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Showing posts from August, 2009

Iron in Summary

Humans contain about 2-4g iron of which most is in hemoglobin and to a lesser extent myoglobin. Iron from diet is found in heme (animal foods) and nonheme (plant foods) forms. The heme iron needs to be hydrolyzed where as the nonheme is enzymatically freed. Heme iron is absorbed intact accross the brushborder of the enterocyte whereas nonheme iron is released as ferric in the stomach, which may be reduced to ferrous. The ferric is absorbed across brush border by binding to transporters and the ferrous facilitated by chelators and membrane proteins.Chelators inhibit or enhance absorption of iron. Absorption is also regulated by hepcidin and ferroportin. Other iron-absorption enhancers are sugars, acids, animal meat, and mucin. Other inhibitors are polyphenols, oxalates, phytates, phosvitin and some minerals.Iron is stored in the liver, bone marrow and spleen. Uptake into tissues depends on transferrin. Iron needs depend on its loss such as through menstrual losses and dietary intake. De

Copper-zinc

A mineral supplement I've taken in the past includes 10mg zinc and 1mg of copper. Thus, the amount of zinc is not at the "higher than 50mg" level that can cause a copper deficiency because of interference with bioavailability (1). This is exactly the 10:1 ratio as suggested to avoid any copper deficiency (2). Someone did his/her homework. 1. http://lpi.oregonstate.edu/infocenter/minerals/zinc/ 2. http://www.pccnaturalmarkets.com/health/2934002/

Top zinc-rich foods I eat frequently

1 chicken drumstick, broilers or fryers, meat and skin, cooked, roasted = 2.98mg 3 Eggs, whole, cooked, scrambled = 1.83mg 1 burrito, bean and cheese, microwaved = 1.33mg 1 cup milk, whole, 3.25% milkfat = .98mg 1 fish fillet, trout, rainbow, farmed = .32mg Data found at: http://www.nal.usda.gov/fnic/foodcomp/

Zinc and copper not effective for acute diarrhea

Purpose of study: Zinc and copper are lost in significant amounts in acute diarrhea and zinc has been suggested as a therapy for its possible facilitation of water and electrolyte transport across intestinal mucosa to prevent villous atrophy and modulate immune response. This study evaluated whether or not zinc and copper supplementation had any beneficial effect on acute watery or bloody diarrhea when given with standard treatment. Type of study: Randomized, double-blinded placebo-controlled trial Method used to conduct study: Children ages 6-59 months with acute diarrhea were given standard treatment and randomized to placebo, zinc only (Zn 20mg/5ml elemental zinc), or zinc and copper (2mg/5ml of elemental copper) together via syrup. There were 808 children chosen for the study out of 1,200 screened over the period of Aug 2003 and Oct 2006. Each provided more than three stool samples in prior 24 hours, who had duration of diarrhea for up to 72 hours and who were able to orally acce

Armour Thyroid vs Synthroid

Armour thyroid is the "natural" therapy from dessicated porcine thyroid gland while Synthroid is produced synthetically as levothyroxine. Armour thyroid contains both T3 and T4 while Synthroid only contains T4. There is debate on whether or not use of both or one is better. Synthroid came into use because it was standardized unlike the natural kind, which varied a lot from batch to batch. But it turns out that patients often don't like T4 alone as much as the natural T3/T4. A new synthetic T3/T4 is now on the market as Liotrix, but is expensive. Reference http://www.netwellness.uc.edu/question.cfm/24516.htm

