Question 3
The results of the meta-analysis showed that there were no significant relationships in HDL, LDL, or total cholesterol levels when on a carbohydrate restricted diet. Considering the main source of calories is coming from fat and protein while on this diet, why do you suppose this is?
posted by Lauren @ 2:33 PM
28 comments
28 Comments:
The researchers concluded that active weight loss can decrease the plasma cholesterol levels (non-steady state values) and thus might not be a correct interpretation of the results. As for the increased intake of fat (particularly saturated fat which is thought to be atherogenic), they were unsure of these results. Perhaps outside factors, such as genetic predisposition for good cholesterol levels or composition of diet and types of fat consumed, may have affected these results.
I am most interested in what kinds of fat and protein individuals added to their diet in response to restricted carbohydrates. If they carelessly added unhealthy fats and proteins that would be a reason for no significant improvements in blood lipids values. Adding heart healthy fats and protein from nuts, lowfat dairy, cold water fish, plant oils might have made improvements in their blood lipid values. The lengths of the studies, genetics, and many others things could also be reasons why no significant improvements were shown!
It is difficult to determine what was going to happen with certain blood lipid levels unless we know exactly what dietary and lifestyle changes were made. Carbohydrate intakes ranged from 4-45% of total daily calories (which is a value we also don’t know) in different studies, and we are completely unsure of what ratios the other macronutrients made up for those remaining calories, or what types of fats/proteins participants were choosing. If they were making poor choices, such as protein sources high in cholesterol and saturated fats, and the study was long enough to represent this, we would’ve seen worsening blood lipid levels. If the participants were counseled to make good protein and fat choices, such as lean non-animal sources of protein and mono/poly-unsaturated fats, as well as increasing activity levels, we likely would’ve seen an improvement in blood lipid levels, provided that the study was long enough. It is difficult to say why there were no blood lipid improvement levels overall in this meta-analysis, a closer look into the specific variables of each individual study would be required.
Vanessa, you also make a good point to look at the trait the genetics might be playing in the blood lipid levels of participants. It’s difficult to tell whether lipid levels should go up or down during a study without taking into account MANY different variables, and genetics is definitely one of them!
I agree with what others have said in the fact that likely genetics plays a large role as well as increased intake of unhealthy protein/fat sources would not lead to improvements in the lipid profile.
I do think that there are so many outside factors contributing to this variety of studies that cannot be simplified as to what exactly is the cause. This does also contribute to my point from question one however, as to why I was surprised triglyceride levels did significantly improve. More specific research I think is necessary to better address this issue.
The study does not state the types of foods that were consumed in which were replacing carbs. So because of this, we do not know whether these subject were consuming foods high in choleterol and saturated fats. If the diet was close to the same diet consumed before the study and the only restriction now was the carbs, then it is likely that there would be no difference in LDL, HDL, and cholesterol. Also, LDL and HDL are highly effected by exercise, and if these study subjects are not participating in physical activity, there will likely be no improvements. Also, like other have mentioned, these subjects may have a genetic trait for overall good or bad cholesterol labs.
The inconclusive nature of the lipid profile could be the result of the short duration of the studies, medication participants were on prior to the program, (meaning the prescribed medication was working), and/or the participants intake. The article did mention there could have been incorrect interpretation of the lab results. The participants could have been consuming healthy fats (nuts, oils etc) and low fat meats/dairy products. Studies could have provided nutrition education resulting in an increase intake of fruits, vegetables, beans and nuts, fish etc.
It is important to look at the dietary choices made by the study participants to determine the quality of the proteins and fats consumed. If they are choosing not choosing heart healthy items, such as lean meats and plant oils, then we would not see a significant positive change in the HDL, LDL, or cholesterol levels. We also need to know the duration of the studies to determine if a change could be seen in that amount of time.
Katherine McCullah
It depends on the types of protein the participants were consuming. By eating meat with more healthy fats or consuming other items with healthier fats, it would change the lab values. Some participants could also have a genetic predisposition for good cholesterol. There are many factors that could contribute to why the results showed no significant effects on cholesterol labs.
Heather,
You made a great point about medications. Most diabetics are on several medications and this may contribute to the results shown about the cholesterol levels.
-Shanell
The participants in this study showed no improvement in their cholesterol levels on a CHO restricted diet possibly due to their unhealthy choices among their fat and protein intake. Their consumption of saturated and trans fats was likely to blame for their lack of improvement in cholesterol levels. However, just as others have stated here, we do not have much information regarding the types of foods consumed that replaced the carbohydrates. Lean protein, heart healthy fats, fruits, vegetables, legumes, and low-fat dairy products should be focused on in the diet education. The inclusion of physical activity into the patient's lifestyle should also be addressed, for a healthy diet plus exercise is very beneficial to heart health. We, being in the field of dietetics, know this, but some patients we see may not have much nutrition and health knowledge.
