Original Article

診療と新薬 2020; 57: 979-983

Eﬀects of Saccharomyces cerevisiae NK-1 in Improving
the Intestinal Environment and Quality of Sleep:

診療と新薬 WebA Randomized, Double-blind, Crossover Study

Norio KANESUGI 1）／ Michiyo KANESUGI 1）／ Yumiko IDE 2）／ Ryuji TAKEDA 3）● Abstract
Background: Saccharomyces cerevisiae NK-1 is a simple, single-celled organism and is a yeast used forindustrial and pharmaceutical purposes in the ﬁeld of genetics and medicine. Yeast has intestinal regulating
properties. Hence, the current study aimed to investigate whether Saccharomyces cerevisiae NK-1 canpromote changes in the intestinal environment and sleep-related quality of life.
Methods: This was a randomized, double-blind, crossover study. Healthy men and women ingested a stick
containing 10 billion Saccharomyces cerevisiae NK-1 or a placebo stick without Saccharomyces cerevisiae
NK-1 three times a day for 4 weeks. Then, the proportion of intestinal ﬂora was evaluated using the terminal
restriction fragment length polymorphism methods, and quality of sleep was assessed with the Obstructive
Sleep Apnea (OSA) questionnaire before and after ingestion. This study was registered in the UMIN Clinical
Trials Registry prior to the study (UMIN-ID: UMIN000025190).
Results: The number of Biﬁdobacteria was signiﬁcantly higher in the Saccharomyces cerevisiae NK-1 powdergroup than in the placebo group. Based on the OSA questionnaire findings, there were significant
improvements in sleepiness and fatigue upon waking up in the Saccharomyces cerevisiae NK-1 powder groupcompared with the placebo group.
Conclusion: Saccharomyces cerevisiae NK-1 improved the intestinal environment by increasing the numberof Biﬁdobacteria and sleepiness and fatigue upon waking up.
Key Words: Saccharomyces cerevisiae NK-1, Bifidobacterium, OSA Sleep Questionnaire, Randomized,
Double-blind Study

1. BACKGROUND
The human intestine has different intestinal bacteria,
which form a complex ﬂora. The balance of microﬂora, or
the intestinal environment, is significantly associatedwith overall health1)-4). In human health, predominance of
the Biﬁdobacterium genus should be maintained5). Yeast
has been utilized for the fermentation of foods since along time ago and has several uses particularly in making
bread, sake, and wine. It has a single cell with a simple
biological structure; hence, it is applied for industrial andpharmaceutical purposes in the genetics and medicalﬁelds. Saccharomyces cerevisiae is a budding yeast. It isa well-known species and is popular due to its nutritional
activity and nutrient and mineral content. Fiber-richyeast is known to improve defecation.
Constipation is an abdominal symptom typically caused

by a lack of fiber, which reduces peristalsis in theintestines, thereby causing difficulties in regular bowel
movements. Prolonged constipation results in theretention of stool in the intestines, which causes loss ofwater and hardening of the stool. Extended retention of
the stool in the intestine also increases the number ofputrefactive bacteria in the intestinal microflora. A
decrease in the proportion of lactobacilli leads thegeneration of indole, skatole, ammonia, and hydrogensulfide in the intestine, thereby causing unpleasant
symptoms such as inﬂammation of intestinal tissues andabdominal bloating.
In addition to abdominal symptoms, constipation can
result in psychological symptoms such as decreased
appetite and depression due to abdominal bloating andadverse effects on sleep. Thus, regular defecation isimportant in improving quality of life (QOL). We
previously reported that the intake of Saccharomyces

1) Nikkenkyo Service Corporation, Sanchome n 12, Konosu, Saitama, 369-0134 Japan
2) Tokyo Center Clinic, Yaesu KT Buildings, Yaesu 1-cyo-me 1-8, Cyuou-Ku, Tokyo, Japan
3) Faculty of Health Sciences for Welfare, Department of Nutritional Sciences for Well-being, Kansai University of Welfare Sciences, 3-11-1 Asahigaoka
Kashiwara Osaka, 582-0026 Japan20 （980）

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第 11 号（2020 年 11 月）

Table 1 Inclusion and exclusion criteria of the study
Inclusion criteria
Participants aged 20‒64 years
Exclusion criteria
Participants with known allergy or sensitivity to any foods
Participants who use any medecines or supplements
Participants with a history of severe disease including intestinal diseases

