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Ben Hawkins, RD
Written by a Collegiate and Professional Sports Dietitians Association Registered Dietitian (RD). To learn more about sports nutrition and CPSDA, go to www.sportsrd.org.
The ACL (anterior cruciate ligament) is one of four main ligaments that provide stability to the knee joint. It is often injured during sports activities such as football, basketball, and skiing. ACL injuries can be severe and often require surgery and months of rehabilitation to fully recover and be able to return to sports. ACL reconstruction surgery is a common procedure for athletes and active individuals who are suffering from a tear or rupture of this ligament, with approximately 100,000 ACL reconstructions performed each year. Recovering from an ACL reconstruction requires a broad and comprehensive approach including physical therapy, rest, and proper nutrition.
Nutrition plays a critical role in the process of healing and recovery to return to sport following an ACL injury. Certain nutrients are vital in helping to rebuild and repair the tissue as well as reducing inflammation in the knee. Nutrients like protein, collagen, and zinc help support the ligament by repairing and strengthening it. While omega-3 fatty acids and antioxidants help with inflammation surrounding the ligament.
Protein
Protein is essential for healing as it provides the building blocks for the tissue repair for ligaments. It is recommended that individuals consume 1.6-3.0 grams of protein per kilogram of body weight per day following surgery (Hirsch, 2021). After surgery, your body requires more protein than usual to help recover from an injury. Studies show that athletes who consumed higher levels of protein had better knee function following an ACL surgery. Providing your body with a sufficient amount of protein during the healing process helps rebuild a strong ligament. It is shown that increased protein intake during rehabilitation training will enhance muscle strength and size. Good sources of protein include lean meats, fish eggs, dairy, legumes, and nuts.
Omega-3 Fatty Acids
Inflammation is an essential and prominent aspect of injury. Although inflammation is beneficial to help increase movement of fluid and white blood cells into the injured area, prolonged and excessive inflammation can lead to muscle loss surrounding the knee. Omega-3 fatty acids have anti-inflammatory properties that have shown to assist in resolving inflammation post-injury. They are also essential when it comes to building and repairing tissue in the body. Omega-3 fatty acids can be found in fatty fish such as salmon, mackerel, and tuna, as well as in nuts and seeds, such as flaxseeds, chia seeds, and walnuts. An omega-3 supplement can be helpful in meeting the adequate intake of 1.6g of omega-3s for healthy adults.
Antioxidants
Antioxidants are nutrients and enzymes that help fight the substances that cause tissue damage in the body. Following an ACL surgery, inflammatory molecules in your body called cytokines induce muscle atrophy (or muscle loss). Antioxidants such as vitamin A and vitamin C help control the activity of these cytokines in your body. These vitamins have been shown to improve and speed up the healing process by reducing cytokines, therefore decreasing inflammation. Since vitamin C plays an important role in collagen production in the body, a lack of vitamin C can result in abnormal and slowed healing coupled with weaker ligaments after an injury. Vitamin C rich foods include citrus fruits (orange, lemon, grapefruit), bell peppers, strawberries, tomatoes, and cruciferous vegetables (broccoli, brussels sprouts, cabbage, cauliflower). Vitamin A also stimulates the production of collagen in the body by helping restore the body’s immune system following an injury. Foods rich in vitamin A include spinach, sweet potatoes, carrots, pumpkin, bell peppers, and dark leafy greens.
Zinc
Zinc is a trace mineral found in small amounts in the body that is necessary for enzymes to carry out several critical reactions throughout the body. This includes DNA synthesis, stabilizing protein structure, and supporting the immune system, which all contribute to the growth and repair of an ACL. A zinc deficiency is one of the most common nutrient deficiencies and is linked to poor wound healing. For that reason, consuming zinc-rich foods such as chicken, fish, red meat, seeds, nuts, and fortified cereals may help you recover from an ACL injury more efficiently.
