Dr. Christine Shaver of Bernstein Medical in New York City tells Romper, “There is little scientific support behind the ability of vitamins and supplements to promote hair growth unless the patient has a nutritional deficiency that needs to be corrected. One of the more common nutritional deficiencies seen in the U.S. is anemia (low iron). In these people, it would be important to receive iron supplementation.” She adds that while biotin gets a lot of attention for helping hair grow, in the average person, it shows to be more beneficial for nail health.

A 2019 review published in the journal Dermatology and Therapy titled "The Role of Vitamins and Minerals in Hair Loss" noted that “Androgenetic alopecia (AGA), telogen effluvium (TE) are two common types of hair loss. Studies show that supplementing the diet with low levels of vitamin D can improve symptoms of these diseases.”

Both the review and Shaver noted that vitamin A is actually correlated with hair loss in certain situations, so if you feel like you’re shedding more hair than normal, you may want to take a look at your vitamin A intake.

I know I just noted that biotin (aka vitamin b7) hasn’t shown to be very effective for hair growth, however, like most things, there’s an exception to this rule. People who are truly deficient in biotin (it's rare to be deficient, according to The National Institute of Health) may notice a difference in their hair by eating foods that are rich in the vitamin. As Dr. Whitney Bowe, dermatologist and author of The Beauty of Dirty Skin tells Romper, “You can get biotin through your diet, as it’s found in foods like eggs, avocados, beans and mushrooms. It’s only found in the yolk of the egg, so if you’re an egg white omelet kind of person, you’re missing out on the biotin of that egg.”

Biotin is water-soluble, which means it won’t be stored overtime in your system, so if hair-growth is your priority, try to eat foods containing biotin each day. Bowe adds, “I actually prefer my patients supplement regularly with small doses of biotin than take large doses sporadically. This keeps a steady flow of biotin reaching the stem cells in your scalp and your nail beds, the places it needs to go to help keep your hair and nails healthy.” If you are taking a biotin supplement, she says it’s essential to tell your doctor or lab technician if you’re getting blood work done because biotin can impact certain lab tests.

Other foods that promote hair growth include berries, fatty fish, spinach, sweet potatoes, nuts, and seeds, according to Healthline.

Healthy hair grows from a healthy scalp, which sounds like something that could be embