Probiotics, live microorganisms that confer health benefits when consumed, have garnered increasing attention for their potential role in weight management. Found in both supplements and fermented foods like Yakult, probiotics have been linked to various health improvements, including benefits for the immune system, digestive health, and even heart health. This article delves into the research surrounding Yakult, a probiotic milk beverage, and its potential effects on weight loss, drawing upon scientific studies and expert opinions.
The Gut Microbiota and Weight Regulation
The digestive system hosts a diverse community of microorganisms, predominantly beneficial bacteria that produce essential nutrients like vitamin K and certain B vitamins. These bacteria also aid in breaking down indigestible fiber, converting it into short-chain fatty acids like butyrate.
Two primary families of bacteria reside in the gut: Bacteroidetes and Firmicutes. Research suggests a correlation between body weight and the balance of these bacterial families. Studies have indicated that individuals with moderate weight exhibit different gut bacteria compositions compared to those with overweight or obesity. Some studies have observed a higher abundance of Firmicutes and a lower abundance of Bacteroidetes in individuals with obesity, although further research is needed to solidify these findings. The gut bacteria of obese individuals tend to be less diverse than those of lean individuals.
These findings suggest that gut bacteria may play a significant role in regulating body weight. Probiotics appear to influence appetite and energy utilization through the production of short-chain fatty acids like acetate, propionate, and butyrate.
How Probiotics May Influence Weight Loss
Probiotics may impact weight management through several mechanisms:
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Inhibiting Fat Absorption: Certain probiotics may hinder the absorption of dietary fat, leading to decreased inflammation and increased fat excretion in feces. This process essentially reduces the number of calories the body extracts from food. Bacteria from the Lactobacillus family have demonstrated this functionality.
Releasing Appetite-Regulating Hormones: Probiotics may stimulate the release of glucagon-like peptide-1 (GLP-1) and peptide YY (PYY), hormones known to reduce appetite. Elevated levels of these hormones can potentially boost calorie and fat burning.
Increasing Fat-Regulating Proteins: Probiotics may elevate levels of angiopoietin-like 4 (ANGPTL4), a protein that can decrease fat storage.
In essence, probiotics can potentially reduce calorie absorption, modulate hormone and protein levels associated with appetite and fat storage, and alleviate inflammation, a known contributor to obesity.
Specific Probiotic Strains and Weight Loss
Research indicates that specific strains within the Lactobacillus and Bifidobacterium families may contribute to weight reduction.
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Lactobacillus gasseri: Studies suggest that Lactobacillus gasseri exhibits promising effects on weight loss in humans. Meta-analyses have revealed that Lactobacillus gasseri can decrease body weight, BMI, waist circumference, body fat mass, and fat percentage in individuals with overweight or obesity. Notably, it has also been shown to reduce visceral fat even without energy restriction. However, more research is warranted to confirm these findings.
Lactobacillus curvatus and Lactobacillus plantarum: Consuming products containing Lactobacillus curvatus and Lactobacillus plantarum has been associated with reductions in body weight, visceral fat mass, and waist circumference, particularly when combined with exercise.
Lactobacillus sakei: In a study involving adults with obesity, those who consumed Lactobacillus sakei experienced significant decreases in body fat mass and waist circumference compared to those who received a placebo.
Bifidobacterium animalis subsp. lactis: A 2020 study indicated that Bifidobacterium animalis subsp. lactis had a positive impact on weight management and reduced inflammation.
Yakult: A Probiotic Beverage
Yakult is a probiotic milk beverage produced by a Japanese company. It is created by fermenting skim milk with Lacticaseibacillus paracasei strain Shirota (LcS). This sweet-citrusy drink contains over 6.5 billion beneficial bacteria per bottle.
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Each 65ml bottle of Yakult contains 50 calories and no fat, cholesterol, or dietary fiber. It includes 15mg of sodium, 12g of carbohydrates, 10g of sugar, and 0.8g of protein.
Yakult is considered safe for consumption by both adults and children, including pregnant women. Drinking one bottle of Yakult daily may provide several health benefits. There is no specific time recommended for consumption; it can be enjoyed at any point during the day.
Health Benefits of Yakult
Yakult's high concentration of beneficial bacteria contributes to overall health and infection resistance. Significant benefits include:
Constipation Prevention: Probiotics can accelerate gut transit time and increase bowel movement frequency, softening stools and facilitating their passage. They can also aid in managing gastrointestinal issues like diarrhea.
Reduced Risk of Upper-Respiratory Tract Infections: Probiotics regulate microbial balance in the gut, strengthening the body's defenses against pathogens and lowering the risk of upper-respiratory tract infections, particularly in children.
Anxiety and Stress Reduction: Research suggests a connection between gut health and brain function. Probiotics may reduce anxiety and depression scores in individuals experiencing these symptoms.
Cancer Prevention: Probiotics possess anti-cancerous properties and may delay the formation of cancerous tumors, promoting sustainable physiochemical conditions in the colon.
Improved Heart Health: Probiotics can reduce inflammation and regulate cholesterol levels, contributing to cardiovascular health.
Skin Health: Intestinal bacteria influence skin health. Probiotics may help manage skin conditions like rosacea, psoriasis, and atopic dermatitis, which are associated with decreased gut diversity.
Yakult and Weight Loss: The Evidence
Research suggests that probiotics may release appetite-regulating hormones, potentially reducing overeating and promoting weight loss. Probiotics also contain proteins that regulate fat metabolism. Animal studies suggest that LcS has anti-obesity effects. Probiotics can prevent constipation and improve digestive health, further supporting weight management.
