Updated October 30th 2023
Fact Checked by Dr Mark Watson
Arthri Flex Advantage + Vitamin D3 is a joint health supplement produced by 21st Century. They claim it uses synergistic herbal extracts and mineral compounds to help support healthy joints from every angle, while being reasonably priced, gluten free, and containing no added yeast, soy, dairy, or artificial flavors.
21st Century say it will boost the health and flexibility of your bones, cartilage, and joints all at the same time. Unfortunately, after we reviewed 21st Century Arthri Flex Advantage ourselves, the supplement facts show that the product appears to be far less effective than they are suggesting.
The Arthri Flex Advantage + Vitamin D3 formula consists of vitamin c, vitamin d, magnesium, copper, zinc, manganese, molybdenum, potassium, glucosamine sulfate, MSM, hyaluronic acid, and a proprietary blend of type II collagen with naturally occurring chondroitin sulfate, hyaluronic acid, boron glycinate, boswellia serrata extract, grape seed extract, and white willow bark extract. And to be positive if you're looking for a glucosamine supplement with some extras this is ok and pretty fairly priced.
Based on the ingredients profile it should well be quite good for stiffness, but it there isn't a lot in here to combat inflammation, which we expect from a good joint supplement, and what there is unfortunately is under dosed.
it also contains some other ingredients in cellulose, stearic acid, croscarmellose sodium, magnesium stearate, magnesium silicate, polyethylene glycol, polyplasdone, polyvinyl alcohol, silicon dioxide, and titanium dioxide, which are intended to make the pills more stable, rather than to improve their efficacy.
While many of the ingredients are useful in medications designed to support joint health, most are used in doses that are either far too high or too low. Some are then also lumped into a blend with unproven ingredients where all of the dosages have been obscured, making the product hard to predict beyond the glucosamine effects.
When you then add in the facts that it is not suitable for people who have a shellfish allergy and has received some complaints of causing side effects in reviews from past customers, there's a fair bit of negativity.
Generally we'd recommend FlexAgain for most people, seeing as it's actually correctly dosed. And ultimately you get far more effective active ingredients for about $15 a month more. Although if youre budget caps off here, then we tend to recommend Joint Buddy.
Reviews by past customers have given the 21st Century product an average review score of 4.6 out of 5 stars on Amazon, which looks pretty good. However, with most of the "reviews" being just a star rating, rather than a real review, it is hard to glean too much from this.
When looking at other customer reviews from sites around the web, the general consensus seems to be that it can provide some mild relief from minor aches and pains, but that it will not help with more serious issues, such as osteoarthritis.
There was then also more than one review which mentioned people experiencing side effects like heart or hearing problems and gas.
These reviews seem to support the conclusion we came to when writing our own review, which is that while the product does contain some useful ingredients, it is not very effective and will not be of much use to most people.
Vitamin C (As Calcium Ascorbate) - 100 MG
Vitamin c (calcium ascorbate) is an essential, water soluble vitamin, found in various fruits, vegetables, and other foods. Well known for its immune boosting, disease fighting properties, it is said to be one of the main building blocks of collagen and vital for the production of neurotransmitters in the brain.
It can also improve tissue repair, support cartilage maintenance and natural joint motion and flexibility, boost bone, muscle and tooth strength, and enhance nutrient absorption.
Unfortunately, studies show that around 2,000 mg of calcium ascorbate must be consumed in a dietary supplement for it to be of any use (1). This means, with Arthri Flex Advantage + Vitamin D3 containing just 5% of this, it is unlikely to do anything at all.
Vitamin D3 (As Cholecalciferol) - 50 MCG
Vitamin d is a fat soluble vitamin that has many functions in the human body. It aids digestion, nutrient absorption, cell division, protein synthesis, and bone, muscle, skin, tooth and immune system health and functions, limits fat storage, and boosts energy and blood calcium levels and your overall health.
However, it is mainly put in a dietary supplement for joint pain to prevent you becoming vitamin d deficient, which can lead to poor joint health and low testosterone levels (2).
