- Half an hour of sun exposure a day to large areas of bare skin will give you a mega dose.
- We should also eat more eggs, organ meats, fish, bones, bone marrow and full-fat dairy.
In the final part of my Vitamin D series, we continue to acknowledge the importance of this all-important vitamin, which the scientific community has recently come to consider a hormone.
Vitamin D exists in two major forms – D2 and D3. They both have to pass through your liver and kidneys to be converted into the active form of vitamin D. Studies have shown that vitamin D3 appears to be more than three times as effective as vitamin D2. D2 comes from plant sources. D3 only comes from animal sources, and is the more bio-available form.
Micronutrients from exclusive plant-based diets are poorly absorbed, due to sub-optimal bio-availability, as previously discussed. Vegans are, therefore, another high-risk group. Mushrooms exposed to sunlight are their best dietary source of vitamin D. However, to meet the daily requirements, an impractically large amount of mushrooms must be consumed. To add insult to injury, mushrooms provide vitamin D2, not D3.
What is worth noting is that while we are fairly clear about the complications of vitamin D deficiency (such as rickets), we don’t actually know how low lab-tested levels need to be before complications of vitamin D deficiency occur. Your vitamin D status can be easily measured in a lab. Levels below 25nmol/L are considered low. However, good quality observational studies have recently associated higher vitamin D levels (of at least 40nmol/L), with significantly lower rates of diseases – many of which I discussed last week.
Interestingly, Asians and black Africans/Caribbeans living outside their country of ethnic origin suffer substantially higher levels of heart disease. Could this be explained, at least in part, by their lower vitamin D levels?
Estimates suggest that approximately 70 per cent of the US population is insufficient in vitamin D. I was surprised to discover that 15 years ago, this figure was 50 per cent. Vitamin D deficiency is now a major issue worldwide, generally, and specifically in countries in the Middle East and North Africa, where full coverage of the body is a cultural practice. It has been estimated that over 80 per cent of Qataris have low levels of vitamin D, despite the country experiencing year-round sunshine.
We’ve been informed that vitamin D deficiency is rising. In the same breath, we are being advised to lower our cholesterol, limit our intake of eggs, eat only low-fat dairy, cover our skin with sunblock, and limit our sun exposure. Sunscreen blocks UVB radiation, preventing vitamin D synthesis. We know that the dangers of this deficiency far outweigh those of excess sun exposure; and cholesterol is a vital nutrient that is essential for life.
With darker skin you need a lot more sun to get the same level of D. When people with darker skin live in northern climates, they are far more likely to have lower vitamin D levels than fairer skinned Europeans, whose lighter skin allows more vitamin D synthesis, in spite of less sunshine.
The totality of evidence available suggests that vitamin D deficiency is a crucial factor that may accelerate insulin resistance. It is clear that vitamin D and insulin are inextricably linked. In fact, a recent analysis of 11 research studies found lower vitamin D levels in Type 2 diabetics compared to controls.
Interestingly, Asians and black Africans/Caribbeans living outside their country of ethnic origin suffer substantially higher levels of heart disease. Could this be explained, at least in part, by their lower vitamin D levels? We know that evidence regarding the link between increased heart attacks and vitamin D is accumulating. We also know that avoidance of sun exposure is a risk factor for death from all causes.
Type 2 diabetes mellitus (T2DM) is now a major health problem worldwide and a leading risk factor for disability-adjusted life years lost globally. A number of genetic and environmental factors have been linked to the development of T2DM. Unsurprisingly, vitamin D deficiency is one of them.
Vitamin D has been identified to play an important role in insulin production and function. Insulin is the major food-energy storage hormone and type 2 diabetics are largely resistant to the actions of this crucial chemical messenger. The totality of evidence available suggests that vitamin D deficiency is a crucial factor that may accelerate insulin resistance.
It is clear that vitamin D and insulin are inextricably linked. In fact, a recent analysis of 11 research studies found lower vitamin D levels in T2DM patients compared to controls.
As this series has sought to highlight, we need to pay attention to this vitamin. While many of us get nowhere near enough of it, adequate levels are, in fact, realistically achievable. Half an hour of sun exposure a day to large areas of bare skin will give you a mega dose.
We should also eat more eggs, organ meats, fish, bones, bone marrow and full-fat dairy. If one must supplement, please ensure that the supplements provide D3, and not the hugely inferior vitamin D2.