As the winter months set in and the days get shorter, the amount of sunlight we receive decreases. As vitamin D is primarily obtained from exposure to the sun’s ultraviolet rays, this means that most Canadians become deficient in this essential vitamin over the winter months, which unfortunately seem to be the majority of the year for us. So why do we care so much about this one vitamin? Well, vitamin D is involved in a variety of biological processes including calcium absorption, bone health, heart health, cell growth and immune function. Without adequate levels of vitamin D we are also at an increased risk for conditions such as cancer, cardiovascular disease, diabetes, autoimmune disease, multiple sclerosis and depression.
Bone Health: Vitamin D plays an important role in the regulation of calcium and phosphorus in the blood and is required to absorb calcium from the small intestine. If blood calcium levels are low, vitamin D stimulates osteoclast activity in the bone, which resorbs calcium from the bone and into the blood, and also keeps calcium from being excreted through the kidneys. In adults, a deficiency in vitamin D can lead to osteoporosis because calcium cannot be absorbed into the blood (and then into bone) without adequate vitamin D present, thus resulting in decreased bone density with an increased risk of fracture.
Diabetes: Vitamin D may play a role in insulin secretion and glucose tolerance, and it has been shown that infants who receive vitamin D supplementation have a markedly reduced risk of developing type 1 diabetes.
Pregnancy: women who are pregnant and deficient in vitamin D have an increased risk of developing preeclampsia and requiring a C-section birth. Additionally, these women are more at risk for developing bacterial vaginosis and gestational diabetes. Low vitamin D status in infants increases the risk for atopic and allergic conditions such as eczema, allergies and asthma.
Cancer Prevention: Vitamin D plays an important role in regulating cell growth and proliferation. Studies have shown that adequate levels of vitamin D can slow the growth of blood vessels in cancerous tissue, can increase cancer cell death and decrease the risk of metastasis, particularly in colorectal and breast cancer as these tissues express the vitamin D receptor. However, it is important to keep in mind that you can have too much of a good thing, and excessive sun exposure can lead to cellular changes and skin cancer.
Infections: Vitamin D enhances the activity of the cells of the immune system, as there are vitamin D receptors on immune cells such as B cells, T cells and Antigen Presenting Cells which are activated in our immune response to pathogens. Therefore, vitamin D can modulate innate and adaptive immune responses, and a deficiency in vitamin D is associated with an increased risk of infection and autoimmune disease. Studies have shown an increase risk of respiratory infection, bacterial vaginosis, HIV and influenza in individuals who have low levels of vitamin D. There is also evidence linking vitamin D deficiency with autoimmune diseases such as SLE (Lupus), rheumatoid arthritis, IBD, multiple sclerosis and diabetes mellitus. Additionally, low levels of maternal vitamin D can lead to an increased risk of diabetes in her offspring as the pancreas has an increased risk of developing autoimmunity.
Without frequent moderate sun exposure or supplementation it is likely that you are deficient in vitamin D, as it is only present in minimal amounts in foods such as fish and fortified milk. Additionally, even when we are exposed to the sun, in order for vitamin D to be made the sun needs to be high in the sky, which is often mid-day and in the summer months. A tip is if your shadow is shorter than you, you are able to synthesize vitamin D, but once it becomes longer later in the day the sun is not intense enough to assist in the production of this vitamin. When the sun is strong enough, you only need to be out for around 15-30 minutes, or half the time it would take your skin to turn pink, and it is important to actually go outside and enjoy the air because vitamin D synthesis cannot happen through windows, clouds or in areas with high air pollution as these block UV rays from reaching the skin. Unfortunately, at this time of year the sun isn’t around as often as we would like, and it is likely not high enough in the sky to deliver adequate UVB exposure, which is why supplementation is important during these months. The recommended dosage for supplementation with vitamin D is 1,000IU per day, but it is important to consult with your healthcare provider as some people may require higher dosages for therapeutic benefit and some medications can affect the metabolism of this vitamin. If you have any questions about vitamin D supplementation, book an appointment with your Naturopathic Doctor for recommended dosages and individual treatment protocols.
