Jean-Louis wrote: >Carbohydrates and heart disease [deleted text] >> Mc Dougall: "Worldwide the lowest incidence of heart disease is found >>where people eat the lowest cholesterol diets and also have the lowest >> HDL-cholesterol levels (Lancet 2:367, 1981)" >...The effect of a low fat diet is that all fractions of cholesterol go down, but >the ratio TC/HDL (which is an independent risk factor) doesn't improve. >Remark: the Lancet article also mentions some ratios HDL/TC. Africa: >0.26-0.32, Europe: 0.20-0.28, Asia and Surinam: 0.15-0.22. >We should mention that hunter-gatherers, despite eating on average more >than 55% of their calories from meat, have low TC and ratio TC/HDL, and low >incidence of heart disease. The main reasons are: high monounsaturated fat intake, low >carbohydrates, high protein [Metabolism 1991;40:338-43] [Clin Invest Med >1992;15:349-5] [Can J Cardiol 1995;11 (supp G):127G-31G], low ratio omega >6/omega 3, no hydrogenated oils [Am J Public Health 1994;84: 722-24] [Am J >Clin Nutr 1997;66:1006s-10], more exercise. The composition of farmed animals is >indeed rather different from the composition of wild animals. [deleted text] Hi Jean-Louis , I have a special interest on cholesterol levels and would like to make some comments on what you wrote and then forward an conference at Cyberounds.com that I came across. I my self have a 119 TC vs. 39 HDL, that is a high (generally speaking) rate, and, as you said, likely to vegans. However LDL is as low as 70. So I wonder whether that TC/HDL rate is that much important on very low TC levels. As says in this conference below, if one has a HDL lower then 50 has to check the LDL. If LDL is OK(<130), then no worry at all Before I had started my lowfat-lowsugar/vegan/antioxidant oriented diet, my levels where 230 TC, 39 HDL and 154 LDL...risky!!! So, what's changed were TC and LDL. HDL supposedly (as I once read on a medical report) is responsable for not "allowing" LDL to cross the arthery walls and be deposited inside the arthery tissue, increasing atherome. If there is low LDL (lower then 130), there would be no problem, no matter the rate TC/HDL. A non harmful cholesterol is 200, and for a 0.25 HDL/TC rate HDL should be >50 and LDL 'round 130. Since LDL is an inference regarding HDL, TC, and triglicerides levels, seems that a low TC , around 120-130 typicall for vegans and low fat/low protein intakers, is quite ok , since there can not be space for a LDL higher then 60-80, that is much lower than the 130 LDL highest desireable level. If other diets like hunters-gathers get lower rates TC/HDL, that does not mean that necessarly that the rate is a risk factor when coming down to very low TC. I came across this conference at cyberounds that refers this stuff. Might be of some interest to some of you. I first selected the part that refers to this subject, and after pasted the whole conference , since the URL needs a restricted registration: http://www.cyberounds.com/conferences/nutrition/conferences/0997/conference. html Sorry everyone for this large Kb post. ----------------------------------------------------------------------- "Current Issues Related to Diet and Cardiovascular Disease" Robert M. Russell, M.D. and Alice H. Lichtenstein, D. Sc. *Educational Objectives* Upon completion of this activity, the participant should be able to: -Enumerate the appropriate course of action for a patient within each category of blood total and HDL cholesterol levels. -Evaluate positive and negative risk factors in a patient. -Provide the parameters for a Step 1 and Step 2 diet. "Here, too, there is no one risk factor that is more important than another (see Table 2). Each risk factor is considered independently. First, we classify individuals on the basis of their total cholesterol level (see Table 1 for more detail). A person with a total cholesterol level of less than 200 mg/dl is considered to be in the desirable range; between 200 and 239 mg/dl in the borderline high-risk range; and 240 mg/dl or above in the high-risk range. Within each of those categories, the physician should enumerate the number of risk factors the individual has. The significant risk factors are: hypertension, family history of cardiovascular disease, current cigarette smoker, hypertension, low HDL cholesterol, diabetes mellitus (see Table 2 for more detail). Although not considered independent risk factors, obesity and physical inactivity should also be taken into consideration. If an individual has two or more risk factors (Table 2), and they are in the borderline high-risk range, then they are considered to be at higher risk and they are treated as though they are in the high-risk range (Table 4). For individuals with low HDL cholesterol or in the borderline-high or high cholesterol categories, an individual should be evaluated on the basis of LDL cholesterol levels (Table 5). This necessitates a fasting blood sample be obtained for the accurate determination of blood triglyceride levels. LDL cholesterol levels are calculated from these data. If LDL cholesterol levels are below 130 mg/dl and the individual is free of CHD, a patient is considered to be in the desirable category. If their LDL cholesterol levels are between 130 and 159 mg/dl with less than two risk factors, they are considered to be in the borderline high-risk range, and above 160 mg/dl or 130 to 159 mg/dl with two or more risk factors in the high-risk range are considered to be in the desirable < a name="table6ret">category (Table 5). Lastly, Table 6 lists the recommended