Update 8/15/22. MET-Rx RTD 51 shake by Met-Rx is a high protein, low carb, ready-to-drink (RTD), meal replacement shake that is sold both online and in local retail stores. It's been around a lot longer than many other shakes you may have heard of like Shakeology and others you may be familiar with. In this MetRX review, you'll learn about the protein and other ingredients in the shake as well as how much fiber it has and its artificial sweeteners. Beyond this, you'll also learn how this RTD shake tastes too.
Other Shake Reviews
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 it's an ingredient in many protein shakes that come in cans and bottles. Carrageenan is a lightning rod for online criticism.
To be fair, these three ingredients are probably in many other products people consume.
MetRX RTD 51 Protein
The RTD 51 has 51 grams of protein per 15 oz can. This equals 101% of the daily value for protein. While the shake is popular with those who exercise, it's unlikely most of those people would be deficient in protein since they likely already eat very well. The better the diet, the more likely someone is to be eating adequate protein, vitamins, and minerals.
What Kind Of Protein?
The protein in the MET-RX 51 shake comes from what they call the “Metamyosin VPR Protein Blend.” The name “metamyosin” is a marketing word – and a good one too. Myosin is one of the major proteins in muscle tissue. That said there is no myosin in MetRx.
The Metamyosion VPR protein blend is a combination of these ingredients:
- Milk protein concentrate
- Whey protein concentrate
- Calcium caseinate (casein)
Calcium caseinate comes from casein, one of the major sources of protein in milk (the other protein is whey). While both whey and casein protein, come from milk, they have different properties. Here is a 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|
Table information was summarized from this book.
Whey protein tends to have a more direct effect on muscle protein synthesis. Casein 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).
So the idea is both casein and whey would be better together than either would alone.
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 multiply the result by 100, we can determine the percentage 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 it's 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, it's 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 canned products as well as other plastic items and is speculated to be linked to 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 aftertaste 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.
Always Look At The Supplement Facts Label
Watch on my Youtube channel if you prefer
Who Makes MetRx?
MetRX supplements are a product of Met-Rx Nutrition, located in Boca Ratan Fl 33487. Their phone number is 800-55-METRX. It turns out, the Met-Rx company, 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|
See the review of the Isagenix shake.
Met-Rx Side Effects
This protein shake has been sold for years. As such its likely safe in most healthy people. That said here are a few things to think about when using this supplement. This list is not complete:
- Start by drinking less than recommended for the first week.
- The protein in the shake can be an issue for those with kidney issues. Talk to your doctor
- The shake may give you gas if you're not used to 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. While I'll always put food first, for healthy people on the run who want to add some extra protein to their diet, this might be something to look at.
Here it is on Amazon if you want to see what others are saying
gino v black says
I have been taking metrx since dr conlley put it on the market, in the 90s and it is a great product, for health and to keep your muscles intact, that said I am 89yrs young and still going strong. ps, their meal replacement is great, try it.
Joe Cannon says
Gino, thanks for stopping by! Im glad to hear Met-Rx has been working so well for you. I will check out their meal replacement too. Thanks for the tip 🙂
Mark Thorson says
You’re confusing casein with caseinate. Caseinate is hydrolyzed casein, i.e. broken down from the protein into the free amino acids. It should be very soluble in water, unlike casein. Caseinate is commonly used in savory foods when you want to add the umami punch of MSG without listing MSG as an ingredient. Caseinate is not pure MSG, but it’s got a lot of free glutamate in it. Here, it’s probably just to boost the amino acid content and perhaps to make it a more balanced complete source.
Mark, Since casinate comes from casein that’s why I call them the same thing. My guess is also that its to increase amino acids in the shake. When I looked I could not find anyone discussing MSG content in the RTD 51 shake.
Jared Adair says
I appreciate what you do Joe and I know most of all posters here do as well. I just find it hard to believe you would give your blessing to something that had Splenda in it.
Hi Jared, I’m not giving it my blessing. I know spelenda etc. matters to some and that’s why I mentioned it. I will always advocate people make their own shake but for those who dont want to do that, this might be an option.