Polyunsaturated fatty acid consumption, plasma cholesterol concentration and neuroendocrine response to mental and physical task load

This study was designed to investigate the relation between fatty acid consumption, total plama cholesterol and neuroendocrine response to exposure to stress, factors thought to play a role in the development of coronary heart disease. For this purpose 32 apparently healthy male volunteers were classified on the basis of their plasma cholesterol concentration and dietary P/S ratio (Quotient of habitual consumption of polyunsaturated and saturated fatty acids), according to complete quantitative food frequency questionnaire. The subjects performed a memory search task (mental task) and a steady-state bicycle ergometer exercise for 30 min at 60% of their individual aerobic power (physical task) in a randomized order. Mental task load caused an increase of heart rate, which remained constant during task performance. In plasma a gradual increase of cortisol, an almost instantaneous increase of adrenaline and a linear decrease of prolactin were observed. Physical task load caused a linear increase of plasma ACTH, cortisol and catecholamines. Heart rate and rating of perceived exertion increased rapidly within 5 min, followed by a moderate increase. Higher dietary P/S ratios were related to higher ACTH and cortisol and to lower prolactin responses to mental task load, and higher plasma cholesterol concentrations to higher dopamine responses to mental task load. Urinary excretion of free noradrenaline and vanilmandelic acid was higher after physical than after mental task load. The opposite was found for conjugated noradrenaline, homovanillic acid and several keto- and corticosteroids. Excretion of free adrenaline after both tasks, of conjugated noradrenaline after mental task load and of tetrahydrocortisol and α-cortolone after physical task load were positively related to plasma cholesterol, whereas the excretion of conjugated adrenaline after physical task load was inversely related to plasma cholesterol. The excretion of tetrahydrocortisol after mental task load was inversely relased to the dietary P/S ratio. It is concluded that there are marked differences between the neuroendocrine responses to mental and physical task load and that the relation of several effects to the plasma cholesterol concentration and dietary P/S ratio suggests an association with the risk of coronary heart disease.