Updated Studies (2020–2026)
Peer-reviewed reviews and trials added in this rebuild. Original library abstracts follow.
These products are not intended to diagnose, treat, cure, or prevent disease. Historic abstracts below are unchanged from the original MD's Choice library.
Added studies and reviews (1998–2026)
Short notes on later trials. Original library abstracts stay below.
Not FDA-evaluated disease claims. Call 1-800-628-0997 if you want help matching a formula to a body.
Calcium
Truth about Calcium…
Hello Again, A few days ago, we received a call from a client that has been actively using some of our products for over twenty years. I met him at a trade show way back when, and usually only saw him face to face for a little while two or three times a year – at the tradeshows. After we ceased doing most of the Tradeshows back nearly a decade ago, we speak on the phone usually 2 or 3 times a year when he calls in to order for himself, and his family. It’s always good catching up with those people we have been able to actually meet and talk with enough to form a bit of a personal relationship with over time. For those that actually know us, we try very hard to treat people THE WAY WE’D LIKE TO BE TREATED… with honesty, integrity, and ethics! Helping when possible. During the conversation, one of his questions stuck out: “I heard this doctor guy talking on the radio yesterday about Magnesium & Calcium, and their importance to the body, and I was thinking ‘WOW – that’s what I’ve been taking from MD’s Choice, but do I need to be taking more?’” The answer to that is generally simple: If you are an adult male, don’t have any bone breaking or density issues, no recent bone surgeries, or kidney stone issues: NOPE (for him, in particular, the 2 to 4 capsules a day is likely all your body needs. More won’t harm you (at least with our product), but it won’t likely help you either, if you don’t have a deficiency of those nutrients; and most men don’t.) For other males… if you don’t have bone density or kidney stone or heart issues… if your diet is reasonably consistent and balanced, and your health is generally good, you probably don’t NEED more ‘calcium’ – or this product. However, IF you are a female, especially one with any bone density issues… had three or more children, or are planning to have children, or have either heart or hormone regulation issues, then you likely would benefit from our quality ‘Mag-Cal Plus’ supplement.
However, calcium supplements are as vastly different as ‘transportation.’ Virtually anyone can quickly see and understand the difference between legs, a skateboard, bicycle, car, bus, commercial airplane, and fighter jet… though they are all technically ‘transportation.’ There are at least 17 different forms of calcium, and whether the body can even see or use them, and how much, is equally as different, and important to the reality of biological availability (bio-availability). Knowing THE TYPE is vital to the math, but figuring all that out can be tough, because many manufacturer’s and supplement sales don’t make it easy. Calcium is probably the most surprising and easiest mineral to misunderstand. There are many different forms: carbonate, citrate, and chelate being the three most common forms found. The most common forms on store shelves are generally not the best, most useful, or most bio-available… especially those ‘big box’ stores; but they continue being on store shelves BECAUSE a) people don’t know any better, b) carbonate and citrate are the LEAST EXPENSIVE FORMS TO PRODUCE, and c) those two have the LONGEST SHELF LIFE (seriously, rocks don’t degrade much in plastic containers). Therefore, FORM MATTERS! The next most important factor is that calcium REQUIRES stomach acid to be freed, on the molecular level, in order to even be used by the body. This is especially true when in a tablet or capsule form. When a company combines calcium with an antacid (like Tums® has done), the benefit is the antacid, NOT the calcium! Sure, there is calcium (carbonate) in those chewable tablets, but there is also ANTACID which reduces the acid levels in your stomach (raising the Ph level) and making it very difficult (if not impossible) to break down any nutrients, much less the calcium. Talk about defying logic and marketing misinformation! There are some prenatal products and osteoporosis advertisements that actually suggest pregnant women take Tums® for their calcium content. At least one prenatal formula actually included a roll of Tums® (stating the roll is included for CALCIUM content! Really! Talk about misinformation and lacking the reality of nutritional needs). Why the OB/GYN’s and Nutritionists didn’t doubt EVERYTHING THAT company said, did, presented, also proves that many ‘regular’ doctors either don’t know, or really don’t care, about nutrition! Science has repeatedly proven stomach acid is absolutely necessary for effective calcium uptake and absorption. Our doctors knew in in 1995, yet 25 years later, most supplement companies and general health doctors remain either unaware of these findings or continue to completely disregard them. While ‘form’ of the ‘combination’ of calcium WITH (fill in the blank) is the most vital information you need to know, there are some that claim ‘liquid’ is the best ‘delivery method’ (and ‘form’ to get your calcium in). That is another thing that isn’t always true for a few reasons. Because calcium is heavy, and tends to settle to the bottom in liquid… but more importantly, some of the stuff that is included with the calcium is NOT STABLE IN LIQUID for as long as it is when it’s dry. In general, liquids require refrigeration after being opened and have a shorter shelf life. Of course, that depends on WHAT OTHER nutrients and ingredients are included. But don’t assume that just because it’s liquid it’s some how magically better, it’s usually not.
