Several vitamins and minerals play direct roles in hair growth, and falling short on any of them can slow your hair cycle or increase shedding. The nutrients with the strongest evidence behind them are iron, vitamin D, zinc, B vitamins (especially B12 and folate), vitamin C, vitamin E, and selenium. Most people who eat a varied diet get enough of these, but specific deficiencies are surprisingly common and worth understanding if you’re noticing thinning or excess hair loss.
Iron and Ferritin
Iron is one of the most well-established nutritional links to hair loss, particularly in women. Your hair follicles are among the fastest-dividing cells in your body, and they need a steady oxygen supply delivered by iron-rich red blood cells. When iron stores drop, your body prioritizes vital organs over hair, and follicles can shift prematurely into their resting phase, leading to diffuse thinning called telogen effluvium.
The key marker isn’t just whether you’re anemic. Dermatologists look at ferritin, the protein that stores iron in your body. A ferritin level below 70 ng/mL is considered adequate for general health but lower than what’s needed for a normal hair cycle. Many people with thinning hair have ferritin levels in the 20 to 70 range and aren’t technically anemic, a condition sometimes called nonanemic iron deficiency. If your hair is thinning and you haven’t had your ferritin checked, it’s one of the first blood tests worth requesting.
Iron from animal sources (heme iron) is absorbed more readily than iron from plants (non-heme iron). If you eat mostly plant-based foods, pairing iron-rich meals with vitamin C significantly improves absorption.
Vitamin D
Vitamin D receptors sit in the outer layer of your hair follicles, specifically in the keratinocyte cells that build the hair shaft. These receptors are essential for initiating new hair growth cycles. Research published in the Proceedings of the National Academy of Sciences found that without functioning vitamin D receptors, hair follicles can’t restart their growth cycle once a hair is shed. The receptor works by interacting with a signaling pathway (called the Wnt pathway) that tells stem cells in the follicle to renew themselves and differentiate into hair-producing cells.
Low vitamin D is one of the micronutrient deficiencies most commonly associated with hair loss, alongside iron, zinc, and B vitamins. Deficiency is widespread, especially in northern latitudes, among people with darker skin, and in anyone who spends most of their time indoors. A simple blood test can reveal whether your levels are low.
Zinc
Zinc acts as a cofactor for many enzymes active in the hair follicle. It contributes to protein synthesis and cell proliferation, both of which are critical during the active growth phase of hair. Zinc also inhibits a process called endonuclease activity, which is involved in follicle regression. In plain terms, zinc helps keep follicles in their growth phase longer and supports the structural proteins that make up each strand.
The link between low zinc and alopecia areata (patchy hair loss driven by the immune system) is particularly well established. Zinc deficiency can also contribute to more general thinning. Good dietary sources include oysters, red meat, pumpkin seeds, lentils, and chickpeas. If you suspect a deficiency, testing is straightforward, though zinc levels can fluctuate and a single test isn’t always definitive.
B12 and Folate
Vitamin B12 and folate are both essential for DNA synthesis, which matters because hair follicle cells are among the most rapidly dividing cells in your body. When either nutrient is lacking, your body can’t produce healthy red blood cells efficiently. Instead, it makes oversized, dysfunctional red blood cells that can’t carry oxygen properly, a condition called megaloblastic anemia.
The result for your hair is a double hit. Follicle cells that divide quickly can’t replicate their DNA correctly, stalling growth. And the abnormal red blood cells can’t deliver enough oxygen to the scalp, which further starves follicles of what they need. Hair may stop growing prematurely and enter the shedding phase early. B12 deficiency is especially common in vegetarians and vegans, older adults, and people with digestive conditions that impair absorption. Folate is found in leafy greens, legumes, and fortified grains.
Vitamin C
Vitamin C plays two roles relevant to hair. First, it’s required for collagen production. Collagen surrounds and supports each hair strand, and as you age, collagen production naturally declines, leaving hair more prone to breakage. Adequate vitamin C helps maintain the structural integrity of your hair.
Second, and perhaps more practically, vitamin C dramatically improves the absorption of non-heme iron from plant foods. Without enough vitamin C, your body struggles to take up iron from sources like spinach, lentils, and fortified cereals. If you’re working to raise low iron levels, getting enough vitamin C at the same meal makes a meaningful difference. Most fruits and vegetables supply it, with citrus fruits, bell peppers, strawberries, and broccoli being especially rich sources.
Vitamin E (Tocotrienols)
Vitamin E is a group of fat-soluble antioxidants, and a specific subgroup called tocotrienols has shown promising results for hair growth. A randomized controlled trial found that taking tocotrienol supplements for eight months increased hair count by about 34.5% compared to baseline. Tocotrienols appear to protect hair follicles from oxidative stress, the accumulation of free radical damage that can shrink follicles over time.
Food sources of tocotrienols include palm oil, rice bran oil, barley, and oats, though the amounts in food are lower than what was used in clinical studies. Standard vitamin E supplements typically contain tocopherols, which are a different form, so if you’re interested in supplementing specifically for hair, look for a product that specifies tocotrienols.
Selenium and Thyroid Health
Selenium’s connection to hair is indirect but significant. Your thyroid gland contains more selenium per gram of tissue than any other organ in your body. Selenium-dependent enzymes handle the conversion of the inactive thyroid hormone (T4) into its active form (T3), and roughly 80% of the active thyroid hormone circulating in your body is produced through this conversion process rather than secreted directly by the thyroid.
When selenium is low, this conversion falters. Thyroid hormone levels drop, and hair follicles respond by altering their growth cycles, leading to brittle hair, progressive thinning, and changes in texture. Selenium also powers the antioxidant enzymes that protect thyroid cells from oxidative damage. Without that protection, inflammation can develop in the thyroid, further impairing hormone production. Brazil nuts are the richest food source of selenium by a wide margin. Just one or two a day can meet your needs, and more than that can actually push you toward excess.
Vitamin A: The One to Be Careful With
Vitamin A supports the growth and differentiation of cells throughout the body, including hair follicle cells. But unlike most other vitamins on this list, getting too much vitamin A is a real and relatively common problem. The tolerable upper limit for adults is 3,000 mcg (10,000 IU) per day, and chronic intake at or above that level can cause sparse, coarse hair and eyebrow thinning.
This matters because many supplements stack vitamin A from multiple sources, and people taking several products at once can easily exceed safe levels. If you’re already eating foods rich in preformed vitamin A (liver, dairy, eggs) and taking a multivitamin, adding a separate hair supplement that also contains vitamin A could push you over the line. Beta-carotene from plant foods like sweet potatoes and carrots is converted to vitamin A on an as-needed basis and doesn’t carry the same toxicity risk.
How Long Before You See Results
Hair grows roughly half an inch per month, and the growth cycle of a single follicle lasts years. When a deficiency has pushed follicles into their resting or shedding phase, correcting the deficiency doesn’t produce overnight results. You’re waiting for follicles to re-enter the active growth phase and then produce enough new length to be visible. Most people need three to six months of consistent supplementation before noticing meaningful changes in density or thickness. The improvements tend to be gradual, so taking periodic photos from the same angle can help you track progress more objectively than relying on what you see in the mirror each day.
It’s also worth noting that supplements only help if you’re actually deficient. Taking high doses of zinc or biotin when your levels are already normal won’t accelerate hair growth and can cause side effects of its own. A blood panel that includes ferritin, vitamin D, zinc, B12, folate, and thyroid function gives you a clear picture of where the gaps are, so you can target what actually needs correcting.