Archive for the ‘Bones’ Category

Dietitian Perspectives on Protein, Calcium and Vegan Bone Health

Thursday, November 6th, 2014

Note: this article is co-authored by Jack Norris, RD and Ginny Messina, MPH, RD and appears on Ginny’s blog as well as this one.

Vegans typically have lower calcium intakes than other vegetarians and meat-eaters. But just how much does this matter?

The popular thinking has long been that it doesn’t matter much at all. According to the acid-ash hypothesis of osteoporosis, vegans experience smaller calcium losses since we don’t eat animal protein. The theory is that calcium is “leached” from bones to counter acidic conditions caused by animal protein.

It’s supported by studies that find higher levels of both calcium and acidic compounds in the urine when people are fed big doses of animal protein (1). This is also supposedly why hip fracture rates are higher in countries with high animal protein intakes (2).

But while the theory had great support several decades ago, it hasn’t held up to the scientific evidence. An article by vegan dietitian Dr. Reed Mangels, based on a presentation she gave at the Sixth International Congress on Vegetarian Nutrition sums up the more recent research very well (3). It should be required reading for all vegan and vegetarian nutrition professionals.

Unfortunately, a quick Google search of “vegan-calcium-bone-health” shows that many vegan educators, including some who are health professionals, are still promoting the idea that protein causes calcium loss from bones.

We thought it would be interesting to see where vegetarian dietitians fit into all of this. So, we created a true/false questionnaire about bone health, protein and vegan diets. We asked dietitians who subscribe to the email list for the Vegetarian Nutrition Dietetic Practice Group (VNDPG) to answer the questions.

Although this was a small, unscientific survey, the results were interesting. They showed that VNDPG members were more aware of the issues than the general vegan community and are sharing better information than what is often available on the internet and elsewhere. But in some cases, even RDs weren’t aware of the newer research on protein and bone health.

Here is the survey with our answers.

1. Protein contributes to bone structure. TRUE

Most RDs got this one right. Bone contains collagen and other proteins and you can’t build and maintain bones without protein (4).

2. Protein from animal foods causes calcium loss from bones. Probably FALSE

According to a 2009 meta-analysis of epidemiological studies, protein is not harmful to bone health and may be beneficial (5). Particularly relevant to vegetarians, in the Adventist Health Study-2, vegetarians who ate the most protein-rich foods like legumes and veggie meats, had the fewest fractures (6). It’s true that studies link higher protein intake with higher urinary calcium losses. But this is in response to eating isolated proteins, not protein-rich foods (7). The phosphorus in those higher-protein foods seems to cancel out the effect on bone loss. Protein also improves calcium absorption when calcium intakes are low (8), so it’s possible that the higher amounts of calcium in the urine simply reflect that greater amounts being absorbed from the diet.

In fact, another 2009 meta-analysis—this one looked at clinical studies—found that the amount of calcium lost in the urine didn’t correlate with calcium balance in the body or with markers of bone health (9). That is, acidic conditions didn’t produce a net loss of calcium from the bones.

The studies comparing hip fracture rates among countries have also been called into question. Since they’re ecological studies, they don’t control for anything and are only marginally useful.

Better information comes from The Hong Kong Osteoporosis Study. This research found that hip fracture rates were lower in Hong Kong than Sweden but that spinal fracture rates were higher (10). And while that seems conflicting, it’s really not. Hip fracture rates are affected less by bone health and more by the likelihood of falling. Spinal fractures, on the other hand, actually reflect bone health. In fact, the researchers said that despite lower hip fracture rates, the Hong Kong women had more osteoporosis.

3. Drinking cow’s milk promotes osteoporosis. Probably FALSE but maybe TRUE

Given the discussion above, it doesn’t seem that the protein in milk would raise risk for osteoporosis. But, research published just last week did raise questions about the effects of milk-drinking on bone health.

The Swedish researchers found that women who drank more than 3 glasses of milk per day had a much higher rate of fracture than those who drank less than a serving (11). In contrast, though, they found that cheese and yogurt were associated with lower rates of fracture. Earlier research in Adventists also found a protective effect of cheese on bone health (12).

