High-Carbohydrate-Induced Hypertiglyceridemia: Study Design Constraints
The following is a summary of some investigational shortcomings and how these may account in large part for the controversy over whether low-fat, high-carbohydrate diets provide net benefit to health.
The studies conducted have been observational in nature. A good portion of our understanding of carbohydrate-induced hypertriglyceridemia is based on observed phenomenon, rather than on results of studies designed to determine the mechanism.
In addition, many of the metabolic studies conducted so far have had small sample sizes (<30 subjects). Efforts should be made to improve our ability to quantify metabolic flux in studies with larger numbers of subjects.
To decrease the variability in dietary intake data, many investigators have used liquid-formula diets. Therefore, it is difficult to extrapolate study findings to the metabolic changes associated with more regular patterns of eating.
This was more of a problem in earlier published studies. In recent years, the use of whole-food diets has become common, although the preparation of such diets requires increased personnel time and expense.
The duration of most dietary studies has been too short to extrapolate the findings to the long-term dietary consumption of individuals over a life span.
In this respect, the question of the transitory nature of carbohydrate-induced hypertriglyceridemia is still not completely answered.
Longer studies in which all food intake is controlled are not feasible; thus, increasing the duration of feeding studies will require an outpatient feeding regimen, ie, one in which dietary compliance is no longer assured.
Nonetheless, understanding the adaptability of persons to low-fat, high carbohydrate diets will be key for predicting the long-term benefits and risks of these diets.
Kinetic studies required to understand metabolic differences elicited by different diets are optimally performed when the subjects are in a metabolic steady state throughout the data collection period.
To accomplish this, studies have frequently been conducted in the fasting state, or when subjects were continually consuming small amounts of energy (liquid or solid) frequently (every half-hour) throughout the day, causing measurements of triacylglycerol production to be conducted in nonphysiologic states.
Again, this design makes it difficult to generalize the findings to normal meal-eating patterns.
Many studies of carbohydrate feeding have not shown a statistically significant change in triacylglycerol concentrations, which may be due to the fact that the subject population consisted of persons with different lipoprotein phenotypes.
Future studies should include characterization of the lipoprotein phenotype of the subjects and assessment of the changes in the various lipoprotein classes (chylomicrons, VLDL, IDL, etc).
*American Journal of Clinical Nutrition, Vol. 71, No. 2, 412-433, February 2000.
"Low Fat Diet Did Not Work!"
Here's a testimonial on effectiveness of the low carbohydrate eating plan:
I ate a lot of carbos while trying to avoid saturated fat. I also increased my exercise but was not able to lose much weight following the low saturated fat diet. And my triglycerides were climbing instead of going down.
So I decided to cut way back on the amount of carbohydrates and see if that helped. I had more low carbohydrate veggies such as broccoli instead of corn, peas, etc. Bread, pasta, rice, potatoes were limited. Concentrated sweets were out.
I would like to report that after about 6 weeks of this modified carbo diet my triglycerides dropped from 400 to 167!!!!
I thought I was doing everything right including increased exercise, low saturated fat diet, lipitor, but it wasn't until I made this diet change that I saw much of an improvement. I even lost a few pounds, something I hadn't been able to do on two years of a low fat diet!
Critics of this diet say it is not nutritionally balanced. I did find the pure form of the diet hard to follow, but on a slightly modified approach I found it easy.
Chris S.
*This testimonial has been presented as a true story. However, it has not been reviewed by Full of Health and is the opinion of the listed individual.
