Nutrition & Bone Health: Selective Literature Review

"A generalization from the literature, without a formal metaanalysis, may be that we need adequate supplies of both vitamin D and calcium to obtain significant reductions in nonvertebral fractures (especially hip fractures), and that those effects may be seen only in those persons who have insufficient vitamin D or calcium (or both). In addition, persons need to consume an overall healthful diet that meets all nutrient requirements. Protein for fracture prevention and healing and plenty of fruit and vegetables for overall health are of particular importance. A well-rounded diet is important, and evaluation of one element or vitamin does not give the whole story. [emphasis added.]

So where does that leave clinicians? The best public health recommendation would be that people should consume an overall healthful diet including adequate consumption of both calcium and vitamin D. This meta-analysis highlights the importance of not  segmenting nutrition into heterogeneous populations and isolated nutrients. Bone is not just calcium, and calcium does not function in isolation.

Source: JW Nieves, R Lindsay
Calcium and fracture risk (editorial)
Am J Clin Nutr. 2007 Dec;86(6):1579-80.

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Today, I'm publishing the "sifted" results of several literature searches I conducted during the past two weeks.

HA Bischoff-Ferrari, B Dawson-Hughes, J A Baron, PBurckhardt, R Li, DSpiegelman, B Specker, JE Orav, JB Wong, HB Staehelin, E O’Reilly, DP Kiel, and WC Willett
Calcium intake and hip fracture risk in men and women: a metaanalysis of prospective cohort studies and randomized controlled trials
Am J Clin Nutr 2007;86(6):1780–90.
Full article (PDF)

JZ Ilich and JEKerstetter
Nutrition in Bone Health Revisited: A Story Beyond Calcium
J Am Coll Nutr 2000;19(6):715-737.
Full article (PDF)

(Note: Though this review is 9 years old, it led me to other valuable research and review articles and has been cited by many so I'm including it here. All other resources have been published within the past 6 years.)

SA New and DJ Millward
Calcium, protein, and fruit and vegetables as dietary determinants of bone health
Am J Clin Nutr 2003;77(5):1340 - 1341.
Letter to Editor

SA Lanham-New
Fruit and vegetables: the unexpected natural answer to the question of osteoporosis prevention?
Am J Clin Nutr 2006;83(6):1254-1255.
Editorial with detailed reference list & links
Full article (PDF)

CJ Prynne, GD Mishra, MA O'Connell, GMuniz, MA Laskey, L Yan, APrentice and F Ginty
Fruit and vegetable intakes and bone mineral status: a cross-sectional study in 5 age and sex cohorts
Am J Clin Nutr 2006;83(6):1420-1428.
Abstract
Full article (PDF)

J-P Bonjour
Dietary Protein: An Essential Nutrient For Bone Health
J Am Coll Nutr 2005;24,(90006):526S-536S
Abstract
Full article (PDF)

A Devine, IM Dick, AF Islam, SS Dhaliwal and RL Prince
Protein consumption is an important predictor of lower limb bone mass in elderly women
Am J Clin Nutr 2005;81(6):1423 - 1428.
Abstract
Full article (PDF)

RP Heaney and DK Layman
Amount and type of protein influences bone health
Am J Clin Nutr 2008;87(5):1567S - 1570S.
Abstract
Full text (PDF)

JW Nieves
Osteoporosis: the role of micronutrients
Am J Clin Nutr 2005;81(5):1232S - 1239S.
Full article (PDF)

RK Rude, FR Singer, and HE Gruber
Skeletal and Hormonal Effects of Magnesium Deficiency
J Am Coll Nutr 2009; 28(2):131 - 141.
Abstract

FA Tylavsky, LA Spence and L Harkness
The Importance of Calcium, Potassium, and Acid-Base Homeostasis in Bone Health and Osteoporosis Prevention
J Nutr 2008;138(1):164S - 165S.
Full article (PDF)

SA Lanham-New
The Balance of Bone Health: Tipping the Scales in Favor of Potassium-Rich, Bicarbonate-Rich Foods
J Nutr 2008;138(1):172S - 177S.
Abstract
Full article (PDF)

Because of my practice area (neuroscience), I've been focused on brains and neglecting bones -- at least in terms of the evidence for best practice. Collecting these resources wasn't too difficult (thank you, OVIDSP databases and Google Scholar) and reading them has been very interesting, informative and even surprising. I hope you find some of these resources helpful, too.