Collagen
Collagen is a vital component of the connective tissue in the knee joint, including the ACL. It is these collagen fibers and elastin fibers that give a ligament its unique properties that allow the joint to move in different directions while stabilizing the bones and muscles. When there is a ligament tear, the body starts synthesizing and rebuilding collagen fibers as part of the healing process. Collagen protein supplementation can support this process following ACL reconstruction, as it is rich in amino acids involved in collagen synthesis. Evidence shows that ingesting collagen protein with vitamin C before training increases the levels of collagen in the blood which will lead to increased synthesis in the tendon or ligament. This can play a beneficial role in tissue repair as well as injury prevention in the future. Collagen supplementation has also shown to effectively reduce pain associated with injuries following surgery (Clark, 2008). In contrast to collagen powder, food sources like gelatin and bone broth also share similar health benefits of collagen.
Conclusion
Protein, omega-3 fatty acids, antioxidants, zinc, and collagen all work together to help optimize healing ability. In addition to these nutrients, it is also important to stay hydrated and consume a balanced diet that includes a variety of fruits, vegetables, whole grains, and lean protein sources. Intentional nutrition following an injury helps assure required nutrients are available and ready for the recovery process. This may also reduce the risk of future complications after the ACL reconstruction. It is important to work with a healthcare provider and registered dietitian to develop a nutrition plan that is individualized for your needs and your goals following an injury.
References
Barker, T., Leonard, S. W., Trawick, R. H., Martins, T. B., Kjeldsberg, C. R., Hill, H. R., & Traber, M. G. (2009). Modulation of inflammation by vitamin E and C supplementation prior to anterior cruciate ligament surgery. Free radical biology & medicine, 46(5), 599–606. https://doi.org/10.1016/j.freeradbiomed.2008.11.006
Clark, K. L., Sebastianelli, W., Flechsenhar, K. R., Aukermann, D. F., Meza, F., Millard, R. L., Deitch, J. R., Sherbondy, P. S., & Albert, A. (2008). 24-Week study on the use of collagen hydrolysate as a dietary supplement in athletes with activity-related joint pain. Current medical research and opinion, 24(5), 1485–1496. https://doi.org/10.1185/030079908×291967
Hein, R., Mensing, H., Müller, P. K., Braun-Falco, O., & Krieg, T. (1984). Effect of vitamin A and its derivatives on collagen production and chemotactic response of fibroblasts. The British journal of dermatology, 111(1), 37–44. https://doi.org/10.1111/j.1365-2133.1984.tb04014.x
Hirsch, K. R., Wolfe, R. R., & Ferrando, A. A. (2021). Pre- and Post-Surgical Nutrition for Preservation of Muscle Mass, Strength, and Functionality Following Orthopedic Surgery. Nutrients, 13(5), 1675. https://doi.org/10.3390/nu13051675
Holm, L., Esmarck, B., Mizuno, M., Hansen, H., Suetta, C., Hölmich, P., Krogsgaard, M., & Kjaer, M. (2006). The effect of protein and carbohydrate supplementation on strength training outcome of rehabilitation in ACL patients. Journal of orthopaedic research : official publication of the Orthopaedic Research Society, 24(11), 2114–2123. https://doi.org/10.1002/jor.20147
Lin, P. H., Sermersheim, M., Li, H., Lee, P. H. U., Steinberg, S. M., & Ma, J. (2017). Zinc in Wound Healing Modulation. Nutrients, 10(1), 16. https://doi.org/10.3390/nu10010016
National Institutes of Health Office of Dietary Supplements (2023, February 15). Omega-3 Fatty Acids. Retrieved March 23, 2023, from https://ods.od.nih.gov/factsheets/Omega3FattyAcids-HealthProfessional/
Nyland, J., Pyle, B., Krupp, R., Kittle, G., Richards, J., & Brey, J. (2022). ACL microtrauma: healing through nutrition, modified sports training, and increased recovery time. Journal of experimental orthopaedics, 9(1), 121. https://doi.org/10.1186/s40634-022-00561-0
Papadopoulou S. K. (2020). Rehabilitation Nutrition for Injury Recovery of Athletes: The Role of Macronutrient Intake. Nutrients, 12(8), 2449. https://doi.org/10.3390/nu12082449
Shaw, G., Lee-Barthel, A., Ross, M. L., Wang, B., & Baar, K. (2017). Vitamin C-enriched gelatin supplementation before intermittent activity augments collagen synthesis. The American journal of clinical nutrition, 105(1), 136–143. https://doi.org/10.3945/ajcn.116.138594