From Volume 48, Issue 5, May 2021 | Pages 359-366
Drinking milk-like fluids made from plant-based materials, such as soya, nuts and peas, is an increasing trend within the population, and regular consumption of these non-dairy alternatives may increase the risk of developing caries. This article focuses on current research relating to caries risk and consumption of milk-like products, and also investigates the sugar content of milk alternatives available in the UK.
Milk is a lacteal secretion, free from colostrum, which is obtained from milking cows, contains fats, casein, albumin, milk sugars and inorganic salts. There are now many plant-based alternatives for cows' (or other ruminants') milk. These milk-like fluids can be derived from many sources including nuts, seeds, legumes and grains. Worldwide sales of dairy-free alternatives grew to £9.2 billion in 2017, with a potential growth of £26.3 billion by 2024. This exponential growth has been attributed to a drop of £852 million in sales of cows' milk in 2018 in the USA alone.1
Dairy-free alternatives are made by soaking plant-based materials in water. They are then processed to resemble cows' milk and marketed as a ‘milk’ or ‘milk beverage’. These milk alternatives are being chosen due to vegan/plant-based diets, allergies or, in some cases, lactose intolerance. Some prefer the taste of alternative milks compared to cows' milk or prefer the consistency of the milk when combined with other beverages, such as tea and coffee. Others may be concerned about animal welfare rights, use of antibiotics and hormones in cattle, and also the nutritional content of cows' milk.
The Scientific Advisory Committee on Nutrition (SACN) guidelines2 on feeding in the first year of life suport exclusive breastfeeding for the first 6 months of an infant's life and the continuance of breastfeeding for at least the first year of life. After 6 months, foods other than breastmilk and formula can be introduced to the baby's diet. Breastmilk contributes to infant and lifelong health in many ways. For example, it has an important role in the development of the immune system and there is evidence that not breastfeeding is associated with a higher risk of hospital admission.2 Public Health England (PHE) recommends whole milk for children younger than 2 years of age. Between the ages of 2 and 5, children can gradually move from whole milk to semi-skimmed milk, as long as they are eating a good and varied diet. Dental professionals should support the guidance offered by PHE.3}
Cows' milk is a source of nutrition for young children, particularly calcium. Other benefits include: protein for growth and repair; vitamin B2 (riboflavin) for healthy skin; vitamin B12 for red blood cells, carbohydrate for energy; and iodine for growth. The dental benefit of consuming cow's milk is well known.
The sugar present in cow's milk is lactose, which is non-fermentable and thus, non-cariogenic. Cows' milk also has a good bioavailability of calcium. Milk alternatives contain oxalates and phytates, which bind to calcium and form insoluble salt complexes, thus decreasing calcium absorption. Current milk alternatives can be considered to be second-best to cows' milk.
What does this mean for the dental profession? The World Health Organization guidelines recommend a daily intake of free sugars that provides no more than 10% of daily energy requirements and suggest further reductions to <5% to protect dental health throughout life. A systematic review demonstrated that a reduced level of dental caries was found when free sugar intake was <5% of daily energy.4 Dairy-free alternatives are beverages that adults and children can consume. Any substance that enters the mouth, however, will react with enzymes in saliva, changing the environment in the oral cavity and, therefore, have the potential to cause dental caries.
Laboratory studies have shown that in the absence of saliva, cows' milk is cariogenic, with further cariogenic potential when consumed in milk with added sugars.5 Although lactose is described as a milk sugar with the least cariogenic ability, rampant and bottle caries do occur in the absence of saliva. These results can somewhat be expected under the extreme measures in the studies.
Munoz-Sandoval et al concluded that milk is less cariogenic than 10% sucrose, although it should not be considered caries-free.6 Limited research exists on milk alternatives; however, studies have concluded that popular alternatives, such as almond and soy milks are potentially cariogenic, especially when supplemented with sugars.7,8
Mammalian milk is a combination of lipids, proteins (mainly casein), salt, minerals (eg calcium), vitamins, sugars and carbohydrates. Lactose is the predominant sugar in cows' milk.
