Date: 20 Aug 1994 07:35:23 -0700 From: taltar@vertigo.helix.net (Ted Altar) Subject: Calcium & Vegetarians (repost) Newsgroups: rec.food.veg Organization: Helix Internet Lines: 508 SOME NOTE ON CALCIUM FOR VEGETARIANS Ted Altar INTRODUCTION: The following topics are briefly covered in the following postings. I Exogenous Factors Affecting Absorption II Exercise: A Key Factor For Increasing Absorption and Bone DensitY III how Much Calcium Do We Need? IV Are Dairy Products A Good Source Of Calcium? V Calcium And Vegan DietS VI Good Plant Sources Of Calcium: VII What If I Don't Eat Enough Green Vegetables? For those who like to complaint that some of my postings are too long, simply jump to the section of interest and ignore the rest. Each section is very short, but rather than post each on separately on r.f.v., it is more convenient to me and to other readers that they all be contained in one single article. Indeed, this way you need only see my name appear on your reader once instead of 7 times ;-) I. EXOGENOUS FACTORS AFFECTING ABSORPTION According to a conventional text on nutrition (Hunt & Groff, ADVANCED NUTRITION AND HUMAN METABOLISM, 1990): "a greater absorption does not necessarily mean greater retention. Sometimes increased absorption of calcium is offset by its increased excretion in urine and/or digestive juices. Calcium economy in the body is very complex being influenced not only by exogenous factors by also by endogenous physiologic conditions". p. 266 Of the exogenous factors, Hunt & Groff list the following as factors making for a decreased or retention of calcium: Purified PROTEINS (e.g., meat & dairy) increase urinary calcium. caffeine increases urinary as well as a increased secretion of calcium into the gut (hence both urinary and endogenous fecal losses. Unabsorbed dietary FAT interferes with absorption by producing "soaps" that simply cannot be absorbed and are excreted in feces. Some "brilliant" nutritionists have therefore thought that increasing calcium intake could benefit the health of the colon by binding free fatty acids and bile acids thereby preventing irritation to the colon by these fat-related substances. Odd that it never occurs to these folk that the simplest and best recommendation is simply not to eat such excess fat (i.e. meat) in the first place. SODIUM increases urinary calcium loss. MAGNESIUM and calcium, both divalent cations, appear to compete with each other for absorption whenever there is an excess of either present in the gut. Magnesium is important for the secretion of PTH which in turn is important for the serum regulation of calcium. Hence, by consuming too much calcium without a commensurate increase in magnesium, one paradoxically inhibits proper serum calcium regulation. FIBER "(specifically cellulose and hemicellulose) decreases absorption not only by increasing the bulk of intestinal contents and decreasing transit time but also by simulating microbial proliferation, a mineral-requiring process". Of course, such microbial proliferation is desirable and cereal fibers being high in hemicellulose (a slowly fermentable component desirable for microbial proliferation), therefore aid in the "detoxification" mechanism provided by microbial action scavenging degradable nitrogenous substances. We should also note that fiber, oxylates and phytates don't decrease absorption of calcium that much (this has been exaggerated while the protein interference has been underplayed in the popular press) and they in turn help to offset the decrease by the fact that a diet high in cereals and vegetables will increase the intake of calcium and other minerals. That is, eat your greens (kale, chard, beet tops, rhubarb, wild poke) along with a cereal like rice. Lest one becomes overly concerned, studies show (e.g., Anderson, "The iron and zinc status of long-term vegetarian woman. Am. J. CLIN. NUTR., 1981, 34:1042) no evidence that vegetarians suffer mineral deficiencies, even though we have here a population maintained on a high-fiber diet. II. EXERCISE: A KEY FACTOR FOR INCREASING ABSORPTION AND BONE DENSITY Regular exercise, esp. jogging or weigh carrying/bearing exercises, increases absorption (see "calcium retention of young adult males as affected by level of protein and calcium intake" TRANSACTIONS OF THE N.Y. ACADEMY OF SCIENCES, 1974, 36:333-40) III. HOW MUCH CALCIUM DO WE NEED? The following is from McDougall A CHALLENGING SECOND OPINION, 1985. calcium need determined by experiment 15-200mg Worldwide calcium intake in most pop. 300-500mg WHO (World Health Organization 300-500mg American FDA 800mg proposed increased by NIH (National 1000-1500 Institute of Health) and one strongly supported of course by the National Dairy Council These recommendations are for women. Personally, I think the WHO is really the best source for RDA recommendations, being