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  • Type 2 diabetes and vitamin D

Diabetes, type 2 Patient friendly summary

 A diet high in carbohydrates and sugar raises risk of type-2 diabetes. Vitamin D together with calcium may lower that risk by 33%.

Type 2 diabetes mellitus (T2DM) is a metabolic disorder. People with Type 2 diabetes have high blood glucose (sugar) and low insulin levels. They also have insulin resistance. This condition makes it harder for their bodies to use insulin.

Risk factors

The most important risk factors for Type 2 diabetes are:

  • Diet high in simple carbohydrates and meat: Simple carbohydrates (white rice, baked goods) are foods that turn into sugar quickly. They cause rapid blood sugar changes. Eating a lot of meat also increases the risk of Type 2 diabetes.
  • Obesity: This health threat causes more than half of all new diabetes cases.
  • Smoking: Smoking contributes to the risk of Type 2 diabetes.

Some factors may reduce the risk of Type 2 diabetes:

  • Healthy diet: Foods with a low glycemic or sugar index do not cause rapid blood sugar changes. They also reduce the chances of Type 2 diabetes. These foods include whole grains.
  • Exercise: Studies have shown that regular exercise may reduce or eliminate Type 2 diabetes.

Sunlight exposure and Type 2 diabetes

Sunlight is the most important source of vitamin D for most people. It is beneficial to be in the sun during mid-day. A Japanese study found that male patients with Type 2 diabetes had:

  • Higher body fat in winter, when there was less sun, compared to summer (This also may be due to colder weather.)
  • Higher levels of blood sugar in winter compared to summer (This may be due to increased insulin resistance in winter.)

Vitamin D and Type 2 diabetes

Studies during the past decade have found that higher vitamin D blood levels and higher calcium intake may reduce the risk of Type 2 diabetes.

How vitamin D works

To control Type 2 diabetes, vitamin D may:

  • Regulate insulin synthesis and secretion by regulating calcium levels in the blood
  • Directly affect function of the pancreas (the organ than makes insulin)
  • Affect genes associated with glucose tolerance
  • May reduce insulin resistance


Vitamin D and calcium  

A Harvard study indicates that vitamin D and calcium work together to reduce the risk of Type 2 diabetes. A 33% lower risk of Type 2 diabetes was noted in people taking more than 800 international units (IU) (20 mcg) vitamin D and more than 1200 mg calcium each day compared to those taking daily doses of 400 IU (10 mcg) vitamin D and less than 600 mg calcium.


Those with Type 2 diabetes should increase their vitamin D blood levels to above 40 ng/mL (100 nmol/L). This may reduce the effects of Type 2 diabetes and possible health risks such as cardiovascular disease and osteoporosis.

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: 27 September 2011