Co-factors (cooperative nutrition): With nearly all nutrients, there are certain combinations of OTHER nutrients and factors, that make them MORE (or LESS) effective within a body. For Calcium, the form it’s initially in (i.e., type of calcium), the Ph level of the stomach acid are just two of the key factors… next are the addition of certain key nutrients: Magnesium, Boron, Zinc, and Vitamin D. (All key active ingredients to Mag-Cal Plus, already combined in the proper quantities to optimize absorption and function within a mammal’s body, which the doctors & nutritionists with MD’s Choice formulated back in 1998 for Women’s Health Group… and those other people AND ANIMALS in need of supplemental calcium). These co-factors & co-enzymes participate as either ‘carriers’ or ‘the catalysis’ (the process of increasing the rate of a chemical reaction) by adding a substance (electrons or ions) that works with, or helps, the other substance (in this case Calcium) work better, faster, more. These ‘cooperative nutrients help the calcium actually get optimized within your body more efficiently, more completely, and in ways that taking calcium by itself, in whatever form, could never accomplish.
Some other Calcium factoids: It is impossible for more than 250mg of elemental calcium to be in a single capsule or even compressed tablet that can be swallowed by a normal human being (not counting chewable tablets, or sword swallowers). This means that all those products claiming 500mg (or higher) calcium tablets on the market are not really giving a person that much calcium. It’s ‘marketing magic’ and scientifically untrue. So, the question then becomes what actually makes up all those milligrams beyond the 250 and what is the density of everything else INCLUDED IN THAT TABLET or capsule? Take a look below to learn HOW to ‘do the math’ to find out if you can determine exactly how much of a nutrient is actually in a supplement. In the nutritional supplement world, it is truly a “Buyer Beware” and you better seek facts from the right people (that know NUTRITION), or you are going to be wasting money trying to solve problems or maintain health with products that just aren’t doing the job; not to mention the fact that you might actually harm your health because you’re not really giving your body the nutrients it needs! (either not enough of some things, or too much of others) Here are two different ways that the amount of minerals (such as calcium and iron) are listed on bottles: 1. In the combined form (no mineral can be delivered to a body in its pure form), which has the name of the mineral and the name of whatever it is combined with listed after the name of the mineral. Or, 2. The elemental form (the actual amount of the mineral minus whatever it is combined with). You ALWAYS want and need to know what the elemental amount (real amount of the minerals) that you will be ingesting. How do you tell the difference? Well, if the company is dishonest, it is nearly impossible. However, based on the March 1999 FDA labeling regulations, all nutritional supplements are supposed to designate the difference between the two forms. This is still a little challenging, but here are some examples that might help: 1. Combined Form – “Calcium Carbonate…..500mg”. Only about 50mg is actually the calcium, approximately 10% of the carbonate version, but there are 500mg of “Calcium Carbonate” in total in that serving. 2. Elemental Form – “Calcium (as carbonate)…..500mg”. There is actually supposed to be 500mg of calcium, which means that there really are about 5,000mg (or 5g) of the ‘Calcium Carbonate’ to get that elemental amount (500mg). Then, there is: 3. Not Specified – Nothing is stated in the Supplement Facts box. It just says “Calcium” with nothing, or meaningless numbers following some unique name (proprietary formula they claim… which supposedly contains a TOTAL of _____ from either a generic list of ingredients, or just ingredient names listed in the “Other Ingredients” (listed at the bottom of the facts box). Down there, it might say “Calcium _______” (fill in the blank) with the combined form of calcium that supplement uses, but no one can really tell just how much calcium is in the product. It is likely just ‘trace amounts’ OR even more commonly, just a bi-product of something else that it’s counting above (for example dried BROCCOLI contains some calcium, as well as a few other key minerals, vitamins, and antioxidants). Odds are they listed the total combined amount in a ‘proprietary formula’ or are trying to maintain some flexibility in the formula, knowing that it changes from batch to batch. Either way, primary actives are supposed to be listed in nutritional supplements box, and failure violates the March ’99 FDA label regulations. The differences on the science side, are as big as the Grand Canyon; but on the consumer side, are down played, subtle, and even hidden a bit. Until the doctors involved in the start of MD’s Choice, and the formulation of all the key products, pointed it out to be in the 90’s, I would have never understood the real world meaning of these subtle differences. They weren’t taught in my college nutrition courses in the 80’s. Sure, I may have noticed the differences in a side by side label comparison, but I thought it was just a “style thing” different companies did. NOT TRUE! It’s important and something we, as consumers, need to learn & pay attention to if health and nutrition are important to us. Not only is it a real FDA regulation, it is also the main difference real science-based companies employ to designate the differences between the forms of ingredients and calculating formula ratios and balances. It’s akin to the difference between a REAL ROLEX and a cheap knock-off sold on some street corner. One is designed with a specific value, clear functional purpose to really work, and do what it’s supposed to… the other designed just to GET YOUR MONEY, and give warm fuzzies for a short time allowing you to fake it! The two are nothing really alike. They do not serve the same purpose, and their results are nothing alike. It’s not like ‘generic drugs’ vs prescription, which – by law – are both regulated and HAVE TO BE VERY CLOSE TO THE SAME in function, usability, efficacy, and contraindications (side effects, and negative interactions with OTHER drugs or treatments). FORM MATTERS! IT really is important. Without knowing the form, a person CANNOT figure out the actual (elemental) amount of a given ingredient in a product, making it impossible to calculate, much less even approximate, the amount of the actual mineral that is available to your body for actual use. Without knowing the form, it is impossible to make serious educated decisions and ensure you are getting enough (or not too much) of the specific mineral your body needs.
Most blood pressure issues react positively to calcium and magnesium supplementation. Under no circumstances should ANYONE stop taking their prescription medication without their doctors’ knowledge, as their doctor has done many tests and knows the individual patient’s medical history. However, there are many (over a thousand) studies that show increasing calcium and magnesium intake (in the proper forms) can help the body maintain a healthier state of being and better regulate the blood pressure levels. Magnesium & Zinc are also key to proper cardio support, and we do have an amino acid chelated (AAC) Magnesium product that can really help most people. It might be worth talking to your doctor about.
Mood swings and PMS are just part of life, and all women have to deal with that. Not True! This is another thing that is only fractionally true. Calcium, magnesium, boron, and zinc can definitely have dramatically positive effects on women suffering from such chemical imbalances. There is a whole lot of real science on those topics, and we’ve personally experienced it with our family, friends, and clients for over 25 years!
Kidney Stones are NOT caused by too much calcium, like many of us were told growing up. They are actually caused by not having enough calcium in your diet (food and supplementation). So, if you have an issue with getting Kidney Stones, odds are you are either NOT GETTING enough of the right type of calcium OR you are eating something that is leaching the calcium from your bones, and having your body think it needs to store calcium some place other than your bones for future use. The following are some scientific abstracts (research results) that might help you understand the importance of nutrition to your body, and life. We broke out many on the topic of Calcium to help those looking for more specific information. https://www.mdschoice.com/articles/research.php
The doctors formulated the “MAG-CAL PLUS” product to specifically address the body’s needs. Combining the correct nutrients, in forms the body can readily use and benefit from. Further, these Mag-Cal Plus capsules aren’t just for people… as they’ve been used by veterinarians to help speed the healing process in dogs, cats, and other mammals that have had broken bones, bone surgery, or other issues requiring these special nutrients. (which are discussed in the Why Supplement? article) If you have any questions, please feel free to ask; and we’ll try to help get you an answer. I know I’ve said this before, but when we are asked the same questions by different people, we try to write up an article, add or adjust a web page, or otherwise create some type of document so many others can see the generic answer and hopefully benefit also. THANK YOU to those that bother to read these emails, our websites, and those that offer help & make suggestions. Education & quality information has been one of our primary goals since 1995. We sincerely appreciate the interaction, and try to respond to all calls and emails in a timely fashion. If ever you don’t hear back from us with 72 hours, PLEASE REMIND US. Odds are we are either looking up or searching out the answers, or the confirmation for the correct answer, or you’ve sadly fallen through the proverbial cracks for some reason. Maybe it was a busy order fulfillment or government inspection day, or something needed repaired, or else required our immediate attention. Orders and phone calls nearly always come first… with emails next.
If you read our last email, the following is just a reminder: We sincerely hope the information we share, and the doctors we’re able to get answers from, can help those of you bothering to read, listen, and interact with us. Our team is here, ready to serve and answer questions when we can; however, we are NOT A REPLACEMENT FOR YOUR DOCTOR, but here to help supplement them in their treatment protocols. We will continue to do things to the best of our ability, and will always hope everyone is doing well. Our ‘products’ are for joints, bones, digestion, and general broad-spectrum health. We have been SHIPPING our product TO doctors, clinics, pharmacies, and customers all around the USA since 1998, and continue doing so on a daily basis.
If you order something you normally get from us before 3pm EST, know that it will usually be processed the same business day, or the next business day. In general, orders of 1 to 12 bottles, or shipments under 20 pounds total, will ship USPS (Postal Service), heavier orders will ship UPS or by semi-truck (if pallets are required). We prefer to ship in quantity to resellers, but if we don’t have a reseller in your area let us know. If you help us get one started by referral or other means, you can earn a rewarded for your help. If you are curious what we have, you can find a list of our most common products at www.VetSupplements.com or www.mdschoice.com You are welcome to call, email, or contact us if you have any questions… or are looking for a reseller in your area. For all those that have emailed, called, and ordered over the last month… THANK YOU. Warmest Regards, Best Wishes… and Stay Safe… Terry Mercer, MD’s Choice, Inc.
- To Find a Reseller Near You, Please Call Us
- M-F, 10am to 6pm, Eastern Time, at 1-865-380-0950
- or send us an email at: FindReseller@VetSupplements.com
Proper Dosing is important to us, and dosing can vary, depending on a few individual factors: age, weight, height, location (of problem), severity, other medication & medically recommended treatment, goals, and care. If the use is helping supplement nutritional needs, or the problems are moderate, effective dosing is on the label. However, IF there are more serious issues, and pain/or is evident, PLEASE CONSULT YOUR DOCTOR or CALL US FOR OPTIMUM DOSING.
Note: The following abstracts are written in extremely technical language and include technical research and case studies. References are provided. For 'user-friendly' informative reading, check out the health topics presented by Dr. Martin and Dr. Davenport. Feel free to contact us for more information or if you have any questions.
Calcium intake: covariates and confounders
One common nutrient postulated to be protective against osteoporosis, hypertension, and colon cancer is dietary calcium. We report here nutrient patterns by calcium intake in older adult residents of a geographically defined community in Southern California. The analysis included all 426 men and 531 women aged 50-79 y with complete 24-h diet data. Nutrient-density-adjusted calcium intake was divided into tertiles: low intake (less than 284 mg/1000 kcal), mid intake (284-440 mg/1000 kcal), and high intake (greater than 440 mg/1000 kcal). The distribution of the reported 24-h nutrient density of protein, fat, fiber, caffeine, trace minerals, vitamin D, and vitamin C was examined in relation to the calcium-intake tertiles. In both men and women, the adjusted intakes of protein, saturated fatty acids, vitamin D, magnesium, and phosphorus were significantly higher in the high-calcium-intake group than in the low- and mid-calcium-intake groups. In both men and women, alcohol intake was significantly lower in the high-calcium-intake group. Studies postulating a protective role for calcium will need to consider the multicolinearity in the Western diet.
Holbrook-TL; Barrett-Connor-E
Am-J-Clin-Nutr. 1991 Mar; 53(3): 741-4
Relationship between vitamin and calcium supplement use and colon cancer
The relationship between vitamin supplement use and colon cancer was assessed in a population-based case-control study among men and women aged 30-62 years. Cases were 251 men and 193 women diagnosed with colon cancer in 1985-1989 in three counties in the Seattle metropolitan area who were identified from the Surveillance, Epidemiology, and End Results cancer registry. Controls were 233 men and 194 women identified by random digit dialing. Supplement use was assessed by questions on frequency, duration, and dose per day (for individual supplements) or type (for multivitamins) during the 10-year period ending 2 years before diagnosis. All results were adjusted for age and sex and were not confounded by other measured behaviors. The average daily intake of supplemental vitamins A, C, E, folic acid, calcium, and multivitamins during the reference period were each associated with reduced risk of colon cancer (all P for trend < 0.03). The strongest associations were for use of vitamin E (odds ratio, 0.43; 95% confidence interval, 0.26-0.71 for > or = 200 IU/day versus none) and multivitamins (odds ratio, 0.49; 95% confidence interval, 0.35-0.69 for daily use versus no use; both P for trend < 0.001). These two associations were also significant using a stricter test of trend limited to supplement users, which reduces the effect of colinearity among these exposures. Because almost all vitamin D supplementation comes from multivitamin pills, the association of vitamin D use with colon cancer could not be distinguished from that of multivitamin use. Clinical trials or cohort studies with long-term assessment would be needed before public health recommendations could be made about supplement use.