One possible explanation, according to the Swedish researchers, is that the sugar galactose—high in milk, but low in cheese and yogurt—is the factor affecting fractures. The research supporting this is in animals, though.

Although it would be premature to say that milk raises fracture risk, there isn’t much evidence that milk-drinkers have any particular health advantage, either. Since we oppose dairy consumption on ethical grounds, it seems like it’s enough to know that nobody actually needs dairy foods in their diet.

4. Research shows that vegans have fewer bone fractures than meat-eaters. FALSE

What evidence we have for this — and admittedly, it’s very little — isn’t especially favorable for vegans. In the EPIC-Oxford study, vegans had a 30% higher risk for fracture after adjusting for numerous variables like age, smoking, alcohol consumption, and physical activity. After adjusting for calcium intake, however, there was no difference in fracture rates. Vegans who got enough calcium were no more likely to break a bone than milk-drinkers (13).

Likewise, in the Adventist Health Study-2, there was a trend toward higher fracture rates among the vegans compared to other vegetarians as well as non-vegetarians (6). (This study didn’t test for statistical significance.)

5. People eating plant-based diets have lower calcium needs than meat-eaters. Probably FALSE

If protein doesn’t have a negative effect on bone health, then there is no reason to think that vegans have lower calcium needs. The EPIC-Oxford study mentioned above suggests that the lower calcium intakes that are typical of vegans may be harmful.

6. The US RDAs for calcium are similar to the World Health Recommendations. TRUE

A common belief is that the WHO recommends just 400 to 500 milligrams of calcium per day. But, the WHO recommends 1000 mg of calcium for adults which is the same as the US RDAs.

Two last questions on our survey looked at the more holistic story of diet and bone health.

7. Weight-bearing exercise is important for bone health TRUE

8. A variety of nutrients including vitamin D, potassium, magnesium, and calcium is needed for healthy bones. TRUE

No surprise that 100% of our respondents knew that bone health is about much more than calcium. No single nutrient or food can make or break the strength of your bones. Keeping bones strong takes a whole diet and lifestyle approach. Getting enough calcium is just one part of that, but it is still an important part. Right now, there is no reason to think that vegans have any particular advantage where this is concerned.

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References

1. Schuette SA, Linkswiler HM. Effects on Ca and P metabolism in humans by adding meat, meat plus milk, or purified proteins plus Ca and P to a low protein diet. J Nutr 1982;112:338-49.

2. Frassetto LA, Todd KM, Morris RC, Jr., Sebastian A. Worldwide incidence of hip fracture in elderly women: relation to consumption of animal and vegetable foods. J Gerontol A Biol Sci Med Sci 2000;55:M585-92.

3. Mangels AR. Bone nutrients for vegetarians. Am J Clin Nutr 2014;100:469S-475S.

4. Boskey AL, Coleman R. Aging and bone. J Dent Res 2010;89:1333-48.

5. Darling AL, Millward DJ, Torgerson DJ, Hewitt CE, Lanham-New SA. Dietary protein and bone health: a systematic review and meta-analysis. Am J Clin Nutr 2009.

6. Lousuebsakul-Matthews V, Thorpe DL, Knutsen R, Beeson WL, Fraser GE, Knutsen SF. Legumes and meat analogues consumption are associated with hip fracture risk independently of meat intake among Caucasian men and women: the Adventist Health Study-2. Public Health Nutr 2013:1-11.

7. Spencer H, Kramer L, DeBartolo M, Norris C, Osis D. Further studies of the effect of a high protein diet as meat on calcium metabolism. Am J Clin Nutr 1983;37:924-9.

8. Kerstetter JE, O’Brien KO, Insogna KL. Dietary protein affects intestinal calcium absorption. Am J Clin Nutr 1998;68:859-65.

9. 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;24:1835-40.

10. Bow CH, Cheung E, Cheung CL, Xiao SM, Loong C, Soong C, Tan KC, Luckey MM, Cauley JA, Fujiwara S, et al. Ethnic difference of clinical vertebral fracture risk. Osteoporos Int 2012;23:879-85.

11. Michaelsson K, Wolk A, Langenskiold S, Basu S, Warensjo Lemming E, Melhus H, Byberg L. Milk intake and risk of mortality and fractures in women and men: cohort studies. Bmj 2014;349:g6015.

