How Milk and Bacteria Help Us Grow
When I was a kid I didn’t like milk much—unless it was chocolate. I have no idea how many times I heard my mother say, “Drink your milk; it’s good for you. It will give you strong bones and muscles.” Little did I know that, from a young age, milk was playing an important role in my health. It turns out milk is beneficial—but only if I have a healthy microbiota (bacteria) in my gut.
Three recent publications highlight the critical importance of the proper microbiota for early development. Stunting (reduced growth during development) “starts before birth and is caused by poor maternal nutrition, poor feeding practices, and poor food quality as well as frequent infections which can slow down growth.”1
To counter stunting, God has abundantly endowed us with bacteria that three recent studies show actually aid growth and development.
Study #1: Gut Microbiota May Thwart Stunting
Prokaryotic bacteria are the most abundant life-form on Earth in both biomass and in sheer numbers. An average adult comprises about 35 trillion human cells, but we each carry 10–100 times more bacterial cells! The diversity of bacteria and their complex interactions with human health is an area of scientific inquiry rich for discovery.
A group from Washington University reported in Science how microbiota from heathy children compared to microbiota from undernourished children.2 By transferring microbiota from healthy and malnourished children to special germfree mice (mice raised in germfree enclosures free from microorganisms), researchers demonstrated that mice receiving the malnourished children’s microbiota showed impaired growth compared to mice receiving the healthy children’s microbiota. This was the result even though all mice received a diet sufficient for normal growth and development.
Additionally, researchers identified two specific types of bacteria in the healthy children’s microbiota that could restore normal growth. These findings suggest that the proper identification of bacterial taxa that contribute to human growth and development might one day provide a probiotic intervention for addressing malnutrition.
Study #2: Gut Microbes Help Offset a Poor Diet
Findings of another study reported in Science, conducted by a group in Lyon, France, suggest that a proper microbiota may even support growth and development in cases of depleted nutrition.3 In this report, researchers injected microbiota from mice into “normal” BALB/c mice (who had an endogenous gut microbiota). They also did parallel studies on germfree mice with no added microbiota. Both groups of mice (germfree and normal) were fed a diet rich in nutrients. The researchers found that the normal mice experienced normal growth and development, but the germfree mice experienced stunted growth, despite receiving a nutritious diet. The stunted growth in the germfree mice was linked to a reduction in a particular hormone (insulin-like growth factor-1, IGF-1) that promotes organ and systemic growth in normal development.
Eventually, researchers injected microbiota into the germfree mice, and when the mice were fed a depleted diet, a normal microbiota helped sustain hormonal levels and postnatal growth. In fact, a single specific type of bacteria, L. plantarum, restored IGF-1 levels in germfree mice and supported postnatal growth. These experiments show that even in situations of acute malnutrition (a depleted diet), a proper microbiota contributes to growth and development.
Study #3: Milk and Bacteria May Even Restore Growth
The first group, in an additional study reported in Cell, showed that in both mice and pigs, a diet supplemented with sialylated bovine milk oligosaccharides (S-BMO)—a bioactive substance that substitutes for human milk oligosaccharides (complex sugars)—promoted growth and development even in the presence of bacteria cultured from an unhealthy child’s microbiota.4 It appears milk oligosaccharides (whether from bovine supplements or presumably those naturally occurring in human breast milk), in the presence of bacteria, can help restore growth and actually compensate for undernourishment.
Although the researchers were unable to link these growth effects to specific bacteria, they were able to point to a bacterial species that is able to metabolize S-BMO-derived sialyllactose to its constituent monosaccharides, which would then be available for use by the host and to other bacteria beneficial to the host.
These findings suggest a proper microbiota for growth and development likely involves a web of diverse cross-feeding bacteria. The roles of minority contributors in the microbiota were not examined in these studies. Much more study is needed to identify the beneficial bacteria and their complex interdependencies relevant for human growth and development.
God Has Made Us Rich in Bacteria
These three studies, taken together, highlight the remarkable importance of bacteria in growth and development. They also highlight the potential of some bacteria to possibly aid in restoring growth and developmental to malnourished children. It’s fascinating that key components to nutritional development (like milk-based complex sugars) are dependent on gut microbes for metabolism. It seems our Creator designed gut microbes to work in complex systems that benefit humanity even in less than ideal nutritional circumstances. My mom had it right all along: Drink your milk—but ask for it with a shot of (good) bacteria, too!
Food for Thought
Some estimates indicate that a gram of soil contains around 10,000–50,000 bacteria. Do you think there is any link to the high percentage of bacteria in soil, the critical role of bacteria in human health, and the biblical verses that say God formed man out of the dust (Genesis 2:7, 3:19; Ecclesiastes 12:7)? Visit TNRTB on WordPress to comment with your response.
- “Chronic Malnutrition: Stunting,” UNICEF, accessed March 14, 2016, https://www.unicef.org/nutrition/training/2.3/20.html.
- Laura Blanton et al., “Gut Bacteria That Prevent Growth Impairments Transmitted by Microbiota from Malnourished Children,” Science 351 (February 2016): 830, doi:10.1126/science.aad3311.
- Martin Schwarzer et al., “Lactobacillus plantarum Strain Maintains Growth of Infant Mice during Chronic Undernutrition,” Science 351 (February 2016): 854–57, doi:10.1126/science.aad8588.
- Mark Charbonneau et al., “Sialylated Milk Oligosaccharides Promote Microbiota-Dependent Growth in Models of Infant Undernutrition,” Cell 164 (February 2016): 859–71, doi:10.1016/j.cell.2016.01.024.