Low Carb Diet- Part 2
The mainstream medical community has been opposed to low-carbohydrate dietary protocols since their onset. Their opposition involves four main concerns:
1. high fat/low carbohydrate protocols and the threat of heart disease.
2. high fat/low carbohydrate protocols and ketoacidosis.
3. high protein/low carbohydrate protocols and osteoporosis.
However, proper balancing of the different types of dietary fats can go a long way to preventing coronary heart disease, and also in promoting good cardiovascular health. Here are five of the most commonly consumed types of fats. Those that are solid at room temperature, like butter and animal fat, are called saturated fats. Those that are liquid at room temperature (oils) fall into two categories: monounsaturated fats (ie.from olive oil, peanut oil, canola oil and avocados) and polyunsaturated fats (ie.omega-3 - from fish oil and walnut oil, omega-6 - from nut oils and certain vegetable oils). There are also the tropical oils, which are saturated fats that are solid or semi-solid at room temperature.
Finally, trans fats are those which have been artificially hydrogenated and thus converted from unsaturated into saturated fats. Saturated fats pose an obvious risk as far as heart disease is concerned and should be kept to a minimum. The American Heart Association recommends taking in no more than 10% of one's total daily caloric intake in the form of saturated fat.(18) On the other hand, mono and poly unsaturated fats are considered to be a healthier choice as far as heart disease is concerned. In fact the AHA states that "Polyunsaturated fats tend to help your body get rid of newly formed cholesterol. Thus, they keep the blood cholesterol level down and reduce cholesterol deposits in artery walls.
Recent research has shown that monounsaturated fats may also help reduce blood cholesterol as long as the diet is very low in saturated fat." (18) Another interesting area that has recently been brought to public attention concerns the omega-3 vs. omega-6 fats. Both omega-3 and omega-6 fats are considered essential fats (ie. the body can not manufacture these fats and thus depends on getting them in the diet). However, they are not processed in the same ways by the body, and their ultimate pathways are somewhat antagonistic. Research involving Inuit populations have shown a very low incidence of heart disease among Inuits despite a diet very high in whale blubber (an obvious saturated fat).
It seems that all the freshwater fish that is consumed by the Inuit has a heart-protecting mechanism. As it turns out, the Inuit diet, despite being very high in saturated fat, is also very high in omega-3 fats found in freshwater fish (especially salmon). It is believed that omega-3 fats predispose the body to less blood coagulation and a lower inflammatory response, and thus less heart disease forming activity (ie.plaque formation in arteries and other cardiovascular diseases).
On the other hand, omega-6 fats are believed to lead to greater rates of blood coagulation and a greater inflammatory response, and are thought to be more of a factor for heart disease. In general, omega-6 fats are much more abundant than omega-3 fats in the average diet, and the average person would be well-advised to consume foods that are higher in omega-3 than omega-6 fats. An obvious dietary adjustment involves simply eating more freshwater fish (particularly salmon and trout). See Fig. 1 for a comparative list. Fig 1. Content of Omega-3 and Omega-6 Essential Fatty Acids in Oils:
Approximate EFA content in grams per 100 grams:
Essential Fatty Acids in NUTS: Fig 2. Content of Omega-3 and Omega-6 Essential Fatty Acids in Nuts
Approximate EFA content in grams per 100 grams:
Essential Fatty Acids in SEEDS: Fig 3. Content of Omega-3 and Omega-6 Essential Fatty Acids in Seeds
Approximate EFA content in grams per 100 grams:
Tropical Oils are another interesting and somewhat ambiguous topic that has been floating around for quite some time. Included in this group are coconut oil, palm kernal oil and the infamous modified palm kernal oil. The tropical oils are interesting because although they are saturated, they have properties which set them apart from other saturated fats. The main difference is their molecular length. The tropical oils consist of a type of fat known as Medium-chain triglycerides (MCT), and as this name implies, they are shorter than the usual saturated fat. This allows them to be absorbed and used differently than other fats. Apparently, MCT's bypass hepatic circulation (the circulation of the liver) and are absorbed intact directly into the blood through the small intestine.
Once they have been absorbed, they are processed by the liver and converted into a form that is used easily for energy. With this in mind, it is logical to assume that medium-chain triglycerides derived from tropical oils may not linger in the blood for a long enough time to pose a threat for heart disease.(3,4,5) The AHA groups the Tropical Oils with other saturated fats, and recommends to restrict their intake along with other saturated fats. Other research points to the fact that because they are processed differently than other longer-chain fats, they do not pose a likely threat for heart disease. Obviously, further research in this area is nesessary.
