Triglyceride integrated concentrations: effect of variation of source and amount of dietary carbohydrate

The effects of sucrose on metabolic health: a systematic review of human intervention studies in healthy adults

We systematically reviewed interventions substituting sucrose for other macronutrients in apparently healthy adults to assess impact on cardiometabolic risk indicators. Multiple databases were searched to January 2012 and abstracts assessed by 2 reviewers. Twenty-five studies (29 papers) met inclusion criteria but varied in quality and duration. Weaknesses included small subject numbers, unclear reporting of allocation, unusual dietary regimes, differences in energy intake, fat composition or fibre between conditions, unhealthy subjects, heterogeneity of results, and selective reporting. Insufficient data were available to draw reliable conclusions except with regard to the substitution of sucrose for starch, where effects on plasma lipids were inconsistent, mostly explicable by other factors, or nonsignificant. Based on fewer studies, there was little evidence for significant effects on plasma glucose or insulin. Sucrose substitution for starch up to 25% energy does not appear to have adverse effects on cardiometabolic risk indicators in apparently healthy adults. Furthermore, there is no consistent evidence that restricting sucrose in an isoenergetic diet would affect risk indicators, except perhaps in people with certain preexisting metabolic abnormalities. Larger, high-quality studies, lasting several months and studying a wider range of outcomes, are needed in order to provide evidence on which to base public health initiatives.

Acute effect of fructose on postprandial lipaemia in diabetic and non-diabetic subjects

We investigated whether the potentiation of postprandial lipaemia by fructose occurs in both non-diabetic subjects and those with non-insulin-dependent diabetes mellitus. Six non-diabetic and six diabetic subjects were studied on two occasions. They were given a meal containing 1 g fat/kg body weight with, on one occasion, 0.75 g fructose/kg body weight, on the other occasion 0.75 g starch/kg body weight. In both groups, plasma glucose and insulin concentrations rose more after starch than after fructose. At 1–2 h after the meal, plasma non-esterified fatty acid concentrations were suppressed more after fructose than after starch, but later they rose more after fructose than after starch. Plasma triacylglycerol concentrations rose more slowly after fructose, but were considerably higher than those after starch from 4–6 h after the meal. There were no differences in post-heparin plasma lipoprotein lipase (EC 3.1.1.34) activity at the end of the test. The potentiation of postprandial lipaemia by fructose was positively related to the fasting plasma insulin concentration, suggesting that insulin-resistant subjects are more prone to this effect. We conclude that the potentiation of postprandial lipaemia by fructose is seen in both diabetic and non-diabetic subjects. Our results suggest that alterations in the dynamics of plasma non-esterified fatty acids might underlie the effects of fructose on triacylglycerol metabolism.

The influence of diet upon liver function tests and serum lipids in healthy male volunteers resident in a Phase I unit

AIM

To investigate the effect of diet upon liver function tests and serum lipids within the restricted environment of a Phase I unit.

METHODS

An open randomized three-way crossover study was designed with subjects consuming three types of diet. The diets comprised, a balanced normal calorie diet, a high-carbohydrate high-calorie diet and a high-fat high-calorie diet. Each diet was consumed in a randomized sequence over 8 days with a recovery period of 14 days between periods. The blood concentrations of various laboratory parameters were measured at intervals throughout each dietary period and during the recovery periods.

RESULTS

Blood transaminase activity and triglyceride concentrations increased significantly whilst subjects consumed a high-carbohydrate high-calorie diet but not when fed either a high-fat high-calorie diet or a balanced normal calorie diet.

CONCLUSIONS

The rises in transaminases and triglycerides were caused by the carbohydrate content of the diet rather than its calorific value. Sucrose rather than starch was the carbohydrate which caused the rise in transaminases and triglycerides. The importance of controlling diet in Phase I studies is stressed.

