作者：Sue Force 6 年以前
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CN, M. (2001). beta-casein A1, ischaemic heart disease mortality and others ilnesses. . Medical hypotheses, 262-267.
Demling, R., & DeSanti, L. (2000). Effect of a hypocaloric diet, increased protein intake and resistance training on lean mass gains and fat loss in overweight police officers. . Annals of nutrition and metabolism .
E.L, K., & al, e. (2003). The impact of protein intake on renal function decline in women with normal renal function or mild renal insufficiency . Annals of Internal Medicine .
EU. (2018, 11 04). Nutrition and Health Claims. Retrieved from European Commision: http://ec.europa.eu/food/food/labellingnutrition
J, C.-D., & al, e. (2006). Effect of dietary supplementation with beta-casein A1 or A2 on markers of disease development in individuals at high risk of cardiovascular disease. Journal of Nutrition , 136-144.
Jager, R. e. (2017). International Society of Sports Nutrition Position Stand: protein and exercise. Journal of Internation Society of Sports Nutritioion.
Mohanty, D. e. (2015). Milk derived bioactive peptides and their impact on human health - A review. Saudi Journal of Biological Sciences, 577-583.
Snijders, T. e. (2015, June 01). Protein ingestion before sleep increases muscle mass and strength gains during prolonged resistance-type excercise training in helthy young men. The Journal of Nutrition, 145(6), 1178-1184.
W.F, M., & L.E, A. (2005). Dietary Protein inatke and renal function . Nutrition and Metabolism .
Useful Websites
https://www.informed-choice.org/
https://www.informed-sport.com/
https://www.olympic.org/the-ioc
https://www.sportaus.gov.au/ais
There are two main forms of casein, the first form is micellar, which has its unique slow digestion rate compared to whey. The second is casein hydrolysate which is an industrial form in which the casein is in a pre-digested state meaning a more rapid absorption compared to micellar but still slower than that of whey protein.
Micellar casein is the form of casein found in milk, the casein molecules are amorphous and form small round type structures. This is what we call micellar. A micellar molecule consist of thousands of casein molecules all clustered together around an inner core, which is rich in calcium phosphate. It is this form of casein which when exposed to acid in the stomach causes a curdling effect due to the presence of casomorphin and causes the slow digestion of up to seven hours; keeping the blood amino acid concentration at a heightened state, increasing muscle protein synthesis and the body in an anabolic state.
Industrial casein or Casein Hydrolysate is different however in that it is pre-digested in order to increase absorption rate. The way in which casein hydrolysate is formed is via hydrolysis, this is a form of digestion that breaks down proteins into small peptide chains or amino acids. Casein and whey are usually hydrolysed by digestive enzymes in the stomach. However this industrial hydrolysis prevents casein micelles from forming. This in turn means the casein doesn’t form its curdling effect when consumed. Instead the pre-digested casein is rapidly absorbed and digested at a similar rate to whey protein. So this type of casein is therefore best suited when protein is needed rapidly, for instance straight after a workout.
Micellar and casein hydrolysate both contain the same protein profiling and are easily digested, absorbed and readily utilised by the muscles within the body. The only difference in the absorption rate in the body because one being pre-digested compared to the other. Therefore, there is no right answer for what is better as they’re effectively the exact same just with different absorption rates.
Meaning comparing them is irrelevant, the only answer to if one is better than the other is based on your own personal goals and what you’re trying to achieve with this supplement. If you are hoping for a quick absorption and want to increase blood AA concertation rapidly for instance directly after a workout the better of the two would be the casein hydrolyse. If however you want a slow releasing protein with a lower blood AA concentration but constant throughout the course of up to 7 hours, while you’re not eating and sleeping for example, you’re better consuming a Micellar casein based food/drink.
All studies mentioning the myth that high protein intake has been disproved and have since highlighted that the are no negative health from consuming protein in healthy individuals. The only exception to this is those who have current kidney/liver diseases. Studies by (W.F & L.E, 2005) (E.L & al, 2003). The only real dangers casein possesses is if someone is allergic in which they may become bloated or experience other digestive symptoms but this will be dependent on the individual.
The A1 vs A2 controversy: One of the proteins (beta-casein) present is casein exists is two forms either A1 and A2 most of cow’s milk contains a mixture of both A1 and A2. However some research undertaken by researchers such as (CN, 2001) started to link A1 beta-casein with health issues and diseases such as type II diabetes and heart disease. Although other studies such as (J & al, 2006) study on A1 beta-casein found there was no real link of detrimental effects on health.
A2 beta-casein milk is currently being marketed by some as ‘healthier’ compared to regular milk containing both A1 and A2, however there is still much dispute over this and no real evidence behind it.
