Creatine

Creatine: What is it?

Creatine is a natural substance derived from amino acids that is stored in muscles and released upon physical activity. It is widely used to elevate exercise performance and strengthen muscles and is naturally found in sources such as meat and fish [181, 182].

How does it work in the body?

Creatine is mainly stored in the skeletal muscle as phosphocreatine, the remainder of the body's creatine is stored in the brain, kidney, and liver. The phosphocreatine stored in muscle has high-energy phosphate groups attached to it which allow it to release energy and significantly enhance the formation of new ATP molecules. This allows for a high-energy burst lasting only a short duration (5-10s) until a drop in phosphocreatine levels occurs. Supplementation with creatine bolsters strength and performance by regenerating ATP that gets used during exercise as well as regenerating phosphocreatine supplies following exercise during recovery [181, 182].

What is it used for?

Creatine is one of the most popular supplements in the world and is mainly used for exercise performance and muscle strength, preventing muscle damage and fatigue, protecting against age-related muscle loss, and enhancing cognitive function [182].

Evidence for and against:

Exercise performance and muscle strength: Creatine supplementation bolsters phosphocreatine stores which increase ATP energy utilization, especially in muscles during short high intensity workouts [181, 182]. In a meta-analysis of 22 studies, creatine supplementation during resistance training was found to significantly increase muscle strength by 8%, weightlifting performance by 14%, and 1 rep max bench press by a high of 45% when compared with just resistance training alone [183]. Another meta-analysis of 100 studies found that creatine supplementation significantly increased lean body mass when doing short-term, repetitive exercises, this same study also found that creatine did not improve endurance-based exercise such as running or swimming, which is consistent with other studies [184]. In a study of 32 healthy men undergoing heavy resistance training, creatine supplementation (6-24 g/day) significantly increased muscle growth better than daily protein (20 g/day) [185]. Creatine was also shown to lower myostatin-induced muscle growth impairment [186].

Muscle damage and fatigue: Creatine has been shown to protect against muscle damage and fatigue and aid in its recovery. One study inclusive of 14 men showed that creatine supplementation significantly increased isokinetic and isometric knee-extension strength during recovery from exercise-induced muscle damage, plasma creatine kinase which is a marker of myocyte damage was also lower [187]. Another study on 22 men showed that oral creatinine supplementation did not lower skeletal muscle damage or aid in muscle recovery after a hypoxic resistance exercise challenge [188].

Age-related muscle loss: Studies suggest that creatine supplementation can protect against age-related muscle loss. In a study on elderly individuals, creatine supplementation was shown to reduce muscle atrophy, increase muscle strength and endurance, and increase bone strength even in the absence of resistance training [189].

Cognitive function: Studies suggest that creatine may have a role in preventing mental fatigue and improving cognitive function. One study found that in sleep-deprived athletes, creatine supplementation improved cognitive skills after 1 week of supplementation. Another study showed that creatine supplementation improved complex cognitive skills, it was taken along with moderate intensity exercise for 1 week prior to sleep deprivation [190, 191]. In another study, creatine supplementation was shown to improve cognitive performance and quality of life in elderly individuals after only 2 weeks [192].

There have been further studies that suggest that creatine supplementation may play a role in elevating testosterone levels, stabilizing musculoskeletal manifestations of Parkinson's disease, improving heart health, lowering blood glucose levels, and increasing bone health. Further clinical studies with human participants should be conducted to explore these claims in more depth.

Dosage:

Creatine dosing typically occurred in phases. The first phase was the loading phase in which patients received a larger amount in about 20 g/day for the first 5-7 days. The second phase was the maintenance phase in which the dose would reduce to 3-5 g/day. This was done to adequately bring creatine levels to an effective concentration [193].

Precautions/side effects:

Creatine is likely safe in doses below 30 g/day. Side effects typically include stomach pain and cramping. This supplement can also lead to water retention and weight gain [194]. Creatine has not been shown to damage the kidneys in the short or long term [193].

Interactions:

Fenugreek: Creatine has been shown to maximize strength and training adaptation when taken in conjunction with fenugreek [195].

Coenzyme Q10: Creatine paired with CoQ10 was shown to delay cognitive decline in subjects with mild cognitive impairment and Parkinson's disease [196].