Arginine is a non-essential amino acid in humans. Foods high in arginine include peanuts, walnuts, almonds, chocolate, as well as some seeds. Arginine has been of interest to nutritionists for some time because of a possible role in wound healing, immune function, roles that may be facilitated through its ability to act as both an insulin and growth hormone secretagogue. Arginine also plays an important role in the formation of nitric oxide (here) and as such may play a role in lowering blood pressure through nitric oxide induced relaxation of the vasculature, and thus may be cardioprotective. Experimental work with wounded animals has shown that they have a higher requirement for arginine, and that a deficiency of the amino acid impairs wound healing somewhat. This had lead to speculation that arginine is a conditionally essential amino acid during times of increased tissue growth such as during development and wound repair. Increasing the arginine content of the diet to around 1 % in animals accelerates wound repair, and this may relate to the ability of arginine to increase the release of growth hormone.
The wound healing effects of arginine supplements have been tested extensively in animals. For example, in one study1, rats were supplemented with 1 % arginine (on top of the arginine in their normal diets). Some of the rats were hypophysectomised in order to remove the function of their hypothalamic pituitary axis. The results showed that the arginine caused improved wound healing as measured by the rate of wound healing, the weight of the wound repair tissue and the strength of wounds formed, but these effects were not present in rats that had been hypophysectomised. The arginine supplements did not affect food or water intake (which was monitored) suggesting that it was not changes in dietary intake of protein (or other macronutrients) that had accelerated wound healing. Hypophysectomised rats given bovine growth hormone showed accelerated wound healing, and increasing the dose of the bovine growth hormone increased the wound healing capacity significantly
Therefore these results suggests that the effects of arginine are dependent on the presence of a functioning hypothalamic pituitary axis and that this further suggests that the wound healing capacity of arginine is instigated through the release or growth hormone. Supplementing 1 % arginine may therefore confer beneficial wound healing capabilities to mammals above those seen with a normal intake of the amino acid from protein. In addition, a high intake of arginine may increase body weight, presumably through the same growth hormone mediated mechanisms. Many studies looking at the effects of arginine have used intravenous administration routes, but evidence suggests that oral arginine supplements are also effective as arginine is not degraded in the gut and is readily absorbed. Other mechanisms may contribute to the wound healing capabilities of arginine including its role as a precursor to proline, an amino acid required for collagen formation, and as a precursor to creatine phosphate, a substance that may be involved in accelerating wound healing.
Dr Robert Barrington’s Nutritional Recommendation: Arginine in high doses may facilitate wound healing and have other beneficial immune enhancing effects. However, the herpes virus requires high host levels of arginine to function and as such it is important to balance a high arginine with a high lysine intake, the latter being able to inhibit the activity of the herpes virus. This further illustrates the idea that balance is required when considering nutritional supplementation.
RdB
