Metabolic Acidosis Definition

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Approach To The Adult With Metabolic Acidosis

INTRODUCTION On a typical Western diet, approximately 15,000 mmol of carbon dioxide (which can generate carbonic acid as it combines with water) and 50 to 100 mEq of nonvolatile acid (mostly sulfuric acid derived from the metabolism of sulfur-containing amino acids) are produced each day. Acid-base balance is maintained by pulmonary and renal excretion of carbon dioxide and nonvolatile acid, respectively. Renal excretion of acid involves the combination of hydrogen ions with urinary titratable acids, particularly phosphate (HPO42- + H+ —> H2PO4-), and ammonia to form ammonium (NH3 + H+ —> NH4+) [1]. The latter is the primary adaptive response since ammonia production from the metabolism of glutamine can be appropriately increased in response to an acid load [2]. Acid-base balance is usually assessed in terms of the bicarbonate-carbon dioxide buffer system: Dissolved CO2 + H2O <—> H2CO3 <—> HCO3- + H+ The ratio between these reactants can be expressed by the Henderson-Hasselbalch equation. By convention, the pKa of 6.10 is used when the dominator is the concentration of dissolved CO2, and this is proportional to the pCO2 (the actual concentration of the acid H2CO3 is very lo Continue reading >>

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  1. minnat3

    The IDEAL DIET Newsletter - April 2004
    (I don't know how many subscribe to this newsletter but it's free and often has good insights. There are a couple more articles at this link.)
    Hair Loss with Low Carb Diet
    "I started doing Atkins about 2 weeks ago. Why is my hair starting to fall out?"
    I received this question on the form at low-carb-diet-physician.com. My initial response was that a lack of vitamins can cause hair loss.
    Many people forget that Dr. Atkins recommends a variety of supplements to go along with his diet, because the vitamins you would normally get in fruits, vegetables and other foods are severely restricted. Whether you use the Atkins diet or not, I recommend a good multivitamin with minerals for everyone. An additional B-complex supplement can be helpful for the hair.
    After posting this response I had some emails from a few people who disagree, and they bring up a good point. Here is what one person had to say:
    "I strongly believe that low-carb (MEAT & FAT) is the way humans are designed to eat and would gladly eat nothing but protein with plenty of natural fat if it wouldn't slow my metabolism down. I have found in the past that eating unlimited amounts of protein tends to bring on hypothyroid symptoms. I think this is why many Atkins & Protein Power dieters complain of hair loss -- it's not because carbs are too low. Rather, it's because protein (unlimited) is too high.
    Broda Barnes MD who also advocates low-carb for hypothyroids states in his book that he had to quadruple his own thyroid meds when eating unlimited amounts of protein (mostly veal, hence also likely too lean). He then adapted the diet to limit protein to no more than 1 gram per kilogram of bodyweight. He also states that a study in the medical literature indicates that excessive amounts of protein use up thyroid hormone very quickly -- unfortunately, there was no foot-note reference. However, it's the only reasonable explanation for this hair-loss side-effect in connection with low-carbing that I've ever heard.
    The notion that it's the stress of losing weight is silly unless someone has lost 100 pounds; the notion that it's a vitamin deficiency is also silly because it's happened to low-carbers who take copious amounts of vitamin supplements; the notion that it's because of ketosis is also silly because obese people have plenty of stored body fat to use for fuel. Therefore, I believe that Broda Barnes is onto something when he mentions the unlimited protein as potentially creating metabolic problems. Also, given that so much meat in the US is trimmed down and skinless chicken breasts abound, it is very easy to eat tons of protein without sufficient fat".
    I have not seen any studies indicating that excess amounts of protein lower thyroid levels, but studies have shown that carbohydrate restriction does have this effect. Studies on dieters who stopped losing weight showed that a carbohydrate-free diet produced a 21 percent decline in RMR (resting metabolic rate), as well as a decrease in circulating T3 (the active thyroid hormone) and insulin. When carbohydrate was added, keeping the same caloric intake, RMR rose toward baseline, and weight loss continued. This was accompanied by a rise in serum T3, but not insulin.
    This study shows that you cannot discount the effect of carbohydrate restriction on thyroid function and weight loss plateau. I have noted this with many of my patients, and find that weight loss is more consistent when carbs are not eliminated from the diet. This is why I designed the Metabolic Switch diet, which uses carbs to "stimulate the metabolism" while still allowing the low-carb aspect of the diet to encourage fat burning. This carb intake apparently keeps the T3 levels from dropping.
    My patients have not complained of hair loss or other symptoms consistent with low thyroid levels, and I did not realize it was a common complaint with the Atkins and Protein Power diets.
    As for high protein intakes being responsible for decreased T3 levels, I have not seen any studies on this. The recommended intake of protein on a typical diet is 0.8 grams per kilogram of body weight (pounds divided by 2.2 equals kilograms). When using a low carb diet, the body converts some protein to glucose for its essential needs, so additional protein should be consumed to provide for this, in order to avoid losing muscle mass.
    The chart in DIET TRUTHS REVEALED indicates the minimum daily protein intake based on weight in pounds, while using a low carb diet. In some weight ranges this will calculate at up to 1.2 grams per kilogram. In the IDEAL DIET I do not place a maximum limit on protein, so more than this amount can be consumed.
    Based on Dr. Barnes' observations, if you are stalled in your weight loss you should calculate your protein intake and keep it in the range given in the chart for your corresponding weight. Remember that as you lose weight your protein needs will be less, so check the chart frequently during weight loss. Replacing excess protein in your diet with fat is reasonable.
    It really is not silly that the metabolism would decrease while a person is in ketosis. Even when a lot of body fat remains for fuel, the body does not want to keep burning it. It is very common that persons on very low carb diets stop losing weight and even have trouble staying in ketosis because the metabolism decreases, probably due to decreased T3 levels. People who have lost weight and then regained it may have this occur quite rapidly when they diet again.
    My recommendation to eat carbs does not mean that carbohydrate intake is necessary for humans. Carbs are not necessary but glucose is, and the body converts protein to glucose for its essential needs. However, this requires energy input, while carbs give the body easy and rapid fuel. The body's response to losing energy - both in weight loss and in converting protein to glucose - is to decrease its metabolic rate in order to save its fat stores.

  2. Kristine

    Interesting, but I strongly disagree that hair loss is common. At most, I'd say it's occasional. I wonder if this person inquired about the soy content in her patients' menus. Between protein shakes, Atkins bars, etc; it can add up really fast. Soy is a known thyroid "mucker-upper".

  3. DianaO

    I disagree about the hairloss though. This can happen with an drastic change in a diet, whether dropping calories or carbs.

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