treatment and target LDL cholesterol levels on the basis of LDL cholesterol levels." (COMPLETE CONFERENCE) : Alice H. Lichtenstein, D. Sc., is an Associate Professor of Nutrition in the School of Nutrition Science and Policy at Tufts, an Associate Professor of Family Medicine, Community Health at Tufts University School of Medicine and a Scientist I at the Jean Mayer Human Nutrition Research Center on Aging at Tufts. She completed her undergraduate work at Cornell, holds masters degrees in Nutrition from Pennsylvania State and Harvard and earned her doctoral degree in Nutrition from Harvard. Her research investigates the kinetic behavior of lipoprotein particles, predictive factors for changes in blood lipids induced by diet in individuals, the impact of body weight changes on blood lipids and the relationship of absolute levels of dietary fat, in contrast to fatty acid composition of the diet, on plasma lipids. Dr. Lichtenstein is on the Editorial Board of the Journal of Nutrition and Atherosclerosis. "Being Thin is Not Necessarily the Solution RMR Alice, we all read something new about dietary fat in the newspapers almost daily. How important a factor is dietary fat intake in the development of coronary artery disease? And, if a person has a high fat diet but stays relatively thin, is that person at greater increased risk of developing coronary artery disease, compared to a person who not only eats a lot of fat but is, in fact, obese? ---------------------------------------------------------------------------- ---- AHL You cannot really tell by looking at someone whether they are of a desirable body weight or overweight; whether they are going to be specifically susceptible to the amount of or type of fat in their diet; or what's their risk of developing cardiovascular disease. Each person is different. Initally, the best way to check this risk is to measure their blood lipid levels (see Table 1 for more detail). Most physicians do this routinely. If someone has blood cholesterol levels in the borderline-high (200-239 mg/dl) or high range (> 240 mg/dl), we know from a dietary perspective that the most important factor affecting blood cholesterol levels is the saturated fat intake and, secondarily, dietary cholesterol. As mentioned a moment ago, there is no single recommended course to follow for every problem and every person. A separate risk assessment needs to be done on each individual--determine how many risk factors a person has (Table 2) and then make some decision about how aggressively to treat the patient. ---------------------------------------------------------------------------- ---- Risk Factors Vary With the Individual, But They Do Add Up RMR Alice, you mentioned the various risk factors for coronary artery disease and I wonder if you would list them in order of importance as a review and, secondly, could you review the main sources of saturated fats in our diet and the mechanism whereby saturated fats give rise to elevated cholesterol levels? ---------------------------------------------------------------------------- ---- AHL Here, too, there is no one risk factor that is more important than another (see Table 2). Each risk factor is considered independently. First, we classify individuals on the basis of their total cholesterol level (see Table 1 for more detail). A person with a total cholesterol level of less than 200 mg/dl is considered to be in the desirable range; between 200 and 239 mg/dl in the borderline high-risk range; and 240 mg/dl or above in the high-risk range. Within each of those categories, the physician should enumerate the number of risk factors the individual has. The significant risk factors are: hypertension, family history of cardiovascular disease, current cigarette smoker, hypertension, low HDL cholesterol, diabetes mellitus (see Table 2 for more detail). Although not considered independent risk factors, obesity and physical inactivity should also be taken into consideration. If an individual has two or more risk factors (Table 2), and they are in the borderline high-risk range, then they are considered to be at higher risk and they are treated as though they are in the high-risk range (Table 4). For individuals with low HDL cholesterol or in the borderline-high or high cholesterol categories, an individual should be evaluated on the basis of LDL cholesterol levels (Table 5). This necessitates a fasting blood sample be obtained for the accurate determination of blood triglyceride levels. LDL cholesterol levels are calculated from these data. If LDL cholesterol levels are below 130 mg/dl and the individual is free of CHD, a patient is considered to be in the desirable category. If their LDL cholesterol levels are between 130 and 159 mg/dl with less than two risk factors, they are considered to be in the borderline high-risk range, and above 160 mg/dl or 130 to 159 mg/dl with two or more risk factors in the high-risk range are considered to be in the desirable < a name="table6ret">category (Table 5). Lastly, Table 6 lists the recommended treatment and target LDL cholesterol levels on the basis of LDL cholesterol levels. However, if an individual has two or more risk factors and they are in the borderline high risk range, they are treated more aggressively, as though they are in the high risk range. ---------------------------------------------------------------------------- ---- Major Sources Of Saturated Fat In The Diet AHL Before we talk about the major sources of saturated fat in the diet, I would like to indicate that the