Climate Change and Diet: Calcium

In the Viva la Vegan article “To retain a habitable planet, what we eat is critical!” and elsewhere, I have highlighted the enormous impact of animal agriculture on climate change. A related issue involves the question of how we can satisfy our nutritional requirements if we move away from animal agriculture as a food source.

To help answer that question, using information from the Department of Agriculture, Fisheries and Forestry’s (DAFF) “Australian food statistics 2010-11” [1]and the United States Department of Agriculture’s (USDA) “National Nutrient Database for Standard Reference” [2], I included in the article some examples of charts depicting the gross production figures of certain nutrients in Australia. The chart for calcium was included in a submission responding to DAFF’s National Food Plan green paper.[3] The results are summarised in Figures 1 and 2:

Figure 1: Calcium Content of Australian Food Production 2010/11 – Plant Products versus Animal Products:

Figure 2: Calcium Content of Australian Food Production 2010/11 by major product

The charts include products that are exported and/or used as livestock feed.  The inclusion of the latter means there is some double-counting of nutrients. The double-counting is more significant for calcium than for some other nutrients, for which animal agriculture’s output is relatively low. However, it appears to be unavoidable due to the nature of government reporting on the issue.

While the charts show the gross amount of calcium produced in Australia during 2010/11 (which was influenced by the volume of plant and animal production), the following chart shows the amount of calcium per 100 grams of product for certain products with a high calcium content. Of note is the low calcium content of milk relative to certain plant sources.

Figure 3: Calcium Content of Selected Foods per 100 grams of product

Not only are plant sources of calcium readily available, it has been found that animal proteins and a high intake of calcium can adversely affect the level of calcium in our bones. Here’s what the Physicians Committee for Responsible Medicine (PCRM) says on the topic:

“Get your protein from plants, not animal products. Animal protein – in fish, poultry, red meat, eggs, and dairy products – tends to leach calcium from the bones and encourages its passage into the urine. Plant protein – in beans, grains, and vegetables – does not appear to have this effect.” [4]

Further comments from PCRM [5]:

• “ . . . clinical research shows that dairy products have little or no benefit for bones. A 2005 review published in Pediatrics showed that milk consumption does not improve bone integrity in children.” [6]
• “Similarly, the Harvard Nurses’ Health Study,which followed more than 72,000 women for 18 years, showed no protective effect of increased milk consumption on fracture risk.” [7]
• “A study published in the Archives of Pediatrics & Adolescent Medicine, which followed adolescent girls’ diets, physical activity, and stress fractures for seven years, found that girls consuming the most dairy products and calcium had no added bone protection. In fact, among the most physically active girls, those who got the most calcium in their diets (mostly from dairy products) had more than double the risk of stress fractures.” [8]
• “While calcium is important for bone health, studies show that increasing consumption beyond approximately 600 milligrams per day – amounts that are easily achieved without dairy products or calcium supplements – does not improve bone integrity.” [9]
• “In studies of children and adults, exercise has been found to have a major effect on bone density.” [10], [11], [12]

Figure 4: Kale – an excellent source of calcium

Similar findings were reported by T. Colin Campbell and Thomas M. Campbell II in “The China Study” [13]. Dr T.C Campbell is a member of PCRM’s advisory board. Some key points:

• A 2000 study from the Department of Medicine at the University of California at San Francisco showed that American women aged fifty and older have one of the highest rates of hip fractures in the world. The only countries with higher rates are Australia, New Zealand and certain European countries, where milk consumption is even higher than in the United States.[14]The study used eighty-seven other studies from thirty-three countries and compared the ratio of vegetable to animal protein consumption to the rate of bone fractures. A chart depicting the findings can be found here. The China Study authors state: “A high ratio of vegetable to animal protein consumption was found to be impressively associated with a virtual disappearance of bone fractures.”
• A 1992 report from Yale University School of Medicine summarised data on protein intake and fracture rates among women aged fifty and over from thirty-four surveys in sixteen countries that had been published in twenty-nine peer-reviewed research publications. It found that the 70% of the fracture rate was attributable to the consumption of animal protein.[15]The China Study authors summarised the Yale study’s reasoning: “These researchers explained that animal protein, unlike plant protein, increases the acid load in the body. An increased acid load means that our blood and tissues become more acidic. The body does not like this acidic environment and begins to fight it. In order to neutralize the acid, the body uses calcium, which acts as a very effective base. This calcium, however, must come from somewhere. It ends up being pulled from the bones, and the calcium loss weakens them, putting them at greater risk for fracture.”
• A study of over one thousand women aged sixty-five or more was published by The Study of Osteoporotic Fractures Research Group at the University of California at San Francisco. After seven years of observations, the women with the highest ratio of animal protein to plant protein had 3.7 time more bone fractures than the women with the lowest ratio.[16]The China Study authors stated: “This 3.7 fold effect is substantial, and is very important because the women with the lowest bone fracture rates still consumed, on average, about half of their total protein from animal sources. I can’t help but wonder how much greater the difference might have been had they consumed not 50% but 0-10% of their total protein from animal sources.”They reported that, in their study of rural China, the animal to plant ratio was about 10%, while the fracture rate was only one-fifth that of the United States. Similarly, Nigeria has an animal-to-plant ratio of around 10% that of Germany, with less than 1% of the hip fracture rate.
• The authors cited other studies extending back more than a hundred years as evidence of either the link between animal protein and poor bone health or the tendency of animal protein to increase the metabolic acid load in the body.
• Mark Hegsted is a former Harvard professor and a principal architect of America’s first dietary guidelines in 1980. In a 1986 paper [17], he stated, “ . . . hip fractures are more frequent in populations where dairy products are commonly consumed and calcium intakes are relatively high”. The China Study authors state: “Professor Hegsted believes that excessively high intakes of calcium consumed over a long time impair the body’s ability to control how much calcium it uses and when.” The reasoning is that excessive calcium intake inhibits the body’s ability to regulate calcitriol, an activated form of Vitamin D, which in turn disrupts the regulation of calcium absorption and excretion.