12. Matthews VL, Knutsen SF, Beeson WL, Fraser GE. Soy milk and dairy consumption is independently associated with ultrasound attenuation of the heel bone among postmenopausal women: the Adventist Health Study-2. Nutr Res 2011;31:766-75.

13. Appleby P, Roddam A, Allen N, Key T. Comparative fracture risk in vegetarians and nonvegetarians in EPIC-Oxford. Eur J Clin Nutr 2007;61:1400-6.

Medscape Report: Calcium & Vitamin D Decreases Fractures & Cancer

Monday, April 28th, 2014

On April 2, 2014, Medscape sent out a Special Report that included a link to a video and article, Calcium + Vitamin D: Surprises From Long-term Follow-up. You probably need to sign up for a free account to view the article.

Here are some excerpts from the article which was about the Women’s Health Initiative study:

“In this large trial, more than 36,000 postmenopausal women aged 50-79 years were randomly assigned to treatment with a combination of calcium carbonate at a dose of 1000 mg elemental calcium plus vitamin D3 400 IU daily, or placebo.

“We now have 3 lines of evidence of benefit for calcium plus vitamin D supplementation: the reduction in hip fracture seen among adherent women, the reduction in vertebral fracture in the intention-to-treat analyses, and the improvement or better results for bone mineral density…

“In terms of all cancers, among the women who had low baseline intake of vitamin D, there was a statistically significant 9% reduction in total cancer with supplementation, and also a marginally significant 9% reduction in all-cause mortality.”

The report also said that there was no increase in cardiovascular disease for women taking supplements.

Meat Alternatives Associated with Lower Hip Fracture Risk in AHS-2

Thursday, October 10th, 2013

Today was a good day: As longtime readers of this blog will know, I love getting good news about my “bad” habits. :)

A study came out that fits in well with past findings, is well-written, and supports my proclivity to eat and recommend soy meats!

It was a report from Adventist Health Study-2 (AHS-2), conducted among caucasian Seventh-day Adventists living in the USA, comparing the intakes of many different foods and hip fracture risk after 5 years of follow-up (1).

First, there was a bit of bad news in that vegans had the highest rates of hip fracture at 3.0 per 1,000 person-years compared to 2.0 for non-vegan vegetarians (including semi-vegetarians) and 1.6 for non-vegetarians. The paper didn’t report whether this finding was statistically significant, but it was not a great trend, obviously. Read on for how to reduce your chances.

Here are findings from the fully adjusted model (2):

– Meat alternatives once a day or more (compared to less than once per week) were associated with a 66% reduced risk of hip fracture in the vegetarians (.34, .12-.95).

– Eating legumes once a day or more (compared to less than once per week) was associated with an 82% reduced risk in non-vegetarians (.18, .06-.54) and an 55% reduced risk in vegetarians (.45, .22-.94).

– Meat more than 3 times per week was associated with a 45% reduced risk in the non-vegetarians (.55, .36-.83), compared to less than once per week.

– Dairy, nuts, soy milk, and “tofu & soy cheese” were not associated with a lower risk. The average amount of tofu & soy cheese per day was only .1 among the vegetarians. They did drink close to a cup of soymilk per day (or “soya milk” as the authors, who apparently think they live in Europe, call it).

The authors emphasize the need for vegans to eat legumes in order to get enough of the essential amino acid lysine:

“[A]n individual who adheres to a vegan diet, which excludes meat and dairy products, will need at least two cups of cooked beans [per day] to meet the recommended lysine intake requirement…Lysine and hydroxylysine are the main amino acids in the cross-linking process of bone collagen…Lysine can also influence bone health through its end product carnitine. Carnitine supplements have been shown to improve bone density in some animal and human studies.”

Note that the requirement for 2 cups of cooked beans assumes no other lysine sources in the diet, which isn’t the case. You can can read more on lysine needs and how to meet them in Protein.

They go on to say:

“Among our participants, intake of meat analogues of at least one serving daily reduced the risk of hip fracture by up to 49%…The main protein ingredients in meat analogues are soya, wheat, gluten, eggs and milk. A typical serving of meat analogues (1 serving ~73 g in AHS-2) contains at least 10 g of protein, but can vary from 9 to 18 g.”

