The sunshine vitamin and diabetes

We have been hearing a lot more about vitamin D since the COVID pandemic and by now we all know it helps to boost the immune system. Kate Bristow highlights why the sunshine vitamin is needed.

First, let’s understand a bit more about vitamin D

Vitamin D is a fat-soluble vitamin which has a role in maintaining the health of bones, teeth and joints. It also assists in maintaining the functioning of the immune system.

Vitamin D is found in some foods, but it’s also known as the sunshine vitamin.  When our bare skin is exposed to the sun, we convert a cholesterol derivative into vitamin D. However, a lot of people are deficient in vitamin D, and this includes people with diabetes.

Time in the sun and the sunshine vitamin

In the past the best way for humans to get vitamin D was through exposure to sunlight. However nowadays we have less exposure to sunlight. This is due to our work being mostly indoors (except for a lucky few).

There is also increased fear of skin cancers, so we use sunscreen, hats, and other sun barriers. Some people have religious beliefs requiring the skin to be covered, and environmental factors, such as pollution and less daylight hours in the northern hemisphere, decrease our daily exposure to sunlight.

How are we affected by a deficiency of vitamin D?

Signs of lack of vitamin D can range from depression, bone pain and muscle weakness as well as a weakened immune system. Severe muscle weakness with pain and difficulty walking is known as osteomalacia.

Statistics also show that long-term deficiency can result in obesity, high blood pressure, psoriasis, osteoporosis, chronic fatigue syndrome, Alzheimer’s, cancer and Type 2 diabetes.

Symptoms of vitamin D deficiency are often very non-specific and thus often missed.

In children, deficiency can affect growth and tooth formation. Severe deficiency results in children with soft skulls or leg bones (legs become bow-legged, and they complain of pain in legs and muscle pain or weakness). This condition is known as Rickets. Rickets, which is very severe, can cause breathing difficulties and seizures requiring hospital admission. Irritability in children may be because of vitamin D deficiency.

Who is more at risk?

  • Ageing skin and skin darker in colour requires longer exposure to sunlight to enable vitamin D synthesis.
  • Certain medical conditions affect how vitamin D is absorbed: Crohn’s disease and coeliac disease (which can be associated with diabetes) and some types of liver and kidney disease.
  • Deficiency can also occur in people taking certain medications. Discuss this with your healthcare practitioner.
  • Vitamin D deficiency is more likely to occur in people who follow a strict vegetarian or vegan eating plan, or one that excludes fish.

How do we make sure that our vitamin d levels are stable?

It is said that exposing your skin daily to 5-30 mins of sunshine, preferably between 10am and 3pm, at least twice a week, can help your body to produce its own vitamin D and thus decrease risk of diabetes and other serious medical conditions. But that isn’t always practical.

  • Dietary choices that can increase your vitamin D levels include foods such as nuts, oily fish, eggs, powdered milk, and some cereals which have been fortified with vitamin D. But most foods don’t contain a lot of vitamin D.
  • Fatty fish and seafood are foods that have the highest levels of vitamin D. Although the amounts may vary depending on the type and where they came from. Choices include tuna, mackerel, oysters, shrimp, sardines and anchovies
  • Eat more mushrooms. Mushrooms are the only vegetarian source of vitamin D. Mushrooms make vitamin D² through exposure to sunlight or artificial UV light.
  • Eat more egg yolks. Egg yolks are a good source of vitamin D, however the amounts may vary. Free range have higher quantities due to the exposure to natural sunlight (20% RDI), and chickens fed on fortified grain may provide eggs yolks with 100% of the RDI.
  • Take a recommended supplement. Discuss this with your healthcare professional as dosages can vary and the amount you need will depend on what your levels are.
  • Artificial UV radiation is a possibility particularly in countries with shorter day length, or in those who do long hours in an office. However, this needs to be very carefully controlled as too much exposure can burn your skin. Recommended exposure is 15 minutes at a time.

How do we know what our levels of vitamin D are?

It is important to discuss this with your healthcare practitioner and have the levels tested in a laboratory.

Ampath lab use the following levels in their testing of vitamin D (National Osteoporosis Foundation of South Africa).

  • Deficiency = Levels below 12ng/mg (30nmol/l)
  • Insufficiency 12-19 ng/ml
  • Sufficiency 20ng/ml (50nmol/l and above)

Ampath in a recent update also commented that vitamin D levels above 30ng/ml may have additional benefits to health, which include decreasing risk of common cancers, autoimmune conditions, Type 2 diabetes, cardiovascular disease and infectious disease, but these claims have not been proved in clinical trials.

That said, Diabetes UK concludes that it is now known that raising the amount of vitamin D in your body to around 60-80 ng/ml can help keep blood glucose levels under control, which is vital for people with diabetes.

