CHO Load Research Articles

Oral Carbohydrate Administration was Suitable for Cesarean Section–A Systematic Review and Meta-Analysis of Randomized Trials

The use of carbohydrate (CHO) drinks prior to elective cesarean section has gained momentum, but its effect on maternal and neonatal outcomes remains controversial. The aim of this meta-analysis was to assess the effect of an oral CHO load prior to cesarean delivery on insulin sensitivity, insulin resistance, maternal glycemia, neonatal glycemia, and breastfeeding. As of May 21, 2023, we searched through five databases for English-language experimental studies on pre-cesarean oral CHO. A total of 3,940 citations were received, of which seven were selected. The concentrations of CHO used in these studies ranged from 5.9% to 14.2%, and the amounts used were 300-400 ml. We found that pre-cesarean CHO loading reduced maternal insulin resistance and increased maternal glucose levels. CHO loading activates the insulin pathway of critical en-zymes to some extent, increasing glucose utilization by peripheral tissues and ultimately reducing postop-erative insulin resistance. Of course, this is also beneficial in improving maternal blood sugar. We did not find that CHO increased maternal insulin sensitivity or neonatal blood glucose levels. Future prospective randomized controlled trials can use nutritional load to increase colostrum production after Caesarean sec-tion to enhance the confidence of these mothers in breastfeeding. In addition, our preoperative beverage could be more individualized to accommodate diabetic women.

Attenuation of metabolic stress response during spinal surgery under general anaesthesia - A comparison between preoperative carbohydrate drink or no carbohydrate load

Background: Surgery is a stress which stimulates the increase of counter regulatory hormones. Pre-operative prolonged fasting increases stress further. Although a pre-operative carbohydrate (CHO) drink has been variably reported to yield benefit in reducing the perioperative stress and is being used frequently for elective surgeries, some recent reports also reports that preoperative CHO loading did not result in increase or decrease in the post-operative complication rates when compared with placebo or fasting group. Aims and Objectives: The present study was designed to determine the stress response in the postoperative period at 24 h in terms of changes in the levels of cortisol and other biomarkers. Materials and Methods: This randomized, parallel group, and double-blind study was conducted in 75 patients aged 18–65 years, of American Society of Anesthesiologists Physical Status Classes I and II, scheduled for elective lumbar spine surgery under general anesthesia. The patients were randomly allocated to receive 300 ml plain water at 9 pm on the day before surgery and 2 h before operation (Group C, control, n=25), or 300 ml plain water at 9 pm on the day before surgery and solution containing 75 grams of glucose dissolved in 300 ml water in the morning 2 h before surgery (Group CHO-1, n=25), or to receive 75 grams of glucose dissolved in 300 ml water at 9 pm in the night before the surgery and again in the morning at 2 h before surgery (Group CHO-2, n=25). In all the three groups, the levels of insulin (C-peptide), lactate, glucose, and cortisol were determined preoperatively (before the induction of anesthesia) and 24 h postoperatively. Results: There was considerable difference between post-operative blood cortisol level among the three groups (583.9 vs. 462.3 vs. 389.6 nMol/L, Control vs., CHO load once or twice, respectively, P<0.0001). A significant difference in post-operative values was also seen with other parameters such as serum lactate, glucose, and C-peptide. Considerable differences were seen in both preoperative and postoperative period in case of cortisol and lactate whereas it was limited to postoperative values in case of glucose and C-peptide. Conclusion: Pre-operative glucose loading showed better efficacy in suppressing perioperative stress response in terms of less rise of serum cortisol and lactate as compared to no CHO load.

Greater Fasting Insulin is Associated with Prevalent Hypertension and Left Ventricular Hypertrophy in Black and White Adults