Or 30 g as Tofurky Italian sausage has!

They point out that their finding for meat being protective is backed up by other research but not all. After a brief analysis of the research they suggest that meat intake is associated with bone health when protein intakes are low. And, finally:

“Protein is recognized for its ability to improve [calcium] balance, suppress parathyroid hormone, increase lean body mass and increase production of the bone growth regulator insulin-like growth factor-1.”

This study had something for everyone – low-fat proponents can relish in the findings for legumes and meat alternative eaters can smugly continue in their bad habits!

I have not yet updated the VeganHealth.org article, Calcium and Vitamin D, with this new study yet, but hope to do so in the next few days.

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References

1. . Lousuebsakul-Matthews V, Thorpe DL, Knutsen R, Beeson WL, Fraser GE, Knutsen SF. Legumes and meat analogues consumption are associated with hip fracture risk independently of meat intake among Caucasian men and women: the Adventist Health Study-2. Public Health Nutr. 2013 Oct 8:1-11. [Epub ahead of print] | link

2. *Adjusted for fruits and vegetables intake, age, height, weight, gender, energy intake, physical activity, smoking, health status and total calcium intake.

Ginny Messina: Calcium and Protein and Bone Health in Vegans

Tuesday, August 20th, 2013

In her latest blog post, Calcium and Protein and Bone Health in Vegans, Ginny has a good reminder about the need for vegans to make sure they’re getting enough calcium and protein. Excerpt:

“The theory is that animal protein, through its acidifying action, “leaches” calcium from bones, eventually weakening them and causing bone fractures. If that’s true, it means that those of us who eat no animal protein are likely to have better bone health. And maybe even lower calcium needs.

“Unfortunately, it’s not true. Or at the very least, the evidence in support of this relationship has fizzled over the years. I’ve written about this before, but it remains such a pervasive and potentially harmful belief that it deserves an occasional revisit.”

Read more…

Calcium and Vitamin D for Vegans: Summarized!

Wednesday, March 20th, 2013

This is an abridged version of Calcium and Vitamin D, which includes references and more details on just about every paragraph below. This should conclude my calcium-vitamin D barrage of the past few weeks!

Calcium

Americans are regularly being urged to consume more calcium in order to prevent osteoporosis. It is practically impossible to meet the recommendations without large amounts of cows’ milk, calcium-fortified foods, or supplements.

Because vegans do not eat dairy products, without fortified foods or supplements their calcium intakes tend to be low (about 400-600 mg per day compared to the U.S. recommended intake of 1,000 mg per day).

Traditionally, the vegan community has responded to this by saying osteoporosis is a disease of calcium loss from the bones, not a lack of calcium in the diet. This was based on two ideas.

The first idea is that ecological studies have shown that the countries with the highest intake of dairy products (northern Europe and the USA) have higher rates of hip fractures than do Asian and African countries where much less milk is consumed. This in turn, can be explained by the second idea, which is that studies show that after ingesting animal protein, people urinate large amounts of calcium.

Therefore, the thinking goes, calcium intake isn’t important for preventing osteoporosis and vegans are protected due to the lack of animal protein in their diets.

Unfortunately, there is a lot of evidence to suggest that this is not correct. It turns out that hip fractures are more indicative of the risk of falling than of osteoporosis in some countries, with a recent study from Hong Kong showing that while men and women in Hong Kong had lower rates of hip fractures, they had higher rates of vertebral factures, and the women had higher rates of osteoporosis than Caucasian women.

As for protein leaching calcium from bones into the urine – it’s a lot more complicated than that. The studies that showed calcium to be urinated out were done using protein isolates whereas eating protein from whole foods does not result in a calcium imbalance. Population studies and clinical trials show that protein, including animal protein, does not have a negative effect on bones (more details here).

So where does that leave vegans?

