Research Digest

Exclusive Sneak Peek

Issue 12, Vol 1 of 2 ◆ October 2015

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Table of ContentsPaying attention to omega-3s for ADHD

With more and more people being diagnosed with ADHD, there’s a continuing hunt for helpful treatments. Researchers tested an omega-3 supplement on young males, and also explored a potential dopamine-related mechanism.

Ask the Researcher: Trevor Kashey, Ph.D.

From jelly to muscle: collagen and body composition Collagen has long been equated to junk protein, at least if you’re looking to gain muscle. Could it be underrated for this purpose? A trial of older men tested collagen protein to see if it could boost muscle gain and fat loss.

Throwdown: plant vs animal protein for metabolic syndromeThe DASH diet is frequently tested in clinical trials, and often performs well. But the diet’s formulation includes strong limitations on red meat, which may be based on outdated evidence. This study compared animal-protein rich diets with a typical DASH diet.

Can omega-3s modulate the mind-muscle connection?While strength gains are usually associated with protein and muscle-related ergogenics, the nervous system isn’t targeted as often. This study explored a different type of ome-ga-3 source (seal oil) for neuromuscular exercise effects.

Throwdown: plant vs animal protein for

metabolic syndromeType and amount of dietary protein in

the treatment of metabolic syndrome: a randomized controlled trial

IntroductionMetabolic syndrome is a cluster of risk factors that greatly increases the risk of dying from any cause (1.5-fold) and especially cardiovascular disease (CVD) specific causes (2.4-fold). This condition is diagnosed as either having or being on medications to treat at least three of the five following criteria:

• Abdominal obesity (waist circumference greaterthan 40 inches (men) or 35 inches (women)),

• Elevated fasting blood glucose (more than 110 mg/dL),

• Elevated fasting triglycerides (more than 150 mg/dL),

• Low HDL-c (less than 40 (men) or 50 (women)mg/dL), and

• Hypertension (systolic blood pressure higher than130 mmHg and/or diastolic blood pressure higherthan 85 mmHg).

Reducing these risk factors for CVD is the primary goal of managing metabolic syndrome, which is often done through lifestyle modification. Notably, changes to diet and exercise that facilitate a 5-10% weight loss can address and significantly improve each risk fac-tor. While a variety of dietary approaches can result in weight loss in overweight and obese adults, as explored in ERD Issue #6 (April, 2015), some dietary approach-es may benefit people with metabolic syndrome more than other approaches.

One currently accepted dietary pattern to reduce CVD risk factors is the Dietary Approaches to Stop Hypertension (DASH) diet, which is high in vegetables, fruit, low-fat dairy products, whole grains, poultry, fish, and nuts. The diet is low in sweets, sugar-sweetened beverages, and red meats. The DASH diet is designed to be low in saturated fat, total fat, and cholesterol, and rich in fiber, potassium, magnesium, and calcium.

In the OmniHeart (Optimal Macronutrient Intake Trial for Heart Health) trial, two variations of the DASH dietary pattern were compared with DASH. One variation replaced 10% of total daily energy from carbo-hydrate with protein, and the other replaced the same amount of carbohydrate with unsaturated fat. Both variations led to greater reductions of estimated CVD risk than the standard DASH diet. Notably, all three tested diets had a roughly even split between animal- and plant-based protein.

This study sought to expand upon the findings of the OmniHeart trial by comparing the effects of three vari-ations of the DASH diet, which differed in protein type (plant vs. animal) and amount (18% vs. 27%), on meta-bolic syndrome criteria.

Metabolic syndrome is a cluster of risk factors that greatly increases the risk of cardiovascular diseases, the treatment of which includes diet and exercise to facilitate weight loss. The DASH diet is considered a prudent dietary pattern to address these risk fac-tors, but other research has shown variations of the diet to be more efficient. The study under review was designed to determine how protein type (plant vs. animal) and amount (18% vs. 27%) affected metabol-ic syndrome criteria.