Casein is one of two types of protein found in mammalian milk and is comprised of proteins from a family of related phosphoproteins. It’s also classed as a complete protein source, meaning it provides all the essential amino acids (AA) your body needs for growth and repair. The different quantity of casein present is different depending on the type of milk; for instance, cow’s milk is typically comprised of 80% casein and 20% whey protein whereas human milk is typically between 20-45% casein and 80-55% whey protein.
What makes casein unique is its slow absorption rate comparable to whey. Whey typically has a fast absorption rate and protein levels in the blood peak roughly one hour after consumption and last for up to ninety minutes. Whereas casein has a much slower absorption rate; casein causes a curdling like effect in the stomach due to it being naturally complexed with Calcium and Phosphorus. These both react with Casomorphin (an opioid peptide) which is derived from the digestion of the casein protein. This curdling effect then causes the slow release of AA into the blood over the next 7 hours, which is why casein is suggested by some sports brands and trainers to be consumed before bed.
In sports, supplements such as casein can be used, as they offer a quick fix to an athlete that may have poor diet or even a very good diet and just needs that extra nutritional boost which some supplements can offer, while also being more time convenient than cooking a whole meal.
As casein is seen as ‘natural’ as it is present in food it therefore has no limitations or regulations around it’s consumption in sport. This however only refers to casein and not to other supplements/ingredients that may be present in the supplement being sold.
The main questions you need to ask yourself before taking any supplements are. . .
Risks for most athletes include but are not restricted to consuming banned substances within sports. It is therefore vitally important to check what supplements you can and cannot take with in your sport. You can check this by looking at your sports personised governing bodies which will outline the do’s and don’ts when it comes to supplements. There are also links in the References to websites that will also give more detailed outlines, these include webpages such as WADA and the IOC etc.
Costs of casein supplements are relatively cheap, although price will vary depending on quality and type of casein, Micellar vs Industrial and the supplement company itself. But remember just because something is more expensive it doesn’t necessarily mean it’s of better quality or more effective.
Contamination can occur when there is a poor practise in the manufacturing process. E.g. when supplements are packaged or produced on the same or similar lines. For instance, If a supplement that contains banned substances in one sport, but is not illegal and can be used by amateur athletes/general public is cross contaminated with banned or illegal substances, this could lead to an elite athlete who is regularly drug tested accidently consuming the banned substance and could therefore result in them being banned from the sport if found with traces of the substance in their body.
There are even some scares as to deliberate spiking of supplements. This is where manufactures will knowingly place banned/illegal substances in their supplements to enhance their supplement vs competitors. Giving the supplement user increased performance and efficiency. Although this can be at risk of health to the user. It is therefore important to be wary when purchasing products and always try to purchase from reliable supplement companies that have their supplements and products batch tested by independent authorities such as
https://www.informed-sport.com/. This will help make informed choices about supplements and provide the relevant information in order to check you’re not consuming any banned substances, which is especially critical if you’re an elite athlete that has supplement restrictions within your sport and is regularly drug tested.
Although casein itself may be perfectly safe; when it is produced into sport supplements such as bars/tablets/powders, this is where the issue can arise. Inadequate labelling, dosage and efficiency can therefore lead to health issues if consumed in to higher doses. Casein itself will cause no harmful side effects but the other ingredients such as vitamins and minerals, that are present in these supplement bars/drinks, if consumed in too higher quantity can be harmful if not deadly to the body.
Insufficient labelling could also lead to harmful side effects and even death in some cases if ingredients are not labelled correctly. E.g. allergens not labelled correctly leading to mild or severe allergic reactions. This can also be troublesome for elite and professional athletes who are monitored by NGB’s (National Governing Bodies) such as UKSport or United States anti-doping agency or who are then also tested by worldwide independent anti-doping agencies such as WADA (World Anti-Doping Agency) or IOC (International Olympic Committee). If athletes are found to be doping or found to have illegal/banned substances within their body they may be subject to a fine and almost guaranteed ban which could even be for life. The only exceptions to this is if the illegal/banned substance is prescribed by a medical professional and is needed by the athlete to help with a genuine medical condition such as asthma. Although the use of these supplements is still frowned upon due to some ‘medicines’ giving athletes an increased performance effect.
Casein is readily available across all markets due to it being present in food and is also easily available from the majority of sport supplementation companies.
As explained the source of casein is ‘natural’ due to being present in food, however it can also be synthesised and is often extracted from foods when it is then ‘cleaned-up’ or hydrolysed.
Casein is legal substance as it is natural, so therefore is not banned in any sports. It is important however, if you decide to take a casein supplement such as a powder or tablets that you check the ingredient list fully for any other banned substances that could be present.
