Head hair comes in many colours, shapes and sizes, and hairstyles are often an expression of personal style or cultural identity.

Many different genes determine our hair texture, thickness and colour. But some people’s hair changes around the time of puberty, pregnancy or after chemotherapy.

So, what can cause hair to become curlier, thicker, thinner or grey?

Curly or straight? How hair follicle shape plays a role

Hair is made of keratin, a strong and insoluble protein. Each hair strand grows from its own hair follicle that extends deep into the skin.

Curly hair forms due to asymmetry of both the hair follicle and the keratin in the hair.

Follicles that produce curly hair are asymmetrical and curved and lie at an angle to the surface of the skin. This kinks the hair as it first grows.

The asymmetry of the hair follicle also causes the keratin to bunch up on one side of the hair strand. This pulls parts of the hair strand closer together into a curl, which maintains the curl as the hair continues to grow.

Follicles that are symmetrical, round and perpendicular to the skin surface produce straight hair.

Life changes, hair changes

Our hair undergoes repeated cycles throughout life, with different stages of growth and loss.

Each hair follicle contains stem cells, which multiply and grow into a hair strand.

Head hairs spend most of their time in the growth phase, which can last for several years. This is why head hair can grow so long.

Let’s look at the life of a single hair strand. After the growth phase is a transitional phase of about two weeks, where the hair strand stops growing. This is followed by a resting phase where the hair remains in the follicle for a few months before it naturally falls out.

The hair follicle remains in the skin and the stems cells grow a new hair to repeat the cycle.

Each hair on the scalp is replaced every three to five years.

Hormone changes during and after pregnancy alter the usual hair cycle

Many women notice their hair is thicker during pregnancy.

During pregnancy, high levels of oestrogen, progesterone and prolactin prolong the resting phase of the hair cycle. This means the hair stays in the hair follicle for longer, with less hair loss.

A drop in hormones a few months after delivery causes increased hair loss. This is due to all the hairs that remained in the resting phase during pregnancy falling out in a fairly synchronised way.

Hair can change around puberty, pregnancy or after chemotherapy

This is related to the genetics of hair shape, which is an example of incomplete dominance.

Incomplete dominance is when there is a middle version of a trait. For hair, we have curly hair and straight hair genes. But when someone has one curly hair gene and one straight hair gene, they can have wavy hair.

Hormonal changes that occur around puberty and pregnancy can affect the function of genes. This can cause the curly hair gene of someone with wavy hair to become more active. This can change their hair from wavy to curly.

Researchers have identified that activating specific genes can change hair in pigs from straight to curly.

Chemotherapy has very visible effects on hair. Chemotherapy kills rapidly dividing cells, including hair follicles, which causes hair loss. Chemotherapy can also have genetic effects that influence hair follicle shape. This can cause hair to regrow with a different shape for the first few cycles of hair regrowth.

Hormonal changes as we age also affect our hair

Throughout life, thyroid hormones are essential for production of keratin. Low levels of thyroid hormones can cause dry and brittle hair.

Oestrogen and androgens also regulate hair growth and loss, particularly as we age.

Balding in males is due to higher levels of androgens. In particular, high dihydrotestosterone (sometimes shortened to DHT), which is produced in the body from testosterone, has a role in male pattern baldness.

Some women experience female pattern hair loss. This is caused by a combination of genetic factors plus lower levels of oestrogen and higher androgens after menopause. The hair follicles become smaller and smaller until they no longer produce hairs.

Reduced function of the cells that produce melanin (the pigment that gives our hair colour) is what causes greying.

Theresa Larkin, Associate professor of Medical Sciences, University of Wollongong

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Julia J Rucklidge, University of Canterbury; Elena Moltchanova, University of Canterbury; Roger Mulder, University of Otago, and Siobhan A Campbell, University of Canterbury

Antenatal depression affects 15% to 21% of pregnant women worldwide. It can influence birth outcomes and children’s development, as well as increase the risk of post-natal depression.

Current treatments like therapy can be inaccessible and antidepressants can carry risks for developing infants.

Over the past two decades, research has highlighted that poor nutrition is a contributing risk factor to mental health challenges. Most pregnant women in New Zealand aren’t adhering to nutritional guidelines, according to a longitudinal study. Only 3% met the recommendations for all food groups.

Another cohort study carried out in Brazil shows that ultra-processed foods (UPF) accounted for at least 30% of daily dietary energy during pregnancy, displacing healthier options.

