Research


A National Survey of Physician-Industry Relationships
Research
Written by Dr. Daniel J. Murphy D.C., D.A.B.C.O.   
Monday, 08 October 2007 16:04

FROM ABSTRACT


BACKGROUND

Relationships between physicians and pharmaceutical, medical device, and other medically related industries have received considerable attention in recent years.

We surveyed physicians to collect information about their financial associations with [the drug] industry and the factors that predict those associations.


 METHODS

We conducted a national survey of 3167 physicians in six specialties (anesthesiology, cardiology, family practice, general surgery, internal medicine, and pediatrics).


 RESULTS

Most physicians (94%) reported some type of relationship with the pharmaceutical industry, and most of these relationships involved receiving food in the workplace (83%) or receiving drug samples (78%).

More than one third of the respondents (35%) received reimbursement for costs associated with professional meetings or continuing medical education, and more than one quarter (28%) received payments for consulting, giving lectures, or enrolling patients in trials.

Cardiologists were more than twice as likely as family practitioners to receive payments.

Family practitioners met more frequently with [drug] industry representatives than did physicians in other specialties, and physicians in solo, two-person, or group practices met more frequently with industry representatives than did physicians practicing in hospitals and clinics.


CONCLUSIONS

The results of this national survey indicate that relationships between physicians and [the drug] industry are common and underscore the variation among such relationships according to specialty, practice type, and professional activities.

 

 

KEY POINTS FROM DR. DAN MURPHY

1) This study shows that most physicians (94%) have some type of relationship with the drug industry. Because "respondents may have underreported their associations with [drug] industry," the relationship between physicians and drug companies is probably higher than the 94% documented in this study.

2) Physician benefits from drug companies include receiving free drug samples, free meals, free tickets to events, free travel from drug companies, financial benefits from drug companies, reimbursement for costs associated with professional meetings or continuing medical education, payments for consulting, payments for giving lectures, and payments for enrolling patients in drug clinical trials.

3) "Family practitioners reported the highest average number of meetings with [drug] industry representatives (16 meetings per month), followed by internists (10 per month), cardiologists (9 per month), pediatricians (8 per month), surgeons (4 per month), and anesthesiologists (2 per month)."

4) The drug industry may focus marketing efforts on "physicians who are perceived as influencing the prescribing behaviors of other physicians."

5) There is a "higher frequency of [drug] industry payments to physicians who have developed clinical practice guidelines."

6) In 2000, the average number of meetings between physicians and drug industry representatives was 4.4 per month. This study showed an elevated average to 16 meetings per month. The reason for this 400% increase in meeting rates "may reflect an intensification of [drug] industry marketing since the 1990’s."


Dr. Dan Murphy graduated magna cum laude from Western States Chiropractic College in 1978. He received Diplomat status in Chiropractic Orthopedics in 1986. Since 1982, Dr. Murphy has served part-time as undergraduate faculty at Life Chiropractic College West, currently teaching classes to seniors in the management of spinal disorders. He has taught more than 2000 postgraduate continuing education seminars. Dr. Murphy is a contributing author to both editions of the book Motor Vehicle Collision Injuries and to the book Pediatric Chiropractic. 

 
Making a Case for Chiropractic Care
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Research
Written by Dr. Daniel J. Murphy D.C., D.A.B.C.O.   
Tuesday, 05 June 2007 10:28

KEY POINTS FROM DR. DAN MURPHY

1) In chronic low back pain, there is an integration between connective tissue fibrosis and the nervous system perception of pain.

2) Adverse connective tissue fibrosis can be remodeled by applying mechanical forces to soft tissues, including chiropractic spinal adjusting. [Note, chiropractic was included as the applying of a mechanical force to reverse adverse connective tissue fibrosis and its influence on the nervous system.]

3) The "association between symptoms and imaging results (X-ray, CT, MRI) has been consistently weak, and up to 85 percent of patients with low back pain cannot be given a precise pathoanatomical diagnosis using these methods."

4) "Ongoing pain is associated with widespread neuroplastic changes at multiple levels within the nervous system and including primary afferent neurons, spinal cord, brainstem, thalamus, limbic system and cortex."