One study monitored the effects of Yakult’s probiotic strain Shirota (LcS) on obese children, finding that it aids weight loss while also improving lipid metabolism. Researchers observed significant weight loss and positive changes in bacterial fecal composition in obese children who consumed an LcS beverage daily for six months, alongside diet and exercise therapy.
Specifically, a significant decline in body weight (-2.9%) and an elevation in high-density lipoprotein (HDL) cholesterol level were observed six months after ingestion of the LcS beverage compared to baseline. Furthermore, a significant increase in the fecal concentration of Bifidobacterium and an apparent increase in the acetic acid concentration were also noted.
Additional Research on Yakult and its Probiotic Strain
Yakult was originally created by Dr. Minoru Shirota. Its probiotic Lacticaseibacillus paracasei strain Shirota is able to live in our gut, withstand the harsh acidity of our stomach acid, and stay in our system for significantly longer.
A 2021 Nutrients study found that Yakult optimized gut microbes (feeding the good stuff, whale reducing the harmful gut pathogens) among people with depression, leading to less constipation. In this study, Yakult was helpful in improving bowel regularity and reducing symptoms of constipation among participants with PD.
A 2016 study found that drinking Yakult once daily for just 8 weeks leading up to final exams was enough to significantly reduce stress-induced gastrointestinal dysfunction (upset stomach) among medical students, leading up to exams.
In a 2021 study by Microorganisms, a small group of 18 participants with major depressive disorder (MDD) or bipolar disorder were given the Lacticaseibacillus paracasei strain Shirota for just 12 weeks, and reported significant improvements in depressive symptoms.
A 2016 randomized control trial published by Neurogastroenterology and motility found that just 8 weeks of daily Yakult was effective at reducing excessive cortisol production (a stress hormone) by stimulating the vagus nerve (part of our gut-brain axis), compared to the placebo.
That being said, it isn’t too surprising that just 4 weeks of Yakult (taken 1x/day) helped reduce infectious bacteria and plaque among participants who started out at increased risk of plaque and dental infections, in a 2013 study.
For example, drinking Yakult just once daily for 6 weeks was shown to have a balancing and optimizing effect among participants, on the cellular level, according to a 2023 randomized, double-blind controlled clinical trial.
In a 1998 study on rodents, orally-administered Yakult inhibited the growth of various cancer cells in mice and other rodents via altering the immune system. A more recent Molecules study from 2018, which included human participants, found that the special probiotic strain found in Yakult was able to enhance the effectiveness of a substance which inhibits oral cancer growth in humans.
The probiotic Lacticaseibacillus paracasei strain Shirota (found in Yakult) was shown in a 2013 study to help prevent diet-induced hepatitis, as well as reduce inflammation in rodents by lowering LPS levels, while also protecting the colon from LPS-induced damage.
Another study concluded that Yakult’s probiotic Lacticaseibacillus paracasei strain Shirota helped significantly reduce oxidative stress (cell damage) among septic (poisoned) mice by altering and optimizing their immune systems.
A small double-blind, randomized, crossover, placebo-controlled trial by Nutrients (published in 2023) uncovered that in just 4 weeks, 1 daily serving of Yakult significantly improved and optimized energy levels, perceived mood, sleep patterns, and heart rate variability among 12 healthy adults with sleep complaints. Again, while this sample is very small, and only one study was conducted, it’s an interesting and noteworthy pattern.
Potential Side Effects of Yakult
While Yakult is generally safe, some individuals may experience side effects:
- Bloating: Some individuals may experience initial bloating as their body adjusts to the bacteria.
- Lactose Intolerance: As a skimmed milk beverage, Yakult may cause allergic reactions in individuals with severe lactose intolerance.
- Weak Immune System: Although probiotics are generally beneficial, they may cause infections in individuals with compromised immune systems.
Yakult and Malnutrition in Older Adults: A Study in Nursing Homes
A study investigated the effects of Lacticaseibacillus casei strain Shirota-containing fermented milk (LcFM) on body weight and nutritional status in older adults residing in nursing homes. Malnutrition impacts physical function and poor prognosis of older adults.
The study involved residents from multiple nursing homes in Tokyo, Chiba, and Saitama, Japan. Participants were divided into an intervention group (receiving LcFM) and a non-intervention group. Residents who had a history of allergies to the components in LcFM, were receiving enteral feeding or total parenteral nutrition, had been administered antibiotics within the intervention period, or were unable to consume dairy products orally, were excluded. The intervention group received one 80-mL bottle of LcFM daily for 1 year. The non-intervention group did not receive LcFM or any other dairy products containing LcS.
Data on dietary intake, physical activity, body weight, care-needs level, and blood parameters (albumin, cholesterol, and hemoglobin) were collected before and after the intervention. Body-weight changes from baseline to 6 and 12 months were compared between the groups.
The study found that supplementation with LcFM suppressed body-weight loss in older adults with lower care needs and a lower BMI (<22 kg/m2). However, the study was conducted in an open-label, non-randomized manner, which is a limitation. Further research with more rigorous designs and diverse backgrounds is required to confirm the present results. The study also did not assess the effects of LcFM on skeletal muscle mass and motor function.
Dosage and Timing
It is generally recommended to consume one or two bottles of Yakult daily as part of a regular diet. Yakult can be consumed at any time of the day. A study by Yakult Central Institute indicated no significant difference between drinking Yakult 30 minutes before or after meals.