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From the Townsend Letter
January 2017

Mercury: The Quintessential Anti-Nutrient
by Sara Russell, PhD, NTP, and Kristin G. Homme, PE(ret.), MPP, MPH
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Autism, Attention Deficit and Other Neurological Disorders
Many scientific studies suggest a connection between mercury and autism spectrum disorder (ASD), yet the subset of studies cited by health authorities fails to find a causal link.56 Such a link is widely viewed as biologically plausible,57 yet remains a taboo subject in mainstream medicine and the media. Autism is documented to involve oxidative stress, mitochondrial dysfunction, immune or inflammatory processes, impaired sensory processing, and abnormal mineral homeostasis, all of which are consistent with mercury toxicity.58 Autistic children have been found to have significantly higher exposure to mercury during fetal development and early infancy, as measured by metals in baby teeth.59 The element most frequently deficient in ASD is zinc.60 Other commonly observed mineral imbalances in ASD include low calcium, iron, magnesium, manganese, and selenium as well as high copper and elevated toxic metals, which can sometimes be difficult to detect through testing, as described later.
Attention deficit disorder (ADD) and attention deficit hyperactivity disorder (ADHD) are common early findings in mercury-exposed children.61 Zinc deficiency has been identified as a biomarker for ADHD62; and the abnormal mineral profile for ADHD appears quite similar to that for autism and mood disorders, with the exception that ADHD typically includes iron overload. Additionally, copper dysregulation is a key factor in ADHD.63

Many studies report a close association between clinical depression and zinc deficiency with severity of symptoms inversely correlated with serum zinc levels. Decreased levels of zinc, calcium, iron, and selenium have been reported as risk factors for postpartum depression.64 Other neurological and psychiatric disorders associated with mercury include narcolepsy, obsessive-compulsive disorder, schizophrenia, bipolar disorder, Tourette syndrome, and borderline personality disorder as well as neurodegenerative disorders – Alzheimer's, Parkinson's and Multiple Sclerosis, for example. Each has been documented to involve oxidative stress, inflammation, mitochondrial dysfunction, and mineral imbalances; all of which can be attributed to mercury. These diseases are complex, such that human studies are unlikely to find a direct causal link with any one risk factor that is strong enough to satisfy skeptics; but a growing body of evidence suggests that mercury plays a major role.65
Exacerbating the mineral dysregulation associated with these many conditions are the neurotransmitter imbalances provoked by mercury. For example, mercury increases extracellular levels of the excitatory neurotransmitter glutamate, thus overactivating glutamate receptors on cell surfaces.66 The amplification of glutamate is further exacerbated by mercury's inhibition of the calming neurotransmitter GABA67: Mercury blocks GABA receptors; it disproportionately destroys GABA-producing Purkinje neurons; and it impairs glutamate decarboxylase (GAD), the enzyme responsible for converting glutamate to GABA. Furthermore, mercury's dysregulation of glutamate and GABA is associated with depression and suicide.68-70

Altered Microbiota, Digestive Dysfunction and Immune Health
Mercury is known to alter the intestinal microbiota, yielding increased levels of undesirable mercury-resistant bacterial species, which may also develop resistance to antibiotics.71-73 For example, the opportunistic yeast Candida albicans may overgrow, causing a host of unpleasant symptoms. This dysbiosis may be exacerbated by mercury's dysregulation of the immune system as well as its promotion of metabolic acidosis. All this has negative implications for digestion, immunity, and mental health.74-76
Mercury also inhibits several enzymes affecting digestion including gastric hydrogen-potassium-ATPase, the enzyme that allows the synthesis of hydrochloric acid via the stomach's proton pump. In addition, by promoting oxidative stress, mercury moves the autonomic nervous system into sympathetic (stress) mode, inhibiting digestion. Furthermore, the mitochondrial dysfunction from which many mercury-affected individuals suffer impairs digestion as well as other bodily functions. By damaging both the gut and the blood-brain barrier, mercury leads to leaky gut, which in turn leads to food allergies and brain disorders caused by maldigested proteins entering the bloodstream. As a fairly common case in point, partially digested proteins in foods containing gluten and casein may be metabolized into the opioid peptides gluteomorphin and casomorphin.77 This is often seen in children with autism spectrum disorder and explains many parental reports of symptom relief on a gluten-free, casein-free diet.
Mercury's effects on the gut can exacerbate mercury's effects on the immune system. Mercury is known to cause allergies, reduced immunity, and autoimmunity78; and such immune dysfunction plays a role in many chronic illnesses. Reduced immunity yields susceptibility to chronic infections such as Lyme and Candida. Finally, although technically not an allergy, multiple chemical sensitivities can result from mercury overloading the body's detoxification system and blocking metabolic enzymes in the liver and other tissues so that common but undesirable chemicals such as fragrances are metabolized incompletely, yielding toxic intermediates.