Who and what was studied?This six-month, randomized, parallel-arm, con-trolled-feeding study recruited 62 sedentary overweight and obese adults with metabolic syndrome. The partic-ipants were free of established cardiovascular diseases, diabetes, or liver, kidney, and autoimmune diseases. Two participants on glucose-lowering drugs and seven participants on lipid-lowering medications were asked to discontinue their use for the duration of the study, but the eight participants taking medication for high blood pressure were allowed to continue.

The entire study consisted of four phases:

1. A two-week healthy American diet (HAD) run-in period to establish a baseline for comparisonduring the subsequent phases and establishweight-maintenance caloric intake for eachparticipant.

2. A five-week weight maintenance (WM) phase fol-lowing one of three experimental diets.

3. A six-week weight loss (WL) phase consumingthe same experimental diet as in WM but with aminimum 500 kcal per day deficit through dietaryrestriction and increased physical activity; and

4. A 12-week free living (FL) phase where partic-ipants were asked to continue their assignedhypocaloric diets and physical activity, but with-out the provision of food and drinks. To preparefor this phase, each participant met with a dieti-tian three times during the WL phase. They wereeducated on the unique features of their assigneddiet and given practical advice, including suggest-ed menus and recipes.

All food and drink were prepared by a metabolic kitch-en and provided to the participants during the HAD,

WM, and WL phases, but only one meal per day was consumed under the supervision of research personnel. The remainder of the food was packed for taking home. This means that even though all experimental diets were tightly controlled, there was no guarantee that the par-ticipants would eat all of the food provided to them, and only the food provided (i.e. no outside food or drink).

The experimental diets were a modified-DASH (M-DASH) diet rich in plant protein (18% of the calo-ries from protein, two-thirds from plants), an M-DASH diet rich in animal protein (BOLD, which stands for Beef in an Optimal Lean Diet; 18% protein, two-thirds from animals), and a higher-protein BOLD diet (BOLD+; 27% protein, two-thirds from animals).

These diets were matched for total fat (as seen in Figure 1), saturated fat, monounsaturated fat, polyunsaturat-ed fat, cholesterol, sodium, potassium, calcium, and magnesium so as to help isolate the effects of differ-ent amounts and sources of protein. However, the M-DASH diet was significantly higher in fiber (55 vs.38 grams) than the other two diets because of the reli-ance on plant-based protein sources. Examples of eachstudy diets are shown in Table 1.

Figure 1: Macronutrient breakdown of the four diets

Overweight and obese adults with metabolic syndrome were randomized to follow a modified DASH diet rich in either plant protein (M-DASH) or animal protein (BOLD), or a higher protein BOLD diet (BOLD+) for a five-week weight maintenance phase and a six-week weight loss phase, with all food and drink prepared and provided by the research staff. Afterward, the par-ticipants were asked to continue their respective diets for 12 weeks under free-living conditions.

What were the findings?Over the entire six-month intervention, there were no

differences in any outcome between the three dietary groups. Most of the significant health improvements occurred only after the WL phase. Accordingly, there was no change in the prevalence of metabolic syndrome among the participants from baseline through WM, but prevalence dropped substantially to 50-60% after the WL phase and was maintained through the FL phase. In other words, roughly half of the participants were no longer classified as suffering from metabolic syndrome after the WL phase. A summary of the study findings is shown in Figure 2.

The resolution of metabolic syndrome was the result of significant improvements in every criterion except for blood glucose levels. On average, after the WL phase

Table 1: Examples of the four study diets: Menus for the test dietsHAD M-DASH BOLD BOLD+

Breakfast

• Pancakes with butterand light syrup

• Peaches, cannedin juice

• Cottage cheese (1%)• Apple Juice

• Pancakes with butterand light syrup

• Blueberries• Skim Milk

• Orange Juice

• Bran flakes withraisins and skim milk• Whole-wheat mini-bagel and margarine

• Orange Juice• Banana

• Bran Flakes withraisins and skim milk• Cottage cheese (1%)