5) Neuroimaging has shown that there are distinct "brain networks" involved in acute vs. chronic pain. Chronic pain is specifically related to regions for cognition and emotions.

6) Chronic back pain results in neuronal or glial loss in the pre-frontal and thalamic gray matter. [Brain atrophy]

7) "Increased connective tissue stiffness due to fibrosis is an important link in the pathogenic mechanism leading to chronicity of pain." [Very Important: The Fibrosis of Repair]

8) "Abnormal movement patterns can have important influences on the connective tissues that surround and infiltrate muscles." [Very important because the subluxation complex includes abnormal movement patterns.]

9) "A hallmark of connective tissue is its plasticity or ‘remodeling’ in response to varying levels of mechanical stress." [This is important because it implies that spinal adjusting can initiate remodeling of abnormal connective tissues.]

10) "Both increased stress due to overuse, repetitive movement and/or hypermobility, and decreased stress due to immobilization or hypomobility can cause changes in connective tissue." [Both increased and decreased motion are deleterious.]

11) A chronic local increase in stress leads to micro-injury and inflammation. [Subluxation can cause micro-injury and inflammation.]

12) "A consistent absence of stress leads to connective tissue atrophy, architectural disorganization, fibrosis, adhesions and contractures." [Fibrosis]

13) "Fibrosis can be the direct result of hypomobility or the indirect result of hypermobility via injury and inflammation." [Very Important]

14) During the early phase of immobilization, loss of muscle length is primarily due to shortening of muscle-associated connective tissue, which is later followed by actual shortening of muscle fibers.

15) Muscle connective tissue fibrosis promotes hypomobility. "Connective tissue fibrosis is detrimental, as it leads to increased tissue stiffness and further movement impairment." [Important: fibrosis]

16) "Tissue microinjury, inflammation and fibrosis not only can change the biomechanics of soft tissue (e.g., increased stiffness) but also can profoundly alter the sensory input arising from the affected tissues." [Very Important: Many contend that the tissue changes associated with the subluxation alter the afferent input into the central nervous system, which is the nerve interference of the subluxation.]

17) "Connective tissue is richly innervated with mechanosensory and nociceptive neurons." [Very Important]

18) Activation of nociceptors can contribute to the development or worsening of fibrosis and inflammation, causing even more tissue stiffness and movement impairment. [Important]

19) Chronic low back pain may be caused by pathological connective tissue fibrosis, which causes adverse changes in movement. This is well documented in ligaments and joint capsules. [Very Important] This pathological connective tissue fibrosis is plastic and can, therefore, be remodeled. However, the remodeling must take place over time.

20) "In fibrosed connective tissue and muscle, blood and lymphatic flow may be chronically compromised by the disorganized tissue architecture and, thus, vulnerable to unusual muscle activity (e.g., beginning a new work activity or sport), or to conditions causing further decrease in perfusion such as prolonged sitting."

21) Pain leads to reduced motion, and movement restriction increases fibrosis, "setting the patient up for more painful episodes." [Very Important: fibrosis]

22) "In addition to its role in the pathological consequences of immobility and injury, the dynamic and potentially reversible nature of connective tissue plasticity may be key to the beneficial effects of widely used physical therapy techniques as well as ‘alternative’ treatments involving external application of mechanical forces (e.g., massage, chiropractic manipulation, acupuncture), changes in specific movement patterns (e.g., movement therapies, tai chi, yoga) or more general changes in activity levels (e.g., increased recreational exercise)."

23) "Manual or movement-based treatments have the advantage of not causing drug-induced side effects (e.g., gastritis, sedation)," but excessive motion may lead to inflammation.

24) A "carefully applied direct tissue stretch may be necessary in cases of long standing hypomobility with pronounced fibrosis and stiffness." [Very Important, as an adjustment may be considered to be a "carefully applied direct tissue stretch."]

Dr. Dan Murphy graduated magna cum laude from Western States Chiropractic College in 1978. He received Diplomat status in Chiropractic Orthopedics in 1986. Since 1982, Dr. Murphy has served part-time as undergraduate faculty at Life Chiropractic College West, currently teaching classes to seniors in the management of spinal disorders. He has taught more than 2000 postgraduate continuing education seminars. Dr. Murphy is a contributing author to both editions of the book Motor Vehicle Collision Injuries and to the book Pediatric Chiropractic.

