MET-Rx RTD 51 shake by Met-Rx is a high protein, low carb, ready-to-drink, meal replacement shake that is sold both online and in local retail stores. It’s actually been around a lot longer than many other shakes you may have heard of like Shakeology and others I’ve looked at. How much protein is in the shake? More than most meal replacement shakes I’ve seen. So, does it work? Let’s take a closer look at RTD 51 ingredients and see what we can discover.
What Does RTD Mean?
The letters RTD is short for “ready to drink” and is a reference to the fact that no mixing needs to be done prior to consuming the shake. The shake comes in a variety of flavors and can be obtained at various local health food stores and online.
RTD 51 Nutrition Facts
According to the Nutrition Facts label, 1 can (15 oz) of MET-RX 51 has the following nutrients:
|Calories 250||Calories from fat 20|
|Percent Daily Value|
|Total fat 2 g||3% DV|
|Saturated fat 1g||5% DV|
|Trans fat 0 g|
|Cholesterol 40 mg||13% DV|
|Sodium 150 mg||6% DV|
|Potassium 430 mg||12% DV|
|Total Carbs 6g||2% DV|
|Dietary fiber 3g||12% DV|
|Sugars 3 g||N/A|
|Protein 51g||102% DV|
|Vitamin A||30% DV|
|Vitamin D||40% DV|
|Vitamin K||25% DV|
|Vitamin B6||50% DV|
|Vitamin B12||60% DV|
|Pantothenic acid||50% DV|
|Zinc||15 % DV|
|Vitamin C||50% DV|
|Vitamin E||45% DV|
|Folic acid||45% DV|
Note that the amounts shown in the percent daily value column (% DV) are based on eating 2000 calories per day.
RTD 51 Ingredients
Here are all the ingredients in 1 can (15 oz) of the RTD shake.
|water||milk protein concentrate||whey protein concentrate|
|calcium caseinate||cocoa (processed with alkali)||cellulose gel|
|natural flavors (contains caramel color)||tricalcium phosphate||sodium phosphate|
|sodium ascorbate||sodium citrate||dl alpha tocopheryl acetate|
|niacinamide||vitamin A palmitate||d-calcium pantothenate|
|ferrous sulfate||phytonadione||manganese sulfate|
|cholecalciferol||zinc oxide||pyridoxine HCL|
|thiamine HCL||riboflavin||copper sulfate|
|chromium chloride||sodium molybdate||potassium iodine|
|sodium selinite||sucralose||cellulose gum|
Read the table from left to right. This will tell you the ingredients that are most abundant and those that are present the least. For example, since carrageenan is the last ingredient, it’s present in the lowest concentration.
Red Flag Ingredients
As you look over the ingredients list above, there are a few ingredients which some people might prefer were not included. These ingredients are:
- Acesulfame potassium
Sucralose (also known as Splenda) and Acesulfame potassium (sometimes called ACE K) are artificial sweeteners. They are in many ready to drink shakes.
Carrageenan is often used as a thickening agent in foods. It comes from red algae and I’ve seen it as an ingredient in many protein shakes that come in cans and bottles. Carrageenan is a lightning rod for online criticism. To help you make sense of this, here is a rational discussion I found for those who are interested in learning more.
To be fair, I’ll point out that these ingredients are probably in several other products people consume. I mention these ingredients in case they matter to some people.
RTD 51 Protein
As the name indicates, the RTD 51 has 51 grams of protein per 15 oz can. For a healthy person eating a 2000 calorie per day diet, this equals 101% of the daily value for protein.
It’s my experience that most of the people who likely would be drinking the RTD51 shake -people who workout regularly – would not be lacking in most of the vitamins and minerals listed. That’s because most people who work out regularly also usually eating a pretty well balanced diet.
The nutrient that stands out in the RTD shake is protein. That’s likely the big reason someone would be choosing this shake over others, so let’s take a look at the protein in this product.
What Kind Of Protein?
As the name implies, there are 51 grams in each serving of the RTD 51 shake. This represents 102% of the daily value of protein -assuming someone was eating 2000 calories per day. For those eating more than 2000 calories per day, the daily value would be less.
