Vitamin D Benefits Diabetes Sufferers

| April 18, 2013

Previously, I reported on research findings that showed a deficiency in vitamin D was linked with an increased risk of type 1 diabetes. Since then, four important new studies have shed further light on the relationship between vitamin D and diabetes. What they show is that:

• Healthy levels of vitamin D cut the risk of type 1 diabetes in half, in young adults;

• In overweight people with type 1 diabetes, those with higher vitamin D levels need to inject less insulin;

• In type 2 diabetes patients, taking vitamin D lowers blood sugar and insulin levels and reduces insulin resistance;

• Giving obese teenagers a vitamin D supplement reduces markers of metabolic syndrome.

Earlier research, at the University of California, established a correlation between people’s blood levels of vitamin D and the subsequent incidence of type 1 diabetes. Those with the lowest vitamin D levels had a 3.5 times greater risk of developing insulin-requiring diabetes than those with blood levels above 60 nmol/l.

A new study carried out at Harvard School of Public Health shows that having adequate levels of vitamin D during young adulthood reduces the risk of adult-onset type 1 diabetes by 50 per cent. The researchers found that healthy young adults with blood levels of vitamin D above 75 nmol/l had about half the risk of developing type 1 diabetes as those whose levels were below this figure. As well as verifying the earlier findings, these results set the bar even higher for what constitutes a protective level of vitamin D.

Other new research, from the University of Frankfurt, in Germany, has found that raising vitamin D levels in overweight people with type 1 diabetes could make a big difference to their insulin requirements. This small pilot study showed a clear link between blood levels of vitamin D and insulin demand in overweight patients. Those with the highest vitamin D levels had the lowest insulin requirements, suggesting that supplementing with vitamin D could help many people with type 1 diabetes to reduce their insulin medication.

For those with type 2 diabetes, more evidence of vitamin D’s essential role comes from a study in Iran. Patients were treated with high doses of vitamin D – 50,000 IU per week (which equates to just over 7000 IU a day) – for eight weeks. At the end of the study there were significant reductions in fasting blood glucose, insulin levels and insulin resistance. This supports the findings of earlier research showing that vitamin D improves both insulin sensitivity and pancreatic function.

In the fourth new study, from the University of Missouri, obese teenagers were given 4000 IU of vitamin D a day, or placebo, for six months. Those taking vitamin D had big reductions in both circulating insulin levels and insulin resistance. Dr Catherine Peterson, who led the study, said “By increasing vitamin D intake alone, we got a response that was nearly as powerful as what we have seen using a prescription drug”. The supplement doubled average blood levels of vitamin D, from 19.6 nmol/l to 39 nmol/l.

Official advice on vitamin D could damage your health

At present, no “normal range” has been set for blood levels of vitamin D, although it has been proposed that less than 25 nmol/l should be considered a deficiency and 75 nmol/l should be the benchmark for an optimal level. The Harvard study shows that anything less than 75 nmol/l could be a risk factor for auto-immune diseases like type 1 diabetes, and this is probably about the level needed to show benefits for cancer and heart disease, too.

Vitamin D deficiency, by which I mean a level below 25 nmol/l, is incredibly common. The vitamin D levels measured in the German and Missouri studies were shockingly low, averaging less than 20 mmol/l. Findings like this make a mockery of the current statement on the NHS website that “Most people should be able to get all the vitamin D they need by eating a healthy balanced diet and by getting some summer sun”.

Forget, too, the official guidance that only people in “high risk groups” need to take a vitamin D supplement of 400 IU a day and that supplements of more than 1000 IU a day could be harmful. Following this advice could seriously damage your health! The latest research shows that 4000 IU a day is a safe and effective dose of vitamin D for most people and that supplementing at this level could reduce your need for side effect-laden diabetes drugs.

As you probably know, vitamin D is made in the body, using cholesterol as a starting material. We also make sex hormones, including testosterone, from cholesterol. Now, Australian researchers are investigating whether giving men additional testosterone will help them to lose weight and avoid diabetes. That will be the subject of my next blog post.

Wishing you the best of health,

Martin Hum
PhD DHD Nutritionist
for Real Diabetes Truth

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Bear in mind we are not addressing anyone’s personal situation and you should rely on this for informational purposes only. Please consult with your own physician before acting on any recommendations contained herein.


1. Gorham ED, Garland CF, Burgi AA, Mohr SB, Zeng K, Hofflich H, Kim JJ, Ricordi C. Lower prediagnostic serum 25-hydroxyvitamin D concentration is associated with higher risk of insulin-requiring diabetes: a nested case–control study. Diabetologia. 2012; 55(12):3224-3227.

2. Munger KL, Levin LI, Massa J, Horst R, Orban T, Ascherio A. Preclinical serum 25-hydroxyvitamin D levels and risk of type 1 diabetes in a cohort of US military personnel. Am J Epidemiol. 2013; 177(5):411-419.

3. Bogdanou D, Penna-Martinez M, Shoghi F, Sandler M, Badenhoop K. Vitamin D, insulin-dependency and other clinical parameters in type 1 Diabetes mellitus. Exp Clin Endocrinol Diabetes. 2013; 121(3):106.

4. Talaei A, Mohamadi M, Adgi Z. The effect of vitamin D on insulin resistance in patients with type 2 diabetes. Diabetol Metab Syndr. 2013; 5(1):8.

5. Belenchia AM, Tosh AK, Hillman LS, Peterson CA. Correcting vitamin D insufficiency improves insulin sensitivity in obese adolescents: a randomized controlled trial. Am J Clin Nutr. 2013; 97(4):774-781.

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Category: Diet and Exercise, Vitamins and Nutrients

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