 
The Importance of Antioxidants with Fish Oil Dietary omega-3 fatty acids for women
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Research
Written by Dr. Daniel J. Murphy D.C., D.A.B.C.O.   
Friday, 04 May 2007 14:09

KEY POINTS FROM Dr. DAN MURPHY

ALA: Alpha-linolenic acid, plant derived 18-carbon long omega-3 fatty acid. Primarily from flaxseed (linseed), walnut, and hemp oils.

EPA: Eicosapentaenoic acid, animal derived 20-carbon long omega-3 fatty acid. Primarily from cold-water fatty fish.

DHA: Docosahexaenoic acid, 22-carbon long omega-3 fatty acid. Primarily from cold-water fatty fish. There are vegetarian sources (algae) for DHA.

1) Adequate maternal omega-3 fatty acid intake “ensures the optimal cerebral and cognitive development of the infant.”

2) Human milk contains both ALA [flaxseed oil, etc.] and DHA, unlike that of other mammals. [This is one of the reasons that cow’s milk is not a substitute for human milk for infants.]

3) Vegetarian and vegan mother’s milk have altered fatty acid profiles which impair the cerebral and cognitive development of their infants. [Very Important]

4) ALA [flaxseed oil, etc.], DHA and EPA are important for preventing ischemic cardiovascular disease in women of all ages.

5) Omega-3 fatty acids can help to prevent the development of certain cancers, particularly those of the breast and colon, and possibly of the uterus and the skin, and are likely to reduce the risk of postpartum depression, manic-depressive psychosis, dementias (Alzheimer’s disease and others), hypertension, toxemia, diabetes and, to a certain extent, age-related macular degeneration.

6) Omega-3 fatty acids play a positive role in the prevention of menstrual syndrome and ostmenopausal hot flushes.

7) The normal Western diet contains little ALA [flaxseed oil, etc.], providing less than 50% of the RDA.

8) The best sources for EPA and DHA are fish, seafood and “omega-3” eggs.

9) Both the omega-6 fatty acid linoleic (LA, 18:2(n-6)) and the omega-3 fatty acid alpha-linolenic acid (ALA) [flaxseed oil, etc.], 18:3(n-3)) are “physiologically essential.” [Important, ALA is physiologically essential]

10) The intake of ALA [flaxseed oil, etc.] is far too low.

11)Pregnant women that consume more fish oil improve the pregnancy for both the mother and the baby, reducing prematurity and low birth weight in the infant, and reducing hypertension and pre-eclampsia in the mother.

12)Vegetarians are more prone to premature births and Caesarean sections.

13)Vegetarian mothers are more likely to have premature babies with low birth weight.

14)Daily maternal supplementation of fish oil containing a DHA/EPA mixture is good for fetal development.

15)“Omega-3 fatty acids are most important as structural elements in the developing nervous systems of the fetus and newborn, and this is linked to the mother’s food.”

16)ALA [flaxseed oil, etc.], influences vision, behavior and brain structure and function.

17)“Adding omega-3 fatty acids to baby formula, to make it more like mother’s milk, influences the visual, cerebral and intellectual capacities of newborn babies.”

18)“The fetus uses most of the portion of dietary omega-3 fatty acids supplied to it for its developing brain.” [Very Important]

19)Maternal DHA status decreases during pregnancy.

20)“The cerebral and overall DHA status of breast-fed babies is better than that of infants fed formula lacking DHA.”

21)Human milk contains considerable concentrations of both DHA and ALA [flaxseed oil, etc.].

22)Eating fatty fish, taking fish oil capsules and eating omega-3 eggs increases the DHA in maternal milk.

23)A diet containing flaxseed oil, which has a high ALA content, increases the ALA and EPA in the milk and erythrocytes of lactating women, but not DHA. [Very Important for vegan mothers]

24)“Although the diets of vegans and vegetarians contain reasonable amounts of ALA [flaxseed oil, etc.], it is unlikely that enough is converted to DHA to satisfy the needs of pregnancy and lactation.” [Very Important]

25)Dietary fish, seafood or omega-3 supplements are advisable and prudent for pregnant and lactating women. [Very Important]

26)Omega-3 fatty acids prevent age-related macular degeneration.