Lactose and galactose occur naturally in milk, and are not considered free sugars. The WHO states that free sugars include monosaccharides and disaccharides added to foods and beverages by the manufacturer, cook or consumer, and also those naturally present in honey, syrups, fruit juices and fruit juice concentrates. Alternative milks contain free sugars because they are added during production.
Cows' milk has been shown to be ‘tooth friendly’ with no increase in plaque acidity. This can be attributed to three factors: tooth remineralization, prevention of bacterial attachment, and inhibition of bacterial biofilm formation ability.8,9,10 Thus, cows' milk is cariostatic.
Calcium aids in the remineralization of the hydroxyapatite layer. Casein, which comprises 80% of milk protein, has the ability to produce higher concentrations of calcium phosphate in the plaque structure. This results in remineralization of enamel subsurface lesions.10 Furthermore, casein prevents adhesion of the bacteria, Streptococcus mutans to the tooth surface.11,12,13 Research shows calcium and vitamin D to be inversely associated with plaque.12 Also, calcium and vitamin D have shown protective affects against tooth loss, with more severe periodontal disease resulting from low dietary calcium.13,14,15 The link between milk and periodontal disease does, however, remain unclear. Table 1 shows that 300–367 mg calcium is present per 250-ml serving of lactose-free dairy milk, with vitamin D fortification where necessary. In the UK, only infant formula is required to be fortified with vitamin D by law.
| Dairy milk (cow and goat) | Sugar/250 ml (g) | Calcium/250 ml (mg) | Vitamin D/250 ml (µg) |
|---|---|---|---|
| St Helen's fresh whole goats milk (1 L) | 10.8 | 300 | 0 |
| St Helen's fresh skimmed goats milk (1 L) | 10.8 | 300 | 0 |
| St Helen's fresh semi-skimmed goats milk (1 L) | 10.8 | 300 | 0 |
| Cravendale filtered whole milk (2 L) | 11.75 | 305 | 0 |
| Cravendale semi skimmed milk (2 L) | 12 | 310 | 0 |
| Arla Bob skimmed milk (2 L) | 12.3 | 367 | 0 |
Although these factors are important for the low cariogenic potential of cows' milk, lactose itself is a fermentable sugar. Parents of young children are advised by paediatric dentists to avoid prolonged night-time bottle and breastfeeding because early childhood caries can be a consequence of regular milk consumption before sleep and during the night. Low levels of saliva during these conditions can favour caries formation despite lactose being designed to be broken down in the lower intestine. Naturally found components both human and cows' milk, such as lactoferrin, offers a protective affect by inhibiting S. mutans attachment to bacterial biofilms.8 Interestingly, milk with a higher fat content has been linked to low caries potential.16 Dairy products, such as cheese, are found to be anti-cariogenic and are advised as an alternative ‘safe’ snack.
Data for dairy-based substitutes and dairy-free alternatives were sourced from popular supermarket websites to produce a comprehensive list of the most popular milk and milk alternatives purchased worldwide, including lactose-free and dairy-free alternatives based on soya, pea plant, nuts, coconut, oats, flax and hemp, and rice.17,18,19,20,21
For each dairy-free alternative, nutritional information was independently verified from the manufacturers' nutritional information and labelling. Manufacturers are only required to list ‘… of which sugars’ on the packaging. The type of free sugar added, often glucose or sucrose, is not usually disclosed. Free sugars are the energy source for oral bacteria to ferment into acid, which can lead to tooth tissue demineralization and breakdown, which eventually results in caries.22
| Lactose-free dairy milk (1 L) unless otherwise noted) | Sugar/250 ml (g) | Calcium/250 ml (mg) | Vitamin D/250 ml (µg) |
|---|---|---|---|
| Lactofree whole lactose free fresh dairy drink (1 L) | 6.5 | 273 | 0 |
| Lactofree semi-skimmed lactose-free fresh dairy drink (1 L) | 6.8 | 285 | 0 |
| Lactofree UHT semi skimmed milk (1 L) | 6.8 | 288 | 0 |
| Lactofree skimmed lactose-free fresh-dairy drink (1 L) | 7 | 303 | 0 |
| Candia just milk lactose-free semi-skimmed milk (1 L) | 12 | 300 | 0 |
| Arla Bob skimmed milk (2 L) | 12.3 | 367 | 0 |
Lactose intolerance can trigger symptoms such as diarrhoea, abdominal pain and vomiting. Individuals with lactose intolerance cannot produce lactase, the enzyme found in the small intestine responsible for the breakdown of lactose. Manufacturers add lactase to cows' milk to produce lactose-free milk. The lactase breaks down the lactose into the simpler sugars, glucose and galactose, which can give the lactose-free milk a sweeter taste.