a respected international body and one not as prone to being ethnocentric in basing it's conclusion on simply one population from one country, especially a country whose average diet is known to be too fatty and rich and one that is incurring significant health problems.. Indeed, National Research Council itself (which set the RDA values in the first place), acknowledges that people have been able to maintain calcium balance on intakes as little as 200 - 400 gm/day. They recommended the 800 mg/day because of the excessively HIGH PROTEIN diet of most Americans (see NRC, RECOMMENDED DIETARY ALLOWANCES, 9TH ed., 1980, p. 120-29) But the really convincing evidence is the primary fact that vegetarians simply have a much lower incidence of osteoporosis, plain and simply (see Ellis et al., "Incidence of Osteoporosis in Vegetarians and Omnivores" AMER J CLIN NUTR, 1970, 100:1425) So, we could talk nutrition theory till we drop from malnutrition, but however you cut it, vegetarians are still better off than omnivores. IV. ARE DAIRY PRODUCTS A GOOD SOURCE OF CALCIUM? Remember, fat (and sodium) also decreases absorption, as mention above, decreasing again the calcium from whole diary products . With respect to the influence of protein on calcium balance, McDougall (ibid) summarizes 5 studies as follows: initials intake balance with balance with of investigator of calcium low-protein high-protein intake intake C.A. 500 +31 -120 M.H. 500 +24 -116 R.W. 800 +12 -85 N.J. 1400 +10 -84 H.L. 1400 +20 -65 average 920 +19 -94 Defs.: "low-protein intake" = 47 to 50 grams of protein "high-protein intake" = 141 to 151 grams of protein. Calcium balance figures are calculated for 24 hours and each of the studies used supplementary mixtures of proteins added to the normal diet in order to raise protein to higher levels. The above high protein intakes are not unusual. Remember, 50 grams of protein can be consume by eating only 6 ozs of chicken without skin, 7 ozs of broiled cod. In contrast you would have to eat 25 lbs of boiled potatoes or 11 cups of cooked rice. If you are one high protein diet one needs to consume more calcium but even with the large intakes of calcium used in 2 of the studies above the calcium balance was still in the red. There is no bodily adaptation of this balance to long-term high protein diets. In general, with each doubling of the amount of protein one will lose by 50% the amount of calcium lost in urine. Anyway, you might want to take at look at McDougall on this issue as he provides a lot of good information and references to other studies that indicate: a) in most experiments eating meat causes a negative calcium balance. b) Eskimos have an average of 10 to 15 % less bone than do comparable U.S. Caucasians, in spite of the fact that the Inuit exercise more. The Inuit women lose 10 -12% of their skeleton per decade as compared with a 9.5% loss estimated for U.S. white females. c) Even a study funded by the National Dairy Council failed to support the use of adding dairy products to one's diet as significantly improving the calcium balance (unless one cuts out other sources of protein like meat or dairy!). We should also note that plant protein does not have quite the same inhibitory effect on calcium as does animal derived protein, not only because there is less protein in plant foods generally, but because they contain less of the sulfur containing amino acids, like methionine, as is found in meats. These amino acids in particular have a calcium losing effect on the kidneys (Zemel, J. "Role of the sulfur- containing amino acids in protein-induced hypercalciurian in men NUTRI., 1981, 111:545) This seems to have been born out by an experimental study (Breslau et al., J. C.IN. END., 1988, 66:140-6) which compared the amounts of calcium excreted in the urine of 15 subjects who followed experiemental diets for 12-day periods. The diets contained constant amounts of calcium (400mg/day) and protein (75g/day), but differed with respect to 3 different protein sources: Protein Source Ca Loss in Urine animal protein 150mg/day vegetable & egg protein 121mg/day vegetable protein only. 103mg/day This result suggests that diets higher in vegetable protein, as opposed to meat protein, may better protect against bone loss, hence osteoporosis. In another experimental study using 12 post- menopausal woman (ages 48 to 82) who for 167 days were carefully feed a regulated diet supplemented with some minerals (including calcium) so that they consumed 600mg of calcium. This diet was low in fruits and vegetables, hence low in boron. With a supplement of 3 mg of boron, calcium and magnesium loss in the urine was reduced (serum oestrogen and testosterone also increased, favouring bone calcium conservation). The authors concluded that a diet high in fruits and vegetables would thus help prevent