White-E; Shannon-JS; Patterson-RE
Cancer-Epidemiol-Biomarkers-Prev. 1997 Oct; 6(10): 769-74
Pharmacologic prevention of colonic neoplasms. Effects of calcium, vitamins, omega fatty acids, and nonsteroidal anti-inflammatory drugs
Dietary supplements of calcium, vitamins A, C, and E, carotenoids, and omega-3 fatty acids can reduce the yield of experimental cancers in animals and reverse the pattern of abnormal epithelial proliferation in animals and humans. Epidemiological studies indicate that diets containing high amounts of these agents convey a protective effect against the development of colon cancer. Moreover, regular aspirin use in humans appears to reduce the risk of colon cancer and sulindac causes regression of polyps in patients with familial polyposis. These agents are promising for the prevention of human colorectal cancer, but their efficacy has not yet been shown in prospective, controlled trials. Thus, although it is tempting to speculate that in the future we may treat our patients who have a predisposition to colon polyps and cancer, or even healthy people at average risk, with such ordinary supplements as calcium, vitamins, fish oil, or aspirin, such advice at this time is premature.
Eastwood-GL
Dig-Dis. 1996 Mar-Apr; 14(2): 119-28
Calcium supplementation modifies the relative amounts of bile acids in bile and affects key aspects of human colon physiology
Use of calcium supplements has increased dramatically in recent years yet little is known about the effect of calcium supplementation on colon physiology. We supplemented 22 individuals with a history of resected adenocarcinoma of the colon, but currently free of cancer, with 2000 or 3000 mg calcium for 16 wk. The effects of supplementation on duodenal bile acids and important fecal characteristics including total fecal output, wet and dry weight, pH, bile acids (in solids and in fecal water), and concentrations and total excretion of calcium, magnesium, phosphates (organic and inorganic), unesterified fatty acids and total fat were determined. Calcium supplementation significantly decreased the proportion of water in the stool (P = 0.03), doubled fecal excretion of calcium (P = 0.006), and increased excretion of organic phosphate (P = 0.035) but not magnesium. Calcium supplementation significantly decreased the proportion of chenodeoxycholic acid in bile (P = 0.007) and decreased the ratio of lithocholate to deoxycholate in feces (P = 0.06). The concentration of primary bile acids in fecal water decreased after 16 wk Ca supplementation. Together with other reports of a "healthier" bile acid profile with respect to colon cancer when changes such as those observed in this study were achieved, these results suggest a protective effect of calcium supplementation against this disease.
Lupton-JR; Steinbach-G; Chang-WC; O'Brien-BC; Wiese-S; Stoltzfus-CL; Glober-GA; Wargovich-MJ; McPherson-RS; Winn-RJ
J-Nutr. 1996 May; 126(5): 1421-8
Randomized, double-blinded, placebo-controlled study of effect of wheat bran fiber and calcium on fecal bile acids in patients with resected adenomatous colon polyps
BACKGROUND: Ongoing epidemiologic and nutritional studies suggest that colorectal carcinogenesis is consistent with complex interactions between genetic susceptibility and environmental and dietary factors. Among the dietary components found to reduce colon cancer risk are high intakes of dietary fiber and calcium. PURPOSE: We designed and conducted a randomized, double-blinded, placebo-controlled trial involving supplementation of the customary dietary intake with fiber and calcium and measurements of fecal bile acids to examine the potential mechanisms by which added dietary interventions might reduce colorectal cancer risk. METHODS: In a randomized, double-blinded, phase II study, we used a factorial design to measure the effects of dietary wheat bran fiber (2.0 or 13.5 g/day) in the form of cereal and supplemental calcium carbonate (250 or 1500 mg/day elemental calcium) taken as a tablet on fecal bile acid concentrations and excretion rates. Measurements were made at base-line randomization (i.e., after a 3-month placebo run-in period using 2.0 g wheat bran fiber plus 250 mg calcium carbonate) and after 3 and 9 months on treatment in a randomly selected 52-patient subsample of the 95 fully assessable study participants who had a history of colon adenoma resection. Concentrations of fecal bile acids, total, primary (i.e., chenodeoxycholic and cholic), and secondary (i.e., deoxycholic, lithocholic, and