Lactose-free milk has the same protective benefits as ordinary cows' milk. They both contain caseins and natural calcium minerals. However, the simple sugars in this milk raise the question of whether lactose-free milk has a higher cariogenic potential. In studies, whole lactose-free milk has been shown to have low demineralization potential.16 The protective benefits of dairy milk are probably contributors to this outcome.
| Soya milk | Sugar/250 ml (g) | Calcium/250 ml (mg) | Vitamin D/250 ml (µg) |
|---|---|---|---|
| Alpro soya unsweetened longlife drink alternative (1 L) (new taste/no sugars) | 0 | 300 | 1.9 |
| Alpro soya unsweetened fresh drink alternative (1 L) | 0 | 300 | 1.9 |
| Alpro soya light fresh drink alternative (1 L) | 0.3 | 300 | 1.9 |
| Provamel organic soya drink unsweetened (1 L) | 0.3 | 0 | 0 |
| Sojade natural soya milk, organic (1 L) | 1 | 0 | 0 |
| Alpro soya light longlife drink alternative (1 L) | 3.5 | 300 | 1.9 |
| Provamel organic soya drink sweetened (1 L) | 6 | 300 | 0 |
| Alpro soya organic longlife drink alternative (1 L) | 6 | 0 | 0 |
| Sojade soya milk, sweetened with calcium, organic (1 L) | 6.25 | 300 | 0 |
| Alpro soya fresh drink (1 L) | 6.3 | 300 | 1.9 |
| Alpro soya longlife growing up drink (1 L) | 6.3 | 300 | 3.75 |
| Alpro soya junior multipack (6 x 1 L) 1–3 years | 6.3 | 300 | 3.75 |
| Provamel organic soya drink vanilla (1 L) | 14.25g | 0 | 0 |
| Alpro soya vanilla longlife drink alternative (1 l) | 16 | 300 | 1.9 |
| Alpro soya chocolate longlife drink alternative (3 x 250 ml) | 18.5 | 300 | 1.9 |
| Alpro soya strawberry longlife drink (3 x250 ml) | 19 | 300 | 1.9 |
Soya milk is plant-based milk. It is produced from the grinding of soya beans. The plant is a native of East Asia and used also to produce soy sauce, tofu, oil, textured vegetable proteins, and even wine. The milk originates from the 3rd century, only receiving mass attention in the 20th century.
Soya milk is a combination of oil, water and protein from the soybean. The milk is close in protein content to animal-derived milk and fortified with calcium, and vitamins A, B and D. Sweet or savoury versions are made, with additions such as cane sugar, cane juice, syrup, salt and vinegar. Soya milk is heavily marketed as a healthier alternative because of its low saturated fat content, with no cholesterol or lactose, in comparison to cows' milk. Table 3 highlights the increase of sugar between the unsweetened and sweetened varieties.
