Q: Can you explain how arginine affects wound healing? I have recently heard that patients with pressure ulcers should receive arginine supplementation, but it is not routinely ordered for these patients at my facility. Is this something we should be doing?
A: Arginine has recently come to the forefront as a nutritional intervention for pressure ulcers (PUs). This is due primarily to the introduction of a supplement called Resource Arginaid, developed and distributed by Novartis Nutrition, Minneapolis, MN. Resource Arginaid-available as a powdered drink mix in cherry, lemon, and orange flavors-provides arginine in a delivery system that is palatable and convenient to administer. Each individual packet provides 4.5 grams of arginine, which is mixed with 6 to 8 ounces of cold water.
As with any new product, it is important to separate the scientific facts from the marketing hype before making a decision that affects your practice. In this case, some background information about arginine is needed and a review of the literature should be conducted.
A "Semiessential" Amino Acid
Arginine is an amino acid. Amino acids are generally classified into 2 categories: essential and nonessential. Essential amino acids are those that the body cannot synthesize; a steady supply of essential amino acids must be provided through the diet. The body can manufacture nonessential amino acids and, therefore, it is not critical to provide an exogenous supply of them in the diet.
Arginine is a unique amino acid that is generally referred to as "semiessential."1,2 This noncommittal label describes the fact that although the body can manufacture arginine, it often does so in an amount that is insufficient to meet physiologic needs. This is often the case during periods of growth, illness, and metabolic stress. In other words, arginine is a nonessential amino acid during periods of maintenance, but essential during periods of growth and healing.
Arginine regulates many metabolic and physiologic body functions and has many attributes that support wound repair:
* Arginine is nitrogen-rich. The average amino acid is 16% nitrogen; L-arginine is 32% nitrogen.3-5
* Arginine is a precursor to proline, which is converted to hydroxyproline and then to collagen.3-5
* Arginine has a positive influence on the body's levels of insulin-like growth factor-I (IGF-I), a hormone that promotes wound healing.3-5
* Arginine is a precursor to polyamines-the cell's building blocks, which are important for wound repair.3-5
* Arginine is the only substrate for nitric oxide synthesis. Nitric oxide has a beneficial effect on circulatory status and increases blood supply to the wound.3-5
* Arginine contains immune-enhancing properties that reduce the risk of infectious complications of a wound.3-5
Arginine and Wound Healing in the Literature
Several studies have been published documenting the effect of arginine in wound healing. Kirk et al6 studied arginine supplementation in people older than age 65. A small catheter was placed subcutaneously and a split-thickness wound was created in 30 healthy volunteers. Half of the subjects received 17 grams of arginine per day orally and half received a placebo for 2 weeks. The arginine-supplemented group demonstrated significantly higher hydroxyproline and protein catheter content, greater lymphocyte responses, and elevated levels of IGF-I compared with the control group. From these results, the authors concluded that arginine supplementation improved wound healing and immune response in the elderly.
Cui et al7 studied arginine in scald-burned rats. Rats were inflicted with a 30% body surface area burn and then examined for the effects of supplemental arginine on protein metabolism. Nitrogen balance in the arginine group was markedly greater than the control group. Whole-body protein turnover rate, fractional protein synthesis rates in tissue, and urinary excretion of polyamines was significantly higher in the arginine group. The authors point out that arginine's role as an important precursor to polyamines may further explain its importance in protein metabolism and wound healing. The authors concluded that an arginine-supplemented diet can increase the level of polyamines, thereby promoting tissue repair.
As more is learned about the role of nutrition in the treatment of PUs, practitioners find there is more to it than simply ordering vitamin C and zinc. Arginine supplementation is a nutritional intervention that should be considered. It is inexpensive, noninvasive, and has virtually no adverse effects. In addition, testimonials of successful wound healing using Resource Arginaid as part of a multidisciplinary care plan have been reported in practice.
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