• Orange Juice

Lunch

• Turkey, provolonecheese, and lettucesandwich on white

bread with mayonnaise• Granola bar

• Spinach/baby greenssalad with cherry

tomatoes, mandarin,oranges, grilled chicken

breast, and dressing• Edamame beans

• Whole-wheat dinnerroll with butter

• Pistachios

• Barbeque beefsandwich on whole-

wheat bun• Spinach salad with

cherry tomatoesand dressing

• Thin pretzels• Pear

• Beef chili withshredded cheddar

cheese (low fat) and while-wheat crackers

• Peaches, cannedin juice

Dinner

• Szechuan stir-fry entréwith pork and white rice

• White dinner rollwith butter

• Romaine lettucesalad with carrots

and italian dressing

• Ratatouille (eggplant/peppers) with pasta

• Spinach saladwith carrots, cherrytomatoes, red bell pepper, chickpeas,

and dressing

• Spinach and beefskillet with ribeye steak

• Brown rice• Mixed baby greenssalad with carrots,cherry tomatoes,

and dressing

• Pot roast with mashedpotatoes and gracy• White dinner roll

with margarine• Broccoli and

edamame beans• Romaine salad with

cherry tomatoes and dressing

Snack• Plain bagel with

cream cheese

• Light yogurt• High-fiber cereal

• Almonds

• Light yogurt• Orange

• Almonds

• Hummus withwhole wheat pita and baby carrots

• Trail mix

and compared to the WM phase, there was a three to four centimeter (about 3%) reduction in waist cir-cumference, a 13-30% reduction in triglycerides, a one to four mmHg reduction in systolic blood pressure, a one to three mmHg reduction in diastolic blood pressure, and a 4-9% increase in HDL-c. Additionally, total and LDL-cholesterol were reduced from baseline during both the WM and WL phases, possibly due to the reduced saturated fat intake among all diets, but returned to baseline values during the FL phase. The WL phase also led to significant improvements in CRP (a marker for inflammation), endothelial function, and vascular stiffness.

The only difference between the WM and WL phases was a 500 kcal reduction in the food provided to the participants and a significant increase in the number of daily pedometer-measured steps taken, from 6,300 to 10,500. Together, this resulted in a significant 5% weight loss across all groups, with roughly 80% coming from fat mass. Since metabolic syndrome resolved only after the WL phase, these findings suggest that weight loss was the primary driver of health improvement.

Compliance during the WM and WL phases was determined through daily questionnaires. Participants were classified as noncompliant on any day that they consumed a non-study food or beverage or did not consume a study food or beverage. Accordingly, dietary compliance ranged from 70-90% throughout the WM and WL phases, but appeared to be higher in the M-DASH (82-90%) group than the BOLD (70-75%) orBOLD+ (77-80%) groups.

Regardless of diet, weight loss appeared to be the primary driver of improved health among the partic-ipants. In all diet groups, the number of individuals with metabolic syndrome was reduced by 40-50% after they lost about 5% of their bodyweight during the weight-loss phase.

Figure 2: Effects of all the diets on metabolic syndrome factors

Note: ranges are based on average changes across all the diets. None of the diets’ effects were statistically different from one another.

What does the study really tell us?The researchers conducting this study sought to explore how protein type and amount affects the health of people with metabolic syndrome through three dif-ferent phases of energy balance: weight maintenance, weight loss, and free living. The results indicate that nei-ther protein type or amount have a significant impact on health at any stage, and that clinically significant weight loss (5% in this study) is the primary driver for reductions in abdominal obesity, triglycerides, blood pressure, and inflammation (CRP).

Current DASH diet recommendations include limit-ing the consumption of red meat. Many other dietary patterns that are considered healthy, such as the Mediterranean diet, tend to have relatively less animal protein, with relatively more protein from whole grains and legumes. The current study used unprocessed lean beef (select grade top round, ribeye, chuck shoul-der, and 95% ground beef) and found that consuming nearly seven ounces (200 grams) per day had no det-rimental (or beneficial) impact on CVD risk factors

compared to a diet supplying mainly plant-based pro-teins. This finding is consistent with numerous other intervention trials (1, 2, 3, 4, 5, 6) showing no differ-ence between lean red and white meats and suggests that red meat can be safely included in an otherwise healthy diet.

