Optimizing Metabolism

by Ingrid Kohlstadt, MD, MPH

My Vote for the Best of Natural Medicine:

Vitamin D

Introduction

As this issue of Townsend Letter celebrates the best of naturopathic medicine, my vote goes to vitamin D. Research in fields as diverse as naturopathic medicine, clinical medicine, anthropology, physics, veterinary medicine, and food science has converged on the topic of vitamin D and has identified clinical and public health applications with a high impact factor. This column spotlights some of the recent findings and questions awaiting answers.

High Latitudes (the Poles) and Outer Space

Vitamin D research has come a long way since 12 years ago when I sailed into the darkness to serve as the winter-over physician at Palmer Station, Antarctica. There I experienced both the polar plunge and a plunge in my vitamin D level. However, a few weeks after the austral winter solstice, my resourceful fellow expeditioners were able to set up full-spectrum lighting. To this day I remember the glorious feeling of that “sunlight.” There has never before or since been a ray of natural sunlight more welcome. I think everyone who used it benefited. You could feel the upsurge of energy throughout our station!

A 2009 research study funded by NASA studied vitamin D levels in a more recent group of Antarctic expeditioners. Participants were supplemented with different doses of vitamin D 5 months into their stay. Even those receiving the highest does of supplementation, 2000 IU per day, had blood levels of vitamin D below (71 nmol/L) the recommended 80 nmol/L. The findings will be used to increase recommended vitamin D intake in those not receiving sun exposure, groups as diverse as space crews, polar workers, and the housebound elderly.

Bones, Muscle, and Fat

I edited a well-regarded medical book on muscle, fat, and bone (Scientific Evidence for Musculoskeletal, Bariatric and Sports Nutrition. Boca Raton, FL: CRC Press; 2006) because of the interconnectedness among these structures. This was somewhat counter to clinical medicine, which has organized itself by disease categories and tends to have a “silo” effect (absence of informational reciprocity). Vitamin D may be changing this.

At first vitamin D was thought of as important for the bone disease “silo.” After decades of being acknowledged for preventing rickets, it had osteoporosis prevention added to its attributes.

Vitamin D is about muscles, too. I hypothesize that the delay in recognizing this may have cost the US Olympic medals. Robust research from the former Soviet Union demonstrated improved athletic performance with use of full-spectrum light exposure.

While osteoporosis is silent, osteomalacia is not. Osteomalacia is the deep bone pain associated with hypovitaminosis D. It may be underdiagnosed in clinical practice because pain tends to get associated with muscles rather than bones. Early studies of osteoporosis and fractures in elderly women demonstrated that vitamin D levels were inversely associated with fractures. A closer look also demonstrated that the women who were vitamin–D replete had fewer falls. This prompted the hypothesis that there is a neuromuscular advantage to vitamin D, more recently supported by the research on vitamin D and diabetes.

And vitamin D is about fat. Since vitamin D is fat-soluble, one might reason that people with excess adipose tissue have higher vitamin D stores, right? Not really. Inactive vitamin D is stored in adipose tissue, but it is only available as fat is metabolized. This may apply to other fat-soluble vitamins and phytonutrients as well. Excess adipose tissue reduces the amount of active vitamin D available in the bloodstream.

In summary, vitamin D may be bringing to life the body’s interconnectedness, not unlike Ezekiel and the Valley of Dry Bones.

Immune System

Several clues from field epidemiology suggest that autoimmune conditions such as rheumatoid arthritis, multiple sclerosis, and immune-related cancers occur at increasing rates the farther one lives from the equator. Could vitamin D mediate this risk factor?

Sunshine has also helped strengthen the immune system against infections. For more than 100 years, doctors have advised patients with active tuberculosis to spend time in the sun. Outbreaks of tuberculosis, plague, and influenza spread more aggressively among populations in higher latitudes than in temperate regions, suggesting a possible vitamin D connection.

A pregnant mother’s vitamin D status shapes the development of her child’s immune system. Studies have shown a protective effect of higher maternal vitamin D status against asthma and allergies. The research propels the hypothesis that optimal vitamin D intake can help protect an unborn child from dysregulation of the neuroimmune system. In other words, vitamin D may reduce whatever environmental insults cause autism. If so, this represents a tremendous public health opportunity for prevention.

Interactions with Marketed Products

Vitamin D is also a big deal because our understanding of this vitamin touches on many products and influences how we view them.

• Cosmetic products such as suntan lotion block vitamin D absorption.

• Tanning beds, although mostly ultraviolet light in the UVA spectrum, also contain enough UVB to boost vitamin D synthesis.

• Several classes of medications interact with vitamin D. Patients with seizures may experience medication-related vitamin D deficiency due to increased metabolism of vitamin D associated with older antiepileptics. Lower vitamin D stores can contribute to loss of seizure control.

• Vitamin D is added to infant formula. If most mothers have less than optimal levels in breast milk and infant formula is based on breast milk levels, optimal vitamin D levels should be considered and are likely to vary based on geographic location.

• Racial differences in disease risk and therapeutic response may be associated with skin pigment and vitamin D absorption.

• Since mushrooms can synthesize vitamin D, the extent to which this should be developed as a vegetarian vitamin D source is being considered.

Updated recommendations on vitamin D levels and the safe upper range are forthcoming at the time this article is being written.

Establishing guidelines is complex. If the average levels of vitamin D are too low, how does one establish a “normal” range? One meaningful way to establish a healthful range is to observe the levels where the optimal effects are observed. For example, what levels of vitamin D will have positive effects on the prevention of osteoporosis and fractures? When vitamin D is low, parathyroid hormone increases. Since study data show that maximum parathyroid hormone suppression occurs with serum vitamin D levels at 31 ng/mL (77 nmol/L), this has been considered by some to be a target blood level.

Could the byproducts of vitamin D synthesis be important? If so, dietary supplementation is not the same thing as sunshine.

Conclusion

In summary:

• If you aren’t getting any UVB exposure, you need at least 2000 IU vitamin D a day to maintain healthful vitamin D levels.

• Maternal vitamin D plays poorly understood roles in fetal development. Adequate vitamin D may help protect against autism.

• A body that is gaining fat weight cannot break down fat to use it for energy. This means that it also cannot access its stores of inactive vitamin D and is more likely to have suboptimal vitamin D levels.

• When sunlight hits the skin, it produces vitamin D and other molecules assumed to be inactive and present to safeguard against vitamin D toxicity. But are these molecules really inert?

Ingrid Kohlstadt, MD, MPH, is an FDA Commissioner’s Fellow, using diet to improve drug safety. She has been elected a Fellow of the American College of Nutrition and is an associate at the Johns Hopkins School of Public Health. She is the founder and chief medical officer of INGRIDients Inc., editing Food and Nutrients in Disease Management (CRC Press, 2009) and Scientific Evidence for Musculoskeletal, Bariatric and Sports Nutrition (CRC Press, 2006).