Are you going to receive any real benefit from taking it? Casein has been proven to help increase muscle protein synthesis and decrease loss of muscle mass. So it could be said that casein is a good supplement to use in any sport where your aim is to maintain and increase muscle mass as efficiently as possible. Casein, as shown, occurs naturally in food such as milk and many dairy products. It would therefore be more efficient for athletes or anyone wanting to consume casein to consume natural sources such as milk as these give additional health benefits such as vitamins and minerals which many supplements do not.
Is casein classed as an ergogenic aid? The simple answer is yes. Ergogenic aids are classed as any external influence that have the potential to give someone the upper hand in sporting performance. Casein is classed as a nutritional and pharmacological ergogenic aid and can even be classed as a psychological aid due to a placebo a person consuming the supplement may feel (due to it being a food that can both be consumed naturally or can be synthesised in the form of casein hydrolysate where it’s pre-digested). It is classified as ‘natural’ as it is found in food and can be extracted even though after extraction it may be chemically cleaned up or even synthesised.
Casein is sold in many different forms as a protein supplement from bars and tablets to powders. Due to it being a protein that has the ability, according to some research, to reduce the loss of muscle mass and increase protein synthesis within cells leading to increased muscle mass, which in turn has the potential to increase sporting performance and potentially reduce recovery rate.
TThe regulation of supplements such as casein is far from ideal when it comes to everyday athletes, unlike elite athletes who are monitored and told what supplements they can and can’t take in their desired sport. This monitoring only at an elite level means that many amateur athletes are at a much higher risk for consuming harmful and potentially banned/illegal substances. Control of these substances is usually via sampling and testing supplements that come into a country such as the UK through means of customs and trading standards. However, with internet purchasing this is becoming harder and harder to keep control of. This along with insufficient labelling of ingredients, levels of each ingredient present and the recommended dose of the supplement, means even if consumers did want to check themselves many a time they are unable to do so, due to this lack of information available.
In addition to poor labelling, the EU in recent years has put a regulation on health claims that can be used on foods and food supplements, stating any claim should be clear, accurate and evidence based (EU, 2018).
Casein is a protein found in milk and other dairy products. For people with milk allergies, casein may be a real issue, not necessarily the lactose. However if casein isn’t the issue it’s a great and effective source of protein for helping to build and maintain muscle mass as well as having many other health benefits ranging from: Antibacterial and immune benefits and even reduce high blood pressure according to one study (Mohanty, 2015). Help maintain triglyceride levels, aid in reduction of free radicals and even help aid fat loss in some cases (Demling & DeSanti, 2000).
Typical and obvious food sources are dairy products such as: Milk, cream, cheese, ice cream, butter and cream-based foods such as custard or soups. Dairy alternatives such as coconut, soy and almond milks etc typically don’t contain casein but it’s always advised to check labelling, ingredients and check with food manufactures to make sure they are safe for you to consume. However, labels that list caseinate will contain gluten and be cautious that just because a food is ‘dairy free’ this doesn’t mean it’s necessarily casein free.
Less obvious foods containing casein include: tuna, processed meats, snack crackers, chocolate and dairy-free cheese. Although if you’re looking at consuming high casein containing foods after exercise you’re better off opting for the richer sources such as milk or casein-based protein powders/bars as recommended by the International Society of Sports Nutrition (Jager, 2017).
The body during exercise or a hard training session expresses large stresses on muscles which cause micro-tears. These micro-tears cause Delayed Onset Muscle Soreness (DOMS), one way of reducing DOMS and helping aid in the repair of muscle fibres is to increase protein intake. This increased protein consumption helps increase blood AA concentration; which in turn increases protein synthesis in each muscle and aids in a faster recovery period. Without this increased source of protein, protein synthesis in the muscles will decrease and could potentially lead to decrease in lean muscle mass. Which is not ideal if you’re looking at increasing muscle mass.
This is what makes casein the Ideal protein supplement. Is the most abundant protein found in milk; and because of the way it forms during the processing of milk tends to be quite a gelatinous substance. Although once formed into protein it becomes a uniquely slow absorbing protein; resulting in a lower peak of blood AA concentration compared to whey protein; however, keeping blood AA concentration higher on average for a much longer period (up to seven hours). This constant release of AA such as Leucine, Isoleucine and Valine into the blood stream over this period therefore helps to prevent muscle breakdown and increase protein synthesis within muscles cells. Which is why casein is sometimes referred to as anti-catabolic.
A study completed by (Demling & DeSanti, 2000) compared three groups: one group consumed casein, one whey and the other a placebo. Results showed the group consuming casein experienced double the muscle growth and triple the fat loss compared with the placebo group and also experienced more fat loss compared to the group consuming whey.
In a second study, casein protein shakes before bed helped increase type II muscle fibres compared to a non-supplement strength-training group. Showing the benefits and role of casein in the body with relation to protein synthesis and muscle mass gain (Snijders, 2015)
