Archive for the ‘Calcium’ Category

Calcium Supplements and Cardiovascular Disease in the News

Monday, March 4th, 2013

In 2010, I wrote about a meta-analysis on calcium supplements and cardiovascular disease, Calcium Supplements: Are They Safe? The association with heart disease was limited to people who started out with a dietary calcium intake of 700 mg/day or more (not including the supplements). Then in 2011, I noted a study on supplement use in older women that found a link between calcium supplements and a lower risk of mortality (Supplement Safety).

Since I recommend that vegans get their calcium levels up to at least 700 mg and preferably the DRI (1,000 mg for adults under 50; 1,200 mg for adults over 50) by whatever means necessary (greens, fortified foods, or supplements), I try to keep track of this research as closely as I can. In February, results from two different studies looking at calcium supplements and cardiovascular disease were reported.

One study was from the USA and followed people aged 50 to 71 at baseline for 12 years (1). No association between cardiovascular disease deaths and calcium intake was found for women. For men, calcium supplements of 400 to 1,000 mg/day was associated with an increased risk of cardiovascular death, but was just barely statistically significant. But supplements of more than 1,000 mg/day were associated with a highly significant increase in cardiovascular mortality:

(mg/day)  
None 1.00
< 400 .99 (.94-1.04)
400–1,000 1.09 (1.01-1.18)
> 1,000 1.20 (1.05-1.36)

When the numbers were stratified for smoking, there was a strong trend towards the risk being mainly in current smokers. The average user of supplements for men had a dietary calcium intake (not including supplements) of 815 mg. So once you figure in another 400 to 1,000+ mg of supplemental calcium, their intakes were anywhere from the DRI to about 50% higher than the DRI.

The second study was from Sweden, on older women (2). All-cause mortality for dietary calcium (not including supplements) was a U-shaped curve, with both low calcium and high calcium associated with an increase in mortality:

(mg/day)  
< 600 1.38 (1.27, 1.51)
600-999 1.00
1000-1399 1.00 (.96-1.04)
≥ 1,400 1.40 (1.17-1.67)

The findings were similar, but even stronger for cardiovascular disease, and were also very similar for dietary plus supplemental calcium.

One thing to consider for this Swedish study is that 1,400 mg of non-supplemental calcium would indicate a pretty high dairy intake. If you assume 300 mg per serving of dairy, that’s at least 3 servings of dairy per day (on top of the calcium they might be getting from other foods). The results did not adjust for dairy product intake so it’s possible that dairy of 3 servings (or more) per day could have caused the increase in cardiovascular deaths.

While it’s not yet clear what is going on here, my conclusion remains that vegans should aim for at least 700 to 1,000 mg/d (or 700 to 1,200 mg/d if over 50) from foods or supplements, but that you should not go much above that.

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References

1. Xiao Q, Murphy RA, Houston DK, Harris TB, Chow W, Park Y. Dietary and Supplemental Calcium Intake and Cardiovascular Disease Mortality: The National Institutes of Health–AARP Diet and Health Study. JAMA Intern Med. 2013;():1-8. | link

2. Michaëlsson K, Melhus H, Warensjö Lemming E, Wolk A, Byberg L. Long term
calcium intake and rates of all cause and cardiovascular mortality: community
based prospective longitudinal cohort study. BMJ. 2013 Feb 12;346:f228. | link

Does (Animal) Protein Leach Calcium from Bones?

Monday, February 25th, 2013

[Thank you for all the responses to my request for information on increasing bone mineral density! I received a lot of responses and am still working my way through them.]

Because I’m planning to write a more reader-friendly version of VeganHealth.org’s Bones, Vitamin D, and Calcium, I decided to check in on the research on protein and bone health. In so doing, I found a 2012 review from a group of researchers in France who declared having no conflicts of interest (1).

There has been an enormous amount of research on protein and bone health and their review had almost 4 pages of references. I will hit the highlights of what they found:

– Many clinical trials show that adding purified proteins to the diet increases calcium excretion through the urine.

– Phosphorus, in which meat and dairy are rich, counteracts the increase of calcium in the urine between 40 and 65%.