Table 2 Composition of the experimental（Saccharomyces cerevisiae NK-1）
and placebo food samples per day *Experimental food9Placebo

Saccharomyces cerevisiae NK-1
LactoseCaramel color

5.40 g（10 × 10 counts）−−−
5.38 g0.02 gTotal

5.40 g5.40 g*3 sticks/day

cerevisiae NK-1 increased the frequency of defecation inconstipated individuals with low defecation frequency.
This result may be attributed to the eﬀects of increased
dietary fiber intake on the intestinal microbiota and thehigher number of Biﬁdobacteria in the intestines, which
may prevent the generation of putrefactive gas.
Therefore, this randomized, double-blind study wasconducted to compare the effect of Saccharomycescerevisiae NK-1 and placebo on the intestinal
environment and sleep.
2. METHODS
2.1. Study Design
This was a randomized, double-blind, crossover study. In
total, 20 healthy adults who met the selection criteria, as
depicted in Table 1, were included. All participants
provided informed consent. The study details werediscussed in advance by the JCCR Ethics Committee andpermission was then obtained. Furthermore, thisresearch was registered in the UMIN Clinical Trials
Registry prior to the study (UMIN-ID: UMIN000025190).
2.2. Randomization
The participants were assigned to either one of twogroups using the stratiﬁed blocked randomization method(stratification factors: gender and age). An independentassignee who was not involved in the trial developed acomputer program using a random number table andclassified the participants into two groups. Blinding ofparticipants and the performer was maintained.
2.3. Experimental and Control Foods
The experimental product was a stick containing
Saccharomyces cerevisiae NK-1. The participantsreceived sticks containing 10 billion Saccharomyces
cerevisiae NK-1 three times a day. Meanwhile, lactose,instead of Saccharomyces cerevisiae NK-1, here was novisual diﬀerence in terms of color, odor, or size between
the two products. The components of the two products
are shown in Table 2.
2.3. Intestinal Flora
Stool samples were collected from the participants before
and 4 weeks after ingestion. Then, the occupancy of fecal
microbiota was assessed using the terminal restriction
fragment length polymorphism method at Techno Suruga
Laboratory Co., Ltd.
2.4. Obstructive Sleep Apnea Questionnaire
Sleep status was assessed using the OSA-MA. The OSAMA was administered at the participant s home soonafter he or she woke up every day and on each of theprevious 2 days. The participants were instructed tobring the questionnaires with them to the hospital forsubmission.
2. 5. Statistical Analysis
The student s paired t -test was used to assess each factor
in the gut flora and the OSA questionnaire. The
significance level was set at 5%. The Fisher s exact
probability test was utilized to evaluate adverse events.
Statistical analysis was conducted using SAS 9.4 atKansai University of Social Welfare Science.

3. RESULT3.1. Subjects
In total, 40 participants, 20 for each testing period,
completed the study (Table 3).

診療と新薬・第 57 巻

第 11 号（2020 年 11 月）

21 （981）(drowsiness and fatigue upon waking up after theingestion of exhaustion) ranged from 12.00 ± 1.82 to
13.14 ±2.24 (difference: 1.14 ±1.91) in the
Saccharomyces cerevisiae NK-1 powder group and from11.46 ± 1.72 to 11.00 ± 1.85 in the placebo group (37 ±1.85 [diﬀerence:− 0.09 ± 1.75). The diﬀerence in score
was signiﬁcantly higher in the Saccharomyces cerevisiaeNK-1 intake group than the placebo group at after 4weeks of intake and change (p ＜ 0.001 after 4 weeks ofintake, change p = 0.0403).

3.2. Intestinal FloraThe results of the intestinal flora study are shown inTable 4. After the ingestion of Saccharomyces cerevisiae
NK-1, a significant difference was observed in thepercentage of Bifidobacterium in the feces between theSaccharomyces cerevisiae NK-1 powder and placebogroups. This finding indicated an increase in thepercentage of Bifidobacterium in the feces. Moreover,
the Saccharomyces cerevisiae NK-1 powder group had ahigher percentage of Clostridium subcluster XIVa in thefeces than the placebo group. This result indicated adecrease in the percentage of Clostridium subcluster
XIVa.

3.4. Adverse Event
Based on the blood test results, both groups did notpresent with any medical problems. Mild adverse events
including bloating occurred. However, there was no
signiﬁcant diﬀerence between the two groups.