Substituting honey for refined carbohydrates protects rats from hypertriglyceridemic and prooxidative effects of fructose

Recent findings indicate that a high fructose diet has a prooxidant effect in rats compared with a starch diet. Because honey is rich in fructose, the aim of this study was to assess the effect of substituting honey for refined carbohydrates on lipid metabolism and oxidative stress. Rats were fed for 2 wk purified diets containing 65 g/100 g carbohydrates as wheat starch or a combination of fructose and glucose or a honey-based diet prepared by substituting honey for refined carbohydrates (n = 9/group). The same amount of fructose was provided by the honey and fructose diets. The hypertriglyceridemic effect of fructose was not observed when fructose was provided by honey. Compared with those fed starch, fructose-fed rats had a lower plasma alpha-tocopherol level, higher plasma nitrite and nitrate (NOx) levels and were less protected from lipid peroxidation as indicated by heart homogenate TBARS concentration. Compared with those fed fructose, honey-fed rats had a higher plasma alpha-tocopherol level, a higher alpha-tocopherol/triacylglycerol ratio, lower plasma NOx concentrations and a lower susceptibility of heart to lipid peroxidation. Further studies are required to identify the mechanism underlying the antioxidant effect of honey but the data suggest a potential nutritional benefit of substituting honey for fructose in the diet.

Functional food science and the cardiovascular system

Cardiovascular disease has a multifactorial aetiology, as is illustrated by the existence of numerous risk indicators, many of which can be influenced by dietary means. It should be recalled, however, that only after a cause-and-effect relationship has been established between the disease and a given risk indicator (called a risk factor in that case), can modifying this factor be expected to affect disease morbidity and mortality. In this paper, effects of diet on cardiovascular risk are reviewed, with special emphasis on modification of the plasma lipoprotein profile and of hypertension. In addition, dietary influences on arterial thrombotic processes, immunological interactions, insulin resistance and hyperhomocysteinaemia are discussed. Dietary lipids are able to affect lipoprotein metabolism in a significant way, thereby modifying the risk of cardiovascular disease. However, more research is required concerning the possible interactions between the various dietary fatty acids, and between fatty acids and dietary cholesterol. In addition, more studies are needed with respect to the possible importance of the postprandial state. Although in the aetiology of hypertension the genetic component is definitely stronger than environmental factors, some benefit in terms of the development and coronary complications of atherosclerosis in hypertensive patients can be expected from fatty acids such as alpha-linolenic acid, eicosapentaenoic acid and docosahexaenoic acid. This particularly holds for those subjects where the hypertensive mechanism involves the formation of thromboxane A2 and/or alpha 1-adrenergic activities. However, large-scale trials are required to test this contention. Certain aspects of blood platelet function, blood coagulability, and fibrinolytic activity are associated with cardiovascular risk, but causality has been insufficiently proven. Nonetheless, well-designed intervention studies should be initiated to further evaluate such promising dietary components as the various n-3 and n-6 fatty acids and their combination, antioxidants, fibre, etc. for their effect on processes participating in arterial thrombus formation. Long-chain polyenes of the n-3 family and antioxidants can modify the activity of immunocompetent cells, but we are at an early stage of examining the role of immune function on the development of atherosclerotic plaques. Actually, there is little, if any, evidence that dietary modulation of immune system responses of cells participating in atherogenesis exerts beneficial effects. Although it seems feasible to modulate insulin sensitivity and subsequent cardiovascular risk factors by decreasing the total amount of dietary fat and increasing the proportion of polyunsaturated fatty acids, additional studies on the efficacy of specific fatty acids, dietary fibre, and low-energy diets, as well as on the mechanisms involved are required to understand the real function of these dietary components. Finally, dietary supplements containing folate and vitamins B6 and/or B12 should be tested for their potential to reduce cardiovascular risk by lowering the plasma level of homocysteine.