In my next post (currently in draft stage) I'll be sharing evidence and practical guidelines on how a plant-based diet can build and maintain healthy bones.

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Other Greens & Berries posts on nutrition and bone health:

Nutrition in Bone Fracture Prevention & Healing: Part 1
Nutrition in Bone Fracture Prevention & Healing: Part 2
Nutrition in Bone Fracture Prevention & Healing: Part 3

Nutrition articles in "Nature Clinical Practice Neurology" (January & February 2009)

Because I work on a Neuroscience unit, I periodically scan the online neurology and neurosurgery literature for nutrition content. Recently I found these free, full-text articles in Nature Clinical Practice Neurology:

Click on image for full size and source

• Food for thought    HTML   PDF

This editorial reminds us nutritional supplements "have real pharmacological effects, not all of which are desirable."  True, too much of a good thing (a nutrient) can be bad thing (work against other medications). I appreciate the editor's closing statement: "It is, of course, understandable that patients will want to pursue all available options for the treatment of their condition, but they need to be provided with realistic expectations of the benefits, as well as being informed of any potential risks."

Application to practice: Be empathetic to people's needs but truthful about what the best evidence tells us.

• The ketogenic diet, four score and seven years later   HTML  PDF   

This commentary discusses the findings of randomized controlled trials.

Application to practice: "The ketogenic diet should be considered in the treatment of children with refractory epilepsy, and not only as a last resort.

• Polyunsaturated fatty acids and their potential therapeutic role in multiple sclerosis  HTML  PDF 

Key points from this article:

■ Epidemiological studies demonstrate an association between saturated fat intake and the incidence of multiple sclerosis (MS)
■ In vivo studies demonstrate that polyunsaturated fatty acids (PUFAs) can exert anti-inflammatory effects through multiple, complex mechanisms
■ Controlled and noncontrolled trials have produced mixed results regarding the efficacy of PUFAs in MS; however, these trials have several limitations that could partially explain the lack of a treatment effect
■ Despite the lack of definitive evidence that PUFAs can be beneficial in MS, the anti-inflammatory potential of these agents is intriguing
■ The potential role of PUFAs as a treatment for MS should be further explored in proof-of-concept studies that use MRI-based outcome measures

Application to practice: Because these researchers believe more, better designed research should be conducted, I cannot discourage MS patients from modifying their diets or hoping some day we may find a nutrient or food that may make a difference in their disease progression, symptom management and/or quality of life; I would support them in making the healthiest fat choices by providing education.

Research article: undernutrition & stroke outcome

Citation: Davis JP, Wong AA, Schluter PJ, Henderson RD, O'Sullivan JD, Read SJ. Impact of premorbid undernutrition on outcome in stroke patients. Stroke 2004;35:1930-1934.

Last week I was looking for information on nutrition risk screening in stroke patients -- specifically, evidence to support including a screening tool in our new acute stroke pathway. (Of course you can guess my bias.)  Google Scholar led me to David et al's article that reports on the prevalence and impact of malnutrition in a cohort of stroke patients. Here's the abstract:

Background and Purpose — To assess the prevalence of premorbid undernutrition and its impact on outcomes 1 month after stroke.

Methods — The study recruited from consecutive stroke admissions during a 10-month period. Premorbid nutritional status (using the subjective global assessment [SGA]), premorbid functioning (modified Rankin scale [MRS]), and stroke severity (National Institutes of Health Stroke Scale [NIHSS] score) were assessed at admission. The associations between premorbid nutritional status, poor outcome (defined as MRS 3), and mortality were examined before and after adjustment for confounding variables, including age, gender, stroke risk factors, stroke severity, and admission serum albumin.

Results— Thirty of 185 patients were assessed as having undernutrition at admission. Significant unadjusted associations were observed between undernutrition and poor outcome (odds ratio [OR], 3.4; 95% CI, 1.3 to 8.7; P=0.01), and mortality (OR, 3.1, 95% CI, 1.3 to 7.7; P =0.02) at 1 month. NIHSS, age, and premorbid MRS were also significantly associated with poor outcomes. After adjustment for these factors, the effect size of associations remained important but not significant (poor outcome: OR, 2.4; 95% CI, 0.7 to 9.0, P=0.18; mortality: OR, 3.2; 95% CI, 1.0 to 10.4, P=0.05).

