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Study under review: Changing to a vegetarian diet reduces the body creatine pool in omnivorous women, but appears not to affect carnitine and carnosine homeostasis: a randomised trial
Vegetarian diets are often praised for their health-related benefits alongside their ecological and ethical implications. Consumption of red and processed meat has been associated with increased mortality risk for certain cancers and cardiovascular diseases, which suggests that a vegetarian diet could act as a counter. Certain healthy nutrients, such as fiber, magnesium, and antioxidants are also increased in a balanced lacto-ovo-vegetarian (milk and eggs included) diet. Some other positives (and a few negatives) of a vegetarian diet are shown in Figure 1. Overall, vegetarian diets appear to limit the risk of excess and deficiency in regard to nutrition and health, though there is a bit of a learning curve. While some benefits are clear, one should be aware of what to look out for when embarking on the ‘vegetarian journey’.
People familiar with vegetarian diets know that some nutrients cannot be obtained from non-meat foods. In fact, vegetarians may be more prone to nutrient deficiencies than omnivores who plan well-balanced meals. Most vegetarians know the importance of fitting vitamin B12 into the diet, and some may even know that omega-3 fatty acids tend to be lacking, but what if there is more missing? What if vegetarians are lacking meat components that influence muscle function, exercise capacity, and sports performance?
Carnitine, carnosine, and creatine are molecules involved in energy metabolism and muscle function. Creatine supports the immediate high power needs of a sprinter by replenishing ATP stores within the first few seconds of extensive exertion. Carnosine is primarily known for its intracellular acid-buffering capacity, but it also exhibits cellular calcium regulation and antioxidant properties. Carnitine plays roles in several energy producing pathways, such as long chain fatty acid (LCFA) oxidation, where it is necessary to shuttle the LCFAs into the mitochondria. These molecules have previously shown beneficial potential for exercise performance and certain diseases and disorders.
Cross-sectional studies suggest levels of carnosine and creatine decrease following adherence to a vegetarian diet. However, carnosine changes are still unclear due to its slow turnover rate and because its constituents, histidine and beta-alanine, can still be found in some non-meat foods (e.g., asparagus and soybeans). All of the molecules are mostly found in animal tissue (especially muscle) and can be endogenously produced to some extent, but carnitine can be found in other foods besides meat (e.g. potatoes, nuts, milk).
Vegetarian intervention studies ranging over a few weeks have demonstrated decreases in creatine and maintenance of carnosine, while carnitine homeostasis has never been investigated in an interventional study. Researchers wanted to determine whether decreases in creatine and maintenance of carnitine would be consistent over a six-month vegetarian dietary intervention, while performing the first longitudinal experiment evaluating the influence of a vegetarian diet on carnosine levels.
Vegetarian diets are often prone to deficiency without proper planning and nutrition understanding, compared to the average omnivorous diet. Carnitine, carnosine, and creatine are molecules involved in energy metabolism and muscle function that may be lacking in vegetarian diets. Researchers wanted to investigate the impact of switching to a vegetarian diet on carnitine, carnosine, and creatine levels over a long duration of six months.
Other Articles in Issue #43 (May 2018)
Eggcellent eggs part II: can people with diabetes safely eat two eggs per day?
This long-term follow-up to a study we covered way back in NERD #7 examined the effects of eggs on people with diabetes and prediabetes.
Whose performance benefits from nitrate supplementation?
The literature examining nitrates’ effects on performance is mixed. Part of the reason for the discrepancy may come down to training status
The misunderstood noodle
Does pasta pack on the pounds? This meta-analysis aimed to find out.
Interview: Andrew Vigotsky
In this interview with biomedical engineering PhD candidate Andrew Vigotsky, we talk biomechanics and the state of sports science research.
Does caloric restriction really make you live longer?
Two major hypothetical mechanisms of aging were put to the test in this human trial, the latest from the CALERIE project.
Interview: Lara Hyde, PhD
We chat with the creator and host of Nourishable about nutritional epigenomics and epigenetics, as well as the nuances of communicating science to the public.
Does whey supplementation help muscle function recover after lifting?
In this review, we cover the first meta-analysis examining whey protein’s impact on muscle function recovery after resistance training.