weeks and wasn’t powered for hard clinical outcomes, larger, longer trials are needed to confirm their findings.

Read abstract here.
This Research Update column highlights articles related to recent scientific inquiry into the process of human aging. It is not intended to promote any specific ingredient, regimen, or use and should not be construed as evidence of the safety, effectiveness, or intended uses of the Juvenon product. The Juvenon label should be consulted for intended uses and appropriate directions for use of the product.