We tested the hypothesis that higher insulin is associated with prevalent Hypertension (HTN) and Left Ventricular Hypertrophy (LVH), and that dietary carbohydrates (CHO) are associated with insulin. Data were analyzed on 14,729 non‐diabetic participants of REGARDS, an observational study of adults aged >45 y. Logistic regression was used to examine the association of insulin quintile with prevalent HTN and LVH, adjusting for covariates. Participants with higher insulin were younger, had higher BMI, and were more likely to be black, male, live in the Southeast, and have a lower income and education. Participants in the highest quintile of fasting insulin had 3.4 times the odds of having HTN than those in the lowest quintile [OR 3.4, (3.04, 3.81), P for trend<0.001]. The relationship was stronger in whites [OR 3.70, (3.24, 4.24), P trend <0.001] than in blacks [OR 2.56, (2.06, 3.18), P trend <0.001; P<0.05 for race x insulin interaction]. The relationship with LVH was similar [OR 2.77, (2.23, 3.45), P trend <0.001]. Quintiles of % CHO, glycemic index, or glycemic load were not associated with insulin (P = 0.08‐0.13). In conclusion, greater insulin was associated with increased prevalence of HTN and LVH in both whites and blacks. Research is needed to determine if this association is causal, and if insulin‐related CVD risk can be decreased by modifying dietary CHO quantity or quality.

Effects of a high-carbohydrate versus high-protein meal on acute responses to hypoxia at rest and exercise

A carbohydrate (CHO) solution consumed before exposure to hypoxia has been reported to reduce arterial oxygen desaturation at rest. The purpose of this study was to determine whether this effect occurred during exercise and when the CHO load is part of a meal. Eleven male subjects (mean age 20.1 ± 1.8 years, BMI 24.3 ± 2.4 kg m(2)) consumed either a high-CHO (2,340 kJ, 70 % CHO, 12 % protein) or an isoenergetic high-protein (35 % CHO, 48 % protein) breakfast meal 60 min before being exposed to 15 min of hypoxia (F(I)O(2) = 13.5 %) followed by 30 min of exercise in hypoxia (60 % of VO₂max). Saturation of oxygen via a pulse oxymeter (SpO(2)), ventilatory parameters, substrate oxidation, interstitial glucose concentrations, and heart rate variability (HRV) were monitored continuously during the whole session. Results showed no effect from the type of meal on SpO(2) at rest but a 3.1 ± 0.4 % reduction of desaturation during exercise (P < 0.005) compared to the high-protein version. This was associated with higher levels of ventilation (P < 0.05) and CO(2) production (P < 0.01). Glucose oxidation was higher after the high-CHO than the high-protein breakfast over the whole session (+19.4 + 4.0 %, P < 0.0001), whereas the interstitial glucose levels were increased only at rest (P < 0.001). HRV indices were not different between conditions. In conclusion, a high-CHO meal consumed prior to moderate exercise in hypoxia condition reduced oxygen desaturation compared to a high-protein meal.

The Latest on Carbohydrate Loading

High dietary carbohydrate (CHO) intake for several days before competition (CHO loading) is known to increase muscle glycogen stores, with subsequent ergogenic performance benefits often seen in events longer than 90 min in duration. CHO-loading strategies vary in characteristics such as type and duration of dietary manipulation and the accompanying exercise/training activities. Additionally, glycogen concentration may remain elevated for up to 5 d. This versatility in CHO-loading strategies allows the athlete greater flexibility in tailoring pre-event preparation. Women who attempt to CHO load should be particularly attentive to both total energy intake and relative CHO intake; dietary CHO should exceed 8 g x kg body mass(-1) x d(-1) or 10 g x kg lean body mass(-1) x d(-1). As long as the amount ingested is adequate for loading, the type of CHO is less important, with the exception of 1-d loading protocols where the glycemic index may be an important consideration.

The thermogenic and metabolic effects of protein hydrolysate with or without a carbohydrate load in healthy male subjects

High-protein diets are beneficial in weight maintenance because of their satiating and thermogenic effects. These effects may be partly mediated by the hormonal effects of proteins. This study investigated the effect of soy protein hydrolysate (SPH) with and without a carbohydrate pre- and afterload on energy metabolism and hormonal secretion in 8 healthy nonobese subjects. In an additional trial, pea protein hydrolysate was compared to SPH, both with a carbohydrate afterload. The study had a single-blind crossover design. In all cases, 0.4g protein and/or carbohydrate per kilogram of body weight was tested. Diet-induced thermogenesis (DIT) was measured by ventilated hood measurements, and postprandial blood samples were drawn over 3 hours. Soy protein hydrolysate consumption induced a higher DIT than a carbohydrate (CHO) load. Both conditions induced similar insulin responses. Soy protein hydrolysate induced a glucagon, but no glucose, response; whereas CHO induced a glucose, but no glucagon, response. Soy protein hydrolysate with a CHO pre- or afterload induced similar DIT and insulin responses. No glucose response was found when SPH preceded the CHO load. Total glucagon responses were similar with CHO as pre- and afterload, but time courses were different. Pea protein hydrolysate with a CHO afterload induced both higher insulin and glucagon responses (area under the curve) than SPH with CHO afterload, but DIT was similar in both conditions. In conclusion, this study shows that the larger DIT after protein than after CHO may be related to the glucagon response that is induced by protein but not by CHO; that the protein-induced DIT and glucagon response are not influenced by a CHO pre- or afterload; and that protein ingestion can fully prevent the plasma glucose increase associated with CHO when CHOs are ingested after proteins.

