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The Cardiometabolic Benefits of Vitamin D

The Cardiometabolic Benefits of Vitamin D

What Is Vitamin D?

Vitamin D2 and D3 are fat-soluble (absorbed with dietary fat and stored in fat and liver tissue) dietary nutrients, that are also hormones. While there is some controversy, most health professionals agree that vitamin D is technically a hormone (or a prohormone, a precursor to a hormone) and not a nutrient because of how it can be synthesized by the body (thank you sun), is activated by the liver and kidneys, and acts to regulate calcium metabolism. Vitamin D is naturally present in few foods and in small amounts. D3 (cholecalciferol) can be found in animal sources such as salmon and egg yolks, while mushrooms are one of the only sources of plant-derived D2 (ergocalciferol). However, the majority of dietary intake generally comes from fortified foods such as milk and cereals. While neither form is better, D3, which your body can also produce in response to exposure to UV B rays, is more effective in raising vitamin D levels in the blood (2). A glass of milk or a daily supplement is a start, but the best way to raise vitamin D levels is to spend a little more time outside; a daily 15-minute walk should do the trick.

Along with regulating calcium metabolism – so you can build and maintain strong bones and teeth – vitamin D is vital for:

Immune and nervous system function.

Brain development and health.

Influencing gene expression involved in the progression of diseases such as cancer and various autoimmune disorders (3).

Regulating blood levels of the vital nutrients magnesium and phosphorous.

If you are having difficulty recovering from illness or are experiencing fatigue and unexplained muscle pain, low vitamin D levels may be a factor. In addition, there is a growing body of evidence that vitamin D is crucial for cardiometabolic health. Difficulty maintaining a healthy weight and regulating blood sugar levels may be other signs that your vitamin D levels are low.

Vitamin D, Obesity, and Insulin Resistance: The Association

Several studies have shown an association between obesity, increased body fat composition, and vitamin D deficiency (4). While there are several theories—primarily that obese individuals have less healthy lifestyles, spending less time under the sun and consuming less foods that are naturally high in vitamin D—there isn’t a consensus within the scientific and medical communities. What we do know is that vitamin D requirements are, in part, dependent on body weight as excess fat decreases the activity of the enzymes necessary to convert vitamin D into its active form (1,25-dihydroxycholecalciferol or calcitriol) (5). The more excess body fat you carry around, the more vitamin D per pound of body weight you need to reach the same blood serum levels (6).

Similarly, research has consistently shown that low vitamin D levels are associated with insulin resistance and the progression of type 2 diabetes (7). Like obesity, the association isn’t entirely clear, but we do know that vitamin D deficiency can reduce the activity of the proteins (GLUT-4) that are responsible for insulin regulating the uptake of glucose into muscle and fat cells (8). Low vitamin D levels, obesity, and insulin resistance seem to begin a progressive cycle of metabolic dysregulation: the lifestyle behaviors that promote low vitamin D increase risk for obesity and insulin resistance, increasing weight increases the need for vitamin D, and low vitamin D levels impair your ability to effectively use the insulin your body produces.

On the sunny side, studies have shown that weight loss can significantly increase vitamin D levels without a change in intake, and the greater the weight loss the greater the improvement (9). Increasing vitamin D levels, whether through outside activity or supplementation, may help reverse the cycle of metabolic dysregulation by impeding the formation of new fat cells and promoting higher levels of the fat-burning hormone testosterone (10-12). Vitamin D levels may also indirectly influence appetite through regulation of serotonin, a neurotransmitter that affects your mood and desire for food (13). Furthermore, supplementing with vitamin D3 may improve insulin sensitivity and promote the healthy function of beta cells (cells in the pancreas that make insulin) in individuals who are at high risk for developing type 2 diabetes (14).

There is far more to vitamin D than milk and strong bones. While the two primary forms of vitamin D, D2 and D3, promote absorption of calcium and regulation of its levels in the blood, that is just scratching the surface of their importance. Current estimates suggest that nearly 1 out of 4 U.S. adults are vitamin D deficient and about 6% are severely deficient, resulting in weakened bones and increased risk for type 2 diabetes (1). Vitamin D is vitally important for cardiometabolic health, so if you are experiencing an increased struggle maintaining your weight or blood sugar levels, one of the first steps may be to consult your Prime Meridian Healthcare™ provider about assessing your vitamin D levels.

