The study, conducted during late summer to fall, found that lactoferrin supplementation could support immune health, such as reducing respiratory symptoms through plasmacytoid dendritic cells (pDCs) activity.
Existing studies showed that the pDCs function as ‘leaders’ in antiviral immunity.
Writing in Nutrients, the researchers said that respiratory symptoms such as runny nose and throat discomfort were significantly lower in the group that took lactoferrin as compared to the placebo group. Systemic symptoms, such as fever, were also fewer in the intervention group.
The randomised, double-blind, placebo-controlled trial took place between August and November last year in Japan.
A total of 157 healthy adults were randomised to take either two tablets each containing 100mg of bovine lactoferrin daily or the placebo for 12 weeks.
They recorded any respiratory and systemic symptoms experienced and tabulated these symptoms into scores. The lower the score, the milder the symptoms.
Findings showed that the total scores for respiratory and systemic symptoms were significantly lower in the intervention group.
The intervention group had a median respiratory symptom score of 11, significantly lower than the score of 32 from the placebo group by the end of the trial.
Also, as the study progresses, the intervention group reported a declining symptom score while the opposite was true for the placebo group.
In the former, symptom score dropped from 11 to four after four weeks, although it rebounded to a score of six by the end of the trial.
In contrast, symptom score for the placebo group went up from 14 to 19 after four weeks of the trial and jumped to 42 by the end of the trial.
Systemic symptom score in the intervention group was also significantly lower – at five versus 30, when the trial ended.
“Alleviative effects of LF (lactoferrin) were clearer in weeks five to eight and weeks nine to 12 than in weeks one to four against both respiratory and systemic symptoms.
“Ingestion of LF for more than four weeks may be preferable to enjoy the benefits. Previous trials have also demonstrated that LF suppresses respiratory and systemic symptoms in healthy adults and children, which supports the results of the present trial,” said the researchers.
The trial was funded by Morinaga Milk Industry Co., Ltd.
pDC activity higher in lactoferrin group
In addition, there were greater pDC activities in the intervention group than the placebo. This is assessed by measuring the amount of glycoprotein CD86 and cell surface receptor HLA-DR in the blood samples.
The pDCs, being ‘leaders’ in antiviral immunity, could upregulate the expression of co-stimulatory molecules, such as CD86, the researchers explained.
These activities in turn alleviate respiratory and systemic symptoms.
The pDCs are detected in the peripheral blood, as well as mucosa-associated lymphoid tissues in the upper and lower digestive tract. This also means that ingested food components may modulate pDC activity.
By the end of the trial, both the intervention and placebo groups saw a reduction in CD86 and HLA-DR levels.
However, the intervention group had a significantly higher level of these molecules.
In the intervention group, CD86 expression levels went down from 2.987 to 2.963, but that of the placebo group saw a greater reduction from 3.013 to 2.960.
“The expression of CD86 and HLA-DR on pDCs was lower at week 12 than at week 0 in both groups and was significantly higher in the LF group than in the placebo group at week 12.
“Our previous study also reported that LF intake (200 mg/day for 4 weeks) enhanced IFN-α and CD86 expression on pDCs.
“Considering the current and previous observations that suggested activation of NK cells, CD4+ helper T cells, CD8+ killer T cells, and B cells by LF, it is considered that ingested LF modulates the entire immune system through maintaining pDC activity and contributes to the maintenance of respiratory and systemic physical conditions,” the researchers said.
Effects of Bovine Lactoferrin on the Maintenance of Respiratory and Systemic Physical Conditions in Healthy Adults—A Randomized, Double-Blind, Placebo-Controlled Trial
Authors: Oda, H et al