27)“There is no doubt that supplements of omega-3 fatty acids, generally taken as fish oil, improve infant visual acuity.” [Important]

28)A lack of omega-3 fatty acids damages hearing and leads to premature aging of the auditory nervous system. “Omega-3 fatty acids are important dietary components for preserving hearing throughout life.”

29)Children given fish oil during the first year of life are less likely to develop type I diabetes, perhaps because of the anti-inflammatory action of very long chain omega-3 fatty acids.

30)Fish consumption reduces the risk of breast cancer.

31)“Excess omega-6 fatty acids seems to increase the risk of breast cancer metastasis, while omega-3 fatty acids have the opposite action.”

32)“There should always be a good intake of antioxidants to restrict the peroxidation of fatty acids, as these peroxide derivatives are genotoxic and cytotoxic.” [Very Important]

33)“Omega-3 fatty acids, if adequately preserved from oxidation,” benefit atherosclerosis, chronic hepatitis, inflammatory bowel diseases, psoriasis, and rheumatoid arthritis. [Important, again: this is why everyone should take antioxidants with each gram of fish oil.]

34)Eating fish and omega-3 fatty acids reduces the risk of suicide attempts, reduces the frequency of bipolar disorder (manic-depressive patients), and reduces the risk of dementia, particularly Alzheimer’s disease.

35)Studies show that ALA [flaxseed oil, etc.] significantly protects against cardiovascular disease.

36)Assuming ALA [flaxseed oil, etc.] intake is sufficient, newborn babies can only in small quantities convert ALA to DHA and, therefore, DHA is considered an essential nutrient for babies. [Important for strict vegetarians.]

37)Both ALA [flaxseed oil, etc.] and DHA are essential nutrients.

38)People who eat no animal lipids are very deficient in DHA. [Important for strict vegetarians.]

39)Omega-3 fatty acids help to prevent menstrual syndromes,  particularly dysmenorrhea and menopausal hot flushes and reduce the risk of osteoporosis.

40)“Only seafood provides adequate EPA and DHA.”

41)“There is practically no toxicological risk from eating too much omega-3 fatty acid.” [Important]

42)“Women, therefore, have specific requirements for omega-3 fatty acids that should be recognized and fulfilled, either by the diet or with capsules.”

COMMENTS FROM DR. DAN MURPHY

A central issue from this article is that alpha-linolenic acid (ALA, from fl axseed oil and other sources) is essential for health and must be included in the diet. Many individuals taking fish oil (omega-3 supplements) are unaware that fish oil capsules usually do not contain ALA. Again, this article supports the importance of using antioxidants when consuming omega-3 fatty acids.

Dr. Dan Murphy graduated magna cum laude from Western States Chiropractic College in 1978. He received Diplomat status in Chiropractic Orthopedics in 1986. Since 1982, Dr. Murphy has served part-time as undergraduate faculty at Life Chiropractic College West, currently teaching classes to seniors in the management of spinal disorders. He has taught more than 2000 postgraduate continuing education seminars.

Dr. Murphy is a contributing author to both editions of the book Motor Vehicle Collision Injuries and to the book Pediatric Chiropractic.

 

 
Chiropractic Works
Research
Written by Dr. Daniel J. Murphy D.C., D.A.B.C.O.   
Wednesday, 04 April 2007 12:48

OBJECTIVE:

To study the immediate sensorimotor neurophysiological effects of cervical spine manipulation using somatosensory evoked potentials (SEP’s).

 

 

METHODS:

Twelve subjects with a history of reoccurring neck stiffness and/or neck pain, but no acute symptoms at the time of the study were invited to participate in the study.

An additional twelve subjects participated in a passive head movement control experiment.

Spinal brainstem and cortical SEP’s to median nerve stimulation were recorded before and for thirty minutes after a single session of cervical spine manipulation, or passive head movement.

 

RESULTS:

 

There was a significant decrease in the amplitude of parietal and frontal SEP components following the single session of cervical spine manipulation compared to pre-manipulation baseline values.

These changes lasted on average twenty minutes following the manipulation intervention.