Should I Supplement?

Current recommendations suggest adults get at least 600 IU of vitamin D per day from diet alone (available from ~4 ounces of salmon) to supplement sunshine (30 minutes of midday sun provides 10,000–20,000 IU) (15). However, remember that the heavier you are, the more vitamin D you need to reach adequate serum levels (20–50 ng/mL), and so a blood test is the only effective way to identify a deficiency.

Along with adding a whole egg and mushroom omelet to the breakfast rotation and spending some more time under the sun, you should talk to your healthcare providers about vitamin D supplementation if:

+ A blood test confirms a deficiency.

+ You are obese and/or insulin resistant, a post-menopausal or expectant woman, or on long-term steroids.

+ You have a condition that affects vitamin D levels, such as chronic kidney disease or parathyroid disease.

Should I Supplement?

Current recommendations suggest adults get at least 600 IU of vitamin D per day from diet alone (available from ~4 ounces of salmon) to supplement sunshine (30 minutes of midday sun provides 10,000–20,000 IU) (15). However, remember that the heavier you are, the more vitamin D you need to reach adequate serum levels (20–50 ng/mL), and so a blood test is the only effective way to identify a deficiency.

Along with adding a whole egg and mushroom omelet to the breakfast rotation and spending some more time under the sun, you should talk to your healthcare providers about vitamin D supplementation if:

+ A blood test confirms a deficiency.

+ You are obese and/or insulin resistant, a post-menopausal or expectant woman, or on long-term steroids.

+ You have a condition that affects vitamin D levels, such as chronic kidney disease or parathyroid disease.

Conclusion

While the benefits of vitamin D, beyond the amount necessary to reach healthy blood levels, are not yet clear, vitamin D toxicity is quite rare and supplementation higher than the current recommended upper limit of 4,000 IU has shown little risk (16).

Whether from the sun, your diet, or a supplement, a little more vitamin D is (almost) never a bad thing. Along with keeping your bones strong, maintaining healthy levels of vitamin D is important for weight management and blood sugar regulation. If you are in a high-risk group or experiencing any of the signs of a vitamin D deficiency, make an appointment with Prime Meridian™ to evaluate your serum levels.

References

1

Vitamin D deficiency 2.0: an update on the current status worldwide. 

Amrein K., et al.

4

A meta-analysis of the relationship between vitamin D deficiency and obesity.

Yao Y., et al.

7

Association of vitamin D with insulin resistance and beta-cell dysfunction in subjects at risk for type 2 diabetes.

Kayaniyil S., et al.

10

Associations Between 25-Hydroxyvitamin D and Weight Gain in Elderly Women.

LeBlanc  E., et al.

13

Effects of vitamin D supplementation on depression and some involved neurotransmitters.

Kaviani M., et al.

2

Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysis.

Tripkovic L., et al.

5

Vitamin D and Obesity.

Vanlint S.

8

Analysis of Association between Vitamin D Deficiency and Insulin Resistance.

Szymczak-Pajor I. and Śliwińska A.

11

Vitamin D and adipogenesis: new molecular insights.

Wood R.

14

Effects of 6-month vitamin D supplementation on insulin sensitivity and secretion: a randomised, placebo-controlled trial.

Lemieux P., et al.

16

The 2011 report on dietary reference intakes for calcium and vitamin D from the Institute of Medicine: what clinicians need to know. 

Ross A., et al.

3

The role of vitamin D in cancer prevention.

Garland C., et al.

6

Volumetric dilution, rather than sequestration best explains the low vitamin D status of obesity.

Drincic A., et al.

9

Effects of weight loss on serum vitamin D in postmenopausal women.

Mason C., et al.

12

Effect of vitamin D supplementation on testosterone levels in men.

Pilz S., et al.

15

Estimated equivalency of vitamin D production from natural sun exposure versus oral vitamin D supplementation across seasons at two US latitudes.

Terushkin V., et al.