Labeled CO 2 production and oxidative vs nonoxidative disposal of labeled carbohydrate administered at rest

Carbon isotopes (*C) have been extensively used in man to describe oxidative vs nonoxidative disposal of an exogenous load of labeled carbohydrate (*C-CHO) at rest in various experimental situations. It is hypothesized that V*CO 2 reflects *C-CHO oxidation. However, when glycogen is synthesized through the indirect pathway (which is responsible for ∼50% of glycogen storage), *C could be lost, diluted, and exchanged in the pyruvate-lactate pool, in the pool of tricarboxylic acid cycle intermediates, as well as at the entrance of the tricarboxylic acid cycle, and along the pathway of gluconeogenesis. This could result in a lower *C/C in the glycogen stored than in the CHO administered, in an increased production of *CO 2, and, respectively, in an overestimation and an underestimation of the oxidative and nonoxidative disposal of the CHO load. Results from the present experiment offer a support to this hypothesis. Over a 10-hour period after ingestion of a 13C-pasta meal (313 ± 10 g dry mass or 258 ± 8 g of glucose) in 12 healthy subjects (6 men and 6 women), exogenous CHO oxidation computed from V 13CO 2 (recovery factor, 0.54) significantly exceeded total CHO oxidation computed by indirect respiratory calorimetry corrected for urea excretion: 154.2 ± 2.6 vs 133.5 ± 3.2 g. In an additional study conducted in rats, 13C/ 12C in glycogen stores was significantly ∼50% lower than in the 13C-CHO ingested, over a wide range of enrichment. These results suggest that because of dilution, loss, and exchange of *C in the indirect pathway of glycogen synthesis, the oxidative vs nonoxidative disposal of exogenous *C-CHO cannot be accurately tracked from V*CO 2.

Assessing How Cultural Practices Influence Long-term Productivity in Asparagus

Asparagus producers have reported a decrease in plant longevity and plant productivity in asparagus fields. Eleven commercial sites (6 in California and 5 in Washington) were monitored starting in Spring 2003. The purpose in monitoring was to evaluate how long-term growth dynamics are affected by harvest pressure. Sites were planted as crowns in Spring 2002 and farm irrigation methods included furrow, sprinkler, and drip. Most sites were harvested starting in Spring 2003 at varying pressures. Harvest yields ranged from 0 to 1300 kg·ha-1. Carbohydrate (CHO) levels in the roots were sampled over the entire growing season and assessed with AspireUS (www.aspireus.com). At the last sampling in Oct. and Nov. 2003, CHO levels ranged from 438 mg·g-1 to 712 mg·g-1 (97% to 158% of the ideal). This resulted in a root CHO load of 2.6 to 6.3 megagrams/hectare. Root mass and distribution was sampled in Spring 2003 and again at the end of the growing season. Root biomass increased by 18% to 487% of the previous year's growth. Fern number, fern mass and plant population were also sampled. Fern number ranged from 3.2 to 6.4 stems per plant and total fern weight ranged from 8.9 to 36.2 megagrams/hectare. Plant populations were reduced by 3% to 19% when compared to the initial planted population. Findings suggest that excessive harvest pressure in the year after planting adversely affects storage CHO accumulation and root growth. Additional site monitoring will occur through 2005.

