Study Review

Image from: http://www.webmd.com/diet/ss/slideshow-high-protein-diet

The following is my review of a study published in the June 2002 publication of Obesity Research titled Effect of Protein Intake on Bone Mineralization during Weight Loss: A 6-month Trial by Annebeth R. Skov, Nikolaj Haulrik, Søren Toubro, Christian Mølgaard, and Arne Astrup. According to Wiley Online Library this article was first published online on September 6, 2012.

Introduction

The purpose of this study was to analyze the long-term effects of dietary protein on bone mineralization. Osteoporotic fractures are an increasing problem with serious implications in health. Low protein intake in the elderly is a problem that can lead to an increase in low bone quality. With the prevalence of obesity increasing, despite the fact that a larger body mass tends to increase bone mineralization, weight loss to prevent the ill effects of comorbidities associated with obesity is generally the desired outcome. The often advised dietary recommendations are for a low fat, high complex carbohydrate diet. However, due to the longer satiation effects of protein, a low fat, high protein diet could possibly reduce excess calorie consumption due to frequent bouts of hunger on a lower protein diet. Nonetheless, it has been claimed that protein from animal sources reduces bone mineral content, in addition to the bone mineral losses seen in weight loss. The authors therefore found that it was relevant to study the influences of reduced-fat diets with high and low protein content on bone mineralization in overweight and obese subjects.

Methods

The study involved sixty-five overweight or obese individuals in a 6-month randomized, placebo-controlled dietary-intervention. It compared two controlled diets with isocaloric fat content (30%), one with high protein (25%) and one with low protein content (12%).

Results

The study found that there was no significant difference in BMC loss between the high protein or the low protein groups. However, they noted a more positive correlation between body fat loss and BMC loss than with body weight loss. At the end of 6 months, after adjusting for the differences in fat loss, there was a greater loss of BMC in the low protein group compared of the high protein group. The study found that independent of weight loss, there was less BMC loss with a high protein diet.

Commentary

Overall I agree with the findings of this study. The issues I have are with the diets. In Table 2 the carbohydrate content increased in both diet from baseline to 6 months. Also, the calcium and vitamin D intake for the low protein group decreased while in the high protein group they increased. I am unsure if this is due to the change in macro-nutrients (increased or decreased protein from baseline). That alone could have greatly contributed to the higher rate of BMC loss in the low protein group. It would be beneficial in a future study if not only the fat content were kept the same between groups, but all other micro- and macro-nutrient levels be kept at about the same level as baseline, if possible.

Skov, A. R., Haulrik, N., Toubro, S., Mølgaard, C., &Astrup, A. (2002, June). Effect of Protein Intake on Bone Mineralization duringWeight Loss: A 6-Month Trial. Obesity Research, 10(6), 432-438.doi:10.1038/oby.2002.60

Protein Intake and Bone Health

Image from robbwolf.com

This week I went about researching protein intake and bone health. The general argument is that too much dietary protein causes your blood/cells to become acidic and to remedy that your body leaches calcium from your bones. This is a common argument that those against the popular Paleo Diet use to discredit the validity of the dietary lifestyle (e.g. http://www.drmcdougall.com/misc/2012nl/jun/paleo2.htm). 
In my search I came across one of my favorite sites http://www.robbwolf.com. Robb's book The Paleo Solution is the first one I read about the Paleo lifestyle. He's also kind of a local guy to me (I grew up less than an hour north of where he lived in Chico, CA. He now lives in Reno, NV). My quick Google search for "protein intake and bone health" lead me to this entry in his blog: http://robbwolf.com/2009/03/19/paleo-vs-osteoporosis/. 
The question that the entry was based upon was asking about the association between osteoporosis and gluten (a plant [wheat] protein!), but in his answer to that question Robb touches on the debate about protein intake and bone health. Robb even quotes Loren Cordain's (author of The Paleo Diet) arguments in favor of protein intake supporting bone health (http://thepaleodiet.com/nutritional-tools/acid-base-balance/).
I like Robb Wolf's writing style; he worked for a number of years as a research biochemist so he understands the literature. However, he writes in such a way that he takes some of the driest reading ever and makes it not only easy to understand but entertaining as well!

(Note: If you were curious about the title of my blog "Caveman Candy"...it should be obvious at this point that it is in reference to the Paleo Diet. Besides, I thought it was a catchy name! ;] )

VIDEO: Is Protein Bad to the Bone?