American Heart Association (AHA) and the National Cholesterol Education Program (NCEP) have issued recommeded guidelines for the dietary treatment of hypercholesterolemia which are shown in Table 3. The patient should be first counseled to follow a Step 1 diet, that is, to decrease their total fat intake to < 30% of calories, saturated fat to 8-10% of calories and cholesterol to < 300 mg/day. If a patient is already on a Step 1 diet, or an acceptable response is not achieved, the patient should be advised to follow a Step 2 diet by further decreasing their saturated fat intake to < 7% of calories and their cholesterol intake to < 200 mg/day. For this strategy to be effective, it usually requires the help of a registered dietitian or other appropriately trained healthcare provider. Usually, decreasing the total fat content of the diet is easier to do than decreasing the saturated fat content. In order to decrease effectively the saturated fat content, it is important to know its major sources. These include animal fats such as meat and full fat dairy products and, depending on one's tastes, a few selected plant oils (Table 7). The plant oils, frequently termed tropical oils, include coconut oil, palm oil, palm kernel oil and cocoa butter and contain a fair amount of saturated fat. However, they do not tend to be used in high levels in the United States. If an American patient is being counseled to decrease their saturated fat intake, the focus should be on full fat dairy products and meat. Fortunately, there is a whole variety of non-fat, reduced-fat and low-fat dairy products that are now available. So, a simple substitution can be made. To reduce the intake of saturated fat from meat, one should counsel patients to use cuts of meats that are lowest in fat. This is best done by suggesting the patient buy cuts of meat with the least amount of visible fat; trim meat of excess fat; with poultry, remove the skin before eating; and, of course, cut down on the size portion of meat actually consumed. Unfortunately, nutrient labeling does not help too much regarding the fat content of meat. Ground beef is now labeled with the percent by weight as lean. The patient should be counseled to choose those packages having the highest percent lean, hence the lowest percent fat. However, this can get confusing because the percentages listed on these packages have nothing to do with the percent of calories as fat listed on the nutrient label of packaged foods. The other potential source of animal fat can come from cooking, as discretionary fat is added during food preparation. We recommend that individuals switch from animal fats such as lard or butter to vegetable oils. Although there is a tremendous amount of evidence to indicate that saturated fat is the major determinant of plasma cholesterol levels, the mechanism by which that occurs is not clear. Blood cholesterol levels are determined by the balance between the rate at which lipoproteins are synthesized and the rate of which they are catabolized. Saturated fat has been implicated to impact in both of those processes, increasing the rate of production and decreasing the rate of catabolism of lipoproteins. The other dietary factor which elevates blood cholesterol levels is dietary cholesterol. Major sources of dietary cholesterol are eggs and animal fats (both dairy and meat). By decreasing the consumption of animal fat, in addition to saturated fat, dietary cholesterol intake should also decrease. ---------------------------------------------------------------------------- ---- Trans Fatty Acids -- Do They Help? RMR In the last couple of years there was quite a debate going on about trans fatty acids and the importance of trans fatty acids as a critical dietary factor resulting in increased coronary artery disease incidence. I believe you took the position that this was an exaggerated concern and I wonder if you could give us a little bit of background on this debate and tell us why you feel that way you do. ---------------------------------------------------------------------------- ---- AHL First, I think we should really talk about what trans fatty acids are. Trans fatty acid is a shorthand term for a fatty acid that contains at least one double bond in the trans configuration. The naturally occurring double bonds or the predominantly occurring double bonds in fatty acids are in the cis configuration, where the hydrogen atoms surrounding the double bond are all on the same side. In the trans configuration, the hydrogen atoms are on the opposite sides of the double bond (Figure 1). It gives the fatty acid a different confirmation, whereas a cis double bond gives fatty acid chain a kink or bend, a trans double bond results in a straight chain. In that way, it is more similar to a saturated fatty acid. Figure 1. Cis and trans configurations of fatty acids. Why are fats hydrogenated and and where do they come from in the diet? Trans fatty acids are hydrogenated to increase their stability and also to increase their plasticity or consistency. One of the original reasons for hydrogenating vegetable oil, which has predominantly unsaturated fatty acids, was to produce products, such as margarine, that could easily be used in place of butter which has predominantly saturated fatty acids. The trans fatty acids also come from animal fat (dairy products and meat). Formed during bacterial metabolism in the rumen of animals, they are incorporated into the animal's tissues and milk. They provide relatively low amounts of trans fatty acids