ursodeoxycholic), were measured in 72-hour stool samples by gas-liquid chromatography. All P values resulted from two-sided tests. RESULTS: All geometric mean fecal bile acid concentrations and excretion rates were lower at 9 months than at 0 months or 3 months on treatment in the high-dose fiber, high-dose calcium, and high-dose fiber/high-dose calcium treatment groups. The high-dose fiber effect at 9 months of supplementation was statistically significant with respect to virtually all geometric mean fecal bile acid concentrations and excretion rates. For example at 9 months versus 0 months, high-dose fiber supplementation caused a reduction in fecal concentrations of total bile acids (52% reduction; P = .001) and deoxycholic acid (48% reduction; P = .003). High-dose calcium supplementation also had a significant, but lower, effect at 9 months versus 0 months on the geometric mean total bile acid (35% reduction; P = .044) and deoxycholic fecal bile acid (36% reduction; P = .052) concentrations. CONCLUSIONS: High-dose wheat bran fiber and calcium carbonate supplements given for 9 months are associated with statistically significant reductions in both total and secondary fecal bile acid concentrations and excretion rates in patients with resected colon adenomas. This study supports the hypothesis that one of the important ways in which a high intake of wheat bran fiber and calcium may reduce the risk of colorectal neoplasia and cancer is by reduction of the concentrations of fecal bile acids. IMPLICATION: Phase III studies of these agents in the prevention of adenoma recurrence are necessary to confirm this hypothesis and have now been initiated at multiple institutions.
Alberts-DS; Ritenbaugh-C; Story-JA; Aickin-M; Rees-McGee-S; Buller-MK; Atwood-J; Phelps-J; Ramanujam-PS; Bellapravalu-S; Patel-J; Bextinger-L; Clark-L
J-Natl-Cancer-Inst. 1996 Jan 17; 88(2): 81-92
Calcium supplementation
Calcium is necessary for the prevention and treatment of diseases such as osteoporosis, hypertension, and, possibly, colon cancer. Supplementation is useful when dietary calcium intake is low, as is the current situation in North America. There are many factors to consider before recommending any one form of supplement. A consideration for calcium carbonate tablets is whether the tablet disintegrates and whether or not a lack of food or acid in the stomach will hinder utilization. Other forms of calcium, particularly the chelated calcium salts, are better absorbed in fasting achlorhydric subjects but have less calcium per gram of supplement. Interaction of calcium with other mineral nutrients and the presence of contaminating metals has focused attention on safety. Based on present evidence, chelated calcium and refined calcium carbonate tablets (including those labeled as antacids) may be safely and effectively ingested by most people at doses generally recommended for treatment or prevention of osteoporosis. One should not exceed 2,000 mg of calcium, except at the advice of their health care provider, as inadvertent mineral deficiencies may arise. Persons at risk for developing milk-alkali syndrome, such as thiazide users and persons with renal failure, should be identified and monitored for alkalosis and hypercalcemia when using calcium supplements.
Whiting-SJ; Wood-R; Kim-K
J-Am-Acad-Nurse-Pract. 1997 Apr; 9(4): 187-92
Calcium supplementation and prevention of pregnancy induced hypertension
In a randomized controlled trial 201 healthy nulliparous women were randomly allocated by means of a computer generated randomization list. From 20 weeks of gestation until delivery they received either 2 g of oral elemental calcium (n = 103) per day or an identical placebo (n = 98). Eleven women (5.47%) were lost to follow-up after randomization. The study groups were very similar at the time of randomization; with respect to several clinical and demographic variables. Treatment compliance was very similar in both groups as was determined by pill count. The rate of pregnancy induced hypertension was lower in the calcium group than in the placebo group 8.24%; vs 29.03%; (RR = 0.28; 95% CI 0.14-0.59). The incidence of gestational hypertension was 6.18% in the calcium group and 17.20% in the placebo group (RR = 0.28; 95% CI 0.08-0.80), and the incidence of preeclampsia was 2.06% in the calcium group and 11.82% in the placebo group (RR = 0.13; 95% CI 0.01-0.64). In conclusion calcium supplementation given in pregnancy to nulliparous women reduces the incidence of pregnancy induced hypertension.