– Findings that older people in Western countries have higher hip fracture rates are confounded by the fact that people in Western countries live longer, protein intakes were not estimated for individuals, and there are ethnic differences in bone structure and lifestyles.

– High protein diets increase acid excretion in the urine, but this can be handled by the body’s acid buffer system without the need for calcium.

– Studies measuring whole-body calcium balance (as distinct from excretion) in relation to high protein diets have been mixed, but this might partly be due to the difficulty in measuring calcium balance and because high protein diets might reduce calcium balance when calcium intakes are particularly low.

– In low-calcium, but not high-calcium diets, higher protein intakes probably increase calcium absorption from the digestive tract causing an increase in calcium excretion in the urine.

– Fruits and vegetables are beneficial to bone health, probably due to their high potassium and magnesium content. This could cause confounding in protein studies because diets high in protein are often low in fruits and vegetables.

– As I describe in my post Protein Intake and Bone Health, Darling et al. (2009) found that a large majority of the cross-sectional surveys and cohort studies have reported either no association or a beneficial association between protein and bone mineral density.

– There is some evidence that a beneficial effect of protein on bones is only seen when calcium intake and vitamin D status is adequate.

– Maintenance of adequate bone strength and density with aging is dependent on adequate muscle mass which is dependent on adequate intake of protein.

– An increase in IGF-1 is most likely the mechanism for increased bone health with higher protein intakes.

They conclude, “Although HP [high protein] diets induce an increase in net acid and urinary calcium excretion, they do not seem to be linked to impaired calcium balance and no clinical data support the hypothesis of a detrimental effect of HP diet on bone health, except in the context of inadequate calcium supply.”

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Reference

1. Calvez J, Poupin N, Chesneau C, Lassale C, Tomé D. Protein intake, calcium balance and health consequences. Eur J Clin Nutr. 2012 Mar;66(3):281-95. | link

Calcium in Selected Plant Foods

Monday, November 12th, 2012

I noticed that the new USDA nutrient database seemed to have changed the amounts of calcium in some of the greens they had listed. I have updated Table 5 in Bones, Vitamin D, and Calcium at VeganHealth.org.

The USDA database lists a number of different versions for foods – for each type of greens, for example, there are a half dozen to a dozen entries. In the past, I’ve tried to take the most usual or average them out. This time, in updating Table 5, I used the exact entry and I included a number of entries for some of the foods.

Unfortunately, the amount of calcium in broccoli was lowered from 50 to 31 mg per serving. Other greens seemed to stay about the same.

Calcium and Stress Fractures in Adolescent Girls

Friday, April 20th, 2012

From March 20, 2012:

I was wondering if you saw this study [showing that increased vitamin D intake, but not increased dairy and calcium, protected adolescent girls against stress fractures] that went around yesterday, and saw PCRM’s release on it. I only read the abstract, but didn’t see that higher intakes of calcium was correlated with higher risk of bone fracture. I was wondering what you thought about this, because I remember you referencing some studies showing that vegans have higher rates of bone fracture, and that the difference went away when the vegans had high enough intakes of calcium. Was that because they were getting the calcium from plant sources, you reckon?

Answer:

It is only one study (EPIC-Oxford, 2007) showing vegans to have a higher fracture rate, the only study measuring fracture rates in Western vegans. It showed that the category of vegans getting less than 525 mg/day of calcium had a higher fracture rate than other diet groups, but that vegans getting more calcium had the same rate.

I did see PCRM’s press release on this study and have since obtained a copy of the paper. Although not mentioned in the abstract, the study found a trend towards increased risk of stress fracture with increased calcium intakes, among girls in the high impact activity category, though the finding was not statistically significant.

These results have little bearing, one way or the other, on my recommendations that vegans get more than 525 mg/day of calcium (and preferably 700 – 1,000 mg/day). The lowest category of calcium intake was 541 mg/day. The second lowest was 825 mg/day and that category didn’t have a practically different risk compared to the lowest category. It wasn’t until the middle category of calcium intake, an average of 1,111 mg per day, that there was a strong trend towards higher risk of stress fracture (though, again, it wasn’t statistically significant).

