BRINGING SCIENCE TO TREATMENT

Nutrition for healing and recovery: Part II

In part one of this article, Andrew Hamilton explored the benefits – or otherwise – of manipulating dietary protein, fat and carbohydrate intake. In part two, Andrew investigates the potential benefits of vitamins, mineral, and other micronutrients. Can they help speed injury healing, and which nutrients are most effective? 

2018 New Orleans Saints defensive end Cameron Jordan (94) eats a turkey leg as he walks off the field. Credit: Derick E. Hingle-USA TODAY Sports

As we explained in the first part of this article, when injury strikes, maximizing the speed of recovery is crucial for athletes seeking a speedy return to sport. In terms of nutrition, any strategy that helps curb excessive inflammation during the early stage of injury, or speeds the repair and healing process in the subsequent stages is worthy of consideration.

The importance of micronutrients

Given that the daily intake of micronutrients such as vitamins and minerals is several orders of magnitude lover than protein, fat, and carbohydrate (measured in milligrams rather than grams!), how is it that these trace nutrients are still pivotal for optimum healing? Apart from calcium, which is needed in comparatively large qualities for bone formation, the reason is largely due to the fact that micronutrients function as activators of enzyme systems in the body, allowing biochemical processes to occur that would otherwise occur too slowly to sustain biological function, or not at all.

A good example of this is the mineral zinc, which activates numerous enzymes in the body involved with protein (amino acid) turnover. One group of these enzymes is the ‘matrix metalloproteinase’family (see figure 1), which are involved in the breakdown of extracellular matrix in normal physiological processes, such as embryonic development, reproduction, and tissue remodelling, as well as in disease processes, such as arthritis and metastasis, as well as articular cartilage turnover and cartilage pathophysiology associated with osteoarthritis. The salient point here is that although the daily requirement for zinc is only around 15mgs per day, even mild insufficiencies in zinc status will inhibit the efficacy of these enzymes, with a negative impact on protein turnover, and thus (potentially at least) wound healing.

Figure 1: Schematic representation of matrix metallopeptidase 13

Micronutrients and the inflammation phase

When it comes to micronutrients and the inhibition of inflammation (phase-1 nutrition), there’s a paucity of data evidence in the literature that supports their use. One possible viable anti-inflammatory micronutrient is not a vitamin or mineral, but an antioxidant phytochemical called curcumin. In fact, such is the potency of curcumin’s antioxidant and anti-inflammatory activity that scientists are currently investigating its potential to treat and prevent a wide array of degenerative and inflammation-related diseases(1-6).

One area where curcumin is proving to be very effective is in the treatment of joint pain and arthritis (both rheumatoid and osteoarthritis). A number of studies have demonstrated that taken as a supplement, curcumin can diminish joint pain and improve mobility compared to an inert placebo, and that these improvements are brought about by a reduction in joint inflammation(7). Indeed, there’s good evidence that curcumin may be as effective in reducing inflammation and pain as over-the-counter Ibruprofen(8).

A 2015 study investigated harnessing this property as a therapy for arthroscopic supraspinatus tendon repair pain(9). The researchers used a dietary supplement containing and Curcuma longa (and Boswellia serrata) in a population of subjects with full-thickness SSP tendon tear treated by arthroscopy. The results showed that the curcumin-supplemented subjects demonstrated significantly lower overall pain scores than a placebo group during the first-week post surgery.

While these results are encouraging, caution is required. A review study examined a range of so-called ‘nutraceuticals’ commonly recommended for the management of tendinopathies, particularly inflammatory conditions(10). These included nutrients such as curcumin, glucosamine and chondroitin sulfate, vitamin C, hydrolyzed type-1 collagen, arginine alpha-ketoglutarate, bromelain, boswellic acid, and methyl-sulfonyl-methane (MSM). A number of these studies showed a possible beneficial effect on inflammation, collagen synthesis, mechanical properties, analgesia, and maturation of collagen bundles. However, the researchers also concluded that in many cases, the methodological quality was poor, and in most of the studies, more than one supplement was administered at the same time – making it difficult to determine the effect of individual Furthermore, the interactions between nutraceuticals and medications taken by subjects are largely ignored, making it difficult to draw firm conclusions

Micronutrients and the evidence for healing

Many studies point to the roles of certain micronutrients in supporting tendon and soft tissue growth and regeneration. However, while the logic is sound, the evidence presented is often more theoretical in nature; it’s still the case that there are very few studies based on properly controlled clinical trials upon which to make firm recommendations.

A review study published a few months sought to ascertain whether amino acids/vitamins provide any influence on musculotendinous healing and if so, by which physiological mechanisms(11). Twelve studies met the criteria for inclusion: eight examined tendon healing and four examined muscle healing. All the studies used animal models, except for two, which looked at human trials.

The results suggested that vitamin C and taurine demonstrated indirect effects on tendon healing through antioxidant activity. Meanwhile, vitamin A and glycine showed direct effects on extracellular matrix tissue synthesis, and vitamin E showed an antiproliferative influence on collagen deposition. However, due to methodological flaws and the heavy reliance on animal studies, the researchers concluded that recommendations on their clinical use should be made with caution.

Another study looked at the general use of micronutrients in the context of tendon healing following injury(12). It concluded (rather vaguely) that

various nutrients such as proteins, amino acids (leucine, arginine, glutamine), vitamins C and D, manganese, copper, zinc, and phytochemicals may be useful in improving tendon growth and healing’while adding ‘because many nutrients are required for tendon health, nutritional interventions involving multiple nutrients may be more effective than single-nutrient strategies, and more research on nutrition and tendon health is needed’.