This short little video says a lot in 33 seconds! The review article mentioned can be found here: "Dietary protein and bone health: a systematic review and meta-analysis (http://ajcn.nutrition.org/content/90/6/1674.long)

Protein: More than just a juicy steak!

       Protein. What is it? Why do we need it? Do I have to eat steak all the time?!

       Like water, protein is a part of everything in our bodies. Everything from cells, tissues, organs and even hormones and DNA! Proteins are composed of chains of amino acids. There are 20 amino acids that combine to make a protein. Most proteins our bodies can manufacture; however, there are a few "essential" amino acids that our bodies cannot produce and must be provided through our diet. When considering dietary sources of protein, there are two types "compete" and "incomplete" proteins. Complete proteins contain all the essential amino acids our bodies require, whereas incomplete proteins are lacking one or more of the essential amino acids. (Centers for Disease Control and Prevention, 2011)

       Dietary sources of "complete proteins" include meat (beef, lamb, pork, game, etc), poultry, fish and other seafood, eggs, and dairy products. Incomplete sources of dietary protein include grains, legumes, some vegetables and fruits (although in very small amounts). Common combinations of incomplete proteins to make complete proteins include rice and beans or corn and beans (i.e. Spanish rice and refried beans or chili and cornbread). Soy and quinoa are the only plant-based proteins that are considered a complete protein (Complete protein, n.d.). For this reason soy is a staple of many vegetarian and vegan diets.  

       Protein has many functions throughout the body. Our muscles and organs are protein, the collagen in our skin and bones is a type of protein, even our DNA is a protein. Proteins can even be bad, like prions and the proteins of cancer cells. In the context of bone and muscle development, protein is an important nutrient for the maintenance and repair of muscle and bone. Without adequate protein in the diet lean muscle mass is sacrificed to maintain more vital functions within the body and can contribute to weakened bones (Bonjour, 2005; Houston, et al., 2008).

References

Bonjour, J.-P. (2005). Dietary Protein: An Essential Nutrient For Bone Health. Journal of the American College of Nutrition, 24(6), 526S-536S.

Centers for Disease Control and Prevention. (2011, October 31). Nutrition for Everyone: Basics: Protein. Retrieved from http://www.cdc.gov/nutrition/everyone/basics/protein.html

Complete protein. (n.d.). Retrieved 9 12, 2012, from Wikipedia: http://en.wikipedia.org/wiki/Complete_protein

Houston, D. K., Nicklas, B. J., Ding, J., Harris, T. B., Tylavsky, F. A., Newman, A. B., . . . Kritchevsky, S. B. (2008). Dietary protein intake is associated with lean mass change in older, community-dwelling adults: the Health, Aging, and Body Composition (Health ABC) Study. American Journal of Clinical Nutrition, 87, 150-155.

Introducing.....Me!

Hi! I'm Megan and a senior at Humboldt State University. My major is Kinesiology with an emphasis in Exercise Science/Health Promotion. If you'd known me when I was younger, you might be amazed that I am majoring in Exercise Science. Sure, I played sports for many years from 4th grade through my senior year of high school, but I absolutely hated PE with a passion. I always felt like it emphasized all the parts of physical activity that I was the worst at. During my 8th grade year our PE class got some weightlifting equipment and I found something I was really good at; lifting heavy things! But it wasn't until 2009 when I decided to take a "Fitness & Nutrition" course that I realized that I really enjoyed exercising. By then I had been working as a Nurse Aide with elderly patients on hospice care or recovering from knee and hip surgeries. I had seen enough that I realized I wanted to help people improve their health and fitness before it was too late and they ended up like the patients I was caring for.

So, why protein? First, I'm an unabashed carnivore. I tried the whole vegetarian thing at one time because I thought it would be healthier than the standard junk I was eating at the time, but I quickly found that things (nutrients) were missing and that I'm allergic to soy! Besides, nothing beats a perfectly cooked steak. Yes, I realize there is protein in more than just meat (i.e. soy, corn, beans, various other veggies too numerous to count.) However, protein from muscle/meat is the only source of complete protein (the only exception being soy); most plant-based proteins must be combined to create a complete protein and even then, they are still lacking in vital nutrients like Vitamin B12. Second, protein is so versatile a nutrient it is absolutely amazing! Many components of bone, muscle, hormones and DNA are made from protein or are a type of protein.