top of page

Thinning hair and hair loss - Could it be a long COVID-19 symptom?

If you’re noticing that your hair has started to thin or fall out it is first worth a brief chat with your GP to check there are no underling conditions such as an underactive or overactive thyroid. Your GP may also be able to check your blood levels of vitamin D, iron, folate and vitamin B12, all of which are crucial to hair growth (Ashique, 2020) and explained below.

A long COVID-19 symptom!

It is also worth sparing a thought to consider the numerous reports of hair loss post COVID-19 infections. A study (Huang 2021) of over 1,655 COVID-19 cases, published in The Lancet, found that 22% of these patients were experiencing hair loss 6 months on from their infection. The frequency of hair loss in this study was reported higher in females. While the cause was not discussed in Huang's study it is widely reported by specialists in this field as being a possible result of significant emotional and physiological stress associated with the infection.

Stress hormones

Hair follicles are delicate requiring a balance of nutrients and hormones both of which are affected during an acute stress response with profound effect. An interesting study in 2017 by (Haslam) demonstrated how something called oxidative stress, a by-product of our stress response, inhibits or stops hair growth and how a substance called sulforaphane found in cruciferous vegetables can prevent this from happening.

There are many studies that link sulforaphane in food with improved liver function. It is interesting to note that our liver works closely with our endocrine system which connects and operates our hormones, and is responsible for removing used hormones once they have done their job. Oxidative stress can occur when used hormones are left circulating in our body. Alongside a balanced diet, ensuring a daily intake of cruciferous vegetables such as cauliflower, cabbage, kale, garden cress, bok choy, broccoli, and Brussels sprouts, may help your liver efficiently remove unwanted chemicals and help to keep hormones in balance. Broccoli has been shown to contain more sulforaphane than most other vegetables.

Thyroid hormones

Endocrine disorders such as hypothyroidism, which is low functioning thyroid can contribute to coarse brittle hair whilst overall hair thinning and hair loss can be related to hyperthyroidism, a condition of high functioning thyroid (Lause 2017). Thyroid hormone is key to the development and maintenance of the hair follicle so getting your thyroid hormones checked is a good place to start.

Insulin and DHT hormones

Androgenetic alopecia, also known as male pattern baldness, is a complicated condition affecting women as well as men. It was originally thought that androgenetic alopecia was caused by genetics alone but new evidence suggests diet may play a role too with hair loss now linked to insulin resistance and metabolic syndrome.

Interactions between hormones in the body are delicate, a change in the level of one hormone will often lead to changes in levels of other hormones.

In women with PCOS insulin resistance is a key theme and known to increase 5α-reductase activity. 5α-reductase is found increased in men with high hormone levels of DHT and male pattern baldness. This association may be why female pattern baldness is a feature of PCOS.

Diet is something we can control and reducing the level of sugar in your diet is an essential piece of the tool kit to restore hair health. As well as reducing sugar in tea and coffee and on our breakfast cereal, check food labels to assess the level of added fructose corn syrup, particularly in drinks, processed cereals and pre-made foods. An early study showed that consuming fructose sweetened beverages, rather than glucose sweetened beverages, decreases insulin sensitivity (Standhope, 2009).

Gut health

Having long term IBS or regular gas and bloating are signs you may want to investigate further to understand how your gastrointestinal system may be impacting your ability to digest and breakdown food and absorb nutrients. Knowing how well your gut is operating will help determine if you have a good mix of the right commensal (good) bacteria that contribute to the making of certain key vitamins, all essential for healthy hair. Having too many of the inflammatory producing bacteria can contribute to insulin resistance and create hormone imbalances.

Fermented foods

Miso, like other probiotic foods such as sauerkraut, kimchi and kombucha, helps to activate specific enzymes found in beans and grains that allow absorption of nutrients. Fermented foods introduce many beneficial bacteria to our gut supporting our immune function and keeping the ecology of the gut balanced and healthy.


B vitamins play a foundational role in cell metabolism. Deficiencies in the water-soluble vitamin B complex are often implicated in hair thinning and hair condition changes.