The current study had a strong design, with ample time in each phase to allow for changes in CVD risk markers to occur. However, the trial was designed to be statisti-cally powered only to detect changes over time in each diet group, meaning that any between-group differenc-es may not have manifested due to a lack of statistical power. This may be most apparent when acknowledg-ing the lack of difference between the normal protein and higher protein diet in terms of changes in body composition.

After all, it is recognized that higher protein diets, such as those used in this study (27%), lead to greater fat loss and retention of muscle mass than normal protein diets. Additionally, higher protein diets facilitate weight loss through increased satiety. Unfortunately, the controlled-feeding design of this study required partic-

The current study used unprocessed lean beef and found that consuming nearly seven ounces (200 grams) per day had no detrimental (or beneficial) impact on CVD risk factors compared to a diet supplying mainly plant-based proteins.

ipants to eat all food provided to them, eliminating the satiety advantage. While not statistically significant, it is noteworthy that only the BOLD+ diet continued to demonstrate weight and fat loss alongside increases in lean body mass during the free-living phase, when the benefits of a higher protein diet could be realized.

Alternatively, the high and low protein diet groups were consuming 2.5 and 1.7 grams of protein per kilogram of lean-body mass, respectively, and it has been sug-gested that optimal intake for resistance-trained obese adults is around 1.9 grams per kilogram. The current study did not utilize resistance training, so an optimal amount of protein would likely be lower and possibly around that of the lower protein diets. Accordingly, the lower protein diet may have been sufficient in protein to account for the insignificant difference in weight loss or lean mass kept from a higher protein intake.

Lastly, the recruitment goals of the study were not met, which may have limited the statistical power to detect significant changes over time within each dietary group. However, there were no trends that presumably may have reached significance with additional participants.

Clinically meaningful weight loss (about 5%) appears to benefit health regardless of protein type or amount. Although this study showed no benefit to higher protein intake, a potential lack of statistical power to detect between-group changes, as has been observed in previous studies evaluating the effect of protein on body composition, suggests the find-ing should be accepted with caution. In agreement with other intervention trials, unprocessed lean red meat may be safely included as part of an otherwise healthy diet.

The big pictureThe DASH diet was developed in the mid-1990s to

address an increasing rate of hypertension among the general public. One of the unique features of the DASH diet is that it focuses on dietary patterns rath-er than single nutrients, based on past observational evidence combined with knowledge of select vitamins and minerals. Accordingly, the DASH diet was built on a foundation of natural foods such including fruit, vegetables, whole grains, nuts, legumes, and seeds that are good sources of potassium, magnesium, and dietary fiber. Additionally, it incorporates low-fat dairy prod-ucts, fish, chicken, and lean meats to reduce total and saturated fat consumption and increase protein and calcium intake.

Because nutrition is not static, this successful dietary pattern has undergone small changes in the last two decades, such as limited red meat in favor of fish and poultry. This change was based on observational evi-dence suggesting a link between red meat and CVD. As follow-up research has shown, this recommenda-tion may have been premature. Associations are not cause-and-effect relationships and there are countless potential explanations for why an association exists. Against that background, it is all the more important to highlight that the study under review — just like sever-al previous studies — found no evidence that lean red meat poses a CVD risk, at least not one that is detect-able by the measurement of common CVD risk markers.

This is certainly not the first time policy makers have based recommendations on associations, only to be unsupported by subsequent intervention trials. In ERD Issue #7 (May, 2015), we discussed the DIABEGG study that sought to clarify whether eggs could be safely included in the diet of people with type 2 diabe-tes. This research was needed because observational evidence showed that people with type 2 diabetes who ate eggs more than once per day were 69% more likely to develop CVD comorbidity than those who ate eggs less than once per week. Other research showed that for each four-per-week increase in egg intake, the risk

of CVD increased by 40%. Not only did the DIABEGG study show that eggs had no impact on blood lipids or glycemic control, it showed that eggs increased post-breakfast satiety and resulted in a more enjoyable dietary experience by the participants.

