Low vitamin B12 levels implicated in the development of diabetes

This study can be accessed in the Public Library of Science 2011;6(11):e26747

Study title and authors:

Status of B-vitamins and homocysteine in diabetic retinopathy: association with vitamin-B12 deficiency and hyperhomocysteinemia.

Satyanarayana A, Balakrishna N, Pitla S, Reddy PY, Mudili S, Lopamudra P, Suryanarayana P, Viswanath K, Ayyagari R, Reddy GB.

Biochemistry, National Institute of Nutrition, Hyderabad, India.

This study can be accessed at: http://www.ncbi.nlm.nih.gov/pubmed/22069468

Diabetic retinopathy is retinopathy (damage to the retina) caused by complications of diabetes, which can eventually lead to blindness. Many studies have indicated an association between high levels of homocysteine (a non-protein amino acid) and diabetic retinopathy.

This study investigated the relationship of B-vitamins and homocysteine in diabetes and diabetic retinopathy. The study measured values of Vitamins B6, B9 and B12 and included 300 people with type two diabetes of which 200 had retinopathy and 100 did not. A further 100 healthy subjects were also included for analysis.

Other clinical measurements were also measured in the study, and it was revealed:
(i) Those with diabetes had 123% higher blood sugar levels than the healthy subjects.
(ii) Those with diabetes had 83% higher HbA1C levels than the healthy subjects.
(iii) Those with diabetes had 19% higher insulin levels than the healthy subjects.
(iv) Those with diabetes had 25% higher triglyceride levels than the healthy subjects.
(v) Those with diabetes had 18% lower (HDL) high density lipoprotein cholesterol levels than the healthy subjects.

Regarding the relationship of B-vitamins and homocysteine in diabetes and diabetic retinopathy the study found:
(a) Homocysteine levels were higher in those with diabetes, (particularly in those with diabetic retinopathy), compared to the healthy subjects.
(b) Vitamin B6, B9 and B12 levels were lower in those with diabetes, (particularly vitamin B12), compared to the healthy subjects. (Vitamin B12 was also significantly lower in those with diabetic retinopathy compared to those with just diabetes).

The results of the study show that deficiencies of vitamins B6, B9 and B12 are associated with high homocysteine levels and the development of diabetes. Low levels of vitamin B12 were significantly associated with the incidence of diabetes and the development of diabetic retinopathy.

The best sources of vitamin B6 are: Tuna, beef liver, chicken liver, pork chops, salmon, halibut, beef and turkey.

Good sources of vitamin B9 include: Calf's liver, beef liver, other organ meats and chicken giblet's.

Vitamin B12 can only be found in foods of animal origin, the richest sources are: Oyster's, mussel's, clam's, beef liver, trout, salmon, beef, pork, egg and chicken.