Written by: Lillian Sando, Ph.D. | Issue # 30 | 2014
- Several studies indicate that regular intake of milk products cultured with probiotic bacteria can help keep the skin hydrated, robust, and healthy looking.
- The effects of cultured milk products on skin health are thought to involve crosstalk between the gastrointestinal and immune systems.
- Proposed mechanisms for the effects include suppression of gut phenols, release of bioactive milk peptides and stabilization of skin sebum.
Since the times of ancient Egypt, women have used milk in various ways to attain beautiful, glowing skin. Today, Cleopatra’s alleged penchant for bathing in milk from 700 donkeys may seem a tad rich, however there is growing evidence that consuming milk products cultured with probiotic bacteria can help you to not only get a healthy gut, but also healthy skin.
In fact, scientists have long suspected that skin health and gut health are two sides of the same coin. After all, the lining of the gastrointestinal tract is—sort of—an extension of the skin. These inside and outside protective barriers are thought to ‘talk’ with each other along a proposed ‘gut–brain–skin axis’, tightly interwoven with the immune system (1). This complex conversation becomes all the more fascinating by the fact that it involves the millions of bacteria living on the skin and gut surfaces.
If the balance between the bacterial communities in the gut is disturbed, such as after an infection or other illness, it has long-range effects linked to, for instance, the immune system. By the same token, encouraging a balanced gut flora can stimulate the immune system and promote overall health.
One way to maintain intestinal health is boosting the so-called probiotics or ‘good bacteria’. Natural inhabitants of the gut, probiotics help to keep ‘bad bugs’ in check. Some probiotic bacteria, for instance lactobacilli and bifidobacteria, are also used in the food industry, typically to make cultured milk products such as yogurt.
Not surprisingly, the manufacturers of such products do a lot of research, not only to improve flavor, texture, and other qualities related to the culturing or fermentation process, but also to study the products’ potential health effects to expand their market range and value.
Fighting the gut phenols
Yakult, the Japanese pioneer behind the now world-known probiotic milk drink of the same name, recently reported several studies demonstrating the beneficial effects on skin health of a test product containing Bifidobacterium-fermented milk (2).
In a clinical trial, Yakult researchers compared the effects of the fermented milk and non-fermented placebo milk (3). After giving each drink to two groups of healthy Japanese women, they measured various parameters in the women’s blood and urine as well as the hydration level of their skin. After four weeks, the women who drank the placebo milk had significantly drier skin than the women who drank the fermented milk.
Could drinking fermented milk really help keep the skin moisturized? Well, Yakult’s research indicated as much, as well as provided some clues as to how. It showed that the women who drank fermented milk had lower blood and urine levels of phenols—a group of toxic by-products produced by some gut bacteria during digestion of proteins. Phenols are to some extent absorbed from the gut, circulated via the bloodstream and excreted from the body in the urine. But as the phenols paddle along with the blood, they may build up in the skin—at least in the skin of mice, as shown by Yakult researchers. In further tests on laboratory-grown human skin cells, they showed that phenols disturbed the cells’ production of a major skin protein, keratin 10, which helps to strengthen the barrier function of the skin.
High levels of phenols are typically seen in people with a disturbed gut environment and are influenced by, among other things, the frequency of bowel movements. While a survey among Japanese women highlighted a popular belief that constipation is linked to various skin problems, including dry skin, there is so far not enough experimental data to prove this link. But based on the studies in humans, mice and skin cells mentioned above, Yakult researchers concluded that excess phenols produced by certain gut bacteria cause skin problems such as dryness. As an antidote, they suggested daily intake of fermented milk containing probiotics, which could help maintain healthy skin by promoting a favorable gut environment that suppresses the production of phenols (2).
Unlocking bioactive milk peptides
Japan has a long tradition for producing fermented milk drinks. Calpis, another manufacturer, recently examined various skin properties in laboratory mice given a diet containing fermented milk whey or non-fermented milk whey (4). They found that the fermented whey, to a modest extent, could reduce water loss from the skin and alleviate dermatitis, an inflammation of the skin. Based on these results, the researchers suggested the fermented whey might strengthen the barrier function of the skin.
As the fermented drink used in this study was milk whey—the liquid remaining after the probiotic bacteria were removed by centrifugation—the bacteria could not have exerted a direct effect in the mice’s gut. Instead, the study’s authors ascribed the effect to biologically active peptides produced during the fermentation process, in which the lactobacilli chomp certain milk proteins into peptides.
Typically, the power of bioactive milk peptides lies hidden inside the protein until it is unlocked by an ‘encryption key’ in the form of chemicals, enzymes or microbes. Probiotic bacteria are known to unlock milk peptides with a number of health-promoting properties. Some peptides promote a healthy gut ecosystem, for instance by binding toxins, inhibiting the binding of harmful microbes to gut cells, boosting the growth of ‘good bacteria’ or regulating immune responses (5). These activities are bound to register on the ‘gut–brain–skin axis’.
Stabilizing the skin sebum
No doubt owing to the long-standing national tradition for sipping fermented milk beverages, such products are researched intensely in Japan—and not only by the companies producing them. Recently, scientists from various universities and a national research organization reported that the intake of fermented milk, compared with the intake of conventional yogurt, increased the skin hydration levels in young women (6). The study attributed the effect to increased levels of sebum. It also indicated that the effect depended on the women’s age and hormone levels, which influence sebum production.