Large variations of sucrose in constant carbohydrate diets in type II diabetes

Several studies show that sucrose does not aggravate hyperglycemia in type II diabetes mellitus, but sucrose is still restricted in dietary recommendations. Since sucrose in high carbohydrate diets elevates fasting triglyceride levels, the effects of sucrose were evaluated in diets with fixed carbohydrate levels. Eighteen diabetic volunteers receiving no medication were given weight maintenance diets with 50 percent carbohydrate, 35 percent fat, 15 percent protein, and 120 g of sucrose for 10 days as inpatients. They were then randomly assigned diets of similar composition with either 220 g of sucrose (high sucrose diet) or less than 3 g of sucrose daily (complex carbohydrate [CHO] diet) for one additional month. There were no differences in fasting, one-, two-, and three-hour post-lunch serum glucose levels; 24-hour glycosuria; glycohemoglobin levels; fasting and postprandial serum triglyceride levels, or fasting high-density lipoprotein-cholesterol levels. Twelve patients with preexisting higher triglyceridemia had similar trends, but the postprandial triglyceride levels were lower in the high sucrose diet group of this subset (p less than 0.05 in the third week). Postprandial serum insulin levels declined in the second week on the complex CHO diet. More than 75-fold difference in sucrose intake with constant carbohydrate and fat did not affect glycemic or triglyceridemic control in type II diabetic patients. The reported high sucrose-carbohydrate-induced rise in fasting triglyceridemia was not present when a diet high in sucrose was given without changing total carbohydrate.

Effect of monounsaturated fatty acids versus complex carbohydrates on high-density lipoproteins in healthy men and women

The effects of two strictly controlled diets, one rich in complex carbohydrates, the other rich in olive oil, on serum lipids were studied in healthy men and women. Serum cholesterol levels fell on average by 0.44 mmol/l in the carbohydrate group and 0.46 mmol/l in the olive oil group. HDL cholesterol levels fell by 0.19 mmol/l in the carbohydrate group and rose by 0.03 mmol/l in the olive oil group. Serum triglycerides rose by 0.19 mmol/l in the carbohydrate group and fell by 0.06 mmol/l in the olive oil group. The changes in both HDL and triglycerides were larger in men than in women. These results clearly show that the olive-oil-rich diet, unlike the complex-carbohydrate-rich diet, caused a specific fall in non-HDL cholesterol while leaving serum triglyceride levels virtually unchanged.

A crossover trial of high and low sucrose-carbohydrate diets in type II diabetics with hypertriglyceridemia

Earlier work shows that hyperlipemic type II diabetics tolerate wide ranges of sucrose and carbohydrate intake without effects on glycemic control, but a rise of fasting serum triglycerides sometimes occurs. To address further the issue of individual susceptibility to carbohydrate, the current study was designed to use each patient as his own control when given diets widely varying in sucrose content. After a stabilization period in the hospital on a normal sucrose content diet, each subject was given either a very low sucrose (less than 3 gm/day)-low carbohydrate (38 +/- 2%) diet or a high sucrose (220 gm)-high carbohydrate (63 +/- 3%) diet for 4 weeks. On a separate admission the opposite diet was assessed, again after an initial normal sucrose content diet. No consistent differences occurred in serum glucose levels or in 24-hr urinary glycosuria. High sucrose-carbohydrate intake raised fasting hypertriglyceridemia after 2 weeks but less thereafter. Severe sucrose-carbohydrate restriction did not significantly decrease fasting serum triglycerides; postprandial triglycerides changed in a trend opposite to fasting levels. No differences occurred in fasting serum insulin or serum cholesterol levels, but postprandial insulin levels were higher in high sucrose-carbohydrate diets. A diet with low sucrose and low total carbohydrate appears to offer no improvement in glycemic control over at least 70-fold higher dietary sucrose levels. However, high sucrose and carbohydrate diets increase fasting triglyceride levels in hypertriglyceridemic type II diabetics.