It is important to know that vitamin D levels vary from person to person, and that vitamin D sufficiency or deficiency is monitored by a medical practitioner, and that different levels apply to different people. And if a person is put on vitamin D supplementation by a healthcare professional, they should be told that it takes about three months for levels to rectify, so retesting levels sooner than that is not going to be significant.

Other health benefits of vitamin D include

  • Assistance in weight loss. Good vitamin D levels help to reduce levels of parathyroid hormone (PTH) which long term may promote weight loss and decrease risk of obesity (of major risk in Type 2 diabetes).
  • Regulation of appetite. Vitamin D can increase the body’s level of the hormone leptin. Leptin controls how the body stores fat and helps us to feel full so we don’t feel so hungry.
  • An increase in vitamin D can help to lower our cortisol level which is a stress hormone produced by our adrenal glands. The function of cortisol includes how we respond to stress and how we regulate blood pressure. Higher levels of cortisol in the blood can lead to increased amounts of abdominal fat, which is linked to various health conditions which include Type 2 diabetes.
  • There is some evidence that there may be a beneficial link in vitamin D improving insulin sensitivity, insulin resistance and that it possibly has some role in the health of the beta cells of the pancreas. But further research is needed in this area, so at this stage this is unsubstantiated.

What types of vitamin D are there?

There are two main forms of vitamin D: ergocalciferol (vit D²) and cholecalciferol (vit D³). Vitamin D² is synthesised by plants (mushrooms and yeast) and vitamin D³ is synthesised by the skin when it is exposed to ultraviolet B rays from the sun. Vitamin D³ is also found in a few foods e.g. fatty fish.

It is difficult to get enough vitamin D from food alone, and both D² and D³ can be synthetically manufactured and are used to fortify some types of foods, such as milk products, soy milk, margarine, and it’s also used as a dietary supplement in tablet form. It is metabolised in the liver and kidneys so diabetic patients with liver or kidney problems have a higher risk of deficiency, and the same applies to patients with gastrointestinal conditions, such as coeliac disease, pancreatitis, or low bile levels or sprue (a disease of the small intestine causing malabsorption of food).

Is there any link between vitamin D levels and diabetes?

It is believed that vitamin D may improve the body’s sensitivity to insulin.  Insulin is a hormone which regulates blood glucose levels, which decreases insulin resistance. Insulin resistance is a precursor to Type 2 diabetes. Some scientists also believe that vitamin D may help how insulin is produced in the pancreas.

According to the American Diabetes Association (ADA), vitamin D and diabetes have a common trait: both are pandemic. The International Diabetes Federation estimate of the number of people worldwide with diabetes is close to 285 million (7% of the world population). By 2030, this number is predicted to exceed 425 million. This number does not include those who have pre-diabetes.

Vitamin D deficiency is thought to affect 13% of the world’s population. ADA say that there is increased evidence that a deficiency of vitamin D is possibly a contributing factor in development of Type 1 and Type 2 diabetes. It seems that treatment with vitamin D can improve glucose tolerance and insulin resistance. Deficiency of vitamin D leads to decrease in the secretion of insulin.  In animals, vitamin D supplementation showed improvement in insulin secretion.

Quoted from ADA Diabetes Spectrum, “Although the role of vitamin D in helping to regulate blood glucose remains poorly understood, vitamin D status appears to play a role in the development and treatment of diabetes. It is possible that optimal levels of serum vitamin D may be different for people at risk for developing diabetes, those with diabetes, and those without diabetes.

According another study1, “Both animal and human studies support the notion that adequate vitamin D supplementation may decrease the incidence of Type 1 and possibly also of Type 2 diabetes and may improve the metabolic control in the diabetes state. However, the exact mechanisms are not clear and need further investigation.”

The bottom line

Vitamin D is an essential nutrient that many people around the world do not get enough of. It is possible to boost your vitamin D levels by getting out in the sun more often, and eating vitamin D rich foods, as well as taking supplements.

It’s an important nutrient which needs to be given credit in our daily eating plan. If you are concerned about a possible low vitamin D level or fall into the risk categories mentioned above, please discuss this with your healthcare provider so that you are given appropriate treatment.

Sister Kate Bristow is a qualified nursing sister and certified diabetes educator.


Sister Kate Bristow is a qualified nursing sister and certified diabetes educator. She currently runs a Centre for Diabetes from rooms in Pietermaritzburg, providing the network support required for the patients who are members on the diabetes management programme. She also helps patients who are not affiliated to a diabetes management programme on a private individual consultation basis, providing on-going assistance and education to assist them with their self-management of their diabetes.

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