Now, isn’t sebum the oily stuff that gives you pimples? Yes and no. In just the right amount, this cocktail of lipids helps protect the skin. Too little can give you dry, cracked skin, but too much can cause acne. And it seems milk could help alleviate the latter as well.
A Korean study (7) reported that daily consumption of fermented milk enriched with lactoferrin—a powerful milk protein (8)—had a therapeutic effect on acne in men and women. The over-production of sebum decreased in the study participants who drank lactoferrin-enriched, fermented milk and also, to a lesser degree, in those who drank ‘plain’ fermented milk. But only those in the lactoferrin group had significant improvement of their acne. So while some of the serum-stabilizing effect appeared to be due to the probiotic bacteria, lactoferrin provided the greatest efficacy. Lactoferrin’s power—probably ‘unlocked’ by the probiotics as explained above—lay in its ability to reduce both skin sebum content and inflammation.
Inducing a ‘glow of health’
As mentioned, anti-inflammatory effects may emerge by modulation of the immune system via the gut-brain-skin axis. Recently, a US-led team of university researchers proposed an interesting, sex-related explanation for the ability of probiotics to trigger this mechanism (9). Feeding probiotic yogurt to aged mice, the researchers found that the probiotic bacteria recreated the thick lustrous fur and ‘glow of health’ typical of young mice. (Fur luster was measured by an instrument as well as evaluated by human panelists unaware of which animals had received the probiotic yogurt or a placebo.) Linking this glow to various signs of youth and fertility, including increased sebum production, acidic skin pH, and anti-inflammatory mechanisms, the researchers suggested the effect was part of an evolutionary mechanism to ensure the reproductive success of both the symbiotic bacteria and their hosts. In other words, radiant skin and shiny hair signal good reproductive health and are therefore inherently attractive to prospective mates.
So what to make of all these studies seemingly suggesting different mechanisms for various beautifying effects of fermented milk products? The common thread among the probiotic-induced effects is the crosstalk between the gastrointestinal and immune systems, probably also involving the endocrine and nervous systems. The proposed mechanisms, whether related to suppressing gut phenols, unlocking bioactive milk peptides, stabilizing skin sebum or inducing a glow of health, are most likely closely related. But a lot more fermented milk needs to be drunk—by women, mice and men—for researchers to gather more evidence and figure out exactly how it works.
As for exactly how much fermented milk you need to drink to get that ‘glow of health’, the evidence isn’t clear-cut either. In Yakult’s study, the women consumed a daily dose of more than 100 billion of probiotic bacteria in total, which is far above the roughly 6.5 billion in a single-serve Yakult bottle (3). Most of the other studies also used higher doses than those typically consumed in actual foods and drinks. So fermented milk products are hardly going to be a magic bullet, especially considering their relatively un-dramatic effects. Perhaps the fermented milk products of the future will include higher doses of probiotics. In the meantime, the science suggests fermented milk can be one ingredient in a healthy lifestyle and for promoting beautiful skin.
1. Arck P, Handjiski B, Hagen E, Pincus M, Bruenahl C, Bienenstock J, Paus R (2010). Is there a ‘gut-brain-skin axis’? Exp Dermatol 19: 401–405.
2. Miyazaki K, Masuoka N, Kano M, Iizuka R (2014). Bifidobacterium fermented milk and galacto-oligosaccharides lead to improved skin health by decreasing phenols production by gut microbiota. Benef Microbes 5: 121–128.
3. Kano M, Masuoka N, Kaga C, Sugimoto S, Iizuka R, Manabe K, Sone T, Oeda K, Nonaka C, Miyazaki K, Ishikawa F (2013). Consecutive intake of fermented milk containing Bifidobacterium breve strain Yakult and galacto-oligosaccharides benefits skin condition in healthy adult women. Biosci Microbiota Food Health 32: 33–39.
4. Baba H, Masuyama A, Yoshimura C, Aoyama Y, Takano T, Ohki K (2010). Oral intake of Lactobacillus helveticus-fermented milk whey decreased transepidermal water loss and prevented the onset of sodium dodecylsulfate-induced dermatitis in mice. Biosci Biotechnol Biochem 74: 18–23.
5. Beermann C, Hartung J (2013). Physiological properties of milk ingredients released by fermentation. Food Funct 4:185–199.
6. Kimoto-Nira H, Nagakura Y, Kodama C, Shimizu T, Okuta M, Sasaki K, Koikawa N, Sakuraba K, Suzuki C, Suzuki Y (2014). Effects of ingesting milk fermented by Lactococcus lactis H61 on skin health in young women: A randomized double-blind study. J Dairy Sci [Epub ahead of print] Doi: 10.3168/jds.2014-7980.
7. Kim J, Ko Y, Park YK, Kim NI, Ha WK, Cho Y (2010). Dietary effect of lactoferrin-enriched fermented milk on skin surface lipid and clinical improvement of acne vulgaris. Nutrition 26: 902–909.
8. Petherick A (2014). Prescriptions for bovine lactoferrin. SPLASH! milk science update June 2014 (https://milkgenomics.org/splash/prescriptions-bovine-lactoferrin/).
9. Levkovich T, Poutahidis T, Smillie C, Varian BJ, Ibrahim YM, Lakritz JR, Alm EJ, Erdman SE (2013). Probiotic bacteria induce a ‘glow of health’. PLoS One 8: e53867.