LEAD
Action News vol 10 no 2, June 2010, ISSN 1324-6011
Incorporating Lead Aware Times ( ISSN 1440-4966) and Lead Advisory Service
News (ISSN 1440-0561)
The Journal of The LEAD (Lead Education and Abatement Design) Group Inc.
Calcium is
one of the most important nutrients to combat lead levels in bone, brain and the
nervous system. Lead and calcium compete for the same locations within the body
and are stored in the bone, though lead has a greater affinity for many calcium
binding sites than calcium itself, making the displacement of lead by calcium
exceedingly unlikely. Higher quantities of calcium should increase the chance of
binding sites being occupied by calcium before lead is bound to them. Small
quantities of lead replace larger quantities of calcium used in activating key
neurotransmitters, notably protein kinase C, impeding message transmission in
the brain and nervous system. The ability of lead to replace calcium is believed
to be a probable cause of its ability to pass through and damage the blood/
brain barrier, though the lack of a blood/brain barrier is believed to be a
reason for the susceptibility of infants to lead neurotoxicity.
Lead
is released from the bone through resorption (the recycling of calcium and other
minerals including lead from the bone to the bloodstream) during pregnancy, and
there is strong evidence that calcium supplements reduce blood lead during this
crucial period, in turn reducing lead levels in the newborn child. Breastfeeding
does not appear to significantly increase the lead burden of the newborn
compared to the period of pregnancy itself, and slight reductions in breast milk
lead can be obtained from ongoing supplementation.
Increasing Milk Consumption Improves Older Women’s Diet Quality.
The above chart show the improvement in serum nutrient levels when individuals over 55 with low dairy consumption (around 400ml or less in milk equivalent) add over 700ml of milk to their diet for 12 weeks. The vitamin D levels obtained are unlikely to be typical outside of the USA since the US practices routine vitamin D fortification of milk. Note that many of the nutrients cited have impact on blood lead or lead toxicity. From Miller at al The Importance of Meeting Calcium Needs with Foods Journal of the American College of Nutrition, Vol. 20, No. 2, 168S–185S (2001)
Unfortunately calcium
interferes with the absorption of iron and should not be consumed in significant
quantities (more than one glass of milk or 2 slices of cheese) in conjunction
with iron rich meals. Calcium can also interfere with phosphorus absorption.
Milk or milk products remain
the best sources of calcium since they also provide a range of other essential
nutrients and are not as reliant on stomach acidity (which declines with age) or
vitamin D (whose effective levels can be lead impaired) for absorption. Calcium,
particularly in the form of low fat milk, also can reduce the risk of
hypertension (and the consequent risk of type 2 diabetes), though the extent of
its impact on lead-induced hypertension is not known, as part of the reduced
risk is due to reduced fat absorption. Cow’s milk should not be fed to infants
less than one year of age as it increases intestinal bleeding, reduces iron
levels and might be linked to type 1 diabetes.
Calcium: This nutrient has many sources Back row: Chinese cabbage, yogurt, milk, cheese, aniseed seeds (fennel), bok choi Middle row: seeds (poppy, sesame), tofu and coriander Front row: Fish (sardines, salmon anchovy), dill, kale, broccoli. Not pictured: Chinese spinach (araminth), mustard greens.
For vegans (who do not consume
animal products) or lactose intolerant individuals (most south Europeans, south
and central Africans, native Americans, Australian aborigines and east Asians)
the best sources of calcium are tofu made with calcium sulfate, bok choi, choy
sum, mustard greens, chinese spinach (aramanth), kale, some seeds (poppy, fennel
or sesame) and various fish, particularly if consumed with their bones (notably
sardines, salmon and anchovy). Calcium absorption is significantly inhibited by
oxalates (in many dark green vegetables, most berries, some nuts or seeds,
legumes, cocoa, chocolate and black tea) though several studies indicate this
predominantly affects only the calcium in the oxalate rich food while phytates
(in whole grains, bran, nuts or seeds) reduce calcium absorption by as much as
65% from any food consumed with them. Caffeine, tannins (found in tea) and
phosphates other than phytates (such as are found in soft drinks) can inhibit
calcium absorption but appear to have little impact on well nourished
individuals. From animal studies it appears alcohol, particularly when combined
with lead, depletes calcium in body organs potentially increasing lead uptake.
The well publicized impact of
soft drink consumption on bone mass seems to be related to the displacement of
calcium and protein from the diet rather than any inherent inhibition of calcium
absorption. Proteins (particularly animal proteins though not soy proteins)
improve calcium absorption though high protein levels can increase resorption
due to changes in body acidity.
Phytates: The items pictured are high in phytates and can reduce the absorption of calcium and zinc by up to 67%, magnesium absorption by somewhat less and iron absorption by up to 90%. Phytate content is reduced when baked with yeast (right rear: wholegrain bread), fermented (as with some soy products) or subject to prolonged soaking in water (used with beans) and iron absorption is improved if consumed with vitamin C (left rear: apple & blackcurrant juice). Middle row: baked beans, beans (black turtle, black eye, lima, white, barlotti), bran, peanuts Front row: sunflower & sesame seeds, peas, beans, nuts (almond, brazil, cashew), muesli. Individuals seeking to boost levels of iron, calcium and zinc should avoid consuming these foods within 2-3 hours of meals rich in the mentioned nutrients. This is less important in the case of magnesium as high phytate food is usually also high in magnesium.