Trans fats are another topic that has been floating around the media lately. The word 'Trans' and it's counterpart 'Cis' refer to the specific molecular geometry of a particular substance. Most substances adopt and maintain a 'cis' geometry in their natural state. Fats are no exception to this rule. There are, however, incidents where a fat becomes artificially converted from a natural 'cis' geometry to an induced 'trans' geometry. One way that this happens is when a fat undergoes the process of Hydrogenation. In this process, an unsaturated fat (a fat that is not completely bound up or 'saturated' by hydrogen atoms) is heated and bombarded by hydrogen atoms, and thus artificially 'Hydrogenated' and rendered into a saturated fat. In this process, part of the newly-hydrogenated fat molecule will adopt a 'Trans' molecular geometry.
It is these artificially induced 'trans' fats which have stirred so much concern among the medical community and the general public. This is because 'trans' fats have been implicated in higher levels of low-density lipoprotein (LDL or 'bad cholesterol')) and lower levels of beneficial high-density lipoprotein (HDL or 'Good Cholesterol'), and pose a greater risk for heart disease than even saturated fats (saturated fats have not been implicated in the lowering of HDL).(1,2)
Companies have been using hydrogenated 'trans' vegetable oils in prepared and packaged foods for years because they do not spoil easily, thereby increasing the product's shelf-life. Besides the obvious issue of converting an unsaturated fat into a saturated fat, of greater interest is the fact that these fats are further altered from their natural state and rendered even more unhealthy. Modified palm kernal oil and margerine are both examples of foods containing hydrogenated trans vegetable oils. The bottom line on 'trans' fats: They are neither natural nor good for us; consume as little as possible.
So, to minimize the risk of heart disease that may be associated with low carbohydrate/high fat/high protein dietary protocols, simply consume no more than 10% of the total caloric intake in the form of saturated fats, consume more omega-3 than omega-6 fats and consume little or no 'trans' fats. Follow these guidelines, and the risk of heart disease associated with high fat intake can be greatly reduced.
However, heart disease is not the only health concern associated with low carbohydrate/high fat/high protein dietary protocols. Another criticism that the medical community has made is that they are Ketogenic. Ketones or Keto acids are normal intermediates in fat metabolism, and their accumulation in the blood is normally tolerated within specific levels. Beyond this, the accumulation of ketones in the blood becomes toxic and potentially lethal, as evidenced in diabetic individuals who can suffer a diabetic coma and even death if their ketone levels are not kept within tolerable boundaries.
Accumulation of ketones happens because of the absence Pyruvic Acid. Pyruvic acid, supplied mainly by the breakdown of glucose through the process of Glycolysis, converts to a metabolite called Oxaloacetate. Oxaloacetate combines with incoming fat that is in the process of being broken down. Without it, fat metabolism will stop here. For this reason it is said that fat burns in a carbohydrate flame.
When fat breaks down, it forms 2-carbon units called Acetyl compounds. These Acetyl compounds convert to form Acetyl Coa, which combines with the Oxaloacetate derived from pyruvic acid. The complex that is formed, Citric Acid, then continues into the next stage of metabolism, the Krebbs or Citric Acid cycle. In the absence of an adequate supply of pyruvic acid, fat can not enter the Krebbs Cycle, can not be processed beyond the stage of Acetyl-CoA, and will convert to ketones. If the rate of ketone production is greater than its removal in the urine, then they will accumulate to intolerable levels.
In normal individuals, pyruvic acid is easily obtained from the breakdown of carbohydrates in food. In the absence of dietary carbohydrates, the body can rely on certain amino acids to make pyruvic acid, as well as the gluconeogenic substances Lactic Acid and Glycerol. These substances can replace glucose as a source of pyruvic acid, and will prevent the accumulation of ketones, but not entirely. Letting ketones accumulate is not healthy, desirable or even comfortable. Any diet that limits carbohydrate intake in favor of fats is certainly going to lead to a state of ketone accumulation or Ketoacidosis. Most people can not endure ketoacidosis for very long and cheat by eating carbohydrates at some point.
Several diets prescribe decreasing carbohydrates and increasing fats. Proponents of these so-called 'ketogenic' diets purport that by chronically reducing carbohydrate intake, somehow the body will become magically 'fat adapted' and burn more fat. Apparently, after a brief period of exposure to a low-carbohydrate protocol, we are supposed to become more efficient at using fat as a source of fuel. Physiologically speaking, this may not be an accurate way of describing what happens.
