Dietary Protein is Associated with
Musculoskeletal Health Independently
of Dietary Pattern: The Framingham
Third Generation Study

This section is compiled by Frank M. Painter, D.C.
Send all comments or additions to:   Frankp@chiro.org

FROM:   American Journal of Clinical Nutrition 2017 (Mar); 105 (3): 714–722 ~ FULL TEXT

Mangano KM1, Sahni S, Kiel DP, Tucker KL, Dufour AB, Hannan MT

Department of Biomedical and Nutritional Sciences,
University of Massachusetts,
Lowell, MA;
kelsey_mangano@uml.edu

---

The Meat Myth is Dead: Plant-Based Proteins Build Muscle Same as Animal Protein, Study Finds By Jill Ettinger Organic Authority ~ February 14, 2017 If you’re vegan for any length of time, you may hear this common question: “Where do you get your protein?”   Well, according to science, plants will do you just fine.   The long-standing myth about the necessity of meat for building muscle has been disproven as a new study found plant-based proteins benefit muscle health the same as animal protein. The study, published last week in the American Journal of Clinical Nutrition, found that the type of protein consumed — be it plant or animal — didn’t matter to muscle mass or strength.   Only the amount consumed; those subjects who consumed the least amount of protein had the lowest levels of muscle mass, but type of protein they ate had no impact on their muscoskeletal health. The University of Massachusetts Lowell researchers compared the health records of close to 3,000 adult mean and women between the ages of 19 and 72, including detailed dietary questionnaires the subjects completed.   Dietary habits, particularly the sources of protein (meat, eggs, fish, chicken, or vegetarian sources like legumes, nuts, or seeds), were compared with lean muscle mass, bone mineral density, and quadriceps strength, “all measures that are important for fitness, health, and better functioning, especially as we get older,” notes Health.com. The conclusion was that increased protein intake from any clean source is directly connected to healthier, stronger muscles, an important consideration as we age and begin to lose muscle mass. Lead study author Kelsey Mangano, PhD, assistant professor of nutritional sciences at the University of Massachusetts Lowell, told Health.com, “As long as a person is exceeding the recommended daily allowance for protein, no matter the source in their diet, they can improve their muscle health.”

Background:   Above-average dietary protein, as a single nutrient, improves musculoskeletal health. Evaluating the link between dietary protein and musculoskeletal health from a whole-diet perspective is important, as dietary guidelines focus on dietary patterns.

Objective:   We examined the prospective association of novel dietary protein food clusters (derived from established dietary pattern techniques) with appendicular lean mass (ALM), quadriceps strength (QS), and bone mineral density (BMD) in 2986 men and women, aged 19-72 y, from the Framingham Third Generation Study.

Design:   Total protein intake was estimated by food-frequency questionnaire in 2002-2005. A cluster analysis was used to classify participants into mutually exclusive groups, which were determined by using the percentage of contribution of food intake to overall protein intake.

General linear modeling was used to

1)   estimate the association between protein intake (grams per day) and

bone mineral density (BMD),
appendicular lean mass (ALM),
ALM normalized for height (ALM/ht2), and
quadriceps strength (QS) (2008-2011) and to

2)   calculate adjusted least-squares mean outcomes across quartiles of protein
(grams per day) and protein food clusters.

Results:   The mean ± SD age of subjects was 40 ± 9 y; 82% of participants met the Recommended Daily Allowance (0.8 g · kg body weight-1 · d-1).

The following 6 dietary protein food clusters were identified:

fast food and full-fat dairy,
fish,
red meat,
chicken,
low-fat milk, and
legumes.

Bone mineral density (BMD) was not different across quartiles of protein intake (P-trend range = 0.32-0.82); but significant positive trends were observed for appendicular lean mass (ALM), ALM/ht2 (P < 0.001), and quadriceps strength (QS) (P = 0.0028).

Individuals in the lowest quartile of total protein intake (quartile 1) had significantly lower appendicular lean mass (ALM), ALM/ht2, and quadriceps strength (QS) than did those in the higher quartiles of intake (quartiles 2-4; (P ranges = 0.0001-0.003, 0.0007-0.003, and 0.009-0.05, respectively). However, there were no associations between protein clusters and any musculoskeletal outcome in adjusted models.

Conclusions:   In a protein-replete cohort of adults, dietary protein is associated with appendicular lean mass (ALM) and quadriceps strength (QS) but not with bone mineral density (BMD). In this study, dietary protein food patterns do not provide further insight into beneficial protein effects on muscle outcomes.