As 50 mcg is the upper end of the optimal range for vitamin d3, this is a rare instance where 21st Century Arthri Flex Advantage actually contains a sufficient dose of a proven ingredient.
Magnesium (As Magnesium Glycinate) - 200 MG
Magnesium glycinate is a mineral involved in over 300 enzyme reactions in the human body.
It reduces inflammation and cramps, boosts muscle and heart health and functions, sleep quality and exercise performance, regulates blood pressure and blood sugar levels, and helps prevent diabetes and depression.
The problem is, the minimum daily dosage of magnesium required to produce these effects is 320 mg for women and 410 mg for men. This means that the 200 mg present in each serving of 21st Century Arthri Flex Advantage is far too low and very unlikely to benefit your joints in any way (3).
Zinc (As Zinc Glycinate) - 15 MG
Zinc glycinate is another essential mineral that is vital to your health, as it can reduce inflammation and the effects of aging, improve growth, DNA synthesis, vision and your metabolism, and enhance immune functions, wound healing, and blood clotting.
However, unless you have a zinc deficiency, at least 25 mg of zinc is required each day for you to notice any of its effects. This means the 15 mg in each serving of Arthri Flex Advantage + Vitamin D3 will be too low to be of any use for the vast majority of people (4).
Copper (As Copper Glycinate) - 0.5 MG
Copper glycinate is a mineral that is essential for antioxidant enzymes in the human body to be produced.
However, studies show that people are extremely unlikely to not get enough copper from their meals, while too much copper can actually cause Alzheimer's disease (5). This means the presence of copper in the pills is much more likely to do you harm than good.
Manganese (As Manganese Glycinate) - 5 MG
Manganese glycinate is an essential mineral and antioxidant that can prevent or reduce inflammation and help you maintain a healthy joint structure. It can then also improve the health of the eyes and brain, and the absorption of iron, and prevent a medical condition like anaemia from developing (6).
The problem is, the recommended daily dosage of manganese is around 2.3 mg. This means, while it does not necessarily mean you will have adverse reactions occur if you exceed recommended dosage guidelines, it is too strong and some people could.
Molybdenum (As Molybdenum Glycinate) - 220 MCG
Molybdenum glycinate is a mineral that keeps the enzymes in the human body functioning correctly, prevents toxins and free radicals from causing inflammation or doing any damage, and aids DNA and protein synthesis, to help the body grow and repair.
However, as there has never been a reported case of molybdenum deficiency and the 220 mcg present will greatly exceed recommended dosage guidelines, its presence is far more likely to produce negative individual results than positive ones (7).
Potassium (As Potassium Chloride) - 195 MG
Potassium chloride is a synthetic compound and proteoglycan synthesis stimulator. It can help increase the production of cartilage, repair damaged or degraded joints, and reduce joint pain and inflammation.
However, studies suggest that dosages of at least 600 mg per day are required to see any real benefits. This means the 195 mg of potassium chloride in a serving of Arthri Flex is too low to be of any use (8).
Glucosamine Sulfate 2KCL - 1,500 MG
Glucosamine sulfate is a compound found in shellfish and it can slow or prevent collagen degradation, alleviate joint pain, and treat the symptoms and prevent the progression of osteoarthritis. The 1,500 mg of glucosamine sulfate present even falls within the optimal daily range (9).
The issue is, the whole dosage is delivered in one serving, as a physician or healthcare provider would recommend highly that you split the dosage into 2 or 3 smaller doses. Taking it all at once could cause you to see adverse reactions occur, like constipation, diarrhoea, heartburn, nausea, and liver problems.
MSM (Methylsulfonylmethane) - 1,500 MG
MSM is a chemical usually found in green vegetables, fruits, and plants that is high in sulphur and known for its anti inflammatory and antioxidant properties. It can improve joint health, ease the symptoms of osteoarthritis, and prevent or reduce inflammation and oxidative damage and stress.
With 1,500 mg falling within the optimal range, this component of the product appears to be both optimally dosed and effective, which is a rarity (10).
Hyaluronic Acid (As Sodium Hyaluronate) - 80 MG
Sodium hyaluronate is a polysaccharide well known for boosting the elasticity and healing time of the skin and reducing wrinkles and the signs of aging. However, it can also improve the health of the cartilage, joints, and eyes as well.
The issue is, most studies say doses of around 200 mg per day are required to produce these effects (11). With only 80 mg being present here, it simply is not going to do what it has been included to.
Proprietary Blend - 1,045 MG
Premium Chicken Sternum Type II Collagen (Naturally Occurring Chondroitin Sulfate)
Type ii collagen from poultry contains naturally occurring chondroitin sulfate. It's rich in compounds that make up the cartilage in the human body. Studies on joint nutrition science show it will support cartilage production, maintenance, and elasticity, and treat joint pain, stiffness, and damage, as well as arthritis.
There are two big issues though. Not only is this considered to be one of the least effective types of collagen to produce these effects, but the lack of any stated dosages means we have no idea how much is actually present in the formula (12).
This means we don't know what, if any, joint health benefits the presence of type ii collagen in Arthri Flex Advantage + Vitamin D3 will provide
Hyaluronic Acid (As Sodium Hyaluronate)
The sodium hyaluronate we see here is exactly the same as the hyaluronic acid we saw previously and it will again work in all of the same ways and provide the same benefits. The only difference is we have no idea of knowing how much is present this time around.
Boron is a mineral and metal element that can boost joint health and bone density, reduce inflammation and cholesterol levels, and improve blood plasma and testosterone production and brain functions (13).
Unfortunately, with boron glycinate being buried in a proprietary blend with no dosages listed, it is impossible to know if enough is present to be of any use or not.
Boswellia Serrata Resin Extract
Boswellia serrata extract is a type of gum produced from frankincense trees that contains boswellic acid. It has long been used in ayurvedic medicine, due to claims that it can reduce inflammation of the joints, treat the symptoms of osteoarthritis, and even reduce swelling of the brain.
While clinical studies on boswellia serrata extract are still in their infancy, the results look very promising.
However, with 100 mg of boswellic acid being required to produce these results and the Arthri Flex Advantage + Vitamin D3 Proprietary Blend not listing any dosages, it is impossible to know if its presence will be of any use or not (14).
Grape Seed Extract (Vitis Vinifera)
Grape seed extract contains a substance called resveratrol, which has long been used in east Asian traditional medicines, due to its potent antioxidant and anti-inflammatory properties.
It can reduce inflammation, oxidative damage and arthritis symptoms, improve gut, heart, and nervous system health and functions, and blood pressure and cholesterol levels, aid fat loss, alter insulin and glucose sensitivity, and combat diabetes, Alzheimer's disease, and some other chronic illnesses (15).
However, while the proprietary blend prevents us from knowing the exact dose present, the weight of the blend and the position of grape seed extract within it tells us that the 300 mg required for optimal results cannot possibly be present.
White Willow Bark Extract (Salix Alba)
White Willow bark extract is used in traditional medicines as it is rich in a chemical called salicin, which is similar to the active ingredient in aspirin. It is said to relieve muscle, back, and knee pain, arthritis symptoms, fevers and flus, and many other types of medical condition.
Unfortunately, joint nutrition science studies have yet to produce any conclusive evidence to support any of these claims. This means there is a good chance that the presence of white willow bark extract in Arthri Flex + Vitamin D3 will do you no good at all (16).
21st Century claim that taking their tablets daily will greatly improve your joint health. And as glucosamine supplements go, it's not terribly priced, but the problem is with a lot of the other ingredients either being unproven or present in incorrect dosages and proprietary blends.
We do however recommend that you don't take it all at once as advised and split Arthri King up into two capsules twice daily to help avoid stomach upset.
We generally wouldn't recommend Arthri King as a go to joint supplement, but its not a bad budget option either.