Effect of protein intake, hyperglycaemia and micronutrients on DNA damage and mitogen responsiveness of peripheral blood lymphocytes

The aim of the study was to comprehensively assess foods differing in protein type (whey vs casein) relative to a low glycaemic index (GI) and high GI carbohydrate (CHO) food for their effects on DNA damage, DNA repair and mitogen response in peripheral blood lymphocytes using the cytokinesis-block micronucleus assay twohours after consumption. We also studied the relationship of these parameters with plasma folate, vitamin B12, zinc, magnesium and selenium immediately before the intervention and change in plasma glucose and plasma insulin during the two-hour period after consumption. There was no effect of protein, CHO or GI on genome damage or immune responsiveness except for a small but significant improvement in resistance to radiation-induced DNA damage in the high-GI CHO food relative to the casein food. Mitogen response was significantly and positively correlated with plasma zinc, magnesium, selenium and folate and baseline genome damage significantly negatively correlated with plasma folate and vitamin B12. There was no significant correlation between plasma micronutrients and change in plasma glucose or insulin except for a positive and significant correlation between change in plasma insulin and plasma selenium. The correlation between change in plasma insulin and change in plasma glucose was weaker. It is apparent from these preliminary data that micronutrient status may have a profound effect on genome stability and immune responsiveness while the effects of short-term changes in glycemia and dietary intake of carbohydrate or protein may have only minor effects on these parameters.