Dairy and health

Milk and other dairy products are polarising. Some claim it is the best option for recovery, others claim there are detrimental health effects. This blog will focus on two health conditions that are linked to dairy. The next blog will deal with the myths surrounding milk.

Inforgraphic about milk, allergies and intolerances

Dairy products are a major part of the Western diet, and also feature heavily in the diets of athletes. Foods like yoghurt, milk and milk-derived protein powders (e.g. whey and casein) are sources of high quality protein for promoting training adaptation, and so are often suggested as good ‘recovery foods’ for athletes of all types. However, like any food group there are a number of health conditions that relate to eating dairy that may prevent some people from incorporating it into their diet. Perhaps the two most common problems are a dairy allergy, and lactose intolerance. This article will explore what they are, and whether dairy products can still ever be used by people with either of these conditions.


What are the conditions?

Dairy allergy (or more accurately bovine milk protein allergy) is a very common allergy in children, with as many as 6% of children having the allergy. As children grow up, the allergy resolves itself in 80-90% of children, but this still leaves many adults suffering from the allergy. The allergy is to one or more of the proteins in milk, which the body incorrectly recognises as harmful, leading to a dangerous histamine response by the immune system. Like any allergy, the exact symptoms and their severity vary between people, but can be life threatening, including anaphylaxis, shortness of breath or acute asthma.


If lactose is not broken down then it passes through the digestive system to the colon, where it disrupts the fluid balance and is fermented by the bacteria there

Lactose intolerance is an unrelated health condition that affects a large proportion of the world’s population. Lactose is the sugar found naturally in milk, and in varying amounts in different dairy products. It is digested by the enzyme lactase, which breaks it down into its constituent sugars which are then absorbed. Although everyone has the enzyme as a child, as some people age the amount of enzyme they have reduces drastically, meaning they can no longer break down lactose (which is known as lactose maldigestion). If lactose is not broken down then it passes through the digestive system to the colon, where it disrupts the fluid balance and is fermented by the bacteria there. This can cause symptoms such as diarrhoea, flatulence and abdominal pain.


Can people with these conditions eat dairy foods?

For adults with a serious and diagnosed dairy allergy, dairy products containing protein must be avoided, usually for the entirety of their life. Some individuals with dairy allergy have much weaker reactions to dairy foods, that may go undiagnosed for many years, if at all. These people often suffer different reactions, such as diarrhoea, vomiting or skin problems. Whilst these symptoms are unpleasant, they are not life threatening, and some people may choose to eat dairy foods in small amounts.


For people with lactose intolerance, the amount of lactose determines the severity of the symptoms they experience, with the vast majority of people with lactose intolerance being able to eat small amounts of lactose

People with lactose intolerance only experience symptoms when they eat dairy products containing lactose, meaning that many dairy foods which are processed or fermented to remove lactose are not a problem (such as butter, whey protein powders and many yoghurts).


For people with lactose intolerance, the amount of lactose determines the severity of the symptoms they experience, with the vast majority of people with lactose intolerance being able to eat small amounts of lactose. Although 25g of lactose (equivalent to around 500ml of milk) triggers symptoms in everyone with lactose intolerance, most people with lactose intolerance can eat 12-15g of lactose (250-300ml of milk) without serious symptoms. This amount can usually be digested by the combination of the low levels of lactase they still have, and by bacteria in the gut that can break down lactose without causing any symptoms.


So, how can dairy foods be used in the diets of people with lactose intolerance?

Lactose intolerant people can still eat a variety of dairy foods, most notably the foods with low lactose content (such as cheeses, butter and cream). It is also relevant for athletes that whey and casein protein powders have low amounts of lactose in, with most whey protein isolate powders containing less than 1g per 20g protein serving. Even the less ‘pure’ whey protein concentrates usually only contain 3g per 20g protein serving. Therefore, lactose intolerant people need not switch to non-dairy protein powders unless they suffer from symptoms with these small amounts. Keeping the amount of lactose eaten in any sitting to below 12-15g for most people with lactose intolerance will reduce or remove any symptoms, so knowing which foods are high in lactose can help to control this (see infographic).


Lactose intolerant people need not switch to non-dairy protein powders unless they suffer from symptoms with these small amounts

There is some research showing that people with lactose intolerance are able to ‘train’ themselves to eat more lactose without suffering symptoms. This training does not increase the amount of the enzyme lactase, but does change the type of gut bacteria, increasing the bacteria that can break down the sugar without causing symptoms. This explains why some people with lactose intolerance are unable to eat even small amounts of dairy foods, whilst others are able to eat much larger amounts.


Studies have shown that increasing the amount of lactose that you eat by small increments (e.g. 1 gram every few days) it is possible to increase the amount of lactose that triggers unpleasant symptoms, up to around 12g. This is useful both because it allows people with lactose intolerance to eat larger amounts of healthy and useful foods for recovery, but also because it means that they are less likely to have side effects if they accidentally eat dairy products.


By increasing the amount of lactose that you eat by small increments (e.g. 1g every few days) it is possible to increase the amount of lactose that triggers unpleasant symptoms, up to around 12g

In the next blog we will discuss the pros and cons of milk and some of the myths.


References

  1. Caffarelli C, Baldi F, Bendandi B, Calzone L, Marani M, Pasquinelli P, Ewgpag Obo. Cow's milk protein allergy in children: a practical guide. Ital J Pediatr. 36(1), 2010

  2. Misselwitz B, Pohl D, Fruhauf H, Fried M, Vavricka SR, Fox M. Lactose malabsorption and intolerance: pathogenesis, diagnosis and treatment. United European Gastroenterol J. 1(3):151-9, 2013

  3. Shaukat A, Levitt MD, Taylor BC, MacDonald R, Shamliyan TA, Kane R, Wilt TJ. Systematic Review: Effective Management Strategies for Lactose Intolerance. Ann Intern Med. 152:797-803, 2010

  4. Odell OJ, Wallis GA. The application of lactose in sports nutrition. International Dairy Journal. 2021.

  5. Johnson A, Semenya JG, Buchowski MS, Enwonwu C, Scrimshaw NS. Adaptation of lactose maldigesters to continued milk intakes. Am J Clin Nutr. 58:819-81, 1993

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