The results showed no relationship in HDL, LDL, or total cholesterol levels on a carbohydrate restricted diet, but there was a significant reduction in triglyceride levels. This arises many questions, but because every patient has their own needs and react differently to certain diets. I would want to know what they are eating and this would then help in determine if there is a relationship in lab values. A healthy diet and exercise should positively affect cholesterol levels. A lack of evidence makes these results questionable, more research is needed.
Samantha McCoy
There are several factors that could have influenced LDL, HDL, and total cholesterol level changes, or lack there of.
First, as included in the limitations, most of these studies were short-term (<120 days). Small, and what appear to be insignificant increases in these levels overtime, can add up to big damages.
Second, because several different studies were used, there were many different approaches to carbohydrate restriction used. Some raised the protein component of the diet, while others increased the fat content with or without eucaloric subsitutions of macronutrients, as the study recorded. Being that there is so much variability possible between diet composition, physical activity, etc. it is difficult to draw any one strong conclusion.
The patients may not be consuming the right types of fats and protein. The needed/wanted more calories so they turned to foods they knew were not carbohydrates. They may not know which types of fats and proteins are better. Nutrition educations is key here and it goes to show that it is an overall diet change that will benefit the individual.
Joanna--I was thinking the same thing, if they only changed the carb intake it probably will not effect the HDL/LDL levels. Also genetics and the amount of exercise is definitely a factor.
I think that no significant relationships in HDL, LDL, or total cholesterol levels shown because the lengths of the studies were too short in length to observe this sort of thing. Most of the studies were less than 10 weeks long in duration. If most were 3-6 months long then a significant relationship might have been noted.
Joanna,
You make a good point. The study doesn't say the types of foods consumed on these low CHO diets and how much they might have (or have not) varied from their normal diets. It would be important to know what type of carbs are being restricted (ex. from fruits and vegeatbles or grains) to determine what kind of long-term effect may be seen in the lipid profile.
It is only logical to think that the types of fats that the subjects are taking in are mostly in the unsaturated form. This would help to explain the lack of a significant change in HDL, LDL, or total cholesterol. More detail of the types of food the subjects were consuming is needed for clairfication. In addition, it is possible that the subjects were not taking in as much fat as we assume. They do not specify how many calories the individuals were taking in. The grams of fat in a 1200 kcal diet would be significantly less than the grams of fat in a 2000 kcal diet. This could have an impact on blood lipid levels as well.
Joanna,
I agree with your comment about physical activity. This can greatly impact blood lipid levels. If the patients are participating in a rigorus exercise routine it could counteract the negative consequences possibly associated with a low carb, high fat and protein diet.
The article states that active weight loss can cause a decrease in plasma triglycerides and cholesterol and may not reflect steady state values, and therefore give faulty results. This might help explain why someone who is consuming more fat on a restricted CHO diet could possibly see improvements in their lipid panels.
One reason could be the types of fat an individual is consuming. If they are mostly PUFAs and MUFAs with less than 10% sat fat and very few trans fats, the individual is not likely to see a significant increase in LDL or a significant decrease in HDL. Are the study participants exercising? Are they on prescribed cholesterol lowering medications? These factors are likely to contribute to the findings in question. If the diet is significantly lower in calories and the participant is losing weight, it would not be surprising to find an accompanying drop in blood lipid levels and cholesterol.
Meredith,
Your comment reminded me how important it is to judge the quality of the study design and the methods of measurement implemented when considering such a phenomenon.
As several other people have pointed out, we can not ignore the significant influence that genetics plays on the lab results. How the body processes what's being consumed, really is the ultimate determinant of future health. For this study, we obviously don't know the specifics of how the patient's body is processing the fats, but it must be considering as an influencing factor when evaluating thier lab values.
Carrie
I agree with you, there were quite a few variables that would potentially skew the results. Add up all the inconsistencies, different diet methods, body metabolism, genetics, etc, the meta-analysis study is part of a bigger picture. This study will spark new ideas and research areas for scientists to explore more in-depth. Also, I agree, we are still learning how the body processes what is being consumed; especially how medication interactions.
There is still so much research that still needs to be done on LDL and HDL. It has been shown that there is a genetic component that plays a role in person's levels, is it the same genetic component that plays a role in weight loss, a person's risk of developing DM, or all they all separate? This is not a cut and dry area yet. Also, their diets weren't regimented to be certain types of fats or proteins; that could be a factor aswell.
Tori McRoberts
Carrie,
I would like to add on to your answer: these subjects were not in a closed environment and watched for the duration of the study. They went about their lives in different environments. As researchers we can't control for every variable, if we do then our results won't correlate to the environments that our patients live, work, and play in everyday.
Sorry the last one above this is mine. I might get the hang of this :)
Tori McRobert
Carrie,
I completely agree that this study may not have been performed long enough to show significant changes in total cholesterol levels. This is an extremely important point that they may not have factored in. Plus, I think it is important to note that each individual body will react differently and some may improve in short periods of time, and others will take longer to show improvements or reductions in cholesterol labs.
Post a Comment
<< Home