Big Mac brekkie 'ups' the blood pressure

Apr 24 2007

According to Canadian scientists even just one high-fat meal can increase stress levels in those who are prone to it and substantially raise the blood pressure.

The researchers at the University of Calgary found that people who ate a a fast-food breakfast from McDonald's were far more prone to suffer the physical consequences of stress than those who eat a low-fat meal of dry cereal with skim milk, cereal bars and non-fat yogurt.

Dr. Tavis Campbell, a specialist in behavioural medicine and senior author of the study says they were shocked at the effect of just one such meal even though it is well documented that a high-fat diet leads to artherosclerosis and high blood pressure.

Dr. Campbell says exaggerated and prolonged cardiovascular responses to stress are associated with high blood pressure in the future.

When even a single, high-fat meal can make a person more reactive to stress, it is a cause for concern because it suggests a new and damaging way that a high-fat diet affects cardiovascular function.

For the study, 30 healthy young adults fasted the night before, then consumed either a high or low-fat breakfast; both meals contained about 825 calories, and the low-fat breakfast included supplements to balance it for sodium and potassium; the fast food meals also contained about 42 grams of fat each.

Two hours later the two groups were subjected to standard physical and mental stress tests while having their cardiovascular responses measured.

They performed a mathematical test designed to be stressful, completed a public speaking exercise about something emotionally provocative, held an arm in ice water, and had a blood pressure cuff inflated around an arm, which gradually causes a dull ache.

A week later, the roles were reversed and the fast food group was given the low fat meal.

The researchers say regardless of the task, greater reactivity was recorded among those who consumed the high-fat meal in the several cardiovascular measures taken, including blood pressure, heart rate and the resistance of blood vessels.

Dr. Campbell however does caution that despite the outcome of even one high-fat meal being so bad for the health, more research is needed to fully understand how the mechanisms work.

Campbell says that the vast majority of high blood pressure cases have no known cause and he suggests that prolonged and frequent exposure to fast food meals could provide an explanation for many of these.

Campbell suggests that recommending that people never eat something is probably not a good way to promote a better diet, but in view of the epidemic of obesity in North America, it is important that people make informed choices about their food.

The research is published in the current edition of the Journal of Nutrition.