Soya milk has a sugar content of 0–19 g per 250-ml serving, compared to 10.8–12.3 g for dairy milk. Calcium and vitamin D levels are similar. Unsweetened varieties have 0–0.3 g of sugar, while organic options can contain 1 g of naturally occurring sugars. Sugar is added to enhance the flavour and to mirror the taste of cows' milk. Sweetened, long-life and flavoured varieties contain the highest levels of sugar – up to 19 g per serving. Although lower in sugar content compared to dairy milk, studies have shown soya milk to possess the highest cariogenic potential – due in part to its low buffering capacity.7
| Pea milk | Sugar/250 ml (g) | Calcium/250 ml (mg) | Vitamin D/250 ml (µg) |
|---|---|---|---|
| Ripple unsweetened original dairy free pea milk (1.42 L) | 0 | 469 | 3.1 |
| Ripple original half & half (473 ml) | 0 | 33.3 | 0 |
| Qwrkee plant-based pea milk unsweetened (X L) | 0.8 | 300 | 0.5 |
| Qwrkee plant-based pea m'lk sweetened (X L) | 4.5 | 300 | 0.5 |
| Bolthouse farms plant protein milk original (1.42 L) | 5.2 | 469 | 4.2 |
| Ripple original dairy-free pea milk (1.42 L) | 6.25 | 469 | 3.1 |
| Bolthouse farms plant protein milk vanilla (1.42 L) | 12.5 | 469 | 4.2 |
| Ripple vanilla dairy-free pea milk (1.42 L) | 15.6 | 469 | 3.1 |
| Ripple vanilla half & half 473ml | 16.7 | 33.3 | 0 |
| Ripple chocolate dairy-free pea milk 1.42l | 17.7g | 469 | 3.1 |
Pea milk is a recent addition to the vegan market. It is marketed as an environmentally friendly alternative to almond and GMO-free soya milks. It is made from yellow split peas that are milled into flour, the proteins are separated and blended with water, oils, salt, guar gum, vitamins and sugars. It is gluten and dairy free, high in protein and fibre, and low in saturated fats. The sugar content ranges from 0 g to 17.7 g per 250-ml serving, with original and sweetened varieties. Calcium content is up to 469 mg per serving, which is higher than cows' milk. It is fortified with vitamin D at 0–4.2 µg per 250-ml serving. The sugar content of the original variety is lower than cow's milk. The cariogenic potential is unstudied; however, the fermentable sugar content of the different varieties means it has the potential to contribute to caries.
| Nut milk | Sugar/250 ml (g) | Calcium/250 ml (mg) | Vitamin D/250 ml (µg) |
|---|---|---|---|
| Alpro almond roasted unsweetened longlife drink (1 L) | 0 | 300 | 1.9 |
| Alpro almond roasted unsweetened fresh drink alternative (1 L) | 0 | 300 | 1.9 |
| Almond breeze unsweetened fresh drink (1 L) | 0.3 | 300 | 1.9 |
| Innocent almond dairy free 750Ml | 0.75 | 0 | 0 |
| Alpro almond longlife milk alternative (1 L) | 6 | 300 | 1.9 |
| Almond breeze original longlife drink alternative (1 L) | 7 | 300 | 1.9 |
| Innocent hazelnut dairy free 750Ml | 7.25 | 0 | 0 |
| Alpro hazelnut fresh drink alternative longlife (1 L) | 7.75 | 300 | 1.9 |
| Rude Health longlife almond & rice drink, organic (1 L) | 11.75 | 0 | 0 |
| Alpro almond dark chocolate longlife drink alternative (1 L) | 17.25 | 300 | 1.9 |
Nut-based milks have been available in the market for a considerable time. They are made by blending nuts with water and straining the solids. It is ideal for vegans and those intolerant to dairy. Nut milks are fortified with calcium, vitamin, minerals and proteins.