Thyroid Disorders, Hypothalamus-Pituitary-Adrenal Dysfunction, and Stress-Related Disorders
Mercury is known to concentrate in glands, including the thyroid and pituitary, and to impair the hypothalamus-pituitary-adrenal (HPA) axis. HPA function and thyroid function are tightly interrelated, with impairment of one system often causing impairment of the other. Mercury blocks the selenium-dependent enzyme that converts the thyroid hormone, thyroxine (T4), to its active form, triiodothyronine (T3). Unfortunately, despite symptoms, the resulting hypothyroidism often goes undetected by routine blood work, which typically only tests levels of TSH, the hormone secreted by the pituitary that signals the thyroid gland to produce T4. Further suppressing thyroid function is the mercury-induced depletion of selenium and zinc, which are cofactors for thyroid enzymes.
The oxidative stress caused by mercury is a type of chronic stress that depletes the HPA axis; thus, mercury is implicated in the cluster of symptoms referred to as adrenal fatigue. Incidentally, an evolving view of this condition suggests that it is not a glandular problem, but rather a brain-stress problem.79 Early-life exposure to mercury also causes epigenetic damage to the HPA axis, which can dysregulate the stress response throughout life. This may involve a tendency toward either high or low baseline cortisol as well as a loss of the dynamic cortisol response to stress.80 The latter yields a disabling feeling of unwellness and stress intolerance. High baseline cortisol, on the other hand, may feel less debilitating, but this is a catabolic state that can promote degeneration of otherwise healthy tissues.

Metabolic Disorders, Obesity, and Cardiovascular Disease
HPA dysregulation and thyroid dysfunction strongly impact metabolism and weight. As an epigenetic toxicant, mercury can cause a host of metabolic issues, including blood sugar problems, insulin resistance, and stress intolerance. These symptoms can persist throughout life and into future generations. In addition, mercury impairs many enzymes needed to metabolize food into energy including pyruvate dehydrogenase, which is required for metabolism of carbohydrates but not fat or proteins. Hypoglycemic symptoms, which are common in mercury toxicity, may not reflect true low blood sugar but may indicate impaired enzymes within the brain and/or HPA axis. Other enzymes impaired by mercury include those of the citric acid cycle and the electron transport chain, leading to low ATP energy. Mercury also blocks the insulin receptor, promoting high insulin and thus fat storage. Mercury can cause weight gain or weight loss, depending on whether metabolic dysregulation or gut dysfunction predominates.
Regarding mercury's role in cardiovascular disease, mercury oxidizes blood vessels as well as cholesterol, leading to arterial plaque. Mercury promotes thrombosis and endothelial dysfunction in blood vessels.81 Mercury can cause high or low blood pressure depending on whether artery calcification or artery deterioration and HPA dysfunction predominate. Finally, in a remarkable example of how mercury accumulates in certain tissues, a biopsy study of 13 patients with a type of heart failure found that mercury levels in the myocardium were 22,000 times higher than normal.82

