Posted on: August 22, 2016 at 3:44 pm
Last updated: September 11, 2018 at 11:54 am

You have between 100,000 and 150,000 hair follicles on your scalp – a number that remains fixed throughout life. As you get older, however, some follicles become inactive and stop producing hair. This can lead to a distinctive pattern of balding, in both men and women, for which there is a strong genetic link.


This link relates to the activity of an enzyme, 5-alpha-reductase, which converts the male hormone, testosterone, to a stronger version called dihydrotestosterone (DHT). DHT causes susceptible hair follicles on the scalp to shrink and produce hair that becomes progressively finer until the follicle switches off altogether. On the chin and elsewhere, however, DHT stimulates hair follicles to cause excess, usually unwanted hair growth. Grrr!

Although women have lower baseline levels of DHT (10 – 360 pg/ml in women versus 250-990 pg/ml in men) its effects are the same. Hormone treatments are available to treat unwanted excess hair in women with polycystic ovaries, for example, and drugs that block 5-α-reductase are also available to


If our follicles could be reprogrammed to respond differently, we could enjoy a more luxuriant head of hair and, at the same time, avoid unwanted whiskers!

How to Block 5-A-Reductase: The Enzyme Responsible For Hair Loss


1. Drug Approaches

There is a rare condition in which males are born with an inability to make the enzyme, 5-alpha-reductase, which is needed to convert testosterone to DHT. During childhood, boys who are affected are often mistaken for girls until puberty when the penis and scrotum enlarge and the voice deepens. In the Dominican Republic, where a genetic deficiency of 5-alpha reductase is relatively common in one village, these boys are known as guevedoces – meaning ‘penis at age 12’. Those affected do not go bald, do not suffer from acne and do not develop prostate enlargement. This led researchers to search for a drug that could block 5-alpha-reductase in order to reduce scalp hair loss, as well as providing a treatment for benign prostate enlargement. The result was finasteride, a drug which is effective in improving scalp hair count. Data from 12 studies, involving almost 4000 men, showed that finasteride was 81% more effective than placebo in improving scalp hair, and increased average hair count by 9.4% after one year, and by 24.3% after two years’ treatment. Unfortunately, finasteride is associated with side effects and increases the chance of sexual problems such as erectile dysfunction. For more information visit the Post-Finasteride Syndrome Foundation website.

2. Natural Approaches

Many people prefer natural approaches for dealing with health and other issues, and luckily there are several diet and lifestyle changes that can help to block 5-α-reductase and lower DHT levels within hair follicles.


3. Eat More Lignans

Lignans are a type of plant hormone which has a weak, oestrogen-like action and also blocks the enzyme, 5-alpha reductase. Small pilot studies suggest that taking lignan supplements may help to improve hair loss after one to two months, as well as decreasing scalp oiliness. The richest dietary source of lignans is flaxseed, which must be ground before eating to boost lignan absorption. Other good dietary sources include pumpkin seeds, sweet potato, pumpkins and their seeds, sesame seeds, kale, broccoli, and apricots. As a bonus, lignans are beneficial for men with an enlarged prostate, too, and are recommended as part of a prostate-friendly diet. Add one to two tablespoons of ground flaxseeds to your diet every day, eat more lignan-rich food, and try my Pecan Punch Trail Mix recipe which includes pumpkin seed to form a hair-friendly snack!

4. Eat More Organic, Whole Soy

Organic whole soy products provide another class of plant hormones, known as isoflavones. These provide an oestrogen-like boost and are beneficial for older women with thinning hair. They also help to reduce menopausal symptoms such as hot flashes and are recommended as part of a menopause diet. To improve thinning hair, select a soy isoflavone supplement supplying between 40mg and 100mg per day.

5. Drink More Green Tea

Over 30 percent of the dry weight of green tea leaves consists of powerful flavonoid antioxidants known as catechins. These green tea catechins can block the enzyme, 5α-reductase and reduce the conversion of testosterone to dihydrotestosterone. Green tea extracts have been shown to promote hair growth in cultures containing scalp follicles cell, so it’s worth drinking more green tea to see if this stimulates hair growth.

6. Use a Caffeinated Shampoo

When caffeine is applied to the scalp, it blocks 5-α-reductase to reduce the conversion of testosterone into dihydrotestosterone. Unfortunately, caffeinated drinks (except for green tea which also provides catechins as described above) do not have the same effect as the caffeine must penetrate directly into the hair follicles to work. Using a caffeinated shampoo helps to reverse the miniaturisation of hair follicles caused by DHT and can increase the cross-section of scalp hairs by as 10% to produce noticeable thickening.

7. Eat More Yogurt

Both lignans and isoflavones are mostly eaten in an inactive form which must be broken down into the activate form by bowel bacteria. Probiotic bacteria convert dietary lignans into enterolignans which inhibit 5-alpha reductase, while some digestive bacteria convert soy isoflavones into a more potent form known as equol. Not everyone is an ‘equol producer’ and eating more yogurt may help to provide more of the beneficial digestive bacteria needed. Probiotic supplements are available, too.

8. Increase Your Vitamin D3

There is mounting evidence that vitamin D interacts with DHT to regulate the growth of prostate cells. Good dietary intakes are linked with a lower risk of developing benign prostate enlargement, for example, and one study found that vitamin D deficiency was linked with larger prostate size. Although it is not yet proven that vitamin D can block 5-α-reductase, it is emerging as a treatment for hair loss. As it has so many other important roles in health, it’s a good idea to take a supplement that includes vitamin D3 if you are experiencing hair thinning.

9. Consider Saw Palmetto

Saw palmetto berries are a traditional herbal remedy that can block 5-α-reductase and lower DHT levels. In the prostate gland, this helps to improve symptoms associated with benign prostate enlargement, and some trials show that saw palmetto is at least as effective as the prescription-only drug, finasteride but without the side effects. Saw palmetto was compared with finasteride in the treatment of male pattern baldness in 100 men. One group took saw palmetto (Serenoa repens) 320 mg every day for 24 months, while the other took finasteride 1 mg every day for the same period. The results showed that 38% taking the herbal remedy showed a significant increase in hair growth, compared with 68% of those taking finasteride.

NB Saw palmetto should not be used by women unless they are under the supervision of a medical herbalist.  

10. Rye Pollen

Extracts from the pollen of rye grass (Secale cereale) is another traditional herbal medicine used to treat benign prostate enlargement. Although its precise mode of action is unknown, some studies suggest that it inhibits 5-alpha-reductase enzyme activity.

Have you tried any of the above approaches to improve hair thinning or hair loss? I’ve found using caffeinated shampoos has made a significant difference.

This amazing guest post was written by Dr. Sarah Brewer, a licensed Medical Doctor, a Registered Nutritionist, a Registered Nutritional Therapist! Check out her website here!

Dr. Sarah Brewer
Dr. Sarah Brewer, MSc (Nutr Med), MA (Cantab), MB, BChir, RNutr, MBANT, CNHC, FRSM, is a medical nutritionist, nutritional therapist and the author of over 60 popular health books.

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