Nutrients worthy of consideration

Despite the cautions and caveats above, there are some nutrients that would make sense in ‘rehab nutrition’ programme – those that are supported by good clinical studies or where sheer logic dictates it simply makes sense to ensure they are well supplied in the diet.

*Zinc nutrition– Given the role of zinc in protein turnover in the body, you might assume that it has been thoroughly researched in an injury healing context. However, while we know that a zinc insufficiency impairs wound healing in hospital patients following injury or surgery(13,14), and that supplemental zinc increases the growth rate and fat-free muscle mass gains in children with a limited diet(15,16), there’s little data regarding its role in terms of muscle tissue accretion following athletic injury. That said, the logic for ensuring an ample zinc status outlined above is compelling – even without clinical studies. The best sources of dietary zinc tend to be high-quality protein foods such as lean meats (beef, liver, pork, chicken etc), shellfish, nuts and seeds, eggs etc. Dietary supplementation may also be useful. However, because of its ability to interfere with iron absorption, athletes should not supplement more than the recommended daily intake (around 11mgs per day).

*Vitamin D– Vitamin D is most known for its contribution to the mineralization of bone and maintenance of bone integrity. It also plays a role in calcium homeostasis. Unsurprisingly, therefore, there’s good evidence that optimizing vitamin D nutrition is important. Studies on military recruits suggest that poor vitamin D status increases the risk of femoral and tibial stress fractures, and that vitamin D supplementation may help with fracture healing in soldiers presenting with stress fractures(17).

More generally, research suggests that in the wider population at large, those most at risk of fracture – the elderly – have a poor vitamin D status and that oral vitamin D supplementation between 700 to 800IUs per day reduces the risk of hip other non-vertebral fractures(18). Athletes suffering from a fracture (stress or otherwise) should consider an evaluation of vitamin D status and supplementation where necessary. This is especially the case given that vitamin D insufficiency is known to be very widespread in athletes of many disciplines, especially during the winter months in the northern hemisphere(19-24).

Vitamin D may also help in tendon injury. The activated metabolite of vitamin D, 1a,25-dihydroxy vitamin D3, affects osteoblast proliferation and differentiation. Likewise, vitamin D plays a significant role in the tendon-to-bone healing process by increasing bone mineral density and strengthening the skeletal muscles. A review study looked at tendon-to-bone healing after rotator cuff repair surgery, which usually has a high failure rate25). They concluded that vitamin D3 binds to vitamin D receptors on myocytes to stimulate growth and proliferation and that vitamin D3  successfully influences bone and muscle healing, increasing the chances of a tendon-bone repair.

Another study analyzed grip-strength recovery after a distal radius fracture in 70 women over age 50 years of age(26). Researchers performed multivariate analysis to identify factors that independently predicted grip strength recovery at six months after injury. While there was no significant correlation between baseline vitamin D status and grip strength recovery, the data showed that improving vitamin D status with vitamin D3 supplementation was significantly associated with better grip strength recovery at 6 months after injury.

*Calcium– Calcium and vitamin D are both needed to achieve and maintain bone health. Calcium should therefore also be considered an important nutrient in the context of injury prevention and recovery. There is very little data on athletes, injury and calcium nutrition. However, a randomized trial in female military recruits demonstrated that calcium/vitamin D supplementation reduced the incidence of stress fractures, and a study in young female runners demonstrated a reduced incidence of stress fractures and increased bone mineral density with increased dietary calcium intake(27). Findings from both studies suggest those who consumed greater than 1500 mg of calcium daily exhibited the largest reduction in stress fracture injuries.

In terms of calcium and injury recovery, one fairly recent study investigated the effects of calcium ß-Hydroxy-ß-Methylbutyrate (CaHMB), vitamin D, and protein supplementation on wound healing, immobilization period, muscle strength in older adult patients with hip fracture(28). This randomized controlled study included 75 older female patients with a hip fracture admitted to orthopedic clinics. The control group received standard post-operative nutrition while the study group received a supplement containing 3 grams of CaHMB, 1000IUs vitamin D, and 36 grams of protein, in addition to standard post-operative nutrition. The results were as follows:

  • *Wound-healing period was significantly shorter in the CaHMB/vitamin D/protein group than in the control group.
  • *The number of patients in the CaHMB/vitamin D/protein group who were mobile on days 15 and 30 was significantly higher than patients in the control group, who were mobile on days 15 and 30 (81.3% vs. 26.7%).
  • *Muscle strength on day 30 was significantly higher in the CaHMB/vitamin D/protein group compared to the control group.

The researchers concluded that the CaHMB/vitamin D/protein combination led to the acceleration of wound healing, shortening of immobilization period, and increased muscle strength without changing body mass index.

Summary

The logic for the use of a number of micronutrients is compelling. However, the clinical data to support their use is far more limited. The wide numerous functions of zinc in protein turnover metabolism suggests that its status should be considered as important by athletes seeking the fastest recovery possible, despite the lack of specific studies. The evidence for the role of calcium and (particularly) vitamin D3 in injury healing and recovery is more robust. Dietary modifications to improve the intake of these foods are recommended (see table 1). Athletes may also wish to consider a supplement supplying in the region of 1000IUs per day of vitamin D3 and 800mgs per day of calcium.

Table 1: Foods naturally high in calcium and vitamin D

CalciumVitamin D
MilkSalmon (fresh and canned)
CheeseMaitake mushrooms
YogurtTrout
SpinachHerring
TofuCanned sardines
Canned sardinesWhole milk (not skim)
Canned salmonEgg yolks
Soy beansButter
Almonds

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