PCRM has also commented on Vitamin D: “Vitamin D controls your body’s use of calcium. About 15 minutes of sunlight on your skin each day normally produces all the vitamin D you need. If you get little or no sun exposure, you can get vitamin D from any multiple vitamin. The Recommended Dietary Allowance is 600 IU (5 micrograms) per day. Vitamin D is often added to milk, but the amount added is not always well controlled.”  [18]

In conclusion, it is clear that we need to consume fewer animal products if we are to retain a habitable planet. We are well placed to do so, while maintaining our nutritional requirements. A high intake of animal protein and calcium may adversely affect bone strength, osteoporosis rates and fractures.

Do you have any thoughts on this issue? I’d welcome your comments below.

Notes:

1. Biography of T. Colin Campbell: Jacob Gould Schurman Professor Emeritus of Nutritional Biochemistry (Cornell) & Author of “The China Study. Startling Implications for Diet, Weight Loss and Long Term Health” (Campbell TC and Campbell, TM II, 2005) T. Colin Campbell, who was trained at Cornell (M.S., Ph.D.) and MIT [Massachusetts Institute of Technology] (Research Associate) in nutrition, biochemistry and toxicology, spent 10 years on the faculty of Virginia Tech’s Department of Biochemistry and Nutrition before returning to the Division of Nutritional Sciences at Cornell in 1975 where he presently holds his Endowed Chair (now Emeritus).”
2. About the Physicians Committee for Responsible Medicine (PCRM): Since 1985, PCRM has been influencing advancements in medicine and science. We advocate for preventive medicine, especially good nutrition, conduct clinical research, and advocate for higher ethical standards in research. Our membership includes 150,000 health care professionals and concerned citizens. PCRM is a nonprofit 501c3 organization headquartered in Washington, D.C.Board of Directors: Neal D. Barnard, M.D., President; Russell Bunai, M.D., Treasurer and Secretary; Mindy Kursban, Esq., Director; Mark Sklar, M.D., Director; Barbara Wasserman, M.D., Director.PCRM’s advisory board includes 18 health care professionals from a broad range of specialties: Leslie Brown, M.D., Pontchartrain Pediatrics; T. Colin Campbell, Ph.D.,Cornell University; Caldwell B. Esselstyn, Jr., M.D., The Cleveland Clinic; Roberta Gray, M.D., F.A.A.P., Pediatric Nephrology Consultant; Suzanne Havala Hobbs, Dr.PH., M.S., R.D., University of North Carolina at Chapel Hill; Henry J. Heimlich, M.D., Sc.D., The Heimlich Institute; David Jenkins, M.D., Ph.D., Sc.D., St. Michael’s Hospital, Toronto; Lawrence Kushi, Sc.D., Division of Research, Kaiser Permanente; John McDougall, M.D., McDougall Program, St. Helena Hospital; Milton Mills, M.D., Gilead Medical Group; Baxter Montgomery, M.D., Houston Cardiac Association and HCA Wellness Center; Carl Myers, M.D., Sonoran Desert Oncology; Ana Negrón, M.D., Community Volunteers in Medicine and family physician; Myriam Parham, R.D., L.D., C.D.E., East Pasco Medical Center; William Roberts, M.D., Baylor Cardiovascular Institute; Joan Sabaté, M.D., Dr.PH., Loma Linda University Nutrition School of Public Health; Gordon Saxe, M.D., M.P.H., Ph.D., Moores Cancer Center, University of California, San Diego; Andrew Weil, M.D., University of Arizona.
3. Dr Campbell and another PCRM Advisory Board member, Dr Caldwell Essylstyn, feature in the documentary, Forks Over Knives. The film’s website states: “The feature film Forks Over Knives examines the profound claim that most, if not all, of the degenerative diseases that afflict us can be controlled, or even reversed, by rejecting animal-based and processed foods.” Dr Essylstyn has been instrumental in the adoption of a vegan diet by former U.S. president, Bill Clinton.
4. Within “Health Concerns about Dairy Products: Osteoporosis” [5], PCRM states (with specific references cited): “You can decrease your risk of osteoporosis by reducing sodium,increasing intake of fruits and vegetables, exercising, and ensuring adequate calcium intake from plant foods such as kale, broccoli, and other leafy green vegetables and beans. You can also use calcium-fortified products such as breakfast cereals and beverages.” [This note was added on 8th January, 2013]
5. None of the material contained in this article should be construed as representing medical, health, nutritional, dietary or similar advice.

