Fitness & Yoga: nutrition

Carnitine is a non-essential nutrient present in the diet that contributes to the transport of long-chain fatty acids into the mitochondria for subsequent oxidation and obtaining energy. L-Carnitine is used as a dietary supplement for athletes to obtain nutritional ergogenic help (substances that are ingested to improve the ability to perform certain physical work or athletic performance). In the article "Supplementation with L-carnitine for athletes" and we delve into the role of carnitine in the body, we discuss some of its effects and its recommended dose. However, this article aims to investigate to what extent marketing can "manipulate" the scientific evidence when it comes to advertising and selling a product. How do they sell us L-Carnitine? In the first place, we are going to expose the effects attributed to L-Carnitine in those web pages (quite numerous, by the way) that are dedicated to the commercialization of this and other similar products. Many websites (Proe Nutrition, My Protein, Fitnasium, EBM, Healthy Food, etc.) advertise and market L-Carnitine, giving it properties such as the following: Increase in strength due to increase in muscle mass. Increase in resistance Increase in power Anti-aging and nourishing properties. It contributes to the loss of weight and body fat. It can help improve mental performance. Suppress the appetite. Reduces fatigue Increases the body's aerobic capacity to help burn more calories. Slow down the process of bone loss. Taking L-Carnitine after a heart attack decreases the chances of suffering a subsequent one. Improvement of male infertility. It helps improve both the sperm count and the quality of the sperm. Taken in combination with the period of breastfeeding helps new mothers lose more quickly the weight gained during pregnancy. It helps diabetics by increasing oxidation, storage and glucose uptake. It acts as an antioxidant, preventing the damage caused in healthy cells by free radicals. It protects the brain from brain damage related to age and stress, which helps this organ function more and better.

The real effects of L-Carnitine

Simultaneously, a bibliographic search has been carried out in scientific articles published in journals with high rigor in their publications. Thus, the results obtained about supplementation with L-Carnitine are the following:

There is no evidence that supplementation with L-Carnitine produces any effect on heart rate.

In activities of medium / low intensity (50% VOmax) it has been observed that long-term supplementation with L-Carnitine reduces the use of muscle glycogen, which means a better and faster recovery after exercise.

L-Carnitine administered in isolation does not produce significant effects compared to its joint administration with carbohydrates, since if it is administered in an isolated manner, it tends to be excreted via the urine.

There is no compelling scientific evidence (there is much controversy) that supplementation with L-Carnitine increases the oxidation of fatty acids. Therefore, there is not enough evidence to help weight loss either.

With supplementation, blood lipid levels (HDL, LDL, cholesterol) are not affected.

Supplementation with L-Carnitine at low doses may produce increased strength.

Likewise, at low doses, a decrease in lactate production is also achieved, delaying the onset of muscle fatigue.

After both searches, we can verify that if we administer carnitine orally the only remarkable and scientifically corroborated effect that we find is that the strength profile increases, which decreases lactate accumulation and reduces the use of glycogen reserves, resulting in a decrease in fatigue. However, the rest of the effects that have been announced on the web pages are not real and lack scientific rigor.

Thus, we can conclude that the Internet is a very useful tool but that you have to know how to manage. At our disposal are many websites that are dedicated to selling ergogenic aids, give dietary advice from inexperienced or non-professional people, etc. These pages seek to sell you a supplement without indicating its possible side effects and highlighting its "prodigious" properties, not always scientifically contrasted. It has also been found in the web search that, in many of the substances sold on the Internet, there is not even a description of their composition and, even if it existed, we would not know with absolute certainty if there were any omissions of components. If so, one of the components omitted could put your health at risk or be on the list of doping substances of the WADA (World Anti-Doping Agency). Be that as it may, the acquisition of these substances via the Internet is never safe for all the issues mentioned above.

Surely many times you have heard that if you consume carbohydrates (HC) while you train you will burn less fat and most of the positive effects of training will go to waste.

It is not so simple... The reason for consuming carbohydrates during training is to produce muscle and liver glycogen savings, while preserving both, we will have the capacity to perform more during a longer time. It is clear that resistance or "endurance" is essential since energy consumption and duration is much greater, but, and in training with loads?

The efforts that are made during training with loads are much shorter and more intense, with energy substrates being different to produce ATP. Phosphocreatine is able to supply energy for muscle contraction for 2-4 seconds, so if we work in maximum strength ranges, this will be the predominant system along with glycogen, since this is necessary to resynthesize phosphocreatine.

Training with weights with a moderate volume, for example, a fullbody workout (3-5 exercises) produces a depletion of 24-40% in muscle glycogen levels. Obviously this will depend on the total volume and intensity of the training. In a study conducted by Tesch et al. in 1986 measurements were made by biopsy of glycogen levels before and after a lower train training, glycogen decreased by 30%.

More are not always better

Reduced glycogen levels can decrease isokinetic strength as well as isoinercial force. In addition, in this last study, greater strength differences were found in multi-joint exercises such as the squat, with no differences in other monoarticular exercises such as leg extension. According to these works, starting strength training with muscle glycogen low minimums may not be a good idea.

However, in other studies such as that of Sawyer JC et al. in 2013 no differences were found in the 1RM bench press and rear squat with high or reduced levels of glycogen

In this last study, the diet contained more than 30% protein and the adaptation period was longer than in other studies. Together with a less aggressive depletion protocol, this may be the reason why such disparate results were found.

Will the HC improve our strength before training?