The protein in the MET-RX 51 shake comes from what they call the “Metamyosin VPR Protein Blend.” Before we go any further, let me just say that that there is no such protein as “metamyosin.” The word however is good marketing. The word myosin is reference to one of the major proteins in muscle tissue.
So by calling it Metamyosin, the subtle message is that this protein blend will help build muscle.
Marketing aside, the Metamyosion VPR protein blend is a combination of these ingredients (in order as they appear on the label):
- Milk protein concentrate
- Whey protein concentrate
- Calcium caseinate
Calcium caseniate comes from casein, one of the major sources of protein in milk (the other being whey protein). While both whey protein and casein protein, both come from milk, they have different properties. Here is a quick breakdown of some of the differences between whey protein and casein protein:
|Whey Protein||Casein Protein|
|More expensive||Less expensive|
|Mixes well||Doesn't mix as well|
|Is digested faster||Is digested slower|
|More muscle protein synthesis effect||Less muscle protein synthesis effect|
|Less anti-catabolic effects||More anti-catabolic effects|
For those who are curious, the information in this table was summarized from this book.
Just to clear things up, you may have noticed in the table that I listed whey protein as having “less anti-catabolic effects” than casein. That’s because it works a bit differently than casein.
Whey protein tends to have a more direct effect on muscle protein synthesis. Casein, on the other hand, has less of a muscle protein synthesis effect. In contrast, casein appears to work by helping to reduce the breakdown of existing muscle (in other words, it has an anti-catabolic effect).
Because of these differences, the logic behind using both whey and casein in the RTD 51 shake is the hope that it would provide a more broad spectrum effect on building muscle – both stimulating new muscle growth and slowly the breakdown of existing muscle fibers. This does make sense in the context that Metrx was originally created to help injured people retain muscle.
RTD 51 Shake Research
Given the idea that the whey and casein combination might result in better overall muscle development, I was curious if there was any research on this product. I was not able to find any when I searched the National Library of Medicine. I thought this was odd because shake was said to be originally developed to help injured people retain muscle mass.
What Percent Fat Is It?
If you look at the Nutrition Facts label above, you can see that 1 can of the RTD 51 shake has 250 calories. We can also see that it has 20 calories from fat. If we divide the total calories (250) into the fat calories (20) and multiple the result by 100, we can determine the percent of fat that this shake is. In other words:
20/250 =0.8. 0.8 x 100 =8%.
So, the RTD 51 shake is only 8% fat. That’s not too bad. According to the FDA, anything that is 5% or less is considered “Low” and anything that is 20% or more is considered “High.”
Fiber In The RTD 51 Shake
Each 15 oz can of RTD 51 has 3 grams of fiber. That’s not too much but given that the shake is not marketed to people who are usually interested in fiber, I’m surprised it has any.
The ingredients list indicates that the product contains “cellulose gum.” Since cellulose is an insoluble fiber, I take that to mean the RTD 51 has insoluble fiber rather than soluble fiber. There is nothing wrong with this. There are benefits to both soluble and insoluble fibers.
How Many Carbs?
The RTD51 shake is a low carb shake. There are only 6 grams of carbs in a 15 oz can. If we consider only the net carbs (total carbs – fiber), then its less, coming in at 6 grams – 3 grams for a total of 3 net carbs. To put things in perspective, there are 28 grams in 1 ounce. Yes, those 3 carbs are coming from sugars but regardless, this is not the shake to take with you during a marathon, when carbs are your main fuel source.
Does It Contain Lactose?
Given that the shake contains milk proteins, its logical to ask the question of the RTD shake has lactose. It doesn’t appear so. I looked for info on this and all I found said that there is no lactose in the product.
Does It Contain Aspartame?
Aspartame, the artificial sweetener, is not in the ingredients. The sweeteners in the RTD shake are Sucralose and Acesulfame-K.
Does It Contain BPA?
Bisphenol A (BPA) is an estrogen-like compound that is used in the linings of some caned products as well as other plastic items and is speculated to be linked some nasty things such as maybe obesity, immune problems and infertility as well as breast and prostate cancer. This is why you may have noticed so many products that are “BPA Free” these days.
When I called Met Rx they informed me that RTD 51 protein shakes are BPA free. There is no BPA in the lining of the cans that contain RTD 51, so that is good.
How Does RTD 51 Taste?
