Hair supplements are among the best-selling beauty products in France. But not all are created equal, and their effectiveness largely depends on your individual circumstances. Here's what you need to know to choose the right supplement for your specific needs and understand how it works to promote hair growth.
How does hair grow?
Hair grows from its root, nestled within the hair follicle. The dermal papilla, located at the base of the follicle, receives nutrients from the blood and redistributes them to the matrix cells, which divide to lengthen the hair shaft. The quality of hair growth therefore depends directly on what the blood delivers to the roots: this is why diet and nutritional supplements can have a direct impact on the speed and quality of hair growth.
Hair growth is also influenced by genetics (which determines the length of the anagen cycle), hair type (straight hair grows slightly faster than curly hair), the season (faster in summer thanks to the sunshine), stress, and hormonal fluctuations. To understand all the factors that influence growth and loss, our article on how to prevent hair loss provides a comprehensive overview.
When are dietary supplements useful?
Hair supplements are truly effective in two situations: in cases of proven nutritional deficiency (identified by a blood test), and during periods of increased stress or hormonal transition (postpartum, perimenopause) which deplete the reserves of nutrients essential to keratin.
In a person without deficiencies and with a balanced diet, the effects are more limited. Before starting a course of treatment, it's helpful to have your ferritin (iron), zinc, and vitamin D levels checked—the deficiencies most frequently associated with hair loss—to target your supplementation rather than opting for a general formula. In cases of significant hair loss, consult a dermatologist.
Supplements come in the form of capsules, tablets, ampoules, or gummies. Gummies offer a popular alternative for people who have difficulty swallowing traditional capsules. To learn everything about hair gummies specifically, our article "Are Hair Gummies Effective?" assesses their true benefits.
Key nutrients for hair growth
Biotin (vitamin B8)
Biotin is the most frequently cited vitamin for hair. It plays a direct role in the synthesis of keratin, the protein that makes up 95% of the hair fiber. Clinical studies have shown that biotin supplementation improves hair thickness and reduces breakage in people with a deficiency. The recommended daily allowance (RDA) is 40 µg, but hair care formulas generally use much higher doses (500 to 5000 µg). Food sources include brewer's yeast, egg yolks, almonds, and avocados.
Zinc
Zinc, an essential trace element for protein synthesis, plays a role in keratin production and regulates the activity of the sebaceous glands. A zinc deficiency manifests as white spots on the nails, slowed growth, and increased nail loss. It is one of the most common deficiencies in the general population. To learn more about its properties, our article "The Health Benefits of Zinc" details its complete action.
Plant silica (bamboo, horsetail)
Silica contributes to the strength and elasticity of the hair fiber. It is present in high concentrations in horsetail and bamboo, two plants traditionally used in herbal medicine for hair and nails. It participates in the synthesis of collagen, which indirectly supports the follicular structure.
Stinging nettle
Nettle is rich in silica, iron, zinc, and B vitamins—an ideal nutritional profile for hair. In traditional herbal medicine, it is used for its remineralizing and scalp-purifying properties. It helps regulate sebum production and nourish the hair fiber from within.
Selenium
A powerful antioxidant, selenium protects hair follicles from oxidative damage caused by free radicals and stress. It also participates in keratin synthesis in combination with zinc.
B vitamins (B6, B9, B12)
In synergy with biotin, vitamins B6, B9, and B12 support the cellular metabolism of hair follicles and participate in the production of red blood cells that transport oxygen to the roots. Vitamin B6 also regulates the hormonal balance that influences seborrhea and hair loss.
How to optimize the effectiveness of supplements?
Hair supplements yield better results when used as part of a holistic approach. Combined with a suitable hair care routine (scalp massages, weekly oil treatments, gentle shampoos), they work synergistically to nourish hair from the inside out. To choose the best plant oils for your hair type, our article on the best plant oils for hair compares all the options.
Consistency is key: effects are only visible after a minimum of 6 to 8 weeks, and a 3-month course is generally recommended for a reliable assessment. Take your supplements preferably with a meal to improve absorption. If your hair loss is stress-related, addressing this cause is just as important as supplementation—our article on stress-related hair loss offers complementary approaches.
Frequently asked questions about hair supplements
How long does it take for supplements to make hair grow?
The first visible effects (reduced breakage, improved shine) generally appear after 4 to 6 weeks. The impact on actual hair growth rate is noticeable from 2 to 3 months. Since hair growth is 1 to 1.5 cm per month, a 3-month treatment can result in 3 to 4.5 cm of additional length by optimizing each phase of the cycle.
Is it safe to take hair supplements during pregnancy?
Some nutrients (biotin, zinc) are safe and even recommended during pregnancy, but complex formulas containing herbs (nettle, horsetail) should be discussed with a doctor beforehand. Postpartum hair loss (telogen effluvium) is normal and temporary—it resolves spontaneously within 3 to 6 months without systematic supplementation.
Should you have a blood test before starting a hair treatment?
This is highly recommended in cases of significant hair loss. A blood test measuring ferritin, zinc, TSH (thyroid), vitamin D, and a complete blood count (CBC) can identify actual deficiencies and target supplementation. Taking biotin without a confirmed deficiency will have little additional effect and may interfere with certain blood tests at high doses—always inform your doctor if you are taking any supplements.