It depends, some research shows improvements in performance. However, others like Kulik et al. (2008) did not find differences. In the latter, the subjects consumed 0.3 g / kg of carbohydrates immediately before the test, in which the total work and the number of repetitions were measured, as well as the load used in series of 5 repetitions with the 85 % of the 1RM in a squat.

Haff GG et al. (2000) examined how isokinetic strength in leg exercises affected the consumption of 1 g / kg (85.7 +/- 3.5 kg) before training and 0.5 g / kg every ten minutes during training.

Both tests (carbohydrates vs. placebo) lasting 39 minutes and consisting of 3 leg exercises were performed by the same subjects separated by seven days. No significant differences were found in isokinetic strength, only a glycogen saving was produced in the group that consumed carbohydrates.

It is difficult to find a determining result that can be applied universally throughout the world, since the results will depend on the following factors:

· Previous glycogen levels.
· Composition of the diet.
· Training level.
· Gender (oxidative metabolism).
· Women consume more fatty acids during exercise.
· Training volume.

What if we consume them during training?

The purpose of ingesting carbohydrates during training is the same as ingesting them before, preventing glycogen levels from depleting, thus decreasing performance.

In works like David M. Laurenson and Danielle Jane Dubé in 2015, for me some of the best, the effect of consuming carbohydrates during training is evaluated along with protein in a ratio (3: 1), 36 g of carbohydrates and 12 gr of protein.

The training consisted of 3 circuits of squat and press bench with a total of 12 series, decreasing the number of repetitions in each. After finishing the circuits were measured the maximum repetitions that were able to do bench press and squat with 60% of 1RM as well as the maximum power generated.

In addition, the respiratory quotient (RER) was measured on 7 occasions, before, during and after.

There were no significant differences in the RER between the group that consumed carbohydrates and protein and the one that consumed a placebo. The RER is a measure that shows the relationship between the CO2 produced and the O2 consumed and therefore the oxidative capacity of the muscle tissue. When RER decreases, (<1) oxidative activity predominates, whereas when RER increases, (> 1) glycolytic activity predominates.

From all this, it can be inferred that consuming carbohydrates during a load training does not diminish the lipolysis nor the oxidation of fatty acids.

Why does not the oxidation of fatty acids decrease?

In order for muscle contraction to occur, ATP is necessary. Each energy substrate is able to produce a certain capacity of ATP in a certain time, for example, phosphocreatine is able to resynthesize ATP very quickly, however, it is only able to do so for 2-4 seconds. At the other extreme we find β-oxidation, which is able to resynthesize ATP for a long time, but at a very slow rate (50-65% VO2 max).

Between both ends we find other metabolic pathways such as anaerobic glycolytic and oxidative glycolytic. To understand how they contribute to the production of energy, we must be clear that none works at 100% or 0%. All work in unison overlapping to a greater or lesser extent.

Returning to the previous study, you can see how the plasma glucose during exercise is similar or even lower (take into account the insulinogenic capacity of the amino acids + CA2 + dependent transport) in the group that consumed carbohydrates and the one that consumed placebo. Together with similar measurements in the RER, this shows that glucose has been used in equal proportion in both groups for the production of ATP.

For more solidity, recent work has shown that the consumption of carbohydrates during training at relatively low intensities 65% VO2 max does not alter the activity of AMPK [9]. It is true that the increase in insulin during training can decrease the release of epinephrine and myokines, thus reducing lipolysis.

I honestly think that the intensity of the exercise must be very low for this interaction to occur. It should be noted that the mobilization of fatty acids from the adipose tissue is only part of the story, since without the correct mitochondrial function dependent on (PGC1; PPAR-alpha) and in turn dependent on AMPK, the ability of lipolysis does not matter , in fact, it can even be harmful as it happens in the case of diabetics (lipotoxicity).

Regarding performance parameters, there were no significant differences in power between both groups, both in the squat and in the bench press. However, the group that consumed carbohydrates was able to perform more repetitions in the bench press.

Then, before or during?

In conclusion, we see that eating carbohydrates during training does not diminish the oxidation of fatty acids, it does not mean a benefit in strength increase, however if it allows a greater volume of training due to the saving of muscle glycogen and the decrease in glucose production hepatic (muscle protection).

Therefore, both possibilities are valid when the volume of training is very high and the diet is reduced in carbohydrates <2 g / kg of body weight. Although it must be emphasized that intra-tennent supplementation has advantages over pre-tenter supplementation, such as a lower risk of reactive hypoglycaemia and associated symptoms, as reported in the work of Koivisto VA et al. [10] The consumption of carbohydrates of high glycemic index 45 minutes before training produces an insulin secretion, which, in combination with the hypoglycaemic effect of physical exercise produces a very aggressive drop in blood glucose, which we know as reactive hypoglycemia.

All this can be solved by consuming the same type of HC during training obtaining a more stable insulin response and a better use of them due to Ca2 + dependent transport. Or using HC complexes one hour before in liquid form as high molecular weight amylopectins or cyclic dextrins.

So, when will I gain intra-tread HC?

· Level of medium-advanced training.

· In diets with a carbohydrate amount less than 2 gr per kilo of body weight.

· High volume of training. A lot of training frequency with moderate volume.

· Men will get more benefits than women.

Essential to individualize amount and type of carbohydrate depending on the duration of exercise [11]: 60 gr of carbohydrates per hour of training, important to include several types of HC such as glucose / polymers and fructose. This will achieve greater oxidation of exogenous HC and glycogen savings. If you have intestinal problems during exercise when consuming carbohydrates may be due to the limitation of transport of them. And accumulation in the intestinal lumen increasing the concentration of water in it. Dehydration can also negatively affect Na + transport.

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