4.2. Potential Health and Economic Impact of Lactose-Free Dairy vs. Dairy Avoidance
The National Institute of Health (NIH) concluded that the vast majority of lactose mal-absorbers will tolerate up to 12 g of lactose per serving and that smaller amounts of lactose will generally not cause major problems [4
]. Still, most subjects with self-diagnosed or physician-diagnosed lactose intolerance will try to avoid all lactose-containing products. However, in its Updated Consensus Statement, the National Medical Association reports that lactose free dairy products are the most ideal substitute for regular dairy products among individuals with lactose intolerance. In addition, evidence indicates that children prefer lactose-free cow’s milk over soy beverages [35
shows the nutritional composition of cow’s milk [36
]. Excluding all dairy products from the diet can lead to nutrient deficiencies because these foods are a major source of nutrients, notably choline, phosphorus, calcium, riboflavin and vitamin B12 and A (Table 1
). In the US and Canada, milk is mandatorily fortified and is an important source of vitamin D. “Dairy alternatives” from soy, rice or almonds are often consumed as a substitute for cow’s milk or yoghurt, constituting a nutritious alternative if fortified with vitamin A, vitamin B12 and calcium. One study found that calcium bioavailability from fortified soy milk was only 75% of the efficiency of calcium from cow milk [37
]. Consequently, most nondairy lactose-free products are fortified with at least 20% more than the recommended intake for calcium.
Alternatives that do not exclude cow’s milk include lactose-free milk products, yogurt containing lactic acid bacteria and cow’s milk combined with an intake of lactase supplements. Lactose-free dairy products and lactase supplements may have an advantage over excluding dairy products from the diet in that they do not reduce dietary intake and its essential nutrients. There is, however, still controversy surrounding the role of lactose in enhancing calcium and divalent mineral bioavailability. Lactose has been recognized as an enhancer of calcium absorption in mammals; in animal studies, lactose was found to enhance calcium absorption, but in humans, this effect is still debated [38
]. It was suggested that conflicting results are due to differences in the control sugars, where the component sugars glucose or galactose gave comparable calcium absorption as lactose, while other sugars did not.
Little information is available about the food choices of lactose intolerant people, but in the US, 75% of people with lactose intolerance avoid dairy with over half of them worrying about the long-term risks to their health due to this dietary restriction [39
]. Dairy avoiders have different reasons to avoid it; in a survey in the US, 61% of respondents indicated an avoidance of dairy for intolerance or allergy/sensitivity, while the remainder avoided dairy for other reasons [40
]. A survey in Canada showed that despite the higher use of calcium and vitamin D supplements, lactose intolerants had lower calcium and vitamin D intake from the combination of dairy products, alternatives and supplements [41
Some studies are available, reporting on the nutrient intake among lactose-avoiding subjects. Results generally show that lactose intolerant compared to tolerant people consume lower amounts of calcium with average amounts below the RDA (recommended dietary allowance) of 1000 mg/d (577 [43
], 692 [44
], 388 [45
], 510 [46
] and 739 [41
Observational studies have shown that the avoidance of dairy foods was associated with adverse health outcomes, including poor bone health [47
], higher blood pressure [49
] and a higher risk of developing diabetes [50
]. The EPIC-Oxford cohort study with 34,696 British people showed that vegans were at 30% higher risk for bone fractures than omnivores and vegetarians (who do consume milk, yoghurt, cheese and eggs), which was attributable to lower calcium intake [51
]. However, the possibility of important confounding bias in observational studies cannot be fully excluded. A recent randomized controlled intervention study investigated the effect of 18 months dairy consumption in healthy boys and girls on bone mass. No effects were found on any of the bone parameters except for tibial bone mineral content gain, which was greater in the group receiving dairy [52
]. However, in a longer study in teenage girls receiving dairy for two years, dairy significantly increased bone mineral density at the trochanter, femoral neck and lumbar spine [53
]. The effect of calcium and vitamin D intake on bone has been well-established. Vitamin D either in combination with calcium or not reduces the likelihood of hip fractures and other types of fracture in postmenopausal women or men aged over 65 years [54
]. As calcium and vitamin D intakes in lactose intolerants are generally below the recommended intakes, it is likely that this may lead to a decreased bone density, especially in older men and women.
Moreover, evidence exists that dairy consumption is inversely related to blood pressure [55
], which may be due to the presence of calcium, vitamin D and bioactive peptides in dairy.
When unaware, lactose intolerance can cause symptoms very similar to Irritable Bowel Syndrome (IBS), which may impair health-related quality of life. Among dairy-avoiding subjects, worry about an accidental lactose intake and a modification of diet may also affect the quality of life to some extent.
Two studies reported on the impact of lactose intolerance on the quality of life. In one study, the self-perception of intolerance was associated with lower health-related quality of life scores (median: 60 vs. 70, p
< 0.01) [56
]. In contrast, another survey did not find a negative impact of being intolerant to lactose on this score [57
One study estimated the potential impact of improved dairy consumption on reducing the disease burden in the Netherlands, France and Sweden. The impact of increasing calcium daily intake by 650 mg (equaling approximately 200 mL milk, 125 mL yoghurt and 30 g cheese) to reach the recommended intake has been modelled. For instance, in France, increasing dairy intake could prevent 2023 hip fractures per year, 6263 Disability-Adjusted Life Years (DALYs) per year and 129 million euro per year [58
]. The impact of increasing dairy intake in the Netherlands was lower as dairy intake is already relatively high. Besides the individual health benefits of dairy consumption, the economic benefits for society are evident, suggesting that the promotion of the consumption of lactose-free dairy products in countries with a high prevalence of lactose intolerance makes sense.