The sugar content varies between 0 g and 17.25 g, with sugar being added to sweetened varieties. Unsweetened nut milk contains 0 g of sugar. The calcium content of nut milk is similar to that of cows' milk. These milks are also fortified with vitamins. Studies have shown that almond milk, when sweetened, may possess high cariogenic potential, whereas unsweetened varieties have limited potential for caries. Again, the limited buffering capacity may be responsible for the cariogenic potential.7
| Coconut milk | Sugar/250 ml (g) | Calcium/250 ml (mg) | Vitamin D/250 ml (µg) |
|---|---|---|---|
| Koko dairy free unsweetened alternative longlife drink (1 L) | 0.5 | 300 | 1.9 |
| Koko dairy free original plus calcium longlife drink (1 L) | 4 | 300 | 1.9 |
| Alpro organic coconut (1 L) | 4.75 | 0 | 0 |
| Alpro coconut fresh drink (1 L) | 4.8 | 300 | 1.9 |
| Koko dairy free original plus calcium drink alternative (1 L) | 5.3 | 300 | 1.9 |
| Coconut dream original plus calcium drink alternative (1 L) | 18.75g | 300 mg | 1.9 µg |
This is a milk alternative that is made from grating coconut meat, which is then diluted with water rather than being made from the ‘milk’ or ‘cream’, which is normally used for cooking. It contains more fibre and iron than cows' milk. It is fortified with 300 mg calcium and 1.9 µg of vitamin D. The sugar content varies from 0.5 g to 18.75 g per 250-ml serving. The cariogenic potential of this beverage is unstudied; however, the potential for caries is there if fermentable sugars are added to sweeten the products.
| Oat, flax and hemp milk | Sugar/250 ml (g) | Calcium/250 ml (mg) | Vitamin D/250 ml (µg) |
|---|---|---|---|
| Alpro oat unsweetened (1 L) | 0 | 300 | 1.9 |
| Braham & Murray long life good hemp dairy free drink, original (1 L) | 0 | 0 | 1.9 |
| Ooomega 100% plant-based flax drink original (1 L) | 0.1 | 0 | 0 |
| Good hemp drink (1 L) | 4 | 300 | 1.9 |
| Ooomega flax seed drink original sweetened (1 L) 5 | 0 | 0 | |
| Alpro oat longlife milk alternative (1 L) | 8.25 | 300 | 1.9 |
| Provamel organic oat drink (1 L) | 9.75 | 22.5 | 0 |
| Oatly foamable (1 L) | 10* | 300 | 3.8 |
| Oatly longlife drink (1 L) | 10.25* | 300 | 3.8 |
| Oatly oat drink semi (1 L) | 10.25* | 300 | 3.8 |
| Oat dream gluten free longlife drink alternative (1 L) | 11.25 | 0 | 0 |
| Oatly oat drink chocolate (1 L) | 17.5 | 300 | 3.8 |
| Oatly chocolate longlife drink alternative (1 L) | 18.75 | 300 | 3.8 |
Oat milk is made from oats that have been cleaned, toasted and hulled. Water is added, along with, in some cases, other grains and beans. It contains between 0 g and 18.75 g of sugar, with an average sugar content of 8 g per 250-ml serving. The higher sugar content is due to the naturally occurring sugars in oat milk.23 The oats are a source of carbohydrate, which is broken into simpler sugars giving it the sugar content. It is fortified with 300 mg of calcium per 250-ml serving and 1.9 µg of vitamin D. The cariogenic potential has not been studied, but with the higher sugar content, it is there.
Flax milk is manufactured by cold-pressing flax oil with water, emulsifiers and thickeners. It has a sugar content from 0.1 g to 5 g per serving. The benefits of calcium and vitamin D are missing as it is not fortified. The sweetened variety has more sugar than the naturally occurring type.
