Joslin Study Shows Vitamin E Helps Reduce Artery Damage in Diabetic Eye and Kidney Disease
BOSTON — August, 1999 — A clinical study by researchers at Joslin Diabetes Center in Boston shows high dose vitamin E supplements to be effective in improving blood flow in the retina of the eye and the kidneys in patients with type 1 (juvenile onset) diabetes.
If further studies confirm these findings, published in the August issue of Diabetes Care, this research may ultimately prove beneficial to the estimated 16 million people in the U.S. and millions more worldwide who have diabetes. People with diabetes are at greatly increased risk of developing a wide range of blood vessel complications, including diabetic eye disease called diabetic retinopathy, which can cause sight loss and even blindness. According to the Centers for Disease Control and Prevention, diabetic retinopathy causes from 12,000 to 24,000 new cases of blindness each year in the United States. Diabetes is the leading cause of end-stage renal disease, accounting for about 40 percent of the more than 50,000 new cases diagnosed in the nation yearly.
Antioxidants, such as vitamin E, have received considerable attention regarding their potential ability to reduce blood vessel complications related to diabetes. Joslin researchers previously found that vitamin E treatment in diabetic rats normalized the activation of a protein called protein kinase C beta, which has been linked with blood vessel damage in the eye and kidneys. Other studies have shown a reduced risk of heart disease in women taking vitamin E supplements. Studies in men found a significant decrease in prostate cancer incidence in men taking the vitamin.
The 8-month Joslin study, headed by George L. King, M.D., and Sven-Erik Bursell, Ph.D., involved 36 people, ages 18-45, who had type 1 diabetes less than 10 years and no or minimal complications. Nine people who did not have diabetes also took part in the study for comparison. The participants were randomly assigned to a group taking 1,800 IU (international units) of vitamin E daily, or a group that took a placebo (an inactive substance resembling the vitamin pill) for four months and then the vitamin for four months.
Before the vitamin E was taken, the baseline blood flow in the retinas of patients with diabetes was 17.3 percent lower than in the non-diabetic subjects. After four months of 1,800 IU per day of vitamin E, on average the retinal blood flow of the patients with diabetes returned to 88 percent of normal. Blood sugar control was unchanged during the study.
"After vitamin E treatment, the blood flow in those patients with diabetes was significantly increased and kidney function appears to be improved as well," Dr. King said. "The treatment was most beneficial in those cases in which blood sugar control was the poorest and the retinal and kidney abnormalities were greatest."
Dr. King heads the Vascular Cell Biology section at Joslin and is Professor of Medicine at Harvard Medical School (HMS). Dr. Bursell is an Investigator in the Section on Eye Research at Joslin and an Assistant Professor in Ophthalmology at HMS.
"We measured blood flow in the eye by doing video recordings of fluorescein dye in the eye blood vessels using a scanning laser ophthalmoscope," Dr. Bursell said. "Kidney function was assessed from laboratory tests that evaluate the amount of a substance called creatinine excreted in the urine. As in other studies, there was a slight trend of increasing cholesterol with vitamin E treatment, but no other side effects were noted.
"The finding that patients with the poorest blood sugar control and the poorest retinal blood flow and creatinine clearance at the beginning of the study had the most benefits from vitamin E treatment was of particular interest," Dr. Bursell continued. "On the other hand, diabetes patients who had good blood sugar control continued to have retinal blood flow and kidney function in the normal ranges with the vitamin E treatment. Thus, it appears vitamin E was effective in reversing abnormal retinal and kidney function, but did not adversely affect function in patients with normal function."
Does this mean people with diabetes should start popping vitamin E pills? "We are not recommending people start consuming vitamin E in large doses," said Dr. King. "Until our findings can be confirmed in further and larger clinical trials, our study results should not be interpreted as a recommendation for widespread use of vitamin E for the treatment of diabetic retinopathy."
Vitamin E is a low-cost, readily available substance. Therefore, if further studies do confirm these findings, it could have dramatic socio-economic impact if it was found to delay onset of retinopathy and/or kidney disease. Vitamin E is found in many common foods, including vegetable oils (such as soybean, corn, cottonseed and safflower) and products made from these oils (such as margarine), wheat germ, nuts and green leafy vegetables, although the researchers evaluated only the pill form of the vitamin. However, it will be very difficult to consume from food the high amount of vitamin E used in this trial.