Graded sucrose/carbohydrate diets in overtly hypertriglyceridemic diabetic patients

Overtly hypertriglyceridemic patients with non-insulin-dependent diabetes mellitus were given a control diet containing 120 g of sucrose and 50 percent carbohydrate, and later randomly assigned to receive isocaloric high- (220 g), intermediate- (120 g), or low- (less than 3 g) sucrose/carbohydrate diets for four weeks. The low-sucrose diet group demonstrated a modest but significant decrease in mean fasting serum glucose level in the first week only, although this change was no different from the other two dietary groups and was not sustained. All groups had little change in late postprandial serum glucose levels from control values, and no significant alterations in 24-hour glycosuria. The high-sucrose diet group demonstrated a significant increase in fasting serum triglyceride levels by the second week of the study, whereas the intermediate- and low-sucrose diet groups showed a decrease in mean fasting triglyceride levels. In contrast, the low-sucrose diet group's late postprandial serum triglyceride levels increased by the fourth week, whereas levels fell in the high-sucrose diet group. Mean fasting serum cholesterol concentrations decreased from control values in the high-sucrose diet group. Thus, although very high sucrose and carbohydrate consumption is clearly deleterious to fasting tryglyceride levels in non-insulin-dependent diabetes mellitus with preexisting hypertriglyceridemia, it appears that low dietary sucrose and carbohydrate proportions do not further improve preprandial glycemia and glycosuria and may adversely affect late postprandial serum triglyceride concentration. This study suggests that isocaloric sucrose and carbohydrate restriction below usual daily levels (120 g per day) offers no consistent benefit in glycemia or lipid control in overt type II diabetes.

Diet-induced changes in serum transaminase and triglyceride levels in healthy adult men. Role of sucrose and excess calories

Serum transaminase levels were measured as part of a study on the physiologic control of food intake. Twenty-one men, 15 nonobese and six obese, were housed on a metabolic ward for 30 days where they received ad libitum a baseline diet of conventional foods containing 25 to 30 percent of total calories as sucrose for 18 days and a calorically diluted diet containing less than 10 percent sucrose for 12 days. Serum glutamic pyruvic transaminase (SGPT) and serum glutamic oxaloacetic transaminase (SGOT) levels rose significantly when subjects consumed the baseline diet and returned to their original levels on the calorically diluted aspartame-sweetened diet. Markedly abnormal transaminase levels developed in two subjects on the baseline diet and they had to be discharged from the study. Correlations between various components of the diet and enzyme changes suggested that both surplus calories and a high sucrose intake played a role in the elevation of enzyme levels. Serum triglyceride levels also showed a significant reduction when the subjects were switched from the baseline to the calorically diluted diet. In a second study designed to test systematically the role of sucrose on SGPT and SGOT levels and on serum triglyceride levels, six nonobese subjects received a carefully controlled liquid diet, relatively high in linoleic acid content, containing 50 percent of total calories as either sucrose or maltose. In comparison with the first study, sucrose had a smaller but still significant effect on the levels of both enzymes, but there was no significant effect on triglyceride levels.

Inhibition of carbohydrate-induced hypertriglyceridemia by a disaccharidase inhibitor

The ability of an inhibitor of intestinal alpha-glucosiadase activity to prevent sucrose-induced hypertriglyceridemia was studied in nonobese rats. The results indicated that plasma triglyceride levels were approximately twice as high in untreated rats, and the reduction in plasma triglyceride levels of drug-treated rats was associated with lowered very low density lipoprotein-triglyceride secretion rates and plasma insulin levels. Since these changes could be produced with an amount of glucosidase inhibitor which did not prevent normal rate of weight gain, the possibility arises that this approach may be useful in the treatment of various hypertriglyceridemic states in man. Finally, the observation that the fall in plasma TG concentration was associated with a fall in plasma insulin concentration provides further evidence for the existence of a causal relationship between the two variables.

Triglyceride concentrations: the disaccharide effect

The mean 24-hour or integrated concentration of triglyceride is significantly higher when dietary sucrose is provided rather than an equivalent amount of its component monosaccharides, glucose and fructose. In contrast, the plasma triglyceride concentration after a 12-hour fast is not significantly different.