calcium loss and bone demineralization. As we know, vegetarians typically do eat more fruits and vegetables than is found in the normal omnivore diet. V. CALCIUM AND VEGAN DIETS Several have recorded calcium intakes among groups of practicing vegans. Gill Langley (VEGAN NUTRITION: A SURVEY OF RESEARCH, 1988) reported that British studies in the 1950's and 1960's "found levels between 500 and 1,000 mg, and in a 1985 report the mean intake of 10 male and female vegans was lower than that of matched omnivores, but just met the British RDA of 500mg". Other studies found intakes to lower then matched omnivores but adequate at 554mg and 585mg Despite these lower intakes of calcium among vegans, the blood levels of this mineral and levels of osteocalcim (serum concentrations of osteocalcium relect bone turnover) were the same, while serum 1,25-dihydroxymitamin D concentrations tend to be higher in vegetarians (see Specker et al., Obstretrics & Genecology, 1987, 70(6):870-4). This indicates that lower calcuim intakes among vegetarians does not result in Ca migration from the bones, but the instead may elevate serum 1,25- dihydroxydihydroxyvitamin D response that in turn increases the fractional intestine absorption of Ca from the vegetarian diet. This all goes to confirm that there is an adaptive increased absorption of calcium among vegans, and we should note that NO reports of calcium deficiency have been reported in adult vegans. Thus, the best evidence to date indicates that vegans, with a slightly lower protein intake and a meat-free diet, probably have a lower requirement for dietary calcium and are better able to absorb dietary calcium and conconserve the existing calcium in their bodies. VI. GOOD PLANT SOURCES OF CALCIUM: As Thrush & Thrush (ibid) point out, the key point to maybe keep in mind is that as long as one sensibly eats a simple but varied and wholesome diet, calcium needs will be amply supplied since one will utilize the available dietary calcium more efficiently. After all, men can easily adapt to calcium intakes as low as 200 -400 mg daily (see Bogert, "NUTRITION AND PHYSICAL FITNESS, 5th edition, p. 154) Also, taking calcium supplements has not proven to reduce the risk of osteoporosis (G. Kolata. 1986, "How important is dietary calcium in preventing osteoporosis?" SCIENCE, 233, Aug1:519-20) Still, we want to make sure that we are consuming adequate amounts but eating quality vegetarian foods. The following table is from Akers (A VEGETARIAN SOURCEBOOK, 1989), a general sourcebook which I highly recommend (if there is only one book you should buy as a vegetarian, this is that one book!): The following table calculates nutrient density of various foodstuffs as follows: % of RDA of calcium in 100 grams of food nutrient density = ----------------------------------------- X 100 % of RDA of calories in 100 grams of food This is really the most meaningful and useful way to assess the nutrient value of foods. Hence, if you eat 100% of your daily caloric requirement for one day by eating nothing but broccoli, you will be consuming 805% or 8 times what the inflated RDAs for calcium would consider adequate! TABLE 1 Nutrient Densities Of Some Common Plant Foods, Relative To RDAs For Adult Woman Aged 25 To 50 (800mg calcium; 2000cal) VEGETABLES CALCIUM LEGUMES CALCIUM turnip greens 2196 soybean 140 watercress 1987 bean, lima 106 collards 1389 chickpea 104 kale 1175 bean, pinto 97 spinach 895 pea, green 81 broccoli 805 lentil 59 okra 639 peanut 31 celery 574 cabbage 511 GRAINS radish 441 oatmeal 42 cucumber 417 wheat 39 lettuce 385 bulgur 30 squash 368 rye 28 onion (green) 354 rice (brown) 25 turnip 325 millet 15 cauliflower 232 carrot 220 NUTS & SEEDS pumpkin 202 sesame (whole) 515 onion (dry) 178 almond 98 tomato 148 sunflower 54 eggplant 120 pecan 27 beet 93 cashew 17 sweet potato 70 walnut (black) 0 mushroom 54 potato 23 FRUITS corn 8 lemon 241 orange 209 blackberry 138 cherry 79 blueberry 61 peach 59 grape 58 pear 33 apple 31 banana 24 avocado 15 Now, one always be careful with such tables. For example, nutrient quantities can vary tremedously within different items of the same food. That is why one will find different figures for organic vs non-organic foods, or different figures for the Amer. Dept. Agric. vs the Brit. Royal Soc. of Chemistry's UK National Nutrient Databank (e.g., McCance & Widdowson's "The Composition of Foods", 5th ed., 1991). Even over time, the quality of foods may decrease as soil conditions deteriorate or new strains of plants are introduced to increase production with no regard for the nutrient quality of the foodstuffs. On note of caution. It is not a wise procedure to try to make some numerical calculations as to whether one is precisely over or under RDAs for some nutrient since such a simplistic approach fails to take into account that: (1) RDA's are