compared to hydrogenated fat. Trans fatty acids have been in the diet for a long time. One of their effects, the increase in the levels of total and LDL cholesterol, was already known, but the other effect on plasma cholesterol levels wasn't suggested until 1990, with the publication of a pivotal paper(1) wherein the authors suggested that trans fatty acids decreased HDL cholesterol levels. It was also suggested at that time that Western diets contained significant enough levels of trans fatty acids that the situation should be reassessed. Since then, a number of studies have been done,(2) most quite consistent with the early work showing that trans fatty acids increase total and LDL cholesterol levels. With regard to lowering HDL cholesterol levels, I think the data are far less clear. Within the range that it is estimated to be consumed in the United States, it does not appear that trans fatty intake has a significant effect on HDL cholesterol levels. Nonetheless, I think it is important to take them into consideration, and do so with an understanding that, if one reduces the level of trans fatty acids in the diet, something else is going to be substituted. I think this is where some of the confusion and arguments in the scientific community have arisen. Right now, the main sources of discretionary trans fatty acids are margarine and prepared foods that use hydrogenated fat in the processing. If you reduce their intake, you increase the saturated fat intake to a greater extent which would probably not have a beneficial effect, for example, substituting butter for stick margarine. On the other hand, if you substitute a liquid oil or soft margarine for stick margarine, then you are decreasing the trans fatty acid intake and increasing the unsaturated fat intake. This would probably have a beneficial effect. ---------------------------------------------------------------------------- ---- The Omega 3 Fatty Acids -- Just Fish Oil? RMR Another fatty acid that has recently moved into the general lexicon are the fish oils, rich in omega-3 fatty acids. Can you explain what the latest thinking is on the importance of these fatty acids in preventing coronary artery disease? ---------------------------------------------------------------------------- ---- AHL Omega-3 fatty acids are long chain fatty acids and usually contain three or more double bonds that come from marine products or some vegetable oils such as soybean or canola. They have very little impact on blood cholesterol levels. What they do have an impact on is plasma triglyceride levels, especially in individuals that have elevated triglyceride levels. They tend to bring elevated triglyceride levels down. This is particularly important because there is an inverse correlation between plasma triglyceride levels and HDL cholesterol levels. If the triglyceride levels are brought down in hypertriglyceridemic subjects, then the HDL cholesterol levels usually come up. Now, there is a certain amount of data suggesting that fish consumption will decrease the risk of developing cardiovascular disease, although it is not consistent. The mechanism is probably not via lowering blood cholesterol levels or even triglyceride levels but through independent effects of omega-3 fatty acids on blood pressure and platelet aggregation (decreasing the risk of thrombosis). The increased use of fish as an entree may displace high saturated fat meat from the diet, having the advantage of providing the independent effects of omega-3 fatty acids and decreasing the saturated fat intake. ---------------------------------------------------------------------------- ---- Exercise, Alcohol and Lower Cholesterol RMR With regard to HDL, we have heard that exercise can increase HDL levels. At least somewhat and recently, there have been epidemiology studies indicating that higher vitamin C levels in the diet and moderate -- one or two drinks a day -- (as opposed to none or large amounts) of alcohol intake are correlated with higher HDL levels. Are there intervention studies that clearly show this and should medical professionals work to modify patients' diets in some ways to "optimize" HDL levels? ---------------------------------------------------------------------------- ---- AHL As opposed to LDL cholesterol levels and saturated fat, the evidence to suggest that individuals who exercise or consume moderate amounts of alcohol may have higher HDL cholesterol levels is a little more difficult to assess. On the other hand, there are other reasons, in addition to HDL cholesterol levels, that one would encourage moderate, not excessive, alcohol intake and regular exercise. Epidemiological data suggest a negative association between moderate alcohol use and risk of CHD. A half hour of exercise a day is important for energy balance, which itself impacts on hypertension, hyperlipidemia, decreased HDL cholesterol levels and diabetes mellitus. The association of HDL levels and vitamin C is weaker. However, diets or dietary patterns that tend to be high in vitamin A tend also to be high in fruits and vegetables (and antioxidant vitamins) and lower in total fat, saturated fat and cholesterol. So I think to argue just from the perspective of increasing HDL cholesterol levels and vitamin C is a little difficult for an individual patient. However, to encourage a prudent diet and active lifestyle, independent of their effect of blood cholesterol level, will probably be beneficial with respect to reducing one's risk of developing cardiovascular disease. (continues on 2/2)