What Controls Basal Metabolic Rate

To regulate basal metabolic rate, the thyroid gland synthesizes hormones thyroxine, or triiodo-L-thyronine (T4), and the more active triiodo-L-tyronine (T3) (1).When secreted into the bloodstream, they associate with transport proteins (thyroxine-binding globulin, albumin, and transthyretin), which circulate the hormones (2). There is nearly 50 times T4 than there is T3, but T3 is more potent. T4 and T3 bind to nuclear receptors that affect gene expression. Increased mRNA and protein synthesis appear to lead to stimulation of oxygen consumption (when awake, at rest or fasting), heat production and also influences enzymes involved in carbohydrate metabolism (3;4). Reference List 1. Devlin TM. Textbook of Biochemistry with Clinical Correlations. Philadelphia: Wiley-Liss, 2002. 2. Gropper SS, Smith JL, Groff JL. Advanced Nutrition and Human Metabolism. Belmont, CA: Thomson Wadsworth, 2009. 3. Pereira BM, Balasubramanian K, Govindarajulu P. Effect of thyroxine treatment on epididymal c

Iron Deficiency Symptoms

As iron deficiency develops gradually without anemia, symptoms can appear that can include pallor and problems of behavior, cognition, learning and attention span. These can particularly manifest themselves in children. Adults may witness problems related to work performance and productivity. The effects may be related to impairment of the neurotransmitter gamma-aminobutyric acid (GABA) used to inhibit dopamine production in the brain and/or immune system impairment leading to more susceptibility to infection and inability to keep a normal body temperature. The first stages of iron deficiency result in diminished liver, spleen and bone marrow iron stores and decreased plasma ferritin. Second stages begin when stores are low and iron transport decreases. Transferrin saturation decreases, which increases total iron-binding capacity, and there is limited iron for function in hemoglobin. This leads to a rise in protoporphyrin, the precursor to heme in hemoglobin. Finally, the anemia occurs

Hemochromatosis a Neolithic adaptation?

Hemochromatosis is a genetic disorder caused by one of several mutations related to double-than-normal iron absorption, which increases susceptibility to iron overload (1). Although the disorder affects about one in 200 in the U.S., it’s still largely unrecognized and can lead to deposits in organs—such as the liver—leading to organ damage and failure if not treated early enough (2-4). Because the disorder is most prevalent in males of Northern European ancestry, particularly Celtic (5), it was hypothesized as recently as 2007 to be a possible Neolithic adaptation (6). The Neolithic period marked an early European dietary transition from high intake of meat to cereal grains (6). Whether or not this hypothesis is correct, the state of the disorder suggests potential dietary management through eating primarily vegetarian foods such as the one eaten during the time of these early ancestors—cereal grains, little red meat, and limited vitamin C intake. This low-iron diet to prevent to iron

Korsakoff syndrome

Korsakoff’s syndrome, or Wernicke encephalopathy, is a serious neurological disorder occurring under conditions of thiamine deficiency. It’s usually caused by long-term abuse of alcohol, which breaks down thiamine in the body. It is characterized at autopsy by lesions in the brain stem. Thiamine is necessary for proper glucose metabolism in the brain (1). As a B vitamin it acts as a cofactor for enzymes in the Krebs cycle including pyruvate dehydrogenase. Brain insults result when metabolism is inhibited, particularly where there is high demand for energy. A cascade of injury to the brain occurs when neuronal death reduces production of succinate and GABA as well as neuron stimulation. Without functioning pyruvate dehydrogenase, lactic acid production increases. Nucleotide synthesis and NADPH production is reduced, which in turn reduces glutathione in blood cells. Individuals carrying apolipoprotein E (ApoE) epsilon 4 (E4) allele are at higher risk of Korsakoff’s syndrome (2). Thus, t

Diabetes: Women and Men

Type 2 diabetes mellitus is considered a major risk factor in cardiovascular disease (CVD) in both men and women, but CVD pathogenesis biochemistry can differ between the sexes. Both sexes are affected by insulin resistance, which generally precedes the diabetes, and accompanying metabolic syndrome factors dyslipidemia and hypertension (1). The insulin resistance leads to elevated insulin levels, which stimulates sodium reabsorption. The sodium levels can induce prolonged hypertension. The hypertension leads to hardening of the arteries and eventual atherosclerosis. The chronic hyperglycemia leads to glycation of myocardial proteins and microvascular disease (1;2). Gradual nerve damage from abnormal signaling leads to autonomic neuropathy (2). Although women have overall lower risk of heart disease than men before age 60 due in part because of estrogen, diabetes abolishes difference in CVD risk. In fact, diabetes in women is reported to increase risk of CVD three- to seven-fold whereas