Hemp milk is ideal for those who cannot have gluten, nut or soy. It is made from hulled hemp seeds. The sugar content is between 0 g and 4 g. Sometimes brown rice sugar is added to sweetened varieties but, naturally, it is low in sugar. It is sometimes fortified with calcium and vitamins.
| Rice milk | Sugar/250 ml (g) | Calcium/250 ml (mg) | Vitamin D/250 ml (µg) |
|---|---|---|---|
| Alpro rice longlife milk alternative (1 L) | 8.25 | 300 | 1.9 |
| Rude health longlife unsweetened brown rice drink (1 L) | 12 | 0 | 0 |
| Rice dream original with added calcium drink alternative (1 L) | 17.75 | 300 | 1.9 |
| Rice dream original organic drink alternative (1 L) | 17.75 | 0 | 0 |
| Rice dream organic vanilla flavoured milk alternative UHT (1 L) | 18 | 0 | 0 |
Rice milk is made from brown rice. It is sometimes sweetened with sugarcane syrup or brown rice syrup. The carbohydrate content is higher and even the unsweetened variety contains 12g of sugar per serving. The sugar content ranges between 8.25 g and 18 g per serving with an average of 14.75 g per serving. It tastes sweeter than cows' milk and can sometimes be fortified with calcium and vitamins, which have their added benefits. Rice milk is the highest in terms of added sugars and has the most potential to cause caries.
The market for dairy, non-dairy and dairy substitutes is saturated, with many products from which to choose. The nutritional information can be overwhelming and may be challenging to interpret.
What has become increasingly clear in the recent years, is that patients are more aware of what they are eating and drinking. Dairy has been advocated since birth for many of the population, with key messages of strong bones and teeth when children consume whole milk. Understanding the roles of vitamin D and calcium will result in relaying information precisely and accurately to patients when discussing dairy alternatives.
Milk alternatives may be necessary for those who have and allergy to cows' milk (CMA) and/or lactose intolerance. CMA is rare, affecting 2–3% of infants.24 However, remission rates of approximately 85–90% are seen in infants by the age of 3 years.25
Lactose intolerance is the inability to digest lactose, the sugar usually found in milk. Humans lose 90–95% of their birth lactase levels by early childhood, with a continuous decline during the course of a lifetime. Diagnosis can usually be made from a thorough history. In these cases, specialist staff are required to diagnose and treat such individuals.26
It is paramount that those patients who present at dental practices are fully aware of the implications of consuming different varieties of milk. Dentists need to be comfortable in providing key messages, particularly when giving dietary advice, to those who fall within this subset. This will involve dentists and other healthcare professionals familiarizing themselves with all the available alternatives to cows' milk. Particular attention needs to be paid to the sugar content of these milks, cariogenicity has to be assessed, as well as the frequency and timing of consumption. Based on the conclusions from the Vipeholm study, it is important to assess dietary addition of milks to beverages such as coffee and tea, which impacts on the frequency of consumption and development of caries.27
Patients must also be informed that soya milk is not dangerous to children when given in small quantities. However, soya milk that is not designed for infants should not be used as a substitute for infant formula. Regular soya milk could lead to nutrient deficiencies. Those with CMA are also warned to not drink soya milk as these children are often allergic to soya as well. Soya may have other interactions for those with conditions such as diabetes, cystic fibrosis, asthma, hypothyroidism and kidney stones/failure.28
Other alternative milk-like products are often not a good source of protein, contain carrageenan, which can lead to digestive problems, are sourced from genetically modified plants, and are high in carbohydrates and saturated fats. Manufacturers may not be keen to disclose this information to consumers fully, and therefore further research must be encouraged.
As some of the milks listed are nut based, care must be taken by those with allergies to nuts. The severity of allergies should be assessed by specialists in this area.
Further research needs to be conducted to investigate the dental effects of the available non-dairy ‘milk’ products. The sugar content needs to be assessed to enable dentists to provide information and knowledge to their patients.
The market for dairy-free milks has increased and will continue to do so as consumers change their dietary habits. Dental professionals need to be knowledgeable in this area so that they are able to give advice to patients relating to cows' milk, its alternatives, and their effects on oral health. Patients should be informed about sugar content, types of sugars and potential links with dental decay as well as the vitamin D/calcium content of the milk. Unfortunately, there is little high-quality research currently available in this area.