EFFECT OF PRE-EXERCISE CARBOHYDRATE FEEDING ON GLYCEMIC AND INSULINEMIC RESPONSES DURING EXERCISE AT DIFFERENT INTENSITIES

Rebound hypoglycemia has been reported after pre-exercise carbohydrate (CHO) ingestion in some studies but not in others. Differences in the experimental design and factors such as the exercise intensity are likely to be responsible for the discrepancies between these studies. Exercise intensity might be a crucial factor since it affects both insulinemia, liver glucose production and muscle glucose uptake. Purpose: Therefore the aim of the present study was to compare the glycemic and insulinemic responses to exercise at different intensities after ingestion of a standardized pre-exercise CHO load. Methods: Eight trained subjects (VO2max 58.4 ± 1.9 ml/kg/min) consumed 75g of glucose 45min prior to 20min of exercise at 55 ± 1, 77 ± 1 and 90 ± 1%VO2max. Blood samples were collected before glucose ingestion, at 15min intervals at rest and 5min intervals during exercise. Results: There were no significant differences in glucose or insulin concentrations between the three trials during exercise. Immediately pre-exercise, plasma glucose concentration had returned to pre-ingestion levels, while the insulin concentration was more than 3 times higher than pre-ingestion (45 ± 10, 62 ± 14, 62 ± 15 vs 16 ± 2, 16 ± 2, 16 ± 1 μU/mL for the 55%, 77% and 90% trials resp.). During exercise, plasma glucose concentration decreased from 4.7 ± 0.3, 5.5 ± 0.3, 4.8 ± 0.3 mmol/L before the start of exercise to 4.1 ± 0.2, 4.0 ± 0.2, 4.1 ± 0.2 mmol/L during the first 5min in the 55%, 77% and 90% trials respectively and then stabilized in all trials. During the 55% and 77% trials, 3 subjects developed hypoglycemia (glucose concentration < 3.5mmol/L), while hypoglycemia occurred in 4 subjects during the 90% trial. Insulin concentrations decreased during the first 10min of exercise and then leveled off at pre-ingestion concentrations. Conclusions: These data suggest that the glycemic response to 75g of CHO 45min pre-exercise is similar during exercise of different intensities. The discrepancies found in studies regarding hypoglycemia after pre-exercise CHO feedings cannot therefore be explained by differences in exercise intensity employed in those studies.

Metabolic responses to high carbohydrate breakfasts in obese patients with impaired glucose tolerance. Comparison of meals containing dairy products and fruits versus bread

Carbohydrate (CHO) enriched diets can improve glucose tolerance in healthy subjects but have controversial effects in NIDDM patients. Their effects on glucose metabolism are not clearly established in obese patients with impaired glucose tolerance (IGT) and might depend on their glycemic index (GI). For that reason, we compared the metabolic responses to 2 isocaloric CHO rich breakfasts with either a low GI (LGI) or a high GI (HGI) in 10 lean healthy controls (group I) and in 9 obese subjects with IGT (group II). The LGI breakfast contained dairy products and fruits while the HGI breakfast was rich in bread. The 2 breakfasts were allocated in a random order and the metabolic and hormonal responses were evaluated both over the post-prandial periods of the breakfast and of the following lunch. Blood glucose concentrations were continuously monitored. Plasma insulin and counter regulatory hormones were measured every 30 min for 360 min. Nutrient oxidation rates were calculated from respiratory exchange data obtained for 60 min in the pre and post-prandial periods. Blood glucose responses and metabolic responses in terms of oxygen consumption and CO 2 production were similar in the two groups after a LGI breakfast but became different after the HGI breakfast. In the two groups taken as a whole, changes in CHO oxidation rates observed for 1 hour following the meal, were negatively correlated with the corresponding incremental areas of plasma glucose, this effect being more marked in obese patients with IGT. Such a limitation in CHO oxidation following a HGI CHO load could impair the glycogen cycle and favour fat synthesis. Consequently, breakfasts rich in dairy products and fruits are more recommended in obesity with IGT than breakfasts rich in bread.

