Lactose is the sugar of mammals and plays a relevant role in the very early life; beside its role as energy provider, it exhibits several health effects in young children, including a prebiotic effect on the gut microbiota and a positive effect on mineral absorption. Bifidobacteria and some lactobacilli have developed uptake and fermentation mechanisms of lactose that are the most efficient among the enteric bacteria and they have a major role in “priming” the immune system of neonates. Nowadays lactose malabsorption is often reported, but frequently as a consequence of an auto diagnosis, without a proper clinical assessment. On the other hand, the genetic basis and the physiology of this malabsorption is still under scrutiny by science and some of the “dogmas” about lactose intolerance are now under revision. Moreover, in case of lactose maldigestion, it is to be considered that the total dairy products avoidance is not an answer, since 1- a small dose of lactose can be digested (12g/day) even by maldigesters and, 2- there is a number of cheeses that, at the end of the ripening period, have no lactose. But, on top of that, as regards yogurt, it is to note that even EFSA, in the frame of its assessment of claims related to health, according to the EU Regulations 1924/2006, concluded that: ”a cause and effect relationship has been established between the consumption of live yogurt cultures in yogurt and improved digestion of lactose in individuals with lactose maldigestion.” The mechanism is related to the survival of lactase contained into the yogurt bacteria through the gastric transit, possibly being protected by the bacterial envelops, even if the cells are no more viable, and facilitated by the buffering action of yogurt. In the less acidic conditions and slow transit time of the small intestine the lactase is then able to digest the residual lactose, avoiding with this action any troubles to lactose maldigesters. This applies to lactic acid bacteria endowed with an ATP-based lactose transport system, such as the yogurt bacteria, whose lactase is active on lactose without any previous phosphorylation. It could be concluded that a more ”science-based” view is necessary for a better approach to understand and manage lactose as a nutrient.

1. Yoghurt and lactose:
cooperation for nutrition
Lorenzo Morelli
Istituto Microbiologia UCSC
Piacenza – Cremona Italy
lorenzo.morelli@unicatt.it

2. Yoghurt and lactose:
«characters of this opera»

3. 1. Lactose
2. Lactose maldigesters
3. Yogurt
4. Yogurt bacteria

4. Main characters of this presentation:
The sugar of «mammals»
At its appearance it was unknown to bacteria
(evolutionary more «ancient» than mammals)
Most bacteria «still» unable to ferment lactose
Some bacteria have solved this evolutionary problem
1.Lactose
mammalian milk is the only known natural
source of significant amounts of lactose

5. Lactose: a young actor or an
actor for the youngs?
As this is the sugar of mammals it plays some positive roles for infant
nutrition:
- Lactose constitutes around 40% of the energy provided by breast milk
- It has been also suggested that it increases mineral absorption
- It has been also suggested that lactose could have a prebiotic effect
Grenov et al, 2016

6. Lactose: a young actor or an
actor for the youngs?
Bifidobacteria are key players for the health of infants…
Some bifidobacteria utilize lactose better that glucose…
Amaretti et al, 2006

7. Lactose digestion in adults
Vonk et al,2012

8. Main characters of this presentation:
2. Lactose maldigesters
3. Biological Mechanism of Lactose Intolerance
About two thirds of the World’s population undergoes a genetically programmed
decrease in lactase synthesis after weaning (primary lactase deficiency) .
Additionally, in individuals with lactase persistence the occurrence of gastrointestinal
infection, inflammatory bowel disease, abdominal surgery and other health issues
can also cause a decrease in lactase activity (secondary lactase deficiency.
Whatever the cause, lactase deficiency results in unabsorbed lactose being
present in the intestinal tract, which has effects that can lead to symptoms of
lactose intolerance in susceptible individuals .
Deng et al, 2015

9. 2. Lactose maldigesters: just to define
LACTASE DEFICIENCY AND LACTOSE INTOLERANCE:
... Lactose tolerance varies widely among individuals with lactose maldigestion.
A single threshold of lactose for all lactose intolerant subjects cannot be determined
owing to the great variation in individual tolerances.
…The vast majority of subjects with lactose maldigestion will tolerate up to 12 g of
lactose as a single dose with no or minor symptoms.
Higher doses may be tolerated if distributed throughout the day.