Purwar-M; Kulkarni-H; Motghare-V; Dhole-S
J-Obstet-Gynaecol-Res. 1996 Oct; 22(5): 425-30
Reversal of hypertension and endothelial dysfunction in deoxycorticosterone-NaCl-treated rats by high-Ca2+ diet
We tested the effect of high-Ca2+ diet on blood pressure and responses of mesenteric arterial rings in vitro in established deoxycorticosterone (DOC)-NaCl hypertension. Ca2+ supplementation (2.5%) of Wistar rats, which was commenced 8 wk after initiation of DOC-NaCl treatment (Ca(2+)-DOC group), reversed the development of hypertension, whereas in animals ingesting a normal diet (1.1% Ca2+; DOC group) blood pressure continued to rise until the end of the 12-wk study. In norepinephrine-precontracted arterial rings, relaxations to acetylcholine (ACh) and sodium nitroprusside were attenuated in the DOC group, but these responses were significantly improved by Ca2+ supplementation. The nitric oxide (NO) synthesis inhibitor NG-nitro-L-arginine methyl ester, in the presence of diclofenac, totally abolished ACh-induced relaxations in the DOC group but only attenuated them in the Ca(2+)-DOC group. The remaining relaxation was further inhibited by apamin, an inhibitor of Ca(2+)-activated K+ channels, and practically abolished after blockade of ATP-dependent K+ channels by glyburide. Interestingly, when endothelium-dependent hyperpolarization was prevented using precontractions induced by KCl, no differences were found in relaxations to ACh between the groups. In conclusion, high-Ca(2+) diet effectively reduced blood pressure in DOC-NaCl hypertension and concomitantly enhanced arterial relaxation. Because the relaxations to ACh in the Ca(2+)-DOC group were augmented in the absence and presence of NO synthesis inhibition but not under conditions of prevented hyperpolarization, these enhanced relaxations could be attributed to promoted endothelium-dependent hyperpolarization in the Ca(2+)-supplemented animals.
Makynen-H; Kahonen-M; Wu-X; Wuorela-H; Porsti-I
Am-J-Physiol. 1996 Apr; 270(4 Pt 2): p250-7
High calcium diet reduces blood pressure in exercised and nonexercised hypertensive rats
The effects of long-term high calcium diet and physical exercise and their combined effects on the development of hypertension, plasma and tissue atrial natriuretic peptide, and arterial function were studied in spontaneously hypertensive rats with Wistar-Kyoto rats serving as normotensive controls. Hypertensive rats were made to exercise by running on a treadmill up to 900 m/day. Calcium supplementation was instituted by increasing the calcium content of the chow from 1.1% to 2.5%. During the 23-week study, calcium supplementation attenuated the rise in blood pressure in both trained and nontrained hypertensive animals, whereas exercise training had no significant effect on blood pressure. The high calcium diet alone was associated with reduced plasma and ventricular tissue contents of atrial natriuretic peptide, both of which were increased by exercise. Responses of mesenteric arterial rings in vitro were examined at the end of the study. Neither increased dietary calcium nor endurance training affected the contractile sensitivity of endothelium-intact preparations to potassium chloride or norepinephrine. However, a high calcium diet enhanced the arterial relaxation induced by the return of potassium to the organ bath upon precontraction with potassium-free solution, and also moderately augmented relaxations to acetylcholine, sodium nitrite, and isoproterenol. Exercise training did not affect the potassium relaxation rate, but enhanced responses to acetylcholine, isoproterenol, and sodium nitrite. In conclusion, enhanced arterial potassium relaxation, a response reflecting the function of the vascular sodium pump, paralleled well the long-term blood pressure lowering action of increased dietary calcium intake in exercised and nonexercised hypertensive rats. However, augmented arterial relaxation to agonists could also be observed in the absence of reduced blood pressure following regular physical exercise.
Sallinen-K; Arvola-P; Wuorela-H; Ruskoaho-H; Vapaatalo-H; Porsti-I
Am-J-Hypertens. 1996 Feb; 9(2): 144-56
Cardiovascular effect of oral calcium supplementation: echocardiographic study in patients with essential hypertension
Oral calcium (Ca) supplementation mildly reduces blood pressure. The authors studied the effects of Ca supplementation on the cardiovascular system in patients with mild to moderate essential hypertension. Twelve patients aged forty-nine to seventy years (7 men and 5 women, mean age with 60.3 +/- 7.2 years) participated. The investigators orally administered Ca (1.0 g/day for one week) under hospitalization, adding to a dietary intake of Ca (0.6 g/day). Left ventricular function and systemic arterial compliance were evaluated by M-mode and pulsed Doppler echocardiographies before and after seven days of Ca supplementation. Left ventricular contractility and afterload were not changed. Preload indicated by end-diastolic volume was significantly decreased after Ca supplementation (109.6 +/- 8.5 vs 107.3 +/- 8.2 mL, P < 0.05). Myocardial relaxation evaluated by IIa-mitral valve opening time (87.7 +/- 6.7 vs 82.1 +/- 6.2 ms, P < 0.01) and maximum descending rate of the left ventricular posterior wall (10.6 +/- 1.0 vs 12.4 +/- 1.0 cm/s, P < 0.01), and atrioventricular net compliance assessed by the descending slope of rapid filling flow in the left ventricular inflow tract (2.63 +/- 0.24 vs 2.26 +/- 0.17 m/s2, P <0.05), as well as systemic arterial compliance (2.05 +/- 0.20 vs 2.73 +/- 0.26 mL/mmHg, P < 0.01) were significantly improved by Ca supplementation. Oral Ca supplementation improved the disturbed left ventricular diastolic function and systemic arterial compliance.