The exact meaning and metabolic conditions associated with being 'fat-adapted' are not entirely clear, and in fact, not everyone experiences the same kind of 'fat-adaptation'. For example, people who are in poor aerobic condition and who are used to high levels of carbohydrates in the diet (especially refined carbs) do not adapt easily to high-fat dietary protocols.(16) One of the ways that an individual might become 'fat-adapted' is by getting used to the chronic state of ketoacidosis caused by increasing fats and decreasing carbohydrates.
In general, there is no way of avoiding a ketoacidotic state when dietary carbohydrates are restricted. This is one of the pitfalls of a high fat/low carbohydrate diet. In the short term, this is uncomfortable and in the long-term it is unhealthy. This is why the medical community has issues with this type of protocol, and rightfully so. Even if you regulate the type of fats in your diet, the inevitability of ketoacidosis renders such protocols ineffective in the long-term, unhealthy and ultimately dangerous.
One of the chief concerns that the medical community has with low carbohydrate/high protein protocols involves the possible risks associated with high protein intake and bone loss. Initial studies showed that omnivores had lower bone density than vegetarians (8,17) and that Inuits, especially females, had significantly lower bone density than Caucasians (11). These studies led the medical community to believe that high protein intake was responsible for bone demineralization.
Later and more sophisticated studies showed that the source of protein is an important factor in the effect of dietary protein on demineralization."When protein is given as meat, subjects do not show any increase in calcium excreted, or any significant change in serum calcium, even over a long period." (13) Earlier studies, using isolated, fractionated amino acids from milk or eggs as a protein source showed that high protein intake led to increased calcium loss (14).Other studies showed that high protein intake increased absorbsion of calcium when dietary intake of calcium was adequate (10). Also, high intake of meat showed no long-term adverse affects when compared with a normal intake of meat. (15)
The final concern that the medical community has regarding low carbohydrate/high protein protocols involves protein balance and nitrogen stress. Presently, the RDA for protein is 0.8 grams/kg body weight. If one were to consume 30% of a 2000 Kcal/day diet in the form of protein (as is prescribed in the zone protocol), that would equate to a total of 150 grams of protein. That is nearly 3 times the RDA. The question is whether or not this is a potentially a dangerous amount for an individual to consume over the short term.
In the absence of dietary carbohydrates, the body will use several non-glucose substances to make glucose (this process is called Gluconeogenesis). Glucose is considered an essential nutrient, and we have several ways to ensure that our blood-glucose levels stay within their normal range. By the process of gluconeogenesis, we can use lactic acid, protein broken down to amino acids, and glycerol derived from the breakdown of triglycerides, all to make glucose.
In the process of converting to glucose, the nitrogen-containing group (Amine group) is removed from the amino acid through the process of deamination. The nitrogen waste product is then excreted in the urine in the form of urea and ammonia. This entire process is both taxing and energetically unfavorable. In fact, there is a net loss of energy resulting from the metabolic cost of converting amino acids into glucose. Proponents of high-protein dietary protocols claim that this net energy loss can contribute to an overall energy deficit, and thus benefit weight-loss.
However, if the body is required to rely heavily on protein to make glucose, besides placing an increased stress on the liver and kidneys in terms of nitrogenous waste, it will lead to a large amount of muscle wasting. This loss of muscle can ultimately lead to a reduction of overall energy expenditure and a slowing of the RMR. Therefore, the net loss in energy resulting from gluconeogenesis is greatly offset by muscle wasting.
In terms of nitrogen stress, the body is a fairly adaptable machine, and the liver is fairly resilient and effective as a detoxifying organ. It can handle a fair amount of toxic stress and still maintain relative health. It is possible to maintain a low carbohydrate/low fat/high protein protocol long enough to lose fat, without enduring any severe short-term or long-term health problems. However, people who suffer from any disease of the liver or kidneys should consult with a physician before making any radical dietary adjustments. These are some of the medical considerations that should be considered before starting a low carb dietary protocol. In the next part of this series, I will go into some of the hormonal and metabolic considerations regaring low carb diets.
He is certified by the National Strength and Conditioning Association (NSCA) as a Certified Strength and Conditioning Specialist (CSCS) and has expertise in a wide variety of areas. His specialties include physique transformation, athletic preparation, muscle balance and posture, flexibility, nutrition and supplementation. He is also an instructor of Muay Thai (an ancient martial art developed in Thailand). He has worked with males and females of all ages and from all walks of life, including students, older adults, teens and professionals. He is presently working at Gym L’Apogée on St. Laurent Boulevard in Montreal, and also works with clients at their homes.