High-carb diet may raise diabetics' blood pressure

Dr Abhimanyu Garg, professor and chief of the division of nutrition and metabolic disease, led a study to investigate the effect of a carbohydrate-rich diet on the blood pressure, compared to one rich in monounsaturated fatty acids.

High blood pressure (130/80 mmHG or more) amongst diabetics is a major cause for concern because it is linked to increased risk of heart attack. About 73 percent of adults with diabetes have blood pressure, and heart disease and stroke account for about 65 percent of deaths amongst all diabetics.

However the disease can also lead to low blood pressure in some sufferers due to damage to the nerves that supply blood vessels, which can cause faintness and anxiety.

Low blood pressure can cause faintness and dizziness, and there is some suggestion that it may be linked to tiredness, depression and anxiety.

Over an initial six-week period, the 42 participants, all type-2 diabetes sufferers, followed either an isoenergic high carbohydrate diet consisting of 55 percent energy as carbohydrate, 30 percent as fat and ten percent as monounsaturated fat, or a high-monounsaturated fat diet.

The latter consisted of 45 percent energy as fat, 25 percent as monounsaturated fat and 40 percent as carbohydrate. The total calories for each diet were the same.

The two groups then switched and received the other diet for a further six week, after which twenty-one patients continued with their second diet for an additional eight weeks.

The researchers measured the participants' systolic and diastolic blood pressure for the last three days of each of the six-week phases. At this time they found little difference in blood pressure, whether the participants were following the high-carb or the high-mono diet.

However in the 13 participants who continued with the high-carb diet for the full 14 weeks, there was a significant increase in blood pressure compared to those who followed the high-mono diet for just six weeks (an average of six points mmHg for systolic blood pressure and seven mmHg for diastolic blood pressure.

The eight who continued the high-mono diet for 14-weeks, on the other hand, showed a small reduction in blood pressure of average three mmHg in systolic and four mmHg in diastolic blood pressure, compared to those following the high-carb diet for six weeks.

"Although the exchange of carbohydrates with monounsaturated fats may not affect blood pressure in the short term, long-term consumption of a high-carbohydrate diet may modestly raise blood pressure in type 2 diabetic patients," wrote the researchers in Diabetes Care​ (28:2607-2612, 2005).

. It is estimated that 20.8 million people in the United States (7 percent of the population) have diabetes. However a third of these have yet to be diagnosed.