Nutritional intake and carbohydrate supplementation at high altitude

A high carbohydrate (CHO) diet has previously been shown to lessen the severity of the symptoms of Acute Mountain Sickness (AMS). The aims of this study were to ascertain whether selected military field rations provided adequate nutritional support, and assess the effectiveness of a high CHO food supplement in reducing the severity of the symptoms of AMS at high altitude. An experimental group (n = 32) received field rations plus a CHO food supplement and a control group (n = 35) only received field rations. Food intakes for 15 consecutive days were recorded using a visual estimation technique and 24-h dietary log. Food acceptability was assessed with a 9-point hedonic scale. Daily urine samples and body weights were obtained from all subjects and a 24-h urine sample obtained from a subsample of the combined groups (n = 30) for the first and last two days of the study.

Results show that energy intake decreased for the first three days at altitude, improved on day four and leveled out thereafter. Mean daily energy intakes were 2265 kcal for the supplemented group and 2140 kcal for the control group; body weight losses were 1.71 kg and 1.68 kg. Mean CHO intake was 271 and 244 g per day; 48 and 46% of energy intake. Ration acceptability was generally good and did not decline over time.

It was concluded that rations used at sea level could also be satisfactorily used at altitude, but given an ad libitum dietary regimen and a CHO food supplement, CHO intake was not automatically increased. Supplementation via a beverage component, rather than a food supplement, may therefore be more effective in increasing CHO intake.