Researchers in a recent article published in the journal Nutrition & Health synthesized data from 17 peer-reviewed publications. They also analyzed the responses of more than 61,332 participants to understand the scientific impact that diet has on hair health.
A review of findings revealed that vitamin D levels showed a strong correlation with the severity of alopecia. This is a good example of how important specific micronutrients are for optimal hair health. However, a large cohort study did not find any association. In contrast, high sugary drink consumption (>3500ml/week), especially among men, was positively associated with hair loss.
These findings highlight the importance of specific nutrients, foods, and supplements in maintaining hair follicle health, as opposed to a general diet.
Background
Evolutionary biologists believe that hair is more than a biological trait; it’s also a secondary sexual characteristic deeply linked to an individual’s identity, their self-esteem and psychological well-being. Alopecia is a common condition that affects millions of people, regardless of age, race/ethnicity, or gender.
A growing body of research highlights the role of hormones and genetics in alopecia, and the general health of hair follicles. However, new evidence indicates that diet and nutrition have a profound impact on optimal hair outcomes (and, by extension, psychological outcomes).
The role of subtler dietary factors, and specific nutrients within the general population is still unclear. The focus of previous reviews on these topics was often alopecia. This left a gap between the scientific understanding of diet and hair health in general (quality, density and growth).
Understanding these relationships will not only help consumers and nutritionists make better choices regarding their diet plans, but also allow public health agencies and psychology to mitigate the growing mental health crisis.
The study
This systematic review will address these urgent needs by providing an overview of scientific literature that is comprehensive and current, and collating and synthesising this evidence in order to guide both individuals and healthcare providers on the best diets for hair health.
The review was performed according to Preferred Reporting Items for systematic reviews and Meta-Analyses (PRISMA), and registered on PROSPERO. The search was a custom, in-depth keyword search across three major scientific databases. Medline (PubMed), Web of Science, and 3. Web of Science and Scopus are the three databases that we use to search for all relevant studies. Scopus for all relevant publications from the database’s inception until June 2024.
The search found 17 peer-reviewed original studies that met the criteria for inclusion (age >=3 years old, language: English, Portuguese, experimental investigations on the impacts of specific foods consumption on specific hair health outcomes). Included studies were primarily 1. The included studies were mainly divided into 1. There are four case-control studies, three clinical trials (randomized), two clinical trials and one cohort study.
The methodological quality of every included study was assessed rigorously to ensure accuracy and reliability in the final systematic review results. This was done using the Newcastle-Ottawa Scale for observational studies, and the Cochrane Collaboration tool for randomised trials. The quality assessments showed moderate scores for observational trials and high bias risk in some clinical trials.
Study Findings
One large cohort study accounted for a large proportion of the participants in this systematic review. The majority of participants (97%) were women, and summary statistics revealed that vitamin D was most frequently investigated among included studies (n=5).
These investigations generally found that lower serum vitamin levels are associated with greater severity in both alopecia autoimmune (autoimmune hair loss) as well as androgenetic (pattern baldness). However, the null result in one cohort shows that the evidence is not uniform.
A Japanese case-control research found that high intakes of retinol, or vitamin A, were associated with greater severity of alopecia areata. This suggests a complex and non-linear relationship between some nutrients and highlights the importance of dosage to achieve optimal hair health.
A cross-sectional Chinese study of 155 women suffering from feminine alopecia found that iron supplementation improved hair growth.
The systematic review warned against the impact of suboptimal lifestyle and dietary choices (such as alcohol consumption or sugary drinks). In a cross sectional study conducted in China, it was found that excessive sugary drink consumption (>3500ml/week), led to a significant increase in hair loss. In another study alcohol consumption was linked to both hair loss and premature depigmentation.
Another nutrient and food was also highlighted. A 1971 clinical study linked protein deprivation with reduced hair bulb size and pigmentation. One cross-sectional research found that higher intakes cruciferous veggies and soy products are associated with reduced loss of hair, although the soy result wasn’t statistically significant.
Many randomized and controlled clinical trials (marine complex protein, eggshell membranes, persimmon leaves extract, INVERSION Femme), showed improved hair density, gloss or reduced hair loss. However, many of these studies were prone to bias, which limited the strength of their conclusions.
Conclusions
The present systematic review highlights nutrition’s crucial role in maintaining healthy, long-lasting hair. According to current scientific evidence, ensuring adequate amounts of key nutrients such as vitamin D and iron is an effective strategy for managing and preventing alopecia. Limiting alcohol and sugary beverages may also help prevent hair loss.
Further research is required to confirm the associations. However, there are also indications that a sufficient intake of protein, cruciferous vegetables, soy, and multi-nutrient supplements may be beneficial. A meta-analysis was not possible due to the heterogeneity of studies. This highlights the preliminary nature these findings.