Written By: Kevin Cann
I know we have been down this road before. Out of all the nutrients that exist within our diet vitamin D is perhaps the most talked about. This comes with good reason. Inadequate vitamin D levels can lead to all kinds of health concerns such as; increased risk of cardiovascular disease, increased risk of cognitive impairment later in life, and even cancer. What many people may not be aware of is that inadequate vitamin D levels are associated with obesity.
In fact, obesity is actually a risk factor for low vitamin D levels. Research has stated that the overall prevalence of vitamin D deficiency is 41.6% with much higher rates being found in minority groups (http://www.ncbi.nlm.nih.gov/pubmed/21310306 ). Other studies have shown that nearly 75% of the US population is deficient in vitamin D (http://www.scientificamerican.com/article/vitamin-d-deficiency-united-states/ ).
The blame tends to fall on our fear of developing skin cancer if we go outside unprotected by clothing and sunscreen. This fear of skin cancer may actually be helping us pack on some pounds in the midsection. Studies have suggested that vitamin D levels of less then 50 nmol/L doubled the risk of newly diagnosed type 2 diabetes cases after adjustments for BMI, sex, exposure to polychlorinated biphenyls, serum triacylglyceride concentration, serum HDL concentration, smoking status, and month of blood sampling. The researchers also noted that blood A1C levels decreased with increasing serum vitamin D levels independent of all other variables (http://care.diabetesjournals.org/content/34/6/1284.full ). This study suggests to me that if we have low vitamin D levels perhaps a lower carbohydrate diet is the answer until we can bring the levels up to an optimal range.
The potential role vitamin D plays with glucose metabolism may explain why certain studies show that people lose weight when vitamin D levels are balanced out. However, this is nothing other than mere speculation. Do low vitamin D levels actually increase the risk of type 2 diabetes or is this just correlation?
Researchers have attempted to answer this question using mouse models. What they have found is really interesting. This research was presented in June of 2014 and the researchers concluded by suggesting that low vitamin D levels do indeed play a role in weight gain and diabetes.
Researchers at the University of Cincinnati injected vitamin D directly into the hypothalamus of rats. Our hypothalamus plays a key role in regulating our circadian rhythm of hormones, sleep, thirst, and our hunger response. They performed this research over short and long term scenarios. After 28 days of receiving vitamin D the rats ate three times less food and lost 24% of their weight when they were compared to the control group. Interestingly enough, despite no change in the way they burned calories (http://www.sciencedaily.com/releases/2014/06/140623092023.htm ).
In the past I have written articles about our energy homeostatic hormones such as leptin and insulin. However, vitamin D may actually play a role as a hormone in this scenario. Leptin and insulin have their own circadian rhythms and vitamin D may be a regulating factor of those circadian rhythms. I stand on the side of the fence that the hyper palatability of foods and our chronically stressed lifestyles are leading to the rises in obesity and modern disease. The key to solving this issue is to find a way to increase satiety and mitigate the negative effects of stress.
It looks as if vitamin D plays a critical role in both aspects. This makes it an extremely critical component of managing someone’s health care. Most annual blood tests performed at the doctor’s office will test for vitamin D levels. Studies have shown that less than 50 nmol/L is associated with increased cardiovascular events, cancer, and increased fracture rates. I recommend having vitamin D levels between 100nmol/L to 150nmol/L. This would be between 40 and 60 ng/ml when converted. Make sure to check the units specified on your lab test.
Getting approximately an hour of sunlight per day can help make sure we do not suffer from vitamin D deficiency as well as including vitamin D rich foods such as eggs. In northern latitudes a vitamin D supplement will be required in the winter months. In these cases I am a fan of cod liver oil as it comes with both vitamin A and omega 3 fatty acids. This is all a great start, but it may not be enough.
The study mentioned earlier injected vitamin D into the hypothalamus. We need to make sure that the vitamin D is crossing the blood brain barrier to have the effect on food intake we are hoping for. Vitamin D requires vitamin A, albumin, and other plasma proteins in order to cross the blood brain barrier (http://www.ncbi.nlm.nih.gov/pubmed/3838342 ). This makes it critically important to not be deficient in any of the nutrients necessary. If we are deficient in any of those nutrients, not just vitamin D, the transport of vitamin d into the brain will be limited.
Unfortunately, our genes may play a role in our vitamin D deficiencies. There has been shown to be a hereditary link in the vitamin D receptor (VDR) and rickets. Current research is showing that VDR polymorphisms can occur in the brain and may actually increase the risk for certain brain cancers (http://www.hindawi.com/journals/bmri/2013/295791/ ). If we have this hereditary mutation of the VDR gene it is not a death sentence. Our genes have the ability to listen to external and internal messages and change their expression. We just need to understand what causes this mutation and what we have to do to present the genes with an optimal environment.
The answer may actually lie in utero. Vitamin D deficiency in utero effects a number of brain functions as well as gene expression (http://www.ncbi.nlm.nih.gov/pubmed/15763180 ). The high rate of mothers to be that are deficient in vitamin D may be leading to some of these VDR polymorphisms that are negatively affecting our health into adulthood. Research has suggested that taking 4,000IU of vitamin D per day during pregnancy is both safe and effective (http://www.ncbi.nlm.nih.gov/pubmed/21706518 ). We tend to be overprotective of newborns in the sun as well. We tend to cover every inch of their body when we take them outside. We definitely do not want to let them get a sunburn, but increasingly small doses of sunshine are definitely beneficial.
Make sure you are testing your vitamin D levels at least twice per year. They should be between 100nmol/L to 150nmol/L and 40ng/ml to 60ng/ml. This critical vitamin is important for bone health, heart health, and preventing cancer. It may also act like a hormone in the brain regulating food intake and weight. If you are pregnant or live in northern latitudes make sure you are taking a vitamin D supplement. A dosage of 4000IU of vitamin D has been shown to be both a safe and effective dose. If you have a New Year’s resolution to lose weight do not forget about the importance of vitamin D in reaching your goals.