Post-menopausal estrogen therapy

Menopause is the eventual reduced production of sex hormones in women. Follicular cells in the ovaries appear to become exhausted by continual cycles of ovulation and atresia (1). The ovaries become less responsive to stimulation from gonadotropin—follicle-stimulating hormone (FSH) and luteinizing hormone (LH)—causing estrogens and progesterone levels to lower. The ovaries degenerate causing further diminished estrogen production until the hormone is only produced in limited amounts by other tissues (1). The loss of estrogens production also reduces cardioprotective effects of this particular hormone. Estrogens, estradiol in particular, protects cardiovascular health because of its binding to estrogen receptors (ERs). ERs in absence of estrogen are associated with heat shock protein (HSP); estrogen binding promotes dissociation (2). Estrogen binding also changes gene transcription, altering levels and kinds of cellular proteins (2). The alterations directly affect myocardial, vascular

Potassium Guards Against Sodium-induced Bone Loss

Reference: Sellmeyer DE, Schloetter M, Sebastian A. Potassium citrate prevents increased urine calcium excretion and bone resorption induced by a high sodium chloride diet. J Clin Endocrinol Metab 2002;87:2008-12. Available at: http://jcem.endojournals.org/cgi/content/full/87/5/2008?ijkey=b46c2855f83d19e380eb6674c66c94e884ed56a0 Purpose of study: To study effects of dietary potassium citrate added to diets high in sodium, as commonly found in industrialized nations, in postmenopausal women. Postmenopausal women are at higher risk of osteoporosis, especially if consuming a high-sodium diet. Type of study: Randomized, double-blinded placebo-controlled trial Method used to conduct study: After three weeks in which 60 post-menopausal women adhered to a low-salt diet, they were provided sodium chloride pills, salt packets (for sprinking on food) and one cup of bouillon per day. They were randomized and either take potassium citrate (90 mmol/d) or placebo. Twenty-four-hour urine samples w

Why Gatorade May Not Rehydrate You Any Faster Than Water

Research Summary Critique Reference: Jeukendrup AE, Currell K, Clarke J, Cole J, Blannin AK. Effect of beverage glucose and sodium content on fluid delivery. Nutr Metab (Lond) 2009;6:9. Available at: http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=19232115 Purpose of study: The objective of many oral rehydration drinks is rapid fluid delivery to correct fluid balance in sports. This study investigated carbohydrate (CHO) and sodium (Na) effects on fluid delivery with a deuterium oxide (D20) tracer. Previous research suggests Na concentration may increase delivery, but that CHO content is more important factor. Type of study: Equivalence trial of eight different solutions. Method used to conduct study: Two groups of 10 male subjects (ages 20 +- 1 y, weight: 81.2 +-7.5kg) were split into a CHO or NA group. The CHO group ingested four drinks, each with 20 mmol/L sodium, and with a stepped increase of 3% glucose from 0-9%. The Na group ingested four drinks, e

Boost brain health by living like an Indian

Getting plenty of sun and eating curry are integral parts of Indian culture. Now scientists have found that this combination also helps guard against Alzheimer's disease. The biochemical mechanism by which the combination works is through immune system macrophages (1). Vitamin D was found to stimulate type I and II macrophages to break down and clear beta-amyloid plaques through genomic pathways. Curcuminoids, specifically bisdemethoxycurcumin, assisted with stimulating type 1 macrophages through non-geneomic pathways. Immune therapies to clear beta-amyloid plaque are a new approach that health scientists hope will assist in prevention and treatment of AD. Because vitamin D and curcumin work in different ways biochemically, both may be used in therapy for most promising effects. Apart from hereditary implications, obesity, diabetes and hypertension are all risk factors in AD. Other promising dietary interventions are caloric reduction, antioxidant intake from fruits and vegetables,