No changes were observed in the passive head movement control condition.

 

CONCLUSIONS:

 

Spinal manipulation of dysfunctional cervical joints can lead to transient cortical plastic changes, as demonstrated by attenuation of cortical somatosensory evoked responses.

 

SIGNIFICANCE:

 

This study suggests that cervical spine manipulation may alter cortical somatosensory processing and sensorimotor integration.

These findings may help to elucidate the mechanisms responsible for the effective relief of pain and restoration of functional ability documented following spinal manipulation treatment.

 

Key Points from Dan Murphy

1. Spinal manipulation is a commonly used conservative treatment for neck, back, and pelvic pain.

2. The effectiveness of spinal manipulation in the treatment of acute and chronic low back and neck pain has been well established by outcome-based research.

3. Spinal dysfunction will alter afferent input to the central nervous system.

4. Altered afferent input to the central nervous system leads to plastic changes in the central nervous system. (Very Important)

5. Neural plastic changes take place both following increased and decreased afferent input. (Extremely Important)

6. Both painful and painless joint dysfunction will inhibit surrounding muscles.

7. Joint dysfunction causes afferent driven increases in neural excitability (facilitation) to muscles that can persist even after the initiating afferent abnormality is corrected. (This suggests that a muscle afferent problem can persist even after the joint component of the subluxation is corrected. The chronic component of the subluxation may be plastic changes that cause long-term alteration of muscle afferentation.) This article clearly supports that the joint component, the muscle component, and the neurological component of the subluxation complex are influenced by traditional joint-cavitation spinal adjusting.

8. The altered neural processing that occurs as a consequence of joint dysfunction provides a rationale for the effects of spinal manipulation on neural processing that have been described in the literature. (Very Important)

9. Spinal dysfunction alters the balance of afferent input to the central nervous system and this altered afferent input may lead to maladaptive neural plastic changes in the central nervous system, and spinal manipulation can effect this. (Very Important)

10.The clinical evidence for joint dysfunction that requires manipulation includes:

A. Tenderness on joint palpation,

B. Restricted intersegmental range of motion,

C. Palpable asymmetry of intervertebral muscle
tension,

D. Abnormal or blocked joint play and end-feel,

E. Sensorimotor changes in the upper extremity.

[I recall in the teachings of Richard Stonebrink, DC, in the orthopedic diplomate program twenty-five years ago, the importance of always documenting (in our daily records) the evidence that the patient had a manipulatable spinal lesion (subluxation). His evidence was identical to these. Dr. Stonebrink would stress that such documentation would always make the case unique to chiropractic and consequently make the chiropractor the only expert in the case.]

11.The most reliable spinal-dysfunction-indicators are tenderness with palpation of the dysfunctional joint, and alterations of segmental range of motion.

12.High velocity, low amplitude thrust spinal manipulation with the head held in lateral flexion, with slight rotation and slight extension is a standard manipulative technique used by manipulative physicians, physiotherapists and chiropractors.

13.High velocity manipulation alters reflex EMG activity and alters afferent input to the central nervous system. (Important)

14.High-velocity manipulation causes significant cortical SEP amplitude attenuation in at least the frontal and parietal cortexes.

15.Passive head movements do not cause changes in cortical firing.

16.A single session of spinal manipulation of dysfunctional joints resulted in attenuated cortical (parietal and frontal) evoked responses. These changes most likely reflect central changes. (Very Important)

17.The cortical function of different individuals responded differently to spinal adjusting. [This indicates that variables other than the adjustment, itself, can influence the cortical responses in a given individual]

18.The significantly decreased somatosensory cortical SEP occurred in all post-manipulation measurements, indicating enhanced active inhibition because the cervical manipulations could have altered the afferent information originating from the cervical spine (from joints, muscles, etc.).

19.The passive head movement SEP experiment demonstrated that no significant changes occurred following a simple movement of the subject’s head. Our results are, therefore, not simply due to altered input form vestibular, muscle or cutaneous afferents as a result of the chiropractors touch or due to the actual movement of the subject’s head. This, thus, suggests that the results in this study are specific to the delivery of the high-velocity, low-amplitude thrust to dysfunctional joints. [Extremely Important]

20.Displacement of vertebrae is signaled to the central nervous system by afferent nerves arising from deep intervertebral muscles, and this is improved with adjusting the adjacent dysfunctional joint.