designed for populations, not individuals (margins of safety for special needs and great population variance results in RDA levels that often are well beyond what most people actually need) (2) Individual differences in what overall foodstuffs they eat will greatly change nutrient need levels 3) Different diets makes for different absorption rates of certain nutrients. The American RDA's are based on the omnivorous population of that country, and are not ideally suited for vegetarians. Better are the WHO figures which are based upon a less ethnocentric sampling of only U.S. citizens, whose fatty diet is much to be desired. In general, simply treat such tables as a rough and ready indicators, never as an exact diagnostic device to determine whether or not one is eating enough of a certain nutrient. Things cannot be so precisely calculated, especially for any particular individual. The more useful data comes from good epidemiological research on vegetarians, which have shown them to be thriving quite well, thank you, much better than omnivores would like to acknowledge (see Millet et al. "Nutrient intake and vitamin status of healthy French vegetarians and nonvegetarians" AM J CLIN NUTR 1989, 50:718). The important thing is to eat sensibly a varied diet of good quality foodstuffs (viz., vegetables, grains, legumes, and fruits). And also one should trust and become sensitive to one's own sense of well-being. Do you feel right after eating certain things or not? Do you feel better when you eliminate certain things from your diet for certain periods of time? Are you in general not feeling well? And so on. Just for comparison purposes of plant sources with cows milk, it might be useful to consider the following table (from Thrash & Thrash, NUTRITION FOR VEGETARIANS, 1982) TABLE 2 (from Thrash & Thrash, NUTRITION FOR VEGETARIANS, 1982) FOOD SOURCE AMOUNT CAL. PROTEIN CARB FAT SODIUM CALCIUM gm gm gm mg mg milk human 1 cup 184 2.4 22.4 9.6 40 80 cow, whole 1 cup 159 8.5 12.0 8.6 122 288 cow, skim 1 cup 88 8.8 12.6 .2 128 289 cow, skim, fort. 1 cup 105 9.8 13.6 1.2 142 359 1 cup soy milk 1 cup soyagen 1 cup 146 7.3 11.0 8.5 303 72 soyamel 1 cup 140 5.0 16.0 6.0 363 150 collards, 1 cup 58 5.4 9.8 1.2 50 304 mustard greens 1 cup 46 4.4 8.0 .8 36 278 sesame, whole 2 Tbs 125 4.1 4.8 10.9 13 258 kale 1 cup 48 4.3 7.5 1.0 94 224 oatmeal cereal, 1 cup 123 5.6 23.3 8 169 191 cream of wheat 1 cup 130 4.4 26.9 .4 96 185 soybeans, 1 cup 260 22.0 21.6 11.4 4 146 broccoli 1 cup 32 4.1 60.0 4 13 117 sunflower, kernals 2 Tbs 124 5.3 4.4 10.5 7 27 *Note: all vegetables, cereals and legumes here listed are cooked quantities ready for eating. VII. WHAT IF I DON'T EAT ENOUGH GREEN VEGETABLES? Hopefully, you will eat more green vegetables. There are many ways of eating greens that a lot of people simply have not even tried or really allowed themselves to the time to grow to enjoy and to really like. Unfortunately, too many people seem to be ignoring eating vegetables. A large survey showed that 48% of people on the day surveyed didn't eat any vegetables whatsoever that day. No wonder there is a concern about people not getting enough proper nutrition through their daily foods. Happily, it turns out that vegetarians are generally much better at eating their vegetables, including green vegetables, but of course here too there is a lot of variability in eating habits. With respect to calcium, green vegetables are certainly not the only dietary source. For example, some non-green sources include: Tofu, firm and made with calcium 1/4 cup = 430 mg Tofu, firm and made with nigari 1/4 cup = 129 Tofu, regular and made with calcium 1/4 cup = 220 Tofu, regular and made with nigari 1/4 cup = 67 natto miso 1/4 cup = 96 hummus (I make it without any oil) 1/2 cup = 81 white beans 1/2 cup = 81 tempeh 1/2 cup = 77 navy beans 1/2 cup = 64 black turtle beans 1/2 cup = 52 pinto beans 1/2 cup = 41 whole sesame seeds 2 Tbs = 176 tahini 2 Tbs = 128 almond butter 3 Tbs = 129 almonds, dry roasted 1/3 cup = 120-176 Hijiki, dry 1/4 cup = 162 Wakame, dry 1/4 cup = 104 amaranth, cooked 1 cup = 276 black strap molasses 1 Tbs = 137 Calcium fortified soy beverage 1/2 cup = 95-160 [from "Becoming Vegetarian", 1994] Ok, the above are just some of the non-green foods that have a good supply of calcium in them. If somebody really is certain that they need to calcium supplements, then consider using CALCIUM NITRATE over calcium carbonate supplements because the former is more bioavailable [J. Bone Miner. Res., 1988, 3(June)]. But be forewarned: if you are predisposed to the formation of kidney stones (e.g. family history), supplements should be avoided. Also, excess calcium can bind with zinc, making zinc less available for absorption. Finally, for people in good health there is no advantage in consuming calcium above RDA levels. Regards, Ted