Vegans’ bone mineral density, a measure of osteoporosis, has been shown in many studies to be slightly lower than non-vegans. More importantly, the one study on Western vegans measuring fracture rates over time found that vegans in the group who got less than 525 mg of calcium per day had a higher fracture rate than vegans in the group getting more than 525 mg. The vegans in the lower calcium group also had higher fracture rates than the meat-eaters and lacto-ovo vegetarians.

Although it is possible to meet the calcium recommendations by eating greens alone, the average vegan probably will not meet recommendations without drinking a glass of fortified drink each day, eating calcium-set tofu, or taking a 250 – 300 mg supplement (in addition to eating an otherwise balanced diet).

The greens highest in absorbable calcium are kale, mustard greens, bok choy, turnip greens, collards, and watercress (more info). In addition to calcium, greens also contain vitamin K, potassium, and magnesium, which also contribute to better bone health.

While spinach, Swiss chard, and beet greens are high in calcium, it is not well absorbed due to their also high content of oxalates, which bind calcium and prevent absorption from the digestive tract.

Research is mixed about whether calcium intakes above 1,400 mg per day can put people at risk for chronic disease. If you take a calcium supplement, it’s best not to go overboard. Most vegans taking 250-300 mg per day would not come close to 1,400 mg.

Vitamin D

Vitamin D is also important for bones, as it can increase calcium absorption when the body signals that it needs calcium. Research has shown that in populations with calcium intakes similar to omnivores in the United States, vitamin D is more important than calcium for preventing osteoporosis.

In recent years, vitamin D has also been linked to many other diseases and some researchers have suggested that the recommended vitamin D levels are too low. However, the Institute of Medicine has reviewed the research and concluded that is not the case. The controversy has resulted in many people thinking they are deficient in vitamin D when they are not.

The only significant, natural, dietary sources of vitamin D are fatty fish, eggs (if chickens have been fed vitamin D), and mushrooms (if treated with UV rays). Most Americans get their dietary vitamin D through fortified milk and fortified margarine. The vegan diet contains little, if any, vitamin D without fortified foods or supplements. On average, vegans’ vitamin D levels are adequate, but somewhat lower than non-vegans.

Most people get a significant amount of their vitamin D from the action of UV rays on their skin. While the body can store vitamin D made in the sunnier months for use during less sunny times, this does not work for everyone. In fact, some people, even those living in sunny climates, develop extremely low levels of vitamin D. This can manifest itself through fatigue and bone pain.

If your arms and face (or the equivalent amount of skin or more) is exposed to the following amounts of midday sun (10 am to 2 pm), without sunscreen, on a day when sunburn is possible (i.e., not winter or cloudy), then you should not need any dietary vitamin D that day:

• Light-skinned: 10 to 15 minutes
• Dark-skinned: 20 minutes
• Elderly: 30 minutes

On all other days, people older than one year should get 600 to 1,000 IU of vitamin D.

Due to skin cancer concerns, some dermatologists recommend getting all your vitamin D from supplements rather than the sun. The amounts of sun above for light and dark-skinned people should be safe, but I have not seen research on how much sun is safe for elderly people and recommend talking to your doctor about how to get vitamin D if you believe you are at risk for skin cancer.

600 to 1,000 IU of vitamin D is only available in supplemental form or specially treated mushrooms.

There are two forms of supplemental vitamin D: D2 and D3. Vitamin D2 is always vegan, made from exposing fungi to UV rays. Vitamin D3 normally comes from fish oil or sheep’s wool, but there is a vegan version made by Vitashine.

A great deal of research has been conducted on vitamin D2 and D3. Vitamin D2 is effective at increasing bone mineral density (when given to people who are deficient). Vitamin D2 can also increase vitamin D levels temporarily, but is not as effective as vitamin D3 at keeping vitamin D levels raised when taken only weekly. If you take vitamin D on a regular basis, D2 should be fine, whereas if you are only going to take it sporadically, without getting sun in the interim, or find that your vitamin D levels will not increase on D2, then you should opt for D3.

If you are trying to raise your vitamin D levels with D2, make sure the laboratory can detect vitamin D2, and not just vitamin D3. Also make sure that you are not trying to raise your levels beyond what the Institute of Medicine says is adequate (50 nmol/l or 20 ng/ml) as there’s no sense in worrying if you cannot seem to get your vitamin D levels twice as high as necessary!