Mercury damage creates a need for extra nutrition, both to repair damage and to prod blocked enzymes. Nutrient-dense diets are of critical importance, and targeted supplementation may help to overcome the unnatural toxic state. Because everyone's nutrient status is uniquely affected by mercury, it is wise to take an individual approach rather than supplement all potentially depleted nutrients across the board. In addition, dietary modifications are sometimes necessary to control the inflammation and other symptoms that result from food sensitivities, which are common in affected individuals. Also, eating foods to which we are allergic or intolerant impairs detoxification by placing undue stress on the organs of digestion and elimination, putting the HPA axis on alert, and increasing the level of inflammation in the body. It is common for people with mercury toxicity to have multiple food sensitivities, particularly to gluten, casein, and soy.
High-quality fat is a preferred fuel in mercury toxicity, because it supplies much-needed fat-soluble vitamins and helps stabilize blood sugar levels. Additionally, because both brain tissue and the phospholipid bilayer of the cell membrane are built in large part from saturated fat, consumption of grass-fed animal fats such as lard, tallow, ghee, and butter contributes to repair. Cod liver oil, liver, extra-virgin organic olive oil, red palm oil, and lard are important sources of fat-soluble vitamins; and it is important to eat a variety of healthy fats from both animal and plant sources. Fat metabolism requires fewer enzymes than carbohydrate metabolism, thus has less opportunity to be blocked by mercury. In addition to slowing energy production, impaired enzymes can create toxic intermediates, which can yield food intolerances to some carbohydrate foods. Carbohydrates can raise insulin, the fat-storage hormone, which may already be high due to mercury toxicity. Finally, high-carbohydrate foods are more likely than high-fat foods to contain anti-nutrients such as phytates, oxalates, and lectins.
Bone broth is ideal for repairing the digestive lining and connective tissue, and for supplying easily assimilated amino acids and other nutrients. Daily consumption of bone broth can help repair the excessive gut permeability that often leads mercury-toxic individuals to food allergies and autoimmunity. Glutamine is one of the most important amino acids needed to repair the lining of the gut; and glutamine and glycine, both abundant in bone broth, are precursors to the body's production of glutathione. Vitamin B6 and magnesium may ease the conversion of glutamate to GABA.83 In the event of sensitivity to glutamate, it is advisable to simmer the broth for no longer than 3-4 hours.
Beet kvass can improve the flow of bile and thus improve excretion of mercury and other toxicants through the bile, particularly in individuals who tend to be constipated. Other probiotic foods, such as sauerkraut, are also helpful as part of a healing program. It is a good idea to start with a small amount of probiotic foods and to increase gradually as tolerated. Organ meats are nutrient-dense and can help supply vitamins and minerals depleted by mercury. For example, liver is high in vitamins A and B-12 as well as zinc, magnesium, and selenium.
Foods high in vitamins A, C, D and E confer important antioxidant and immune-modulating benefits. Vitamin C helps rebuild damaged collagen and can be obtained from a variety of food sources as tolerated, taking care not to rely entirely on the sweeter fruits, which can be problematic for people with blood sugar issues. Good sources of the vitamin include rose hips, guava, acerola cherry, lemons, limes, oranges, grapefruit, kale, broccoli, cauliflower, Brussels sprouts, papaya, mango, pineapple, kiwi, and strawberries. People who suffer from thiol sensitivity, discussed below, will need to avoid or limit the vegetables included on the list. Because grapefruit can stimulate phase II of the liver's detoxification and slow down phase I, it is wise to consume grapefruit only occasionally unless phase I is already known to be overly active with respect to phase II.
The two minerals most commonly depleted by mercury are magnesium and zinc. Liver, leafy green vegetables, nettles, properly soaked lentils (if tolerated), and properly prepared almonds are good sources of magnesium. Nettles are a great source of numerous vitamins and minerals, including magnesium, and can be added to soups or enjoyed as a tea. Zinc-rich foods are critical, but unfortunately oysters, the richest source of zinc, also tend to be high in cadmium and other heavy metals. Thus, red meat and poultry, along with properly soaked sesame and pumpkin seeds and pine nuts, are important sources of zinc for mercury-affected people, keeping in mind that we absorb zinc much more efficiently from animal foods than from plant sources.
Brazil nuts are a good source of selenium, and, unlike fish that are also high in selenium, do not contain potentially problematic levels of mercury. The selenium content of Brazil nuts varies according to the soil where the nuts are grown, as is the case for all foods. Brazil nuts are high in unsaturated fat and may not keep well if soaked extensively, but overnight soaking works well in temperate climates. Regarding the consumption of fish, the evidence suggests that once the body's natural defenses have been overrun by mercury the selenium in seafood is less effective in buffering the mercury. Thus, people who know or suspect a mercury problem must consider the benefits and the risks in determining their fish consumption level. For example, those who limit their seafood intake should consider taking cod liver oil and perhaps fish oil as well in order to derive some of the nutritional benefits of fish while keeping mercury exposure as low as possible.

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