Dazai-Y; Kohara-K; Iwata-T; Sumimoto-T; Hiwada-K
Angiology. 1996 Mar; 47(3): 273-80
Effect of calcium supplementation on pregnancy-induced hypertension and preeclampsia: a meta-analysis of randomized controlled trials
OBJECTIVE: To review the effect of calcium supplementation during pregnancy on blood pressure, preeclampsia, and adverse outcomes of pregnancy. DATA SOURCE: We searched MEDLINE and EMBASE for 1966 to May 1994. We contacted authors of eligible trials to ensure accuracy and completeness of data and to identify unpublished trials. STUDY SELECTION: Fourteen randomized trials involving 2459 women were eligible. DATA EXTRACTION: Reviewers working independently in pairs abstracted data and assessed validity according to six quality criteria. DATA SYNTHESIS: Each trial yielded differences in blood pressure change between calcium supplementation and control groups that we weighted by the inverse of the variance. The pooled analysis showed a reduction in systolic blood pressure of -5.40 mm Hg (95% confidence interval [CI], -7.81 to -3.00 mm Hg; P<.001) and in diastolic blood pressure of -3.44 mm Hg (95% CI, -5.20 to -1.68 mm Hg; P<.001). The odds ratio for preeclampsia in women with calcium supplementation compared with placebo was 0.38 (95% CI, 0.22 to 0.65). CONCLUSIONS: Calcium supplementation during pregnancy leads to an important reduction in systolic and diastolic blood pressure and preeclampsia. While pregnant women at risk of preeclampsia should consider taking calcium, many more patient events are needed to confirm calcium's impact on maternal and fetal morbidity.
Bucher-HC; Guyatt-GH; Cook-RJ; Hatala-R; Cook-DJ; Lang-JD; Hunt-D
JAMA. 1996 Apr 10; 275(14): 1113-7
Effects of dietary calcium supplementation on blood pressure. A meta-analysis of randomized controlled trials
OBJECTIVE: To review the effect of supplemental calcium on blood pressure. DATA SOURCE: We searched MEDLINE and EMBASE for 1996 to May 1994. We contacted authors of eligible trials to ensure accuracy and completeness of data and to identify unpublished trials. STUDY SELECTION: We included any study in which investigators randomized people to calcium supplementation or placebo and measured blood pressure for at least 2 weeks. Fifty-six articles met the inclusion criteria, and 33 were eligible for analysis, involving a total of 2412 patients. DATA EXTRACTION: Two pairs of independent reviewers abstracted data and assessed validity according to six quality criteria. DATA SYNTHESIS: We calculated the differences in blood pressure change between the calcium supplementation group and the control group and pooled the estimates, with each trial weighted with the inverse of the variance using a random-effects model. Predictors of blood pressure reduction that we examined included method of supplementation, baseline blood pressure, and the methodological quality of the studies. The pooled analysis showed a reduction in systolic blood pressure of -1.27 mm Hg (95% confidence interval [CI], -2.25 to -0.29 mm Hg; P=.01) and in diastolic blood pressure of -0.24 mm Hg (95% CI, -0.92 to 0.44 mm Hg; P=.49). None of the possible mediators of blood pressure reduction explained differences in treatment effects. CONCLUSIONS: Calcium supplementation may lead to a small reduction in systolic but not diastolic blood pressure. The results do not exclude a larger, important effect of calcium on blood pressure in subpopulations. In particular, further studies should address the hypothesis that inadequate calcium intake is associated with increased blood pressure that can be corrected with calcium supplementation.
Bucher-HC; Cook-RJ; Guyatt-GH; Lang-JD; Cook-DJ; Hatala-R; Hunt-DL
JAMA. 1996 Apr 3; 275(13): 1016-22
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