Diabetes, type 1Patient friendly summary

  •  The amount of UVB light during mid-pregnancy affects the risk of infant Type 1 diabetes.   
  • Low levels of UVB light in winter is also a risk factor for infant Type 1 diabetes.
  • Vitamin D lowers the risk of Type 1 diabetes, especially early in life.

Type 1 diabetes mellitus (T1DM) is an autoimmune disease. An autoimmune disease causes the body to attack its own tissues.

In Type 1 diabetes, the body’s immune system destroys the ability of the pancreas to produce insulin. The lack of sufficient insulin results in T1DM. This causes poor blood sugar control.

Risk factors

The risk factors for Type 1 diabetes are largely unknown. It may be triggered by:

  • Viral infection
  • Genetics
  • Infant diet containing wheat or cow's milk (depending on when foods are introduced)

Omega-3 fatty acids are found in cold water ocean fish. They may reduce the risk of Type 1 diabetes.

Sunlight exposure and Type 1 diabetes risk

Several studies have reported a connection between sunlight and Type 1 diabetes:

  • People with Type 1 diabetes are more frequently born in summer than in winter. This has been reported for a number of countries. Low maternal vitamin D blood levels in late winter or early spring may be a risk factor for Type 1 diabetes.
  • In New Zealand, more people develop Type 1 diabetes in the winter. Respiratory viral infections are most common. There is also less ultraviolet-B (UVB) light and less vitamin D production.
  • A study of 51 countries found higher rates of Type 1 diabetes in countries with higher latitudes. Countries further from the equator have lower levels of UVB light.

Vitamin D and Type 1 diabetes

Vitamin D levels

In Finland, some infants were given 2000 (IU) (50 mcg)/day of vitamin D3. This is the active form of vitamin D produced by the skin. These children had a greatly reduced risk of developing Type 1 diabetes. However, infants in Finland now receive only 400 IU (10 mcg)/day of vitamin D3. The incidence of Type 1 diabetes in that country has increased dramatically.

How vitamin D works

Vitamin D appears to reduce the risk of autoimmune disease by strengthening the immune system.


Vitamin D supplements may improve poor blood sugar control. Based on the information presented here, the risk of Type 1 diabetes may be reduced if:

  • Maternal vitamin D levels are above 30–40 ng/mL (75–100 nmol/L) during pregnancy.
  • Infants obtain 1000-2000 IU (25–50 mcg)/day of vitamin D3 from supplements or mother’s milk.
  • Infants maintain vitamin D blood levels above 30 ng/mL (75 nmol/L).

However, further research is needed to confirm these values.


People with Type 1 diabetes are at risk for coronary artery calcification or hardening. This is an important risk factor for coronary heart disease and death.

A study in Colorado found that both genetics of vitamin D receptors and low vitamin D levels predicted development of artery hardening. To avoid complications, those with Type 1 diabetes should maintain vitamin D levels greater than 30–40 ng/mL (75–100 nmol/L).

Find out more...

We will be adding a detailed evidence summary on this topic in the near future.  Please check back soon to find out more.

Page last edited: 17 May 2011