---

From the FULL TEXT Article:

INTRODUCTION

Age-related musculoskeletal losses are a major public health burden because they can cause physical disability and increased mortality. Osteoporosis accounts for ~50% of all hip fractures. [1] Consequences of hip fracture include a substantially increased risk of mortality (≤30%) [2] and a decline in physical function. [3, 4] Osteoporosis is commonly accompanied by sarcopenia, a syndrome characterized by progressive and generalized loss of skeletal muscle mass and strength with risk of adverse outcomes such as physical disability, poor quality of life, and death. [5] The prevention of age-related losses of bone and muscle strength during adulthood via low-risk approaches such as nutrition and dietary alterations is of increasing research interest.

Greater dietary protein has been shown to reduce age-related loss of bone density [6–8], muscle mass [9–11], and muscle strength. [12–15] Although the benefits of attaining adequate protein in the diet to optimize musculoskeletal health have been well established, it remains unknown whether these benefits occur as a result of absolute protein intake (i.e., attaining a specific dietary allowance in grams per day) or whether maximizing protein intake from specific food sources is of importance. Individual protein food sources may be beneficial to the musculoskeletal system because a specific food source may differ in its amino acid composition, digestibility, and nonprotein nutrient composition. [16] Studies that have separated protein foods by animal protein compared with plant protein have had conflicting results regarding their associations with bone [17] and muscle. [13, 18]

This controversy is due in part to the complexity of what seems to be a simple research question. The influence of dietary protein on the musculoskeletal system is dependent on many other dietary factors such as other nonprotein nutrients (i.e., calcium, magnesium, and vitamin D) and the acidity of the diet. [17] Although it is recommended that adults attain adequate protein intake for musculoskeletal health, it remains unclear if specific protein food sources or dietary patterns possess greater benefit to the musculoskeletal system. The assessment of whether dietary protein food patterns are differentially associated with bone and muscle health will have important public health implications, because precise recommendations on the type of protein-containing foods are lacking. The objective of our study was to examine the prospective association of novel dietary protein food clusters [derived from established dietary pattern techniques [19] and used by our group previously [20]] with appendicular lean mass (ALM),6 quadriceps strength (QS), and bone mineral density (BMD) in 2,986 men and women from the Framingham Third Generation Study. We hypothesized that not all protein food clusters would be equally beneficial to bone and muscle health.

---

DISCUSSION

When dietary protein was examined as grams of intake per day (continuous and ranked intake into quartiles), overall intake was not associated with any measure of hip or spine BMD in this age-diverse cohort of men and women from the Framingham Third Generation Study. Participants with the lowest quartile of total protein intake showed significantly lower ALM and QS compared with those of individuals in the upper quartiles of protein intake. Six protein food clusters were identified with the use of novel protein-centric food cluster modeling. There were no significant differences in BMD, ALM, or QS across protein food clusters after accounting for other known confounders.

Results of the current study from the Framingham Study Third Generation cohort showed no association between BMD and dietary protein when assessed as total daily intake. This result is contrary to previous research in large population-based cohorts in older adults (>60 y of age), which showed dietary protein to be positively associated with BMD cross-sectionally [29] with reduced bone loss over time in the Framingham Original Cohort [5] and with reduced risk of falls [30] and fracture in the Framingham Original Cohort [31, 32] longitudinally. Null results in the current study may be explained by the overall young age of the cohort (mean age: 40 y) of whom only 15% of subjects were aged >50 y, which is a time when the age-related loss of bone mass typically becomes evident. However, this cohort was specifically chosen because of their wide age range to examine more-diverse protein food intake (because older adults typically show comparable protein intakes from similar sources). In addition, the Framingham Third Generation Cohort was largely protein replete with 82% of the sample meeting the RDA for dietary protein (0.8 g · kg–1 · d–1). Dietary protein may maximally benefit bone health in older, more frail, or protein-insufficient populations.

Randomized controlled trials have shown inconsistent results on whether additional protein intake can improve bone health. Daily supplementation with whey protein showed no change in BMD, measured by dual-energy X-ray absorptiometry, or in volumetric BMD that was measured with the use of a quantitative computed tomography in either a 2-y [33] or 18-mo [34] follow-up period compared with placebo. In a weight-loss trial, a high-protein diet (24% of kilocalories from protein) attenuated the loss of BMD at the radius, spine, and total hip over 1 y compared with the effect in the normal-protein group (18% of kilocalories). [35] Women were counseled to increase their protein intake with lean meat, fish, legumes, and dairy with an optional whey-protein supplement if needed. Supplementation with protein from dietary sources compared with a whey-protein supplement may account for the differences in results between these studies.