Biochemistry of Metabolic Syndrome

Connecting the biochemical dots that lead to atherosclerosis is what is best attempted by the term metabolic syndrome (MS) (1). The term, of which is still under controversy, is used as a predictor of cardiovascular disease and type 2 diabetes mellitus (2-4). MS can begin with abdominal obesity (MS dot 1), a consequence of overeating and a sedentary lifestyle (1;5). The additional adipose tissue can then reduce affinity of insulin receptors and/or create abnormal post-receptor responses resulting in insulin resistance (MS dot 2) (1). Once insulin resistance overwhelms capacity to produce insulin to overcome it, then type 2 diabetes mellitus (T2DM) ensues (1). T2DM is accompanied by hyperglycemia and often by hyperlipidemia (MS dot 3) (1). The hyperlipidemia results because VLDL and chylomicrons are not cleared by the enzyme lipoprotein lipase of which is dependent on insulin (1). The high levels of free fatty acids then impair insulin action further (1). Plus, new research suggests tha

Glycosylated Hemoglobin to Detect Diabetes

Glycosylated hemoglobin forms when prolonged hyperglycemia leads to glucose in the blood not used for energy to attach itself to hemoglobin (1;2). The reaction does not require an enzyme, but occurs spontaneously (1). The concentration of glycosylated hemoglobin determined by an assay can be used to determine the status of a diabetic patient and effectiveness of treatment (1;2). The glycosylated hemoglobin assay has been found to be a more effective tests than others such as the oral glucose tolerance test for the detection of diabetes (3). Reference List 1. Devlin TM. Textbook of Biochemistry with Clinical Correlations. Philadelphia: Wiley-Liss, 2002, pp893-4. 2. Diabetes and Hormone Center of the Pacific. Glycosylated hemoglobin testing. Available at: http://www.endocrinologist.com/Hemoglobin.htm 3. Dods RF, Bolmey C. Glycosylated Hemoglobin Assay and Oral Glucose Tolerance Test Compared for Detection of Diabetes Mellitus. Clin Chem 25/5, 764-768, 1979. Available at: http://www.clinc

Metabolic Syndrome and Physicians

Despite controversy over the current definition of "metabolic syndrome", physicians are using it as a useful clinical tool. It can be used to help with counseling patients and to recommend treatments. Metabolic syndrome is currently defined as a combination of several risk factors that ultimately lead to diabetes and cardiovascular disease. They include obesity, hypercholesterolemia, hyperlipidemia, hypertension, insulin resistance and inflamation (1). Each of the several risk factors that makes up metabolic syndrome requires varying treatments, so physicians may find that lumping them together is not useful. In fact, controversy exists on if the term "metabolic syndrome" is even defined correctly (1). But a 2007 Mayo Clinic meta-analysis found that metabolic syndrome is beginning to find development as a useful clinical tool (2). The review focused on heart disease factors and found that metabolic syndrome increased risk strongly (2). Reference List 1. Cheng AY, Le

Personal magnesium intake

These are the foods I eat on a daily basis with highest magnesium intake: Mixed Nuts - 308 mg per cup Spinach - 150mg per cup Yerba Mate - 90mg per cup Chocolate Soymilk - 39mg per cup Coffee (espresso) - 96mg per 4 oz Total magnesium: 683mg Luckily I'm meeting my recommended intake of 400mg per day. Check your intake here: http://www.nal.usda.gov/fnic/foodcomp/search/

Is High Phosphorus Intake in the U.S. Diet Hazardous?