For adolescents, high calcium
diets can reduce bone resorption by a third when compared to low calcium diets,
though it appears, from studies of children, that supplementing calcium rich
diets may have little or no impact. Moderate alcohol consumption (1-4 standard
drinks a day, particularly red wine and beer), tea (particularly green tea),
vegetable based diets and moderate physical exercise have also been linked to
lower rates of resorption while low magnesium levels, sugar, chocolate, soft
drinks (particularly cola drinks), cereal based diets (including whole grain),
heavy alcohol consumption (> 4 standard drinks a day) and thyroid problems
may increase resorption. Taking calcium three hours before exercise can reduce
bone resorption associated with exercise. There is evidence that lead itself
increases bone resorption.
High lead exposures require
continuing maintenance of calcium levels as bone resorption in individuals who
have achieved their peak bone mass density (achieved in the mid- to
late-twenties) results in a net loss of minerals, including lead, from the bone
to the bloodstream, and the decline of cognitive abilities caused by the ongoing
release of lead may continue for at least two decades. Resorption releases
significant lead from the bone during pregnancy, lactation and menopause, making
women particularly vulnerable.
Bone resorption: Dietary
elements pictured above decrease resorption: vegetable based diets
(eg capsicum, carrot, broccoli [front row, left]), up to four
glasses of alcohol per day particularly beer and red wine and tea,
particularly green tea. [rear row, left] dietary elements pictured
to the right increase resorption potentially releasing more lead
from the bones: cereal based diets (bread and crackers-
wholegrain. [front row, right]), chocolate [centre row ,right],
sugar, soft drinks-particularly cola and more than four standard
glasses of alcohol. [rear row, right].
High levels of calcium intake
can result in hypercalcaemia, the deposition of calcium in soft tissue leading
to heart and renal problems, so consumption should not be overdone. This is more
likely to be a problem if intakes of magnesium, phosphorus, vitamin B6, vitamin
D and/or vitamin K are low, since calcium is used in bone formation in
conjunction with these and other nutrients (zinc effects bone strength and lead
content but not necessarily the amount of bone deposition). The US Food and
Nutrition Board of the Institute of Medicine recommends an upper limit of 2.500
mg a day (the equivalent of a little under 2.5 liters of unfortified milk) of
calcium consumption (for a maximum absorption of approximately 750 mg). To give
an idea of magnitude, compare this with a maximum daily absorption of under 5mg
and an average closer to 1mg of iron from food sources.
Calcium or zinc
supplementation reduces lead toxicity: assessment of behavioral dysfunction in
young and adult mice Rantham P.J. Prasanthi, Gadi H. Reddy, Gottipolu R. Reddy
Nutritional Research Volume 26, Issue 10, Pages 537-545 (October 2006) http://www.nrjournal.com/article/S0271-5317(06)00194-1/abstract
[Finds that
calcium has more of an effect on lead-Impaired neural related performance than
zinc, though both have significant impact]
How Does Lead affect the
Nervous System? Anjali Patel Bryn Mawr College, Biology 202 paper http://serendip.brynmawr.edu/bb/neuro/neuro00/web2/Patel.html
[A good brief summary of the impact of lead on the brain and nervous system,
particularly as it relates to calcium]
Effects of Micronutrients on
Metal Toxicity Marjorie A. Peraza, Felix Ayala-Fierro, David S. Barber,
Elizabeth Casarez, and Leonard T. Rael Environ Health Perspect 106(Suppl
1):203-216 (Feb 1998). http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1533267/pdf/envhper00536-0213.pdf
[Has a good summary of research on calcium and lead and lead absorption, on p
206-207]
Impact of Diet on Lead in
Blood and Urine in Female Adults and Relevance to Mobilization of Lead from Bone
Stores BL Gulson, KR Mahaffey, CW Jameson, N Patison, AJ Law, KJ Mizon, MJ
Korsch & D Pederson Environ Health Perspect 107:257-263 (1999) http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1566515/
[Demonstrates that release of lead stored in the bone can outweigh other lead
inputs]
Maternal Blood Lead
Concentration, Diet During Pregnancy, and Anthropometry Predict Neonatal Blood
Lead in a Socioeconomically Disadvantaged Population Schell, LM; Denham, M;
Stark, AD; Gomez, M; Ravenscroft, J; Parsons, PJ; Aydermir, A; Samelson, R
Environ Health Perspect Vol 111, No 2, Feb 2003 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1241350/pdf/ehp0111-000195.pdf
[Shows that higher calcium consumption can lower the lead levels of the fetus]
Effect of Calcium
Supplementation on Blood Lead Levels in Pregnancy: A Randomized Control Trial
Adrianse S Ettinger, Héctor Lamadrid-Figueroa, Martha M. Téllez-Rojo,
Adriana Mercado-García, Karen E Peterson, Joel
Schwartz, H Hu, and M Hernández-Avila Environ Health Perspectives Vol
117 No 1 Jan 2009 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2627861/
[Finds that a calcium supplement of 1200mg administered to pregnant women can
safely reduce both blood lead levels (by over 20% in some groups) and possible
hypertensive side effects of lead exposure]
Influence of Maternal Bone
Lead Burden and Calcium Intake on Levels of Lead in Breast Milk over the Course
of Lactation AS Ettinger, MM Te´ llez-Rojo, C Amarasiriwardena, KE Peterson, J
Schwartz, A Aro, H Hu and M Hernández-Avila Am J of Epidemiology 2006 Vol. 163,
No. 1 http://aje.oxfordjournals.org/content/163/1/48.full
[Demonstrates that for the infant, lactation is not a significant source of lead
relative to pregnancy, and that lead release during lactation can be slightly
reduced by maintaining high calcium levels.]