Our study sought to determine whether individuals from a large community-based cohort would have different BMDs that were dependent on their protein-derived dietary pattern. A recently published study in the older Framingham Offspring Cohort (mean age: 60 y) showed that individuals in the protein food cluster who had high protein intakes from red meat and processed foods had lower BMD than that of individuals in the low fat–milk protein food cluster. [20] In contrast, the current study showed no differences in BMD across protein food clusters in the younger generation of the Framingham Heart Study cohort. Age may have played a role in the different results. In addition, there was a stark difference in protein intake between the 2 cohorts, which may also partially explain the contrast in results (93 g/d in the younger cohort compared with 78 g/d in the older cohort).

Dietary protein is an important contributor to muscle status because it is an important building block for muscle-fiber synthesis, and the breakdown of muscle has been widely shown under conditions of inadequate protein intake. Consistent with the literature [9, 10], we showed that total protein intake was positively associated with ALM. Although studies that have examined the relation between total protein intake and strength in adults have shown nonsignificant results [11, 36, 37], the current study showed that individuals in the lowest quartile of dietary protein had significantly lower QS than did individuals in the higher quartiles of intake. Previous research in the older Framingham Offspring Cohort showed that greater plant protein intake was positively associated with QS, whereas animal protein intake showed no significant association (13).

Therefore, the current study further examined protein intake by dietary patterns. With the use of this novel protein-centric dietary pattern methodology, no significant differences across protein food clusters were shown with either ALM or QS after other known risk factors were taken into account. These results suggest that, in a protein-replete population of largely middle-aged adults, higher intake of dietary protein is linked with lean mass and strength, but the dietary protein food pattern does not further clarify the associations with these measures of muscle health. The lack of differences in either muscle mass or strength across protein food clusters is an important finding because future public-health messages that encourage older adults to meet required protein intakes do not need to provide complicated recommendations about specific protein-containing foods. Increased dietary protein intake, regardless of the food source, will likely aid in the success of reaching required amounts in a population in whom adequate energy intake is already a problem.

Because of the single time point of the bone and muscle assessment, this study was unable to determine whether dietary protein food choices and patterns would alter bone and muscle health over time. In addition, there were some inherent limitations of the cluster methodology used such as its sensitivity to outliers. [26] To overcome these limitations, individuals who fell >5 SDs from the mean of any one protein food group were removed in addition to participants who formed a cluster with <10 individuals. The naming of protein food clusters is subjective; therefore, the current study described methods of interpreting cluster formations in detail. Note that, although the clusters were named by their greatest contributions to overall protein intakes (such as the chicken cluster), the clusters all contained a mix of protein food sources. However, the cluster analysis offered advantages over alternative quantitative approaches because it classified participants into mutually exclusive, relatively homogenous clusters on the basis of a specified attribute (i.e., the percentage contribution of food groups to total protein intake). The use of the FFQ had inherent limitations because of the lack of detailed information on portion sizes and specific recipes with the potential for systematic errors that could have been due to the underreporting or overreporting of food intakes. Systematic errors can be partially mitigated through energy adjustment as was used in the current study. The use of the FFQ is best suited for ranking the typical nutrient intakes of individuals and for food-patterning techniques as were used in the current study.

To our knowledge, the use of the percentage contribution of protein intake from foods to total dietary protein intake is novel. The only other use of this methodology that was specific to protein intake was in the older Framingham Offspring Cohort. [20] Each cohort produced a different number of clusters (5 clusters in the Offspring Cohort and 6 clusters in the Third Generation Cohort). Although some of these clusters showed similar patterns of protein intake (both cohorts identified a low fat–milk cluster, a red-meat cluster, and a chicken cluster) there were some differences whereby the younger generation classified some participants into a cluster of legumes, nuts, seeds, fruit, and vegetables. It is important to take these differences in intakes of dietary protein food patterns across generations into consideration when interpreting studies with varied results on this topic.

In conclusion, in this large cohort of non-Hispanic white men and women aged 19–72 y, total protein intake is positively associated with ALM and QS but not with BMD. The protein intake pattern, as described by a cluster analysis, is not associated with differences in BMD, muscle mass, or muscle strength in this population. Null results may be explained by the protein-replete population studied with intakes well in excess of the RDA for dietary protein (on average, 30–40 g above the RDA). In protein-replete adults, protein food pattern (source) may not contribute to musculoskeletal outcomes in a meaningful manner.

Return to SOY PROTEIN

Since 3–05–2017