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VeganHealth.org: Vitamin D2 in Mushrooms

Monday, March 11th, 2013

I added some research on vitamin D2 in mushrooms to the Bones, Vitamin D, and Calcium page at VeganHealth.org:

Vitamin D2 in UV Treated Mushrooms

Food manufacturers are now creating large amounts of vitamin D2 in mushrooms by exposing them to commercial ultraviolet light or direct sunlight (55, 56). The vitamin D is well-retained in the mushrooms over the course of the typical storage life of fresh mushrooms, up to two weeks (55, 57). This vitamin D is effective in improving vitamin D status and no different from a vitamin D2 supplement (2).

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References

2. Urbain P, Singler F, Ihorst G, Biesalski HK, Bertz H. Bioavailability of
vitamin D₂ from UV-B-irradiated button mushrooms in healthy adults deficient in
serum 25-hydroxyvitamin D: a randomized controlled trial. Eur J Clin Nutr. 2011
Aug;65(8):965-71. doi: 10.1038/ejcn.2011.53. Epub 2011 May 4. | link

55. Kalaras MD, Beelman RB, Elias RJ. Effects of postharvest pulsed UV light treatment of white button mushrooms (Agaricus bisporus) on vitamin D2 content and quality attributes. J Agric Food Chem. 2012 Jan 11;60(1):220-5. | link

56. Simon RR, Phillips KM, Horst RL, Munro IC. Vitamin D mushrooms: comparison of the composition of button mushrooms (Agaricus bisporus) treated postharvest with UVB light or sunlight. J Agric Food Chem. 2011 Aug 24;59(16):8724-32. | link

57. Roberts JS, Teichert A, McHugh TH. Vitamin D2 formation from post-harvest UV-B treatment of mushrooms (Agaricus bisporus) and retention during storage. J Agric Food Chem. 2008 Jun 25;56(12):4541-4. | link

VeganHealth.org Update: Vitamin D2 vs. D3

Sunday, March 10th, 2013

In continuing to bone up on the bones research, I have summarized some recent findings on vitamin D2 vs. D3 and updated the Bones, Vitamin D, and Calcium page at VeganHealth.org.

So that I do not have to continue updating this page to reflect the VeganHealth.org page, I have cut the article from this post and readers should just refer to the link above. Thank you.

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Fracture Rates in China and Sweden

Thursday, March 7th, 2013

My two biggest concerns about vegan nutrition are vitamin B12 and calcium. The message about vitamin B12 has gotten through to anyone who has been paying attention and isn’t in nutrition la la land (unfortunately, this are still a lot of vegans on both accounts). But even today, calcium and bones is a particularly tough sell among people who are interested in mainstream science and have been paying some attention.

Normally when I harp on the need for calcium, explaining that animal protein does not cause osteoporosis and so vegans are not protected by virtue of not eating any, someone will point out that countries that have higher intakes of dairy (northern Europe and the USA) have higher rates of osteoporosis than do Asian and African countries where much less milk in consumed. Here is a study that helps explain this paradox for Asians.

The first prospective study measuring clinically diagnosed vertebral fractures in an Asian population, the Hong Kong Osteoporosis Study, was released in March of 2012 (1). It measured the vertebral and hip fractures in a Chinese population and compared the rates to Sweden. Data from Japan was also included, but the measurements of vertebral fracture were estimated for Japan.

Rather than typing out the numbers for the various age groups, which are tedious to read, the results can be seen in the diagram below (or you can click here for an easier version to see).

The Swedish have higher rates of hip fracture while the Chinese have higher rates of vertebral fractures (much higher after age 80).

The authors state:

“The observed ethnic differences in fracture incidences may be due to the fact that hip fracture risk was affected by fall risk, whereas the risk of vertebral fracture mostly depends on bone strength. Despite the low hip fracture rate in our population, Hong Kong women had a higher prevalence of osteoporosis (bone mineral density T- score à “2.5 at any one site in reference to ethnic-specific peak young mean according to the ISCD recommendation) than US Caucasian women (35.8% vs. 20%, respectively) and a similar prevalence of about 6% in Hong Kong and US Caucasian men.”