21.Joint dysfunction leads to bombardment of the central nervous system with Ia afferent signaling from surrounding intervertebral muscles. Spinal manipulation reduces excessive afferent signals from adjacent intervertebral muscles, which improves altered afferent input to the central nervous system. This changes the way the central nervous system responds to any subsequent input.

22.Episodes of acute pain following injury induce plastic changes in the sensorimotor system, prolonging the episode of pain and playing a roll in establishing chronic neck pain conditions. (Very Important) The reduced cortical SEP amplitudes observed in this study following spinal manipulation may reflect a normalization of such injury/pain-induced central plastic changes, which may reflect one mechanism for the improvement of functional ability reported following spinal manipulation. (Extremely Important)

23.Spinal manipulation of dysfunctional joints may modify transmission of neuronal circuitries, not only at a spinal level, but at a cortical level, and possibly also deeper brain structures such as the basal ganglia. (Very Important)

24.Cervical spine manipulation alters cortical [brain] somatosensory processing and sensorimotor integration.

25.These findings may help to elucidate the mechanisms responsible for the effective relief of pain and restoration of functional ability documented following spinal manipulation treatment.

 

Comment by Dan Murphy

One of the central themes of the neurology diplomate program taught by Ted Carrick, DC, is that chiropractic spinal adjusting influences the cortical brain, creating plastic changes. This article very much supports that perspective.

 

Dr. Dan Murphy graduated magna cum laude from Western States Chiropractic College in 1978. He received Diplomat status in Chiropractic Orthopedics in 1986. Since 1982, Dr. Murphy has served part-time as undergraduate faculty at Life Chiropractic College West, currently teaching classes to seniors in the management of spinal disorders. He has taught more than 2000 postgraduate continuing education seminars. Dr. Murphy is a contributing author to both editions of the book Motor Vehicle Collision Injuries and to the book Pediatric Chiropractic.

 

 
What you and your patients need to know about Fish and Mercury
Research
Written by Daniel J. Murphy, DC and Michael L. Underhill, DC   
Sunday, 04 March 2007 11:26

Many patients are familiar with at least some of the health benefits of fish oil supplementation and dietary consumption of fatty fish, especially species higher in the n-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). There are a multitude of benefits, including improved cardiovascular health, better functioning immune system, help with arthritis, atherosclerosis, depression, adult-onset diabetes mellitus and some cancers. There is reduced risk for stroke, asthma, dementia and kidney disease. In recent research, it was noted that modest consumption of fish (e.g., 1-2 servings/wk), especially species higher in the n-3 fatty acids EPA and DHA, reduces risk of coronary death by 36 percent (95 percent confidence interval, 20-50 percent; P<.001) and total mortality by 17 percent (95 percent confidence interval, 0-32 percent; P=.046) and may favorably affect other clinical outcomes.1

Many of the benefits are attributed to the anti-inflammatory effects of these fatty acids. There are thousands of research articles touting the benefits of polyunsaturated fatty acids or omega-3’s obtained from our diet as well as supplementation. (A search of Medline with the key word "omega-3" results in just under 10,000 articles.) Many well-known organizations, such as the American Heart Association, recommend eating fish as a regular part of a healthy diet. However, we are being made increasingly aware that, along with these benefits, come risks. As a result, consumers are rightly concerned about health risks of contaminants from eating. Many Americans have dangerous levels of methylmercury in their bodies, including 5- 8 percent of American women of childbearing age.