Met RX RTD 51 has a rich creamy taste which is not what I expected from a shake that was only 250 calories per 15 oz can. I know taste is an individual thing and some have said it tasted chalky, but I for one did not mind the taste. For this review I picked Frosty Chocolate. While there will always be a personal preference, I tasted the shake when it was both cold and at room temperature and liked the taste both ways. I did not really notice an after taste either.
I thought the shake had a thick texture to it which I thought was satisfying. Even though the can does provide 15 ounces (pretty good in my book), I experimented with adding some water to the shake as a way to add extra volume (for those not satisfied with only 15 oz).
While adding some ice water to the shake did dilute the texture of the shake and the chocolate flavor a bit, it was still not a bad taste. I could still taste the chocolate.
RTD 51 For Weight Loss?
There is evidence that protein can help preserve muscle during dieting. Because of this, I thought it was interesting that the product label actually states “not to be used for weight loss.” I think this may have more to do with some legal things as well as the focus of MET-Rx, the company, than anything else. By that I mean that these days MET-Rx usually markets to bodybuilders and strength trainers rather than people trying to lose weight.
The shakes are designed to provide a lot of protein without providing a lot of calories, something fitness and strength competitors are usually looking for.
That said, people who are on a weight loss program should consume a bit extra protein to reduce the body from digesting its own natural proteins. Met Rx – as well as any other high quality protein supplement or food – could meet this need.
Who Makes RTD 51?
The can I have says “manufactured in the USA for Met-Rx Nutrition, Boca Raton FL33487.” There is also a phone number to call: 800 55-METRX (800-556-3879). The statement about being “manufactured for MET-RX” made me wonder who actually did the making. Was RTD 51 made at MET-Rx itself or did they farm this out to someone else.
So I called them. The customer service person I spoke with told me that Met-Rx makes RTD 51 in a facility that they own. As such, I’m not sure why they say “manufactured for” on the product? The Met-Rx company in turn, is owned by Natures Bounty, which owns several brands many people are likely familiar with ranging from Puritans Pride to Osteo Bi-Flex.
RTD 51 vs. Isagenix Shake
The meal replacement shake from Isagenix is another high protein shake that is popular with fitness-minded individuals as well as those trying to lose weight. In a nutshell, here is how they compare to each other:
|Metrx RTD 51 Shake||Isagenix IsaLean Shake|
|Calories 250||Calories 240|
|Calories from fat 20||Calories from fat 20|
|Total fat 2 g||Total fat 6 g|
|Saturated fat 1 g||Saturated fat 2 g|
|Trans fat 0 g||Trans fat 0 g|
|Polyunsaturated fat N/A||Polyunsaturated fat 0.5 g|
|Monounsaturated fat N/A||Monounsaturated 3 g|
|Cholesterol 40 mg||Cholesterol 45 mg|
|Sodium 150 mg||Sodium 265 mg|
|Potassium 430 mg||Potassium 430 mg|
|Total carbs 6 g||Total carbs 24 g|
|Dietary fiber 3 g||Dietary fiber 8 g|
|Sugars 3 g||Sugars 11g|
|Protein 51 g||Protein 24 g|
Met-Rx Side Effects
I believe the RTD 51 shake is safe in healthy persons. It’s been around a long time and Ive never heard anything bad about it. Because it has a lot of protein, those with kidney problems or other issues where restricting protein may be in order, speak to your doctor or dietitian first.
I’ve drank this shake on several occasions, mostly as “lunch” during classes I teach, when I don’t get time to eat food. During those times, I often drink if faster than I normally would because of time constraints. Under those conditions, I’ve noticed it gives me gas. If I drink it at a more leisurely pace, it doesn’t happen. Based on my experiences, I’d say dont gulp it.
Does The RTD 51 Shake Work?
The Met-Rx RTD 51 is a tasty, high protein, low calorie, meal replacement shake that tastes good whether it’s cold or at room temperature. I know there are those who may balk at some of the ingredients like Splenda, acesulfame K, caramel coloring and carrageenan, which is why I listed them in the tables above. While I’ll always advocate people make their own shakes, using food, for healthy people on the run who want to add some extra protein to their diet, this might be an option.
Here is Metrx RTD 51 on Amazonif you want to check it out further.
What Do You Think?