Observational evidence is important for notic-ing potential links between diet and health, but it serves only as a starting point that requires further and more rigorous testing. It is not uncommon for dietary recommendations to incorporate observa-tional evidence that is later shown to be incorrect by experimental trials. The study at hand is a great example, showing that the observational link between red meat and CVD may be a bit misleading, based previous trial evidence plus this study showing a lack of difference in CVD risk markers between the plant- and animal-based protein groups.

Frequently asked questionsAre there other dietary patterns with evidence for improving metabolic syndrome? Ultimately, any diet that results in fat loss will help with metabolic syndrome. However, some dietary patterns may better facilitate the necessary caloric deficit. For instance, a paleolithic diet excluding cereal grains, dairy, and legumes in favor of lean meats, fruit, fibrous and starchy vegetables, and nuts has been shown to result in more favorable health outcomes than a healthy refer-ence diet, as discussed in ERD Issue #6 (April, 2015).

The paleo diet referenced above is unique in that it pro-motes the consumption of lean unprocessed meats. This is in contrast to observational evidence that suggests protective dietary patterns are low in red and processed meats, providing yet more evidence that the exclusion of lean red meat is not what makes these other dietary patterns beneficial.

What is the difference between red meat and white meat, other than color? Red meat is a general term referring to meat from land mammals, including cattle, lamb, goat, and sheep, whereas white meat is a general term referring to meat from poultry, lean game like rabbit, and non-fatty fish, such as cod and pollock. The primary difference between these types of meat is their primary muscle fiber type: red meat is “slow-twitch” and white meat is “fast-twitch.” It should be noted that both types of fibers exist in the meat, and these terms refer to the dominant fiber type.

Ultimately, any diet that results in fat loss will help with metabolic syndrome. However, some dietary patterns may better facilitate the necessary caloric deficit.

Slow-twitch fibers are designed to contract continu-ously for long periods of time and thus rely heavily on oxygen for energy production via the aerobic path-way. The protein myoglobin stores oxygen in muscle cells and is richly pigmented, so the more myoglobin there is in the cells, the redder, or darker, the meat. By contrast, fast-twitch muscles are designed to contract forcefully and rapidly for very short periods of time and rely more on glucose than oxygen to function properly. Therefore, they don’t store a lot of myoglobin, instead favoring glycogen, and thus appear more glossy white.

From a nutritional perspective, the two types of meat are very similar. White meat is much leaner on average, but there are also many types of lean red meat such as bison and beef steak cut from the round of the cow. Red meat also tends to be higher in vitamin B12, zinc, and iron, while white meat contains more niacin and panto-thenic acid.

What should I know?Metabolic syndrome is a cluster of cardiovascular dis-ease risk factors, the treatment of which includes diet and exercise to facilitate weight loss. The DASH diet is

considered a prudent dietary pattern to address these risk factors, but some components of it are based largely on observational evidence, such as the suggestion to limit red meat.

The current study tested the validity of this recommen-dation and showed that consuming up to seven ounces (200 grams) of unprocessed lean red meat per day as a primary protein source has no differential impact on CVD risk factors and metabolic syndrome than a diet where the majority of protein is obtained from plants. Overall, the results suggest that clinically meaningful weight loss (about 5%) will benefit health regardless of protein type or amount. However, protein-specific benefits on other health outcomes like body composi-tion require further research, as the current study may not have been adequately powered to detect significant differences. ◆

The DASH diet has been studied in countless trials, but this is the first to show that its low-red-meat stipula-tion may be misguided. Head over the ERD Facebook forum to talk more about this study.

Overall, the results suggest that clinically meaningful weight loss (about 5%) will benefit health regardless of protein type or amount.