In 2004, the Food and Drug Administration and the Environmental Protection Agency issued a joint consumer advisory about mercury in fish and shellfish. The significance of this becomes apparent when one considers that this is the first time these two organizations have combined their advice to form a single uniform advisory.2 Their advice was directed toward women who might become pregnant, women who are pregnant, nursing mothers, and young children. In July of 2003, the Food Standards Agency in the United Kingdom issued a similar precautionary warning, however they also included children under sixteen years of age.3

In a 2004 article published in the Annals Of Internal Medicine, Wilson states that "studies have linked over consumption of certain fish (particularly popular ones such as swordfish, tuna steaks, Chilean sea bass, and some kinds of salmon) to neurologic deficits, cancer, autoimmune and endocrine disorders, and even some heart disorders. The risks stem mainly from two toxins: mercury, which accumulates over the lifetime of larger, longer-living fish, and polychlorinated biphenyls (PCB’s), which are found in fish living in polluted waters and in some farmed fish."4

In adults, methylmercury poisoning causes tremor, difficulty with concentration, vision deficits, and numbness and tingling. In children, numerous health problems may result, including brain damage, mental retardation, blindness, and seizures. With lower levels of methylmercury exposure in the womb, there may be subtle but irreversible deficits in learning ability as well as altering the male reproductive organs and increased risk for cancer.4

Mercury is an element that is naturally found in the environment. It is also released into the air through industrial pollution, including the burning of fossil fuels and solid wastes. This mercury accumulates in streams and oceans where bacteria cause chemical changes that transform mercury into methylmercury. Fish and shellfish absorb the methylmercury as they feed in these waters and tend to build up in the larger predatory species. Of these, shark, tilefish, tuna and bottom-feeders, such as certain crab, tend to accumulate the highest levels. Essentially, the higher up the food chain, the higher the bioaccumulation of toxins. According to Wilson, exposure to methylmercury comes almost solely from eating fish. She also notes that "methylmercury is absorbed from the gastrointestinal tract and binds readily with proteins; the highest levels in the body are found in the kidneys."

Methylmercury crosses the blood-brain barrier, affecting the brain. According to some researchers, the health effects of low-level methylmercury in adults are not clearly established.1 However, we suggest it is best to err on the side of caution and limit our exposure to toxic elements.

In addition to the dangers posed by methylmercury, fish are also the main source of concentrated polychlorinated biphenyls (PCB’s) with the highest dietary levels found in farmed salmon. PCB exposure is associated with liver and breast cancer, neurologic and endocrine problems, and possibly even increased risk for heart disease. "In children, PCB exposure in utero and from breast milk consumption has been linked with neurodevelopmental delays, impaired cognition, immune problems, and alterations in male reproductive organs…. Generally, freshwater fish that live in inland lakes, such as bluefish, lake trout, and smelt, are more likely to be contaminated."4

Farmed salmon sounds innocent enough until you know a little more about it. Wilson states that "any more than a single eight-ounce portion of farmed salmon a month posed an ‘unacceptable cancer risk’ to consumers."

Foran, et al., analyzed farmed vs. wild salmon and reported that organic arsenic was significantly higher in farmed than in wild salmon, whereas cobalt, copper, and cadmium were significantly higher in wild salmon. In addition, he stated that none of the contaminants exceeded federal standards or guidance levels.5 In a follow-up article, he stated that "health risks (based on a quantitative cancer risk assessment) associated with consumption of farmed salmon contaminated with PCB’s, toxaphene, and dieldrin were higher than risks associated with exposure to the same contaminants in wild salmon."6

In the journal Science, Hites, et al., note, "The annual global production of farmed salmon has increased by a factor of forty during the past two decades." He and fellow researchers analyzed over two metric tons of farmed and wild salmon for organochlorine contaminants and discovered that concentrations of these contaminants are significantly higher in farmed salmon than in wild.7

This data is frightening, considering over 90 percent of the salmon sold in the United States is farmed and that farmed salmon is sometimes labeled as "wild" in grocery stores.

Many researchers recommend purified fish oils that have been tested and found to be free of contaminants. We noted previously, "Untainted fish oils containing abundant levels of omega-3 fatty acids should be a routine supplement during pregnancy and lactation."8 Our suggestion is that you consider for your patients a high quality purified fish oil as a daily supplement to help reduce exposure to environmental toxins and yet reap the benefits of a diet high in polyunsaturated long chain fatty acids.

After reviewing a number of articles and studies including information from the EPA, FDA and the Food Standards Agency in the United Kingdom, we have produced a guide of fish and shellfish to avoid and those that are lower in mercury. In addition, we list some commonly eaten fish with their mercury levels. Note that this list does not include PCB and other contaminants.