Here are some excerpts from the paper’s discussion:

“Our findings are not consistent with those reported in a prospective study of 125 young adult female competitive distance runners, which found that higher intakes of calcium and dairy products predicted lower rates of stress fracture and that higher intakes of vitamin D, calcium, and dairy foods were all associated with significant gains in hip bone mineral density during the 2 years of follow-up.

“Our findings are supported by several studies that have found no association between dairy intake and bone health in children and adolescents. While 2 randomized trials reported a positive relationship between dairy product consumption and measures of bone health, most cross-sectional, retrospective, and prospective studies did not. A review of calcium intake, dairy product intake, and bone health found that the vast majority of controlled studies of dairy supplementation or total dietary calcium intake show that, although very low calcium intake may be harmful to bone development, increases in dairy or total dietary calcium intakes higher than 400 to 500 mg/d are not correlated with nor represent a predictor of bone mineral density or fracture rate in children or adolescents.”

The evidence appears to be mixed as to whether calcium intakes higher than 400 to 500 mg in children and adolescents is protective, harmful, or neutral. EPIC-Oxford remains the most important finding for vegans.

Reference

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. 2012 Mar 5. [Epub ahead of print] | link

Do greens lose calcium from cooking?

Friday, April 6th, 2012

Edited Question:

I buy 3 lbs of collards every week (lots of cabbage and broccoli as well). I don’t like them raw, so I steam them for about 15-20 minutes. Is the calcium content of leafy vegetables greatly reduced from cooking/overcooking? Do I overcook my greens? I have no idea about how long I need to steam them. I simply follow the instructions of the steaming machine’s manual. As I don’t wish to lose too much nutrition, can you please tell me if I’m overdoing my greens?

Answer:

If you compare raw collards to boiled and drained collards at PeaCounter.com, you will see that they have, respectively, 4.8 and 5.4 mg of calcium per calorie. In this case, cooking the collards miraculously increased their calcium! I think it’s safe to assume this was from variance among batches of collards.

If you compare raw kale to boiled and drained kale, you will see that they have, respectively, 2.7 and 2.6 mg of calcium per calorie.

So, it appears that cooking greens results in only negligible calcium loss, if any.

15-20 minutes seems rather long to cook collards, but steaming can take longer than steeping (which is what I do), so I’m not sure. You could try steaming for 10 minutes to see if that’s long enough.

Calcium Recommendations and Prostate Cancer

Wednesday, April 4th, 2012

Do you have any thoughts on the possible risk of prostate cancer from higher calcium intakes? In this study it seems unrelated to the animal/vegetable source, particularly for men with low BMI: cancerres.aacrjournals.org/content/70/12/4941.long

Those findings seem fairly weak. Back in 2003, I reviewed all the research on dairy and prostate cancer and it appeared that there might be a correlation, particularly in colder climates. There was a suspicion that it could be due to higher calcium intakes depressing vitamin D levels which in turn cause prostate cancer. I haven’t followed the research carefully since then.

But, in any case, I recommend 700 to 1,000 mg per day for vegans and that upper limit is the RDA so I do not think, and not that you were suggesting this, that I am endangering men with prostate cancer by suggesting such an amount.

Prehistoric Calcium Intakes

Sunday, April 1st, 2012

Question I received:

[I]t has always bugged me that the fact that humans need to consume other animal’s milk to meet their calcium requirements seems to be evolutionarily illogical or odd. As you said vegans and people who do not eat diary have a lower calcium intake and are in the deficiency range, yet this somehow doesn’t make sense to me from a philosophical point of view….I wonder, have there been studies on vegan children and their calcium requirements? Are they lower than their non-vegan counter-parts?

On average, vegans have lower calcium intakes, with studies showing average intakes well below the RDA of 1,000 mg. But a vegan diet can have a much higher calcium intake if the person eats large amounts of greens every day. It’s just that most vegans do not eat this many greens (at least 3 servings per day of collards, kale, broccoli, mustard greens, turnip greens, or bok choy). And, of course, a vegan eating fortified foods would have higher calcium intakes.