USE OF 13C-GLUCOSE BREATH TESTS IN THE CHARACTERIZATION OF ABSORPTION OF CARBOHYDRATE IN FORMULA BY INFANTS WITH DIARRHEA

The appearance time (AT) of the first detectable levels of 13CO2 (> .01% dose/min) in breath following the oral administration of UL-13C-glucose (13C-G, 5 mg/kg) provides an estimate of the time required for orally administered 13C-G to reach the primary site of absorption and utilization. The AT for 13C-G will increase as the absorption of glucose occurs at more distal sites, until a maximum is reached when the glucose enters the colon where it is rapidly oxidized to CO2. The AT of 13C-G administered alone and with formula (60-240 ml) has been used to characterize glucose absorption and utilization in 6 infants (16-93 d) with diarrhea and malnutrition (arm/FOC < 0.28). A maximum value of 27 min for the AT of 13C-G from formula was determined in an infant with congenital glucose-galactose malabsorption, in whom colonic utilization of CHO was demonstrated by breath H2 production and partial recovery of 13C in stool. AT for 13C-G in formula, obtained for the 6 infants measured, were 5,7,15,20,30,30 min, respectively, providing indirect evidence for the colonic utilization of dietary glucose in at least 2 of the infants. In the absence of formula, AT for 13C-G decreased to 10,15,10,10,2,10 min, respectively. This suggests that the CHO load in the formula may have contributed to the small bowel malabsorption of glucose in those infants with near maximal formula AT values.

Nutritional influences on lipogenesis and thermogenesis after a carbohydrate meal.

In vivo lipogenesis and thermogenesis were studied for 24 h after ingestion of 500 g of carbohydrate (CHO) in subjects who had consumed either a high-fat, a mixed, or a high-CHO diet during the 3-6 days preceding the test. CHO oxidation and conversion to fat was significantly less in the high-fat diet group (222 +/- 5 g) than in the mixed (300 +/- 13 g) or high-CHO diet (331 +/- 7 g) groups, resulting in a greater glycogen storage in the high-fat (278 +/- 6 g) than in the other two groups (197 +/- 11 and 170 +/- 2 g). Net lipogenesis occurred sooner and lasted longer in the high-CHO group, amounting to 0.8 +/- 0.5, 3.4 +/- 0.6, and 9 +/- 1 g of lipid synthesized in the high-fat, mixed, and high-CHO groups, respectively. The thermic effect of the CHO load was 5.2 +/- 0.5% on the high-fat, 6.5 +/- 0.4% on the mixed diet, and 8.6 +/- 0.4% on the high-CHO diet. Significant relationships were demonstrated between the postabsorptive nonprotein respiratory quotient and net lipogenesis after the CHO load (r = 0.82) and between net lipogenesis and the increase in energy expenditure (r = 0.71). It is concluded that the antecedent diet influences the amount of net lipogenesis and the magnitude of thermogenesis after a large CHO test meal. However, lipogenesis remains too limited even after such large CHO intakes to cause an increase in the body's fat content.

Glycogen synthesis versus lipogenesis after a 500 gram carbohydrate meal in man

The respiratory exchange and urinary nitrogen excretion of 6 healthy male subjects (age 21 ± 1 yr; body weight 70 ± 2 kg; means ± SD) were followed for 10 hr after ingestion of a large amount of carbohydrates (CHO) in the form of bread, jam, and fruit juice, equivalent to 479 g of starch. Peak values for blood glucose (6.6 ± 0.6 mM; mean ± SEM) and plasma insulin (139 ± 26μU/ml) were reached after 90 min at which time the nonprotein respiratory quotient (NP-RQ) had risen to 0.97. During the next 8 hr glucose levels remained near 5.5 mM while insulin declined gradually to 22 ± 7 μU/ml. The average NP-RQ remained in the range of 0.91 to 0.98, though individual values exceeding 1.0 for very short periods were observed. The increase in energy expenditure above basal rates corresponded to a specific dynamic action (SDA) of 5.9 ± 0.6%. Assuming the CHO load to be completely absorbed after 5 hr, and allowing for glucose oxidation calculated from the gas exchange data, the glycogen content of the subject's body tissue had then increased by 408 ± 19 g. During the 10 hr after the meal, 133 g CHO, 17 g fat and 29 g protein were oxidized, providing respectively 66%, 19% and 15% of caloric expenditure, and leaving a gain in glycogen stores estimated at 346 ± 12 g. The data imply that: (1) The capacity for glycogen storage in man is larger than generally believed, and (2) Fat synthesis from CHO will not exceed fat oxidation after one high-carbohydrate meal, even if it is uncommonly large. When a single high-carbohydrate meal is consumed, dietary CHO merely has the effect of reducing the rate of fat oxidation. These findings challenge the common perception that conversion of CHO to fat is an important pathway for the retention of dietary energy and for the accumulation of body fat.