Several vitamins and minerals play direct roles in hair growth, and falling short on any of them can lead to thinning, shedding, or slow regrowth. The nutrients with the strongest evidence behind them are iron, vitamin D, zinc, biotin, vitamin E, vitamin A, and vitamin C. Most people can get enough through diet alone, but knowing which nutrients matter (and why) helps you spot gaps before they show up in your hair.
Iron and Ferritin
Iron is one of the most well-studied nutrients in hair loss, especially for women. It helps red blood cells carry oxygen to hair follicles, and when iron stores drop too low, follicles can shift prematurely into their resting phase, a pattern called telogen effluvium. The result is diffuse shedding across the scalp rather than bald patches.
What matters most isn’t your total iron intake on a given day but your stored iron, measured by a blood protein called ferritin. In a case-control study of women aged 15 to 45, those with hair loss had an average ferritin level of just 16.3 ng/mL, compared to 60.3 ng/mL in women without hair loss. When ferritin dropped to 30 ng/mL or below, the odds of telogen effluvium increased 21-fold. That 30 ng/mL threshold is worth knowing because many standard lab ranges list ferritin as “normal” well below that number.
Red meat, shellfish, lentils, and spinach are all good dietary sources. If you eat mostly plant-based foods, pairing iron-rich meals with vitamin C makes a significant difference in absorption, which is covered further below.
Vitamin D
Vitamin D receptors are concentrated in two key parts of the hair follicle: the outer root sheath and the dermal papilla, the small cluster of cells at the base that signals the follicle to start growing. Research in animal models shows that when vitamin D receptors are absent, follicles fail to initiate their growth phase entirely. In one experiment, mice lacking the vitamin D receptor could not restart hair cycling even when it was manually triggered, while mice with the receptor restored behaved normally.
The mechanism appears to involve communication between the skin’s outer layer and the tissue beneath it. Without functional vitamin D receptors, that signaling breaks down and follicles stay dormant. Interestingly, this process may not even require vitamin D itself circulating in the blood; the receptor alone seems to play a structural role in follicle cycling. Still, maintaining adequate vitamin D levels (generally above 30 ng/mL in blood tests) supports the broader system. Fatty fish, egg yolks, and fortified dairy are dietary sources, though sunlight exposure is the primary way most people produce it.
Zinc
Zinc is an essential 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 when follicles are producing new hair fiber rapidly. Zinc also acts as a potent inhibitor of a process called endonuclease activity, which is involved in follicle regression. In simpler terms, zinc helps keep follicles in their growth phase longer and supports the structural proteins that make up each strand.
Deficiency tends to cause diffuse thinning similar to iron deficiency. Oysters are the single richest food source, but beef, pumpkin seeds, chickpeas, and cashews all provide meaningful amounts. The recommended daily intake for adults is 8 mg for women and 11 mg for men. Vegetarians may need up to 50% more because plant compounds called phytates reduce zinc absorption.
Biotin
Biotin (vitamin B7) is the supplement most commonly marketed for hair, and it does play a real role in producing keratin, the protein that makes up hair strands. True biotin deficiency causes hair thinning, skin rashes, and brittle nails. The adequate daily intake for adults is 30 mcg, a level most people reach easily through eggs, nuts, seeds, salmon, and sweet potatoes.
Here’s the catch: clinical evidence that biotin supplements improve hair in people who aren’t actually deficient is thin. Biotin deficiency is rare in the general population. It’s more common in people taking certain anti-seizure medications, those on long-term antibiotics, or during pregnancy. If you suspect a deficiency, it’s worth noting that biotin supplements can interfere with common blood tests (including thyroid panels and troponin), so let your doctor know before lab work.
Vitamin E (Tocotrienols)
Vitamin E is a family of compounds with strong antioxidant properties, and a specific subgroup called tocotrienols has shown real promise for hair. A randomized controlled trial found that taking tocotrienol supplements for eight months increased hair count by about 34.5% compared to baseline. The likely mechanism is reduced oxidative stress in the scalp. Free radicals damage the lipid layer surrounding follicle cells, and tocotrienols are particularly effective at neutralizing them because they penetrate cell membranes more efficiently than other forms of vitamin E.
Dietary sources of tocotrienols include palm oil, rice bran oil, barley, and oats. Standard vitamin E supplements typically contain a different form (tocopherols), so if you’re specifically looking for the hair-related benefit, check the label for tocotrienols.
Vitamin A: Essential but Easy to Overdo
Vitamin A supports the production of sebum, the natural oil that moisturizes your scalp and keeps hair from becoming dry and brittle. It also plays a role in cell growth and differentiation throughout the body, including in hair follicles. Sweet potatoes, carrots, and leafy greens are rich in beta-carotene, which your body converts to vitamin A as needed.
The important caveat with vitamin A is that more is not better. The tolerable upper intake for adults is 3,000 mcg (10,000 IU) per day. Chronic intake at or above that level causes a recognizable pattern: sparse, coarse hair and thinning of the eyebrows. This is one of the few vitamins where supplementation can directly cause hair loss rather than prevent it. If you’re already eating a balanced diet and taking a multivitamin, adding a separate vitamin A supplement puts you at risk of exceeding that ceiling.
Vitamin C and Iron Absorption
Vitamin C doesn’t act on hair follicles directly, but it plays a critical supporting role by enhancing iron absorption. This matters most for non-heme iron, the form found in plant-based foods like lentils, beans, and spinach. Without adequate vitamin C, your body absorbs significantly less of this iron, which can contribute to the low ferritin levels linked to hair shedding.
Vitamin C is also necessary for collagen production, which provides structural support to the skin surrounding hair follicles. Citrus fruits, bell peppers, strawberries, and broccoli are all excellent sources. Since vitamin C is water-soluble, your body doesn’t store large reserves, so consistent daily intake matters more than occasional high doses.
What Actually Matters for Most People
If your hair is thinning, the most productive first step is checking for specific deficiencies rather than starting a handful of supplements at once. Iron (ferritin), vitamin D, and zinc are the three most commonly low in people with unexplained hair loss, and all three are easily measured through standard blood work. Correcting a genuine deficiency often produces visible improvement within three to six months, which is roughly how long it takes for a new hair to grow long enough to notice.
For people without deficiencies, a diet that includes eggs, leafy greens, nuts, fatty fish, and a variety of colorful vegetables covers nearly every nutrient on this list. Supplements make the biggest difference when they’re filling a real gap, not layering excess on top of adequate intake. In the case of vitamin A, that excess actively works against you.