Prehistoric human diets may have contained much larger amounts of calcium than what the average vegan gets without consuming dairy. I spent a few minutes looking around for this information today and the most recent source I could find was a paper by Eaton & Nelson from 1991. They conclude that “Stone Agers” consumed 1500 mg/day of calcium or more without dairy (1). It is a free download so if you are real interested you can take a look at the various foods that provided calcium.

To further complicate this question, sodium can cause significant loss of calcium from bones and there is evidence that our prehistoric ancestors did not consume anywhere close to as much sodium as the average person does today, which could result in a higher RDA than otherwise necessary.

All that said, there are a tremendous number of differences between modern and prehistoric lifestyles, and our ability to study prehistoric diets is rather limited, so I do not put much importance on using diets of our ancestors in order to shed much light on how we need to eat today for optimal health. And just because they might have had calcium intakes of 1500 mg, doesn’t mean that was the ideal amount even for them.

Unfortunately, there have not been any studies on the bone health of vegan children, though, anecdotally, I’m not aware of any vegan children with bone problems.

References

1. Eaton SB, Nelson DA. Calcium in evolutionary perspective. Am J Clin Nutr. 1991
Jul;54(1 Suppl):281S-287S. | link

Acid Not Linked to Calcium Loss

Friday, September 2nd, 2011

I’ve been reviewing the scientific literature on protein and bone health. As many readers know, there has been a theory that animal protein, by way of increased sulfur amino acids, causes calcium excretion leading to osteoporosis. This theory was always on shaky ground and more recent evidence has contradicted the theory. I just read a meta-analysis on the subject and added the following to the article, Bones, Vitamin D, and Calcium, on VeganHealth.org:

“Another 2009 meta-analysis found that among five well-designed studies measuring calcium balance, net acid excretion was not associated with either decreased calcium balance or a marker of bone deterioration (48).”

The paper had an interesting list of cohort studies in the discussion:

“First, during 8 yr of follow-up, fracture risk was not reduced among a cohort of 36,217 postmenopausal women who consumed either lower protein or lower NAE [net acid excretion] diets (37). Second, wrist fracture risk was highest among 1865 peri- and postmenopausal women who consumed the lowest protein intakes over 25 yr of follow-up (38). As well, a recent 2-yr trial in 276 postmenopausal women either supplemented with potassium citrate (expected to neutralize the acid of the Western diet) or encouraged to consume increased fruit and vegetables showed that these interventions did not reduce bone turnover or decrease bone loss (36).”

The take home message, which I’ve written about before, is that not eating animal protein does not protect you from osteoporosis. Make sure you get enough calcium, vitamin D, and even (plant) protein.

References

36. Macdonald HM, Black AJ, Aucott L, Duthie G, Duthie S, Sandison R, Hardcastle AC, Lanham New SA, Fraser WD, Reid DM. Effect of potassium citrate supplementation or increased fruit and vegetable intake on bone metabolism in healthy postmenopausal women: a randomized controlled trial. Am J Clin Nutr. 2008 Aug;88(2):465-74. (Link) Free article available.

37. Dargent-Molina P, Sabia S, Touvier M, Kesse E, Bréart G, Clavel Chapelon F, Boutron-Ruault MC. Proteins, dietary acid load, and calcium and risk of postmenopausal fractures in the E3N French women prospective study. J Bone Miner Res. 2008 Dec;23(12):1915-22. (Link) Free article available.

38. Thorpe DL, Knutsen SF, Beeson WL, Rajaram S, Fraser GE. Effects of meat consumption and vegetarian diet on risk of wrist fracture over 25 years in a cohort of peri- and postmenopausal women. Public Health Nutr. 2008 Jun;11(6):564-72. Epub 2007 Aug 9. (Link) Free article available.

48. Fenton TR, Lyon AW, Eliasziw M, Tough SC, Hanley DA. Meta-analysis of the effect of the acid-ash hypothesis of osteoporosis on calcium balance. J Bone Miner Res. 2009 Nov;24(11):1835-40. (Link)

What Should I Be Tested For?