10. 2. Definitions: just to summarize
Szilagy,2015

11. Vonk et al,2012
What happens with undigested lactose ?

12. 2. Lactose intolerance
3. Biological Mechanism of Lactose Intolerance
 About 2/3 of the World’s population undergoes a genetically programmed
decrease in lactase synthesis after weaning (primary lactase deficiency) .
 Additionally, in individuals with lactase persistence the occurrence of
gastrointestinal infection, inflammatory bowel disease, abdominal surgery and
other health issues can also cause a decrease in lactase activity (secondary
lactase deficiency).
 Whatever the cause, lactase deficiency results in unabsorbed lactose being
present in the intestinal tract, which has effects that can lead to symptoms of
lactose intolerance in susceptible individuals .
Deng et al, 2015

13. Long-term effects of lactose restriction
 Although restricting dietary lactose or FODMAPs (fermentable oligo-, di-,
monosaccharides and polyols) may improve gastrointestinal complaints,
long-term effects of a diet free of dairy or FODMAPs products may be of
concern => Dairy products are the major source of calcium in many
individuals. No study has addressed the safety and effectiveness of
calcium replacement for patients with lactose intolerance; …
 Diet also has effects on the colonic microbiome. Altering the dietary
intake of FODMAPs alter gastrointestinal microbiota and a significant
decrease in the concentration of probiotic bifidobacteria after four
weeks of a low FODMAP diet has been reported . Whether this change
has any long-term implications is unknown.
Deng et al, 2015

14. Main characters of this presentation:
3.YOGURT

15. Main characters of this presentation:
4.YOGURT BACTERIA
Streptococcus thermophilus
Lactobacillus delbrueckii
subsp bulgaricus

16. The plot: how bacteria have solved this
evolutionary drama
Uptake via
ATP
permease
Uptake via
PEP PTS
It requires metabolically active bacterial cells

17. The plot: how bacteria have solved this
evolutionary drama
Only the Leloir
pathway is active
in unviable, lysed
bacterial cells
Yogurt bacteria
use the Leloir
pathway

18. Also on stage
• Yogurt is characterised by the presence,
when consumed, by an high bacterial
count.
• Streptococci and Lactobacilli are then
viable at the moment of the ingestion
• And afterwards?

19. Costumes: yogurt bacteria must wear «viability»

20. Savaiano, 2014
Scenario :
Low survival to intestinal transit
but HIGH lactase activity

21. Scenario : the viability of yogurt cultures make the difference !
Savaiano et al, 1984

22. Hydrolysis of lactose by unviable
bacteria also in ripened cheeses
«ITEMS»
Istituto Danone, 1998

23. A first conclusion
It is then possible to assume that lactose hydrolysis is deeply
related to the evolutionary history of mammals and bacteria .
Some bacteria inhabiting the human intestine and relevant for our
health are potent lactose fermenters, in a «prebiotic» way
Yogurt bacteria (as well as some other lactic acid bacteria) are able
to hydrolyze lactose even if unviable (but they have to be viable
at the moment of ingestion) thanks to their specific uptake system.

24. A regulatory view.
In the European Union the use of health claims made
on food is strictly regulated (Reg EC1924/2006)
Very few claims approved after the assessment of the
available data by the European Food Safety Authority
BUT
The lactose hydrolysing ability of yogurt bacteria has
been successufully recognized

25. A regulatory view.

26. A regulatory view.

27. A regulatory view.

28. A regulatory view.

29. A regulatory view.

30. To conclude…
we may use the EFSA conclusions

31. To conclude…
we may use the EFSA conclusions

32. To conclude
THANKS FOR
YOUR
ATTENTION