3.3. OSA Questionnaire
The OSA questionnaire and OSA-MA findings of theSaccharomyces cerevisiae NK-1 powder and placebogroups are shown in Table 5.
The mean and standard deviation of the first factor(sleepiness upon waking up) from pre-intake to 4 weeks
after ingestion ranged from 11.20 ± 1.57 to 12.14 ± 2.22
(diﬀerence: 0.94 ± 1.78) in the Saccharomyces cerevisiae
NK-1 powder group and from 11.43 ± 1.98 to 11.43 ±1.76 (difference: − 0.23 ± 0.97) in the placebo group.
The difference in score was significantly higher in theSaccharomyces cerevisiae NK-1 powder group than in
the placebo group (20 ± 1.76 [difference: − 0.23 ± 0.97
points], p = 0.0139).
The mean and standard deviation of the fourth factor

4. DISCUSSION
The participants ingested Saccharomyces cerevisiae
NK-1 powder (10 billion/pack) three times a day, and its

Table 3 Proﬁle of the participants
Item
Number of individuals
Sex ratio（male-to-female）
Age（mean ± SD）

20
16/4
43.59 ± 8.72

Table 4 Changes in fecal microbiota（％ occupancy）
Microbiota

Foods

Biﬁdobacterium

Before4 weeks

Δ 4 weeksN

Mean ± SD

p -value*N

Mean ± SD

p -value*N

Mean ± SD

p -value*NK-1Placebo

2020

10.69 ± 8.72
12.16 ± 9.30

0.20202020

13.51 ± 10.21
10.91 ± 9.41

0.13262020

2.83 ± 4.37
− 1.25 ± 5.67

0.0210Lactobacillales

NK-1
Placebo2020

2.45 ± 3.06
3.41 ± 4.38

0.35682020

3.24 ± 3.05
2.70 ± 2.85

0.552120200.80 ± 3.75
− 0.71 ± 3.43

0.1687Bacteroides

NK-1
Placebo202050.96 ± 11.86
48.56 ± 13.68

0.41762020

45.64 ± 11.69
45.04 ± 11.33

0.77172020− 5.33 ± 7.80
− 3.52 ± 7.89

0.5024

Prevotella

NK-1
Placebo2020

2.86 ± 8.185.33 ± 12.82

0.36272020

2.86 ± 8.11
3.25 ± 10.01

0.761320200.00 ± 6.72
− 2.08 ± 8.29

0.4166

Clostridium
cluster IV

NK-1
Placebo2020

7.64 ± 4.72
7.25 ± 4.10

0.67492020

7.30 ± 4.84
7.74 ± 4.49

0.47892020− 0.33 ± 5.23
0.49 ± 3.70

0.5039

Clostridium
subcluster XIVa

NK-1
Placebo2020

13.41 ± 4.92
12.76 ± 6.60

0.60562020

12.97 ± 4.77
16.93 ± 8.30

0.04502020− 0.43 ± 4.04
4.17 ± 6.50

0.0192

Clostridium
cluster IX

NK-1Placebo

2020

4.46 ± 5.01
3.01 ± 3.110.1818

2020

4.92 ± 8.25
3.95 ± 6.48

0.46912020

0.46 ± 6.23
0.94 ± 6.120.6884

Clostridium
cluster XI

NK-1
Placebo2020

0.61 ± 1.62
0.43 ± 0.68

0.56432020

0.55 ± 1.19
0.39 ± 0.82

0.48042020− 0.06 ± 1.20
− 0.04 ± 0.70

0.9528

Clostridium
cluster XVIII

NK-1
Placebo2020

1.68 ± 2.05
1.91 ± 2.28

0.57852020

1.34 ± 1.38
2.64 ± 3.520.0253

2020− 0.34 ± 1.07
0.73 ± 3.30

0.1905Others

NK-1
Placebo2020

5.25 ± 2.96
5.18 ± 2.170.9207

2020

7.66 ± 4.83
6.45 ± 2.960.3734

2020

2.41 ± 6.18
1.27 ± 2.560.4995*Between Saccharomyces cerevisiae NK-1 and placebo using the student s paired t -test22 （982）

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Table 5 Result of the OSA questionnaire
OSA factors