Tuesday, November 30th, 2010

I am regularly asked by vegans what they should be tested for. Here is a run down:

Vitamin B12

As I say in Should I Get My B12 Status Tested? -

Vegans do not need to get their homocysteine or B12 levels checked merely because they are vegan. Rather, being vegan means that you should get a regular, reliable source of vitamin B12 from fortified foods and/or supplements. (Though if you’ve gone a month or so without a reliable source of B12, you should replenish your stores as described in Step 1 of the Recommendations.)

About 2% of people do not absorb B12 well. While this has nothing to do with being vegan, it is nice to know if you are such a person. You will not be able to tell unless you first have a reliable source of B12 for at least a few weeks before your B12 level is checked. Additionally, there are specific tests that directly measure B12 absorption.

If you get your B12 level checked, please note that eating seaweeds can falsely inflate B12 levels. Methods for determining B12 levels do not distinguish between B12 and some inactive B12 analogues. Many seaweeds contain a variety of inactive B12 analogues. Someone who is eating large amounts of seaweed may have serum B12 levels well above normal, but much of it could be inactive B12 analogues.

Vitamin D

This is probably the one nutrient that vegans really can benefit from getting tested even if they do not have any symptoms of poor health.

Calcium

The body keeps blood calcium levels relatively constant regardless of your diet, so getting calcium levels tested doesn’t tell you much of anything (other than that you are not seriously ill). Getting your bone mineral density tested is the best way to find out what shape your bones are in. I don’t necessarily recommend this, unless you have reason to believe you might have osteoporosis. I’ve said it many times before, but I’ll say it again – most vegans should drink calcium-fortified non-dairy milks (or other foods) or take a calcium supplement.

Omega-3s

If you are taking a DHA supplement, then you are probably fine. If you are not and want to see what your DHA levels are, here are some testing places.

There is a more common test that could shed some light on your EPA status – blood clotting time. Most doctors test for this routinely. If your blood is clotting too fast, you might be lacking EPA. But, I rarely hear from a vegan whose blood is clotting too fast. If blood clotting time is normal, it doesn’t necessarily mean you have enough DHA.

Iron

If a doctor is going to draw blood, getting an iron panel to see if you have enough (or too much) iron is a good idea, especially for menstruating women.

Iodine

There is no direct test for iodine. Like B12, it’s best to just make sure you’re getting enough (but not too much). Iodine deficiency (and excess) can lead to thyroid problems, so getting your thyroid tested would be an indirect indicator. Click here for more on iodine.

And that covers it for any routine nutrients to test for regarding the vegan diet.

Calcium Supplements: Are They Safe?

Monday, October 11th, 2010

In July, a meta-analysis of the effect of calcium supplementation on heart attacks was published in the British Medical Journal (1). They found that people taking calcium supplements were more likely to have a heart attack. People have asked me if I think this means vegans should not supplement with calcium.

If you look at the study (the full paper is available for free at the link in the abstract below), they found that the increased risk of heart attack was limited to people who started out with a dietary calcium intake of 700 mg/day or more. Most vegans do not get that much calcium through foods. In most of the studies they examined, the level of calcium supplementation was substantially higher than 500 mg.

This study indicates that if you are an adult who gets 700 mg of calcium from your diet (including fortified foods), you probably shouldn’t take more than about a 300 mg supplement of calcium per day.

The DRI for calcium for ages 9 to 18 is 1,300 mg. This meta-analysis was conducted on older people trying to prevent osteoporosis and is probably not applicable for teenagers, whose bones are still building.

The DRI for calcium for people over 50 is 1,200. My recommendation for people in this age group who want to meet the DRI is to get at least 700 mg per day through foods and only supplement enough to make up the difference.

It’s worth noting that some observational studies of calcium intake (from foods, not supplements) have shown higher intakes to be protective against heart disease.

1. Bolland MJ, Avenell A, Baron JA, Grey A, MacLennan GS, Gamble GD, Reid IR.
Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis. BMJ. 2010 Jul 29;341:c3691.