Our recommendation is, "Do Not Eat: shark, swordfish, king mackerel, tilefish, farmed salmon and marlin." (The FDA recommends that pregnant and breast-feeding women, and women who intend to become pregnant limit their consumption of tuna to no more than two medium size cans or one fresh tuna steak per week.)

Five of the most commonly eaten fish that are low in mercury are shrimp, canned light tuna, salmon, pollock, and catfish. Others include flounder, rainbow trout, sole, anchovies and clams. Lower levels of mercury are also found in lobster (spiny), oysters and sardines.

For those of your patients that are fishermen, it is recommended that they check local advisories about the safety of locally caught fish. If no advice is available, eat one average meal per week of fish from local waters, but don’t consume any other fish during that week.

"Lean ocean fish, such as cod, flounder, and haddock, are the least likely to be contaminated with PCB’s."4

Earlier this year in the Journal Environmental Science and Technology, Oregon State University and the EPA published the results of a survey of over 2700 fish involving 600 rivers and streams in the western United States. The fish were analyzed and found to contain alarmingly high levels of mercury. According to Associate Professor Alan Herlihy, mercury was literally in every single fish sampled. Based on this and other information presented, it would be wise to exercise caution in our dietary selection of fish. In addition, our suggestion for you and your patients is to consider a high quality purified fish oil as a daily supplement to help reduce exposure to environmental toxins and yet reap the benefits of a diet high in polyunsaturated long chain fatty acids.


Dr. Dan Murphy graduated magna cum laude from Western States Chiropractic College in 1978. He received Diplomat status in Chiropractic Orthopedics in 1986. Since 1982, Dr. Murphy has served part-time as undergraduate faculty at Life Chiropractic College West, currently teaching classes to seniors in the management of spinal disorders. He has taught more than 2000 postgraduate continuing education seminars. Dr. Murphy is a contributing author to both editions of the book Motor Vehicle Collision Injuries and to the book Pediatric Chiropractic.  


Michael L. Underhill, D.C., C.C.S.P., C.C.S.T., is a 1981 graduate of Western States Chiropractic College. He is certified in Chiropractic BioPhysics® as well as being certified as a sports chiropractor and in spinal trauma. He holds a diplomate in thermography. Dr. Underhill is also a contributing author to both editions of the book Motor Vehicle Collision Injuries: Mechanisms, Diagnosis, and Management. He has been in private practice in Beaverton, Oregon, for the past twenty-five years and has taught both chiropractic postgraduate and undergraduate classes. Dr. Underhill can be reached by email at This e-mail address is being protected from spambots. You need JavaScript enabled to view it .


References

1. Mozaffarian D, Rimm EB. Fish intake, contaminants, and human health: evaluating the risks and the benefits. JAMA. 2006 Oct 18;296(15):1885-99

2. US Food and Drug Agency website: http://www.fda.gov/fdac/features/2004/304_fish.html

3. United Kingdom Food Standards Agency, www.food.gov.uk/multimedia/faq/mercuryfish/

4. Wilson JF. Balancing the Risks and Benefits of Fish Consumption. Annals of Internal Medicine 2004 Dec;141:12, pp977-980

5. Foran JA, Hites RA. A Survey of Metals in Tissues of Farmed Atlantic and Wild Pacific Salmon. Environmental Toxicology and Chemistry: 2004 Sep;23, pp. 2108–2110.

6. Foran JA, Carpenter DO, Hamilton MC, Knuth BA, Schwager SJ. Risk-based consumption advice for farmed Atlantic and wild Pacific salmon contaminated with dioxins and dioxin-like compounds. Environ Helath Perspec. 2005 Oct;113(10):p655-6

7. Hites RA, Foran FA, Carpenter, Hamilton M, Knuth B, Schwager SJ. Global Assessment of Organic Contaminants in Farmed Salmon. Science 92004 January: Vol. 303. no. 5655, pp. 226-229.

8. Murphy DJ, Underhill ML. Omega-3 Fatty Acids in Pregnant Women and Infants. The American Chiropractor. Jan 2007:1, pp16-20.

9. US Food and Drug Administration website: http://www.cfsan.fda.gov/~frf/sea-mehg.html

 

 

 

Daniel J. Murphy, DC and Michael L. Underhill, DC
 
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