Vitamin D, known as the “sunshine vitamin” as it can be synthesised from cholesterol if adequate sun exposure if forthcoming, is actually a group of fat soluble steroids that functions as hormones. The reference to hormones simply means that they are used as chemical signallers in a complex chain of instructions that we will refer back to shortly. From a scientific standpoint, Vitamin D does not truly own the name “vitamin” because it does not have to be obtained from the diet.
The study of Vitamin D rose to prominence when it was discovered that an abject lack of the substance led to a bone deficiency affecting children- known as Rickets. This brings to mind that fact that Vitamin Ds play a vital role in mineralisation and bone health.
Vitamin D in the blood reflects both sunlight exposure and dietary intake. An important point to grasp is, whereas the sunlight –driven synthesis of Vitamin D operates in a feedback loop to prevent toxicity (e.g., it is self regulating), this does not apply to supplemental intake.
In fact, little is understood about the potential for toxicity following over supplementation. Of course, a debate still rages about the cancer risk that may or may not be caused by sunlight exposure, which renders it difficult for health bodies to make recommendations on the amount of time that should be spent in the sun to maximise Vitamin D synthesis. Calcitriol, the biologically active form of vitamin D produced in the kidneys circulates as a hormone in the blood, and thus regulates the concentration of calcium and phosphate in the bloodstream and promotes bone growth and deposition. Other functions include controlling inflammation and the natural cycle of cell repair.
In terms of the proposed health benefits of supplementation, the evidence is contradictory. The most reliable finding is that taking Vit-D supplements may contribute to greater longevity and bone health in older women. The very latest research is digging a little deeper and coming up with some interesting findings on the hormonal role that vitamin Ds play, suggesting they are used as signallers in the natural process of cell repair known as autophagy. This is thought to be a factor in the many anecdotal reports (including those we have seen in our client groups) that Vitamin-D supplementation has beneficial effects on immune functioning (e.g., less likely to get colds etc.).
Here at Motivating Max, we acknowledge the recent raft of research that has shown the widespread winter vitamin-D deficiencies in adults living in the Northern Hemisphere (particularly northern Europe). However, we feel there is not enough research on the long-term (> 4 years) effects of supplementation to advocate chronic ingestion of a high dosage regimen. There is a concern that this supplementation can down-regulate and otherwise adversely affect the natural process of cell repair that Vitamin-D plays a part in- i.e., the body does not protect itself as well when excess nutrients are being consumed. Another example of this is the way the body reduces endogenous (internal) production of Creatine when supplements are taken.
Better ways to stimulate the natural immune responses that Vitamin-D may govern include exposing the body to mild, periodic stress of the type we have discussed in our work on intermittent fasting. The body has evolved its own systems to self-manage nutrient levels over millennia and it is doubtful that we need a constant supply of a synthetic nutrient in order to function optimally, especially when we are not adapted to receive Vitamin-D in this form. It is also worth noting that we should not aim to deprive ourselves entirely of sunlight over cancer fears, a natural balance needs to be sought.
Ultimately, the decision to supplement is a personal one, and in so doing we must consider how much sunlight we are getting during each season.