Folate and vitamin B12 play a role in the development of the hair follicle. Folate is present in a variety of foods, with some of the highest food sources including liver, spinach, asparagus, and Brussels sprouts. Foods naturally rich in vitamin B12 include liver, trout, and salmon. Fortified nutritional yeasts also contain B12.

Deficiencies in riboflavin vitamin B2 may also contribute to hair loss. Riboflavin is important for cell function, growth, and development. The best sources of riboflavin are organ meats, with beef liver topping the list. Lean meats, mushrooms, almonds, eggs, quinoa, and salmon also contain moderate amounts of vitamin B2.

Lastly, biotin vitamin B7 is one of the most recommended supplements for supporting hair loss. Skin rashes, brittle nails, and hair loss are all signs of biotin deficiency. Beef liver again is a rich source of biotin followed by whole eggs, salmon, sunflower seeds, and sweet potato containing a fair but comparatively lower amounts.

Trace elements

Iron deficiency has been linked to androgenetic alopecia presenting in female pattern hair loss and male pattern baldness. Oran meats, shell fish, spinach and beans are good sources of iron in the diet.

Zinc deficiency has been shown in cases of alopecia and dry brittle hair. The main dietary sources are fish, meat and seeds.

Selenium plays a key role in preventing oxidative damage and improves scattered hair growth. Brazil nuts, seafoods and organ meats are good food sources of selenium.

Note: please be aware that studies show that too much vitamin A and selenium can contribute to hair loss.

Autoimmune implications and vitamin D

Several studies show evidence of vitamin D receptors within the hair follicle and a clear connection between vitamin D deficiency and the development of alopecia areata, a form of hair loss with autoimmune implications. It is difficult to determine if alopecia areata is solely due to a vitamin D deficient state or that this is one part of a larger picture (Cerman 2014).

Sun exposure provides an abundance of vitamin D and in winter month’s supplementation with the bioavailable vitamin D3 as opposed to vitamin D2 is recommended. Fatty cold-water fish such as wild-caught salmon, sardines, and mackerel provide a moderate dose of vitamin D3.

Where do I start ?

In all cases check-in first with your GP. Take steps to increase the vitamins and minerals in your diet required for hair growth mentioned above and try to reduce your sugar intake. Eat three balanced meals each day with protein to help control your blood sugar metabolism. Check and manage your levels of stress and ensure you get good quality sleep.

If you are experiencing hair thinning, particularly across the top part of your head, consider hormonal influences and conditions of insulin resistance along with the level of stress you are experiencing in your life. A functional home test from urine and saliva (DUTCH test) can assess your level of hormones responsible for changes in hair growth patterns.

Internal stress and inflammation from conditions such as SIBO, IBS, food intolerances or other chronic digestive disorders can negatively impact your hormonal balance, particularly the androgen pathway. A clinical review will determine any dietary changes you need to consider and requirement for digestive testing (GI Effects).

In cases of autoimmune triggered alopecia an anti-inflammatory diet can help keep the condition stable. Understanding and avoiding food intolerances can help to reduce immune reactions frequently behind this condition. An at home performed Food IgG test (FoodPrint200) can explain which foods are causing autoantibody reactions.

Nutritional deficiencies can be causes by high levels of retained heavy metals. A review of any associated symptoms can highlight the need to test for trace and toxic metals.

Don’t fuel the fire

Strong chemicals within many brands of hair care products may cause additional or contributing problems to the quality and texture of your hair or condition of your scalp. Try to avoid products containing the following chemicals in hair care products if you have hair or scalp problems.


Sulfates: Sodium Lauyl Sulfate (SLS), Sodium Laureth Sulfate (SLES)


Polyethylene Glycols (PEGs)

Phthalates, DEHP, 2-ethylhexyl


Silicones: Dimethicone

Colours: Coal Tar P-phenylenediamine, Toluene, Resorcinol

Para-phenylenediamine (PPD)

Retinyl palmitate

Synthetic fragrances

Selenium Sulfide


Denatured alcohols

If you would like to understand more about the causes of thinning hair and hair loss, or would like to discuss functional testing for hormone balance, food intolerances and digestive health please contact:

Henley Nutrition 07831 120423


Related Posts

See All


bottom of page