Conclusions— Premorbid undernutrition, as assessed using the SGA, appears to be an independent predictor of poor stroke outcome. Stroke prevention strategies should target undernutrition in the population at risk for stroke to improve outcomes.

I extracted from the authors' thorough discussion this 4-item "take-home" message:

(1) The study found a significant crude association among premorbid nutritional status and mortality and poor outcome at one month. (2) After adjustment for factors such as age, premorbid dependence, and stroke, the associations were not statistically significant.  (3) This study measured premorbid undernutrition, which was the only modifiable risk factor to show an important effect on morbidity and mortality that approached statistical significance. (4)  "In keeping with previous studies, we also found older people, especially those with impaired functional capacity, and those living in aged care facilities to be more susceptible to undernutrition. These groups in particular need to be targeted by nutrition improvement strategies to limit the impact undernutrition has on stroke outcomes."

You can read the full text of the article here. If you aren't able to access it, please contact me.

A mini-primer on epidemiology for dietitians

Caveat lector: I am not an epidemiologist. (If you've been reading this blog, I'm sure you already knew that.) I also do not have a graduate degree in research. But I have completed Dietitians of Canada's (DC) Evidence-Based Decision-Making (EBDM) course so if anything, I am more aware of what I don't know. And I'm working on becoming more evidence-based  by  selectively acquiring, critically appraising and judiciously applying the literature. If this sounds like considerable mental effort requiring hours of concentrated reading and reflecting, well it is and it does.  But the results are worth the time and energy inputs: I have greater confidence I am using"best practice" based on information that is up-to-date, valid, makes a difference to outcome, and applies to the specific situation.

Gary Traubes' recent New York Times Magazine article, Do we know what makes us healthy? (see previous post) motivated me to review my  very rudmentary knowledge of epidemiology. If you've read this article  you will recall  the author extensively discussed the different types of  potential bias in epidemiological studies.  Mr. Traubes ended his article with the guiding principles  "skeptical epidemiologists" recommend:

1.  "[A]ssume that the first report of an association is incorrect or meaningless, no matter how big that association might be."
2. "If the association appears consistently in study after study, population after population, but is small — in the range of tens of percent — then doubt it."
3. "If the association involves some aspect of human behavior, which is, of course, the case with the great majority of the epidemiology that attracts our attention, then question its validity."  (The exception to this rule:  pay close attention to an association of unexpected harm.).
4. In summary, "remain skeptical until somebody spends the time and the money to do a randomized trial and, contrary to much of the history of the endeavor to date, fails to refute [the results of the epidemiological study]."

This skeptical or "question everything" mindset is part of what I learned in my EBDM course, which equipped me with tools and build knowledge and skills to critically evaluate whether a study is valid (true), important (clinically significant) and applicable to the specific situation. 

You can read an overview of the 10-unit interactive online course here. I believe DC will be offering the course at least once in 2008. The current  course is already in progress.

In the meantime, you can begin self-directed study on evidence-based practice by using online resources. Over the next couple of weeks, I will share ones that I've found helpful.

Here are some resources specifically about Epidemiology:

Epidemiology Supercourse  (a link on UBC's Health Care & Epidemiology so I feel confident recommending it)

You may find it easiest to navigate the site by going to the page that is organized by topic.  Here are some basic courses that I liked because they had detailed speaker's notes in addition to the slides.

Descriptive Epidemiology for Health Professionals (4-part series)
Different Kinds of Epidemiologic Studies
Potential Errors in Epidemiologic Studies (a good one to read before or after the NYT Magazine article)

What to believe about what to eat

I subscribe to Marion Nestle's blog and read as many posts as time permits. When she recommends a resource, I pay attention. (She has very impressive credentials.) Yesterday, in her post titled "Does Nutritional Epidemiology Work?", she suggested reading this "thoughtful" [Marion's word] article on epidemiology. After reading the piece, I decided I needed to review my notes from DC's Evidence-Based Decision-making course. These, unfortunately, are in my office at work and I am currently on vacation.

So because I don't have ready access to my notes, I'm in the process of compiling some resources and processes for dietitians to use when evaluating epidemiologic studies. Doing this will be a good review for me, too. I'll try to get these up within the next couple of days. In the meantime, you may want to read the article. It is 9 pages so you will need to set aside a chunk of time for reading and reflecting.