Controversy arises as to whether or not a high dietary intake of phosphorus is hazardous to health because in the U.S. the typical diet tends to be high in phosphorus and low in calcium (1). But although the need for increasing calcium for bone health has been clearly established, reducing phosphorus to re-balance the calcium:phosphorus ratio has not been shown to have any additional benefits (1;2). Serum phosphate levels, for example, when high can reduce vitamin D formation in kidneys reducing serum calcium (2). But high phosphorus also appears to reduce urinary calcium indicating a reversal of the prior detriment (2). In addition, the kidney is effective in maintaining normal phosphorus balance by increasing excretion of phosphorus when necessary (1). At this time no research including at least one controlled trial has not found any adverse effect from a diet high in phosphorus at levels common in the U.S. (1;2). The exception is in those with impaired excretion such as those with k

Calcium with or without vitamin D

Criteria for recommending calcium to a patient should not go without considering a patient’s vitamin D status. Vitamin D status is critical for improving intestinal absorption, for maintaining calcium homeostasis, for promoting reabsorption of calcium in the kidney and is involved in bone mineralization (1;2). Calcium supplementation along with vitamin D has been subject of at least two randomized controlled trials in Australia. The first performed on 300 elderly women (77+/- 4.6 years) found no short-term benefit as to improving absorption or promoting bone health (3). But another, longer randomized controlled trial evaluated the effects of calcium with or without vitamin D over five years (4). The researchers studied hip bone mineral density and bone turnover in elderly women (ages 70-80) in a sunny climate (4). Thus, while short-term benefits weren’t found, long-term benefits were, which where likely produced by reduced bone turnover rate over time (3;4). In response to the studies

High-magnesium diet to beat colorectal cancer

At least three cohort studies have been published relating to the possible role of magnesium in reducing risk of colorectal cancer in women. The first was prospective study from Sweden and reported in JAMA in which researchers found a reduced occurrence of colorectal cancer in women who had a higher dietary intake of magnesium (1). Hanging on the coat-tails of the Swedish study, U.S. researchers assessed magnesium status of a cohort in Iowa women and found the similar results of reduced risk (2). The latest was from the Netherlands, which found a few differences from the first two, indicating that there was no significant trend of lowering risk of colorectal cancer except in populations of overweight subjects (3). According to the latest study, the method by which magnesium has a protective effect is thought to be through decrease of insulin resistance (3). However, as suggested by the U.S. researchers, more observational studies are necessary and, perhaps, clinical trials to assess wh

Is spinach a good source of magnesium?

Japanese researchers evaluated spinach’s magnesium bioavailability in rats in a study published in 1995 (1). Their conclusions were that spinach was a "one of the most promising" sources of magnesium and that oxalic acid in spinach after cooking (boil or fried) would not affect magnesium bioavailability. Looking at their data, though, cooking did affect calcium absorption and, of course, oxalic acid had additional effects. The researchers had divided rats into six groups, which led to this data: Mg-deficient diet o Serum magnesium decrease o Ca absorption 87.0% o Increase of calcium and phosphorus in liver and kidneys o Especially large calcium accumulation in kidneys Mg-deficient diet supplemented with raw powdered spinach o Mg absorption 88.9% o Ca absorption 84.1% o Large calcium accumulation in kidneys o Significantly higher liver and kidney Mg and phosphorus Mg-deficient diet with boiled powdered spinach o Mg absorption 88.4% o Ca absorption 57.3% o Large calcium accumul

Which exercise should I do to improve calcium status?

We’ve known for awhile that exercise improves bone health, but unsure what effects it has on calcium absorption and loss. There have been recent studies trying to find out more. Just last April, researchers from San Diego State published a study in which they had investigated urinary calcium excretion in two groups of men—one sedentary and the other on a “high-impact and resistance-exercise program”—in a randomized crossover study of three weeks (1). The active men were found to have “significantly less” urinary calcium loss in comparison to week of restricted activity (1). But, we should note, an earlier study in 2007 reported that exercise actually increased calcium losses through sweating (2). Quite different than the other study, this one which was evaluating effects of calcium supplementation, came to the conclusion that supplementation should be used to correct the negative calcium balance from dermal loss from exercise (2). What’s the deal? While the 2009 study used exercise tha

“No Single Universal Calcium Requirement”

