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Vitamin “D” and its Role in Retinopathy

Vitamin D is a fat-soluble vitamin that plays a key role in maintaining a healthy body. However, despite being a necessary component for bone growth and immune system health, more than one-third of people living in the United States have a reported vitamin D deficiency.

Low vitamin D can lead to many adverse effects, including reduced insulin sensitivity in those with diabetes. If left unchecked long-term, insulin resistance may be a slippery slope that could lead to suboptimal diabetes control and eventually to an increased risk of developing diabetes complications.

According to a recent study published in Clinical Nutrition ESPEN in June 2023, vitamin D deficiency may increase the risk of developing diabetes retinopathy in those with type 2 diabetes.

Diabetes retinopathy (DR) is one of the more well-known diabetes complications and was estimated to affect more than 25% of individuals living with diabetes in 2021. DR is a condition that causes damage to the retina, or the light-sensitive area in the back of the eye. This area of the eye consists of blood vessels that, when exposed to consistent and long-term hyperglycemia, can cause damage that may lead to leaking blood vessels, damaged nerve cells, and ultimately vision loss.

Diabetes retinopathy occurs primarily in two forms:

  • Non-proliferative diabetes retinopathy (NPDR) is characterized by weakened or damaged retinal blood vessels
  • Proliferative diabetes retinopathy (PDR) is characterized by weakened blood vessels that leak blood and fluids into the eye

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In their cross-sectional study of individuals with type 2 diabetes, Zahedi and colleagues compared about 200 people with DR to an equal number of individuals without the retinal disease. Results showed that although the mean concentration of 25-hydroxyvitamin D, the main form of vitamin D in the body, was low in both groups, it was significantly lower in those with DR compared to those without DR.  Additionally, researchers found that low vitamin D may also be associated specifically with the progression to PDR in those with type 2 diabetes.

Although this study focused on a population of those with type 2 diabetes, vitamin D deficiency has also been shown to impact people with type 1 diabetes.

Previous evidence supports that vitamin D supplementation can improve glycemic control and insulin sensitivity in people with both type 1 and type 2 diabetes. Additionally, research has shown that vitamin D treatment may improve glycemic control during the honeymoon period, as it may improve the survival of islet cells and maintain insulin production. Although we can only speculate that the DR findings observed by Zahedi et al. can be expanded to those with type 1 diabetes, it is clear that getting enough vitamin D can go a long way in improving and maintaining our health.

What are the sources of Vitamin D:

There are multiple strategies for increasing your vitamin D intake.

  1. Since the sun is our primary source of this fat-soluble vitamin, getting outside and exposing your skin to at least 15 minutes of sun a day can be a good goal, as long as you are also protecting your skin with sunscreen.
  2. Though limited in number, it is also suggested to consume vitamin D-rich foods, including fatty fish like tuna, sardines, and salmon, as well as egg yolks and fortified foods like orange juice, milk products, and cereals.
  3. If getting enough vitamin D through the first two options is still too challenging, a supplement may be the way to go.

However, before choosing this route, best to speak with your healthcare provider, or schedule some time to with one of the clinicians at Integrated Diabetes Services.

Article by IDS Intern, Krystal Bosenbark, MPH, MS