Image:

Freshly harvested kale cabbage in a wooden crate, © Peter Zijlstra, Dreamstime.com

References:

[1]     Dept of Agriculture, Fisheries and Forestry, “Australian Food Statistics 2010-11”, http://www.daff.gov.au/__data/assets/pdf_file/0015/2144103/aust-food-statistics-2011-1023july12.pdf

[2]     USDA “National Nutrient Database for Standard Reference” via Nutrition Data at http://www.nutritiondata.com

[3]     Mahony, P, “The Urgent Need for a General Transition to a Plant-Based Diet”, Sep 2012, http://www.daff.gov.au/__data/assets/pdf_file/0011/2211014/Mahony-Paul.pdf

[4]     Physicians Committee for Responsible Medicine (PCRM), “Calcium and Strong Bones” http://www.pcrm.org/health/health-topics/calcium-and-strong-bones, citing Remer T, Manz F. Estimation of the renal net acid excretion by adults consuming diets containing variable amounts of protein. Am J Clin Nutr. 1994;59:1356-1361

[5]     Physicians Committee for Responsible Medicine (PCRM), “Health Concerns about Dairy Products: Osteoporosis”, http://www.pcrm.org/health/diets/vegdiets/health-concerns-about-dairy-products

[6]     Lanou AJ, Berkow SE, Barnard ND. Calcium, dairy products, and bone health in children and young adults: a reevaluation of the evidence. Pediatrics. 2005;115:736-743, cited in PCRM “Health Concerns about Dairy Products

[7]     Feskanich D, Willett WC, Colditz GA. Calcium, vitamin D, milk consumption, and hip fractures: a prospective study among postmenopausal women. Am J Clin Nutr. 2003;77:504-511, cited in PCRM “Health Concerns about Dairy Products”

[8]     Sonneville KR, Gordon CM, Kocher MS, Pierce LM, Ramappa A, Field AE. Vitamin D, Calcium, and Dairy Intakes and Stress Fractures Among Female Adolescents. Arch Pediatr Adolesc Med. Published ahead of print March 5, 2012, cited in PCRM “Health Concerns about Dairy Products”

[9]     Feskanich, D. et al, ibid, cited in PCRM “Health Concerns about Dairy Products”

[10]   Lunt M, Masaryk P, Scheidt-Nave C, et al. “The Effects of Lifestyle, Dietary Dairy Intake and Diabetes on Bone Density and Vertebral Deformity Prevalence: The EVOS Study”. Osteoporos Int. 2001;12:688-698, cited in PCRM “Health Concerns about Dairy Products”

[11]   Prince R, Devine A, Dick I, et al. “The effects of calcium supplementation (milk powder or tablets) and exercise on bone mineral density in postmenopausal women”. J Bone Miner Res. 1995;10:1068-1075, cited in PCRM “Health Concerns about Dairy Products”

[12]   Lloyd T, Beck TJ, Lin HM, et al. “Modifiable determinants of bone status in young women”. Bone. 2002;30:416-421, cited in PCRM “Health Concerns about Dairy Products”

[13]   Campbell, T.C. and Campbell, T.M. II, “The China Study: Startling Implications for Diet, Weight Loss and Long-Term Health”, Wakefield Press, 2007, pp. 204-211

[14]   Frassetto, L.A., Todd, K.M., Morris, C, Jr., et al. “Worldwide incidence of hip fracture in elderly women: relation to consumption of animal and vegetable foods”, J. Gerontology 55 (2000): M585-M592, cited in Campbell, T.C. and Campbell, T.M. II , ibid.

[15]   Abelow, B.J., Holford, T.R. and Insogna, K.L. “Cross-cultural association between dietary animal protein and hip fracture: a hypothesis” Calcif. Tissue Int. 50 (1992): 14-18, cited in Campbell, T.C. and Campbell, T.M. II , ibid.

[16]   Sellmeyer, D.E., Stone, K.L., Sebastian, A., et al. “A high ratio of dietary animal to vegetable protein increases the rate of bone loss and the risk fo fracture in postmenopausal women”, Am. J. Clin. Nutr. 73 (2001): 118-122, cited in Campbell, T.C. and Campbell, T.M. II , ibid.

[17]   Hegsted, D.M., “Calcium and osteoporosis”, J. Nutr. 116 (1986): 2316-2319, cited in Campbell, T.C. and Campbell, T.M. II , ibid.

[18]   Physicians Committee for Responsible Medicine (PCRM), “Calcium and Strong Bones”, http://www.pcrm.org/health/health-topics/calcium-and-strong-bones and “Protecting Your Bones”, http://www.pcrm.org/pdfs/health/pv_strongbones.pdf [Amended on 8th January, 2012]

Blog Author: Paul Mahony (Also on Twitter & Slideshare)