FoodFirst factor:
sleepiness upon waking

Before4 weeks

Δ 4 weeksN

Mean ± SD

p -value*N

Mean ± SD

p -value*N

Mean ± SD

p -value*

NK-1
Placebo202011.20 ± 1.57
11.43 ± 1.98

NS202012.14 ± 2.22
11.20 ± 1.76

NS20200.94 ± 1.78
− 0.23 ± 0.970.0139

Second factor: onset andmaintenance of sleep

NK-1
Placebo2020

11.46 ± 2.30
11.76 ± 2.71

NS202012.33 ± 2.05
11.35 ± 2.55

NS20200.87 ± 1.72
− 0.42 ± 1.63

0.0201

Third factor:
frequent dreaming

NK-1
Placebo202015.63 ± 3.37
16.05 ± 3.33

NS202016.71 ± 3.91
16.01 ± 3.55

NS20201.08 ± 4.08
− 0.03 ± 3.38

NSFourth factor:feeling refreshed

NK-1
Placebo202012.00 ± 1.82
11.46 ± 1.72

NS202013.14 ± 2.24
11.37 ± 1.85

＜ 0.001

20201.14 ± 1.91
− 0.09 ± 1.75

0.0403

Fifth factor:
sleep duration

NK-1
Placebo202012.43 ± 1.92
11.54 ± 2.23

NS

202011.78 ± 2.22
11.59 ± 2.33

NS2020− 0.65 ± 2.84
0.05 ± 1.89

NS

*Between Saccharomyces cerevisiae NK-1 and placebo using the student s paired t -test

eﬃcacy in improving defecation was assessed. Yeast is a
non-motile, eukaryotic, unicellular microorganism withcell walls. It has no photosynthetic capacity, and its
nutrients are derived from the decomposition andabsorption of external organic matter. Morphologically, it
has an almost featureless circular or oval shape, and it
multiplies by budding and division. These features
facilitate its production in the intestinal tract andexpression of a higher number of good bacteria in theintestine. Moreover, since its a eukaryote, it has a ﬁberlike effect and has been a source of food for
Bifidobacteria. There are various theories about how
yeast improves bowel movement via its ﬁber-like action.
In general, ﬁber is a substance that is not easily broken
down in the wild, even if left their, nor is broken down by
animal substances. Fibers that are not digested by humandigestive enzymes are referred to as non-digestible
fibers. This type of fiber has low nutrient contents andhas not received much attention. However, they are now
known as enzymes that are highly involved in humanhealth functions and that have an important role inmaintaining health. There are two types of fiber:
insoluble and soluble. Insoluble and water-soluble dietaryfibers have extremely different physiological effects.
Insoluble fiber has good water retention, and it
contributes to increased stool volume and promotes
peristalsis in the intestines. Soluble fiber has
physiological functions in the small intestine, including
inhibiting the production of digestive enzymes involved in
the breakdown of carbohydrates, such as alphaglucosidase, and cholesterol by reducing the reabsorptionof bile acids. In particular, water-soluble fiber can be
broken down by the enzymes of intestinal bacteria, but
not human digestive enzymes. Moreover, it can be asource of energy. Hence, it is believed to be a source for
Bifidobacteria and lactobacilli, and it can reduce thepercentage of putrefactive bacteria 8) . In the OSA
questionnaire, sleepiness and fatigue upon waking up
significantly improved in the Saccharomyces cerevisia e

NK-1 powder group compared with the placebo group.
There are different yeast strains. Among them, sakeyeast was associated with improvement in sleep
electroencephalogram (EEG) results. Improvement insleep quality among individuals who consume sake yeast
is attributed to the activation of adenosine A2A
receptors9) and increased secretion of growth hormone9).
The secretion of growth hormones increases with greaterdelta wave power in sleep EEG10)-12), and an increase indelta wave power value promotes deep sleep9). These
results showed that Saccharomyces cerevisiae NK-1 may
have a similar effect. However, this is a subjective
evaluation only. Thus, further research should beconducted to determine improvements in sleep EEG
results.

5. CONCLUSION
A randomized, placebo-controlled, double-blind study wasconducted using Saccharomyces cerevisiae NK-1 powder.
Results showed that the percentage of Bifidobacteria in
the intestinal flora was significantly higher in theSaccharomyces cerevisiae NK-1 powder group than in
the placebo group. In addition, based on the OSA
questionnaire, there was improvement in sleepiness andfatigue upon waking up. These results indicated that
Saccharomyces cerevisiae NK-1 powder was eﬀective in
improving the intestinal environment and sleep-related
QOL.
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