Let the Sun Shine
If you have type 2 diabetes, or if you’ve been diagnosed with a pre-diabetic condition, you may be deficient in one vitamin that could help make a big difference in your health.
I’m not talking about vitamin C or vitamin E, although both of these vitamins have been shown to be essential in helping prevent kidney disease in diabetics (see the e-Alert “Take 2” 7/28/03).
According to new research from the American Journal of Clinical Nutrition, vitamin D may play a key role in glucose metabolism. But how do you know if you’re vitamin D deficient? And what are the best sources?
My “what” level?
Off hand, do you know what your 25-hydroxyvitamin D level is?
Neither do I. But the next time my doctor draws blood I’m going to ask him to make a note of the level of this marker (also known as 25(OH)D), because it’s the best way to tell if you’re getting enough vitamin D.
Researchers at the University of California-Los Angeles School of Medicine (UCLA) recently examined the relation of 25(OH)D to insulin sensitivity in a group of 126 adults with normal glucose- tolerance. After determining the subjects’ 25(OH)D levels, the UCLA team gauged the responsiveness of the pancreas to glucose using a technique called hyperglycemic clamp.
Compared to subjects with the highest vitamin D levels, those with the lowest levels had symptoms of type 2 diabetes, including weaker pancreatic function and greater insulin resistance. In addition, 30 percent of the subjects with low vitamin D levels had one or more of the symptoms associated with metabolic syndrome x (MSX). Only 11 percent of those with normal vitamin D levels showed similar symptoms.
In the e-Alert “X Marks the Spot” (4/15/04), I told you about the primary MSX indicators:
* Excessive abdominal fat
* Elevated blood pressure (130/85 or higher)
* Low HDL cholesterol level (Less than 50 in women, less than 40 in men)
* Elevated Triglyceride level
* Elevated C-reactive protein level
* Fasting glucose level that indicates insulin resistance/glucose intolerance
A combination of just three or more of these symptoms creates an elevated risk of heart disease and type 2 diabetes.
Light of day
The best dietary sources of vitamin D are eggs, liver, fish liver oils, and oily fish such as salmon, sardines, trout, and tuna. But by far, the best source of vitamin D is through sun exposure. When your skin is exposed to ultraviolet light, your body responds by manufacturing vitamin D.
Of course, the idea of sun exposure runs against the current popular “wisdom” that you should completely avoid sunlight unless covered scalp to ankles with sunblock. But as Dr. Jonathan V. Wright, M.D., has pointed out in his Nutrition & Healing newsletter, sun exposure is not only good, it’s essential. The damage that can set the stage for skin cancer comes when exposure is extreme and results in sunburned skin.
Unfortunately, the amount of sun needed to prompt the body to create vitamin D is only available in most of the U.S. during the summer months. For the remainder of the year – and for those who live in extreme northern and southern latitudes – the most accessible source of vitamin D is from fish oil supplements.
Good values
As I mentioned above, the first step in determining if your vitamin D intake is sufficient is to assess blood serum levels of 25(OH)D. According to natural medical physician Dr. Joseph Mercola, the optimal 25(OH)D value is 115-128 millimicromolar (nmol/L). A value below 50 is considered a serious deficiency that increases the risk of chronic diseases, including breast and prostate cancer.
By some estimates, as much as 40 percent of the population is vitamin D deficient, with a relatively small percentage qualifying in the optimal 25(OH)D range. So how can you make sure you’re getting enough D? In addition to sun exposure and dietary sources, fish oil supplements provide a convenient way to boost 25(OH)D.
In a 1999 issue of the American Journal of Clinical Nutrition, Reinhold Vieth, M.D., of the University of Toronto laid out some guidelines for supplementing above the vitamin D recommended dietary allowance of 200 IU per day. Dr. Vieth wrote that in order for 25(OH)D to exceed 100 nmol/L, a daily vitamin D intake of 4,000 IU is necessary. And Dr. Vieth notes that, except for people who have a hypersensitivity to vitamin D, there are no adverse effects with 25(OH)D levels under 140 nmol/L. But to reach that upper level you’d need to take 10,000 IU per day.
But before you begin taking fish oil supplements, there are two important details to keep in mind:
* If you get regular, daily sun exposure during the summer, chances are you don’t need a D supplement during those three months of the year
* Choose a fish oil supplement that’s “molecularly distilled” to insure that toxins are kept to a minimum
And, as always, talk to your doctor or health care provider before starting any new dietary supplement regimen.
Sources:
“Hypovitaminosis D is Associated with Insulin Resistance and Beta Cell Dysfunction” American Journal of Clinical Nutrition, Vol. 79, No. 5, May 2004, ncbi.nlm.nih.gov
“Low Vitamin D Linked to Insulin Resistance” David Douglas, Reuters Health, 6/29/04, reutershealth.com
“Test Values and Treatment for Vitamin D Deficiency” Dr. Joseph Mercola, 2/23/02, mercola.com
“Vitamin D supplementation, 25-Hydroxyvitamin D Concentrations, and Safety” Reinhold Vieth, M.D., American Journal of Clinical Nutrition, Vol. 69, No. 5, May 1999, ncbi.nlm.nih.gov