In 2000, with a bit of an incendiary tone, professor Christopher Nordin of Australia called for a rational position on calcium requirements based on individual variances and culture. The matter was one of controversy, lacking human studies because of their difficulty, but despite plenty of evidence that low calcium causes osteoporosis in animals. Modern human studies in which researchers deprive subjects of calcium for long periods would be immoral, Nordin points out, although there have been at least a couple in the past. One in particular was performed 50 years ago on Norwegian prisoners that showed deprivation led to negative calcium balance, which would result in osteoporosis. We also know that diet higher in animal protein and sodium increase urinary calcium; thus, the implication would be that populations of the developed world would need more calcium intake. And status of vitamin D influences calcium absorption; thus, living at a higher latitude, darker skin color, and less exp

Allosteric enzymes

Allosteric enzymes are those that are controlled by the binding of an allosteric effector. The effector may be positive or negative in activating or inactivating the enzyme, respectively, and creates a conformational change of the enzyme. The product may be the allosteric effector in itself producing feedback or feedforward control. There are two classes of allosteric enzymes based on the effect of the effector on Km and Vmax. If the effector alters Km it is in K class and if the effector alters Vmax it is in V class. There are also enzymes that have both Km and Vmax affected. K class allosteric enzymes are affected by negative effector binding because it affects the affinity of the binding site for the substrate. V class allosteric enzymes are affective positively or negatively by effectors that increase or decrease rate of enzyme-substrate complex breakdown to products. Given the conformational change and resulting activation and inactivation of an enzyme, catalysis of reactions woul

Why So Many Hormones?

Hormones are any substance in the body that carries a signal to regulate growth, differentiation and function of a variety of cells. The more signals needed, the more hormones in an organism. The big-brained human body is no different. In higher animals signal pathways of many hormonal systems originate in the brain. Because hormones are so specific in communicating between cells, we can expect yet more discovery of hormones in the future to add to the large number already found. Their are major categories of hormones: peptide and protein, thyroid, catecholamine and steroid. The hormones are specific in targeting cognate receptors that are expressed for specific hormones (1). For example, catecholamine hormones epinephrine and norepinephrine as well as peptide hormones target specific cell surface receptors while steroid hormones target intracellular receptors. Endocrine hormones are those synthesized in a gland and travels to reach distant target cells. Paracrine hormones are secreted

Can vitamin D prevent autoimmune diseases?

Vitamin D, apart from its role in calcium nutrition, has been recently studied for its surprising immunomodulation effects, which could have far implications (1). Not only does the hormone-like vitamin acts on vitamin D receptors, which are present on immune cells such as dentritic cells, but it has also been discovered that activated dentritic cells appear to produce vitamin D (2;3). Because autoimmune diseases such as systemic lupus erythematosus, multiple sclerosis and rheumatoid arthritis have each been linked to low vitamin D status, vitamin D supplementation is thought to have potential use as a treatment (3-5). Its use for HIV infection and cancer are also being studied (6;7). Prevention of autoimmune diseases are also associated with immunomodulation from vitamin D. A higher levels of vitamin D is associated with lower risk of multiple sclerosis (8) and with lower risk of type 1 diabetes mellitus (9;10). Vitamin D’s action for preventing type 1 diabetes and other autoimmune dis

Which Vitamin K for Heart Disease?

The most meaningful (and exciting) new data on vitamin K is on it’s relationship with coronary heart disease (CHD), but it’s a bit confusing. A cross-sectional study published in Atherosclerosis in 2009 indicated menaquinone reduced coronary calcification, but maybe not phylloquinone (1). This supported a hypothesis made earlier that menaquinone, but not phylloquinone reduced risk of cardiovascular disease (2). However, an intention-to-treat analysis in Am J Clin Nutr also published this year found phylloquinone supplementation appeared to slow coronary artery calcification (3). This study was performed on older adults with preexisting calcification (3). One more piece of the puzzle is another not-yet-published September cohort study from Nutr Metab Cardiovasc Dis (4). The study followed 16,057 women ages 49-79 who did not have CHD at baseline (4). Questionnaires were used to determine estimation of vitamin K intake and multivariates were reduced as needed (4). According to its conc