In other words, the Chinese don’t have lower rates of osteoporosis.

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Reference

1. Bow CH, Cheung E, Cheung CL, Xiao SM, Loong C, Soong C, Tan KC, Luckey MM, Cauley JA, Fujiwara S, Kung AW. Ethnic difference of clinical vertebral fracture risk. Osteoporos Int. 2012 Mar;23(3):879-85. | link

Soy vs. Cow’s Milk and Bone Mineral Density Take Two

Wednesday, March 6th, 2013

Yesterday, I wrote about a clinical trial comparing soy vs. cow’s milk’s impact on bone mineral density (BMD) in Chinese women (link). To sum it up, the cow’s milk fared better than soy, which fared better than nothing.

Today I found a prospective study from the Adventist Health Study-2 (2011) comparing soy vs. cow’s milk (1). They followed 337 post-menopausal, Caucasian women, who had not been previously diagnosed with osteoporosis, for two years. 61% were considered vegetarians because they ate meat less than once a month.

The authors sum up the results:

“Those drinking soy milk at least once a day or more (highest category) were 57% less likely to have osteoporosis than those who never used soy milk [.43 (.21–.89)]. Likewise, those eating dairy products at least once a day or more were 62% less likely to have osteoporosis than those consuming dairy less than twice a week [.38 (.17–.86)].”

There was not a separate soymilk group and cow’s milk group, both findings were comparing the entire group of women to each other, though the results for each milk were adjusted for intake of the other milk.

The researchers did not measure total calcium intake, but they seemed to assume that most of this soymilk was calcium-fortified. They also found no correlation between calcium or vitamin D supplement usage (amounts not measured) and better bone health.

Interestingly, cheese was the only dairy product that, when separated out, was correlated with better bone health (the other categories were “milk,” and “yogurt/ice-cream”). The authors speculated that it was due to the higher calcium and protein content of cheese.

In conclusion, it appears to be about equally beneficial for bone health for Caucasian, postmenopausal women to be drinking either soymilk or cow’s milk.

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Reference

1. Matthews VL, Knutsen SF, Beeson WL, Fraser GE. Soy milk and dairy consumption is independently associated with ultrasound attenuation of the heel bone among postmenopausal women: the Adventist Health Study-2. Nutr Res. 2011 Oct;31(10):766-75. | link

Soy vs. Cow’s Milk and Bone Mineral Density

Tuesday, March 5th, 2013

I’m going through my backlog of research on bones in order to write a reader-friendly version of the tome that is Bones, Vitamin D, and Calcium on VeganHealth.org.

In January 2012, a report from China was released of a randomized clinical trial comparing the effects of cow’s milk and soymilk on bone mineral density (BMD) in postmenopausal women (1).

The women were divided into three groups: soy, cow’s, and control. The women knew which treatment they were receiving, while the control group got nothing. The milk and soymilk had 250 mg of calcium and they drank one serving per day.

BMD was measured in the spine, hip, and femur at 6, 12, and 18 months.

In the cow’s milk group, BMD increased in the hip and femur. In the soymilk group, BMD did not change significantly, but showed a downward trend in all three locations. In the control group, there was a downward trend in all three locations that only reached significance in the femur at 18 months.

It should be strongly noted that the participants were asked to avoid calcium from other milks and supplements during the trial which means their total calcium intake was probably quite low and I’m somewhat amazed that their BMD didn’t decrease more or in all three groups. Total calcium intake during the study period was not reported.

Compliance was 93.1% in the cow’s milk group and 82.5% in the soymilk group. This might explain a small amount of the differences between those groups. Other possibilities are that calcium in fortified soymilk is known to quickly settle to the bottom of the milk where it might not be ingested but left in the container, and that milk contains phosphorus and growth factors that might increase BMD.

This is just one small study and more work needs to be done before any conclusions should be drawn.

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Reference

1. Gui JC, Brašić JR, Liu XD, Gong GY, Zhang GM, Liu CJ, Gao GQ. Bone mineral density in postmenopausal Chinese women treated with calcium fortification in soymilk and cow’s milk. Osteoporos Int. 2012 May;23(5):1563-70. Epub 2012 Jan 27. | link