UPFs are chemically manufactured and contain additives to improve shelf life, as well as added sugar and salt. Importantly, they are low in essential micronutrients (vitamins and minerals).

The consumption of these foods is concerning because a nutrient-poor diet during pregnancy has been linked to poorer mental health outcomes in children. This includes depression, anxiety, hyperactivity, and inattention.

Increasing nutrients in maternal diets and reducing consumption of UPFs could improve the mental health of the mother and the next generation. Good nutrition can have lifelong benefits for the offspring.

However, there are multiple factors that mean diet change alone may not in itself be sufficient to address mental health challenges. Supplementing with additional nutrients may also be important to address nutritional needs during pregnancy.

Micronutrients as treatment for depression

Our earlier research suggests micronutrient supplements for depression have benefits outside pregnancy.

But until now there have been no published randomised controlled trials specifically designed to assess the efficacy and safety of broad-spectrum micronutrients on antenatal depression and overall functioning.

The NUTRIMUM trial, which ran between 2017 and 2022, recruited 88 women in their second trimester of pregnancy who reported moderate depressive symptoms. They were randomly allocated to receive either 12 capsules (four pills, three times a day) of a broad-spectrum micronutrient supplement or an active placebo containing iodine and riboflavin for a 12-week period.

Micronutrient doses were generally between the recommended dietary allowance and the tolerable upper level.

Based on clinician ratings, micronutrients significantly improved overall psychological functioning compared to the placebo. The findings took into account all noted changes based on self-assessment and clinician observations. This includes sleep, mood regulation, coping, anxiety and side effects.

Both groups reported similar reductions in symptoms of depression. More than three quarters of participants were in remission at the end of the trial. But 69% of participants in the micronutrient group rated themselves as “much” or “very much” improved, compared to 39% in the placebo group.

Participants taking the micronutrients also experienced significantly greater improvements in sleep and overall day-to-day functioning, compared to participants taking the placebo. There were no group differences on measures of stress, anxiety and quality of life.

Importantly, there were no group differences in reported side effects, and reports of suicidal thoughts dropped over the course of the study for both groups. Blood tests confirmed increased vitamin levels (vitamin C, D, B12) and fewer deficiencies in the micronutrient group.

Micronutrients were particularly helpful for women with chronic mental health challenges and those who had taken psychiatric medications in the past. Those with milder symptoms improved with or without the micronutrients, suggesting general care and monitoring might suffice for some women.

The benefits of micronutrients were comparable to psychotherapy but with less contact. There are no randomised controlled trials of antidepressant medication to compare these results.

Retention in the study was good (81%) and compliance excellent (90%).

Beyond maternal mental health

We followed the infants of mothers enrolled in the NUTRIMUM trial (who were therefore exposed to micronutrients during pregnancy) for 12 months, alongside infants from the general population of Aotearoa New Zealand.

This second group of infants from the general population contained a smaller sub-group who were exposed to antidepressant medication for the treatment of antenatal depression.

We assessed the neuro-behavioural development of each infant within the first four weeks of life, and temperament up to one year after birth.

These observational follow-ups showed positive effects of micronutrients on the infants’ ability to regulate their behaviour. These results were on par with or better than typical pregnancies, and better than treatments with antidepressants.

Infants exposed to micronutrients during pregnancy were significantly better at attending to external stimuli. They were also better able to block out external stimuli during sleep. They showed fewer signs of stress and had better muscle tone compared to infants not exposed to micronutrients.

They also displayed greater ability to interact with their environment. They were better at regulating their emotional state and had fewer abnormal muscle reflexes than infants exposed to antidepressant medication in pregnancy.

Reassuringly, micronutrients had no negative impact on infant temperament.

These findings highlight the potential of micronutrients as a safe and effective alternative to traditional medication treatments for antenatal depression.

The prenatal environment sets the foundation for a child’s future. Further investigation into the benefits of micronutrient supplementation would gives us more confidence in their use for other perinatal (from the start of pregnancy to a year after birth) mental health issues. This could provide future generations with a better start to life.

We would like to acknowledge the contribution of Dr Hayley Bradley to this research project.

Julia J Rucklidge, Professor of Psychology, University of Canterbury; Elena Moltchanova, Professor of Statistics, University of Canterbury; Roger Mulder, Professor of Psychiatry, University of Otago, and Siobhan A Campbell, Intern Psychologist, Researcher – Te Puna Toiora (Mental Health and Nutrition Research Lab), University of Canterbury

This article is republished from The Conversation under a Creative Commons license. Read the original article.