A Randomized Trial of Calcium
Supplementation for Childhood Lead Poisoning Morri E. Markowitz, Mark Sinnett
and John F. Rosen PEDIATRICS Vol. 113 No. 1 January 2004, pp. e34-e39 http://pediatrics.aappublications.org/content/113/1/e34.full
[Finds no impact on blood lead from calcium supplementation of children under 6
who are already consuming sufficient calcium]
Cumulative Lead Dose and
Cognitive Function in Adults: A Review of Studies That Measured Both Blood Lead
and Bone Lead Regina A. Shih, Howard Hu, Marc G. Weisskopf, and Brian S.
Schwartz Environ Health Perspect, Vol 115, No 3, Mar 2007 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1849945/pdf/ehp0115-000483.pdf
[A review of some of the many studies that demonstrate ongoing cognitive decline
as lead leaches from bone.]
Do You Have Strong Bones Or
Are You At Risk For Osteoporosis? Priscilla Slagle M.D. The Way Up Newsletter
12/01/08 Volume 40 http://www.thewayup.com/newsletters/120108.htm
[This is an excellent short summary of the importance of many vitamins and
minerals to bone health and why it is a mistake to focus on calcium in
isolation, particularly if you are relying on calcium supplements.]
Protein and Bone Health Jane
E. Kerstetter Dairy Farmer’s of Canada: Research summaries http://www.dairynutrition.ca/nutrients-in-milk-products/protein/protein-and-bone-health
[This research appears to demonstrate that the increased urinary calcium
excretion associated with higher protein intake (mentioned in the Slagle
newsletter) is due to higher absorption and blood levels rather than reduced
retention]
Moderate alcohol consumption
and increased bone mineral density: potential ethanol and non-ethanol mechanisms
R. Jugdaohsingh, M. A. O’Connell, S. Sripanyakorn and J. J. Powell Proceedings
of the Nutrition Society (2006), 65, 291-310 http://journals.cambridge.org/download.php?file=%2FPNS%2FPNS65_03%2FS002966510600036Xa.pdf&code=e709a3f11d734082ff41ae708a1ef5e1
[Reviews the growing evidence that alcohol itself can reduce resorption and that
other elements such as polyphenols found in beer and red wine can reinforce this
tendency.]
Dietary Intake of Dairy
Products, Calcium, and Vitamin D and the Risk of Hypertension in Middle-Aged and
Older Women Lu Wang, JoAnn E. Manson, Julie E. Buring, I-Min Lee, Howard D.
Sesso Hypertension 2008;51;1073-1079 http://hyper.ahajournals.org/content/51/4/1073.full.pdf+html
[found that dietary, though not
supplementary calcium and vitamin D, significantly reduced the risk of
hypertension, particularly when delivered in the form of low fat dairy products.
Note that full fat diary products do not have significant effects.]
The Importance of Meeting
Calcium Needs with Foods Gregory D. Miller, Judith K. Jarvis, Lois D. McBean,
Journal of the American College of Nutrition, Vol. 20, No. 2, 168S–185S (2001)
http://www.ncbi.nlm.nih.gov/pubmed/11349940
[Provides a good overview
of why one should seek to obtain calcium from food sources rather than
supplements. Table 2 (p 177S) provides a good comparison of bioavailability of
calcium in various foods and can be particularly recommended to lactose
intolerant individuals or vegans.]
Absorption of zinc and
retention of calcium: Dose-dependent inhibition by phytate Kerstin Fredlund,
Mats Isaksson, Lena Rossander-Hulthén, Annette Almgren and Ann-Sofie Sandberga
J. of Trace Elements in Medicine & Biology Vol 20, Is 1, 10 May 2006,
p 49-57 http://www.sciencedirect.com/science/article/pii/S0946672X0600037X [demonstrates
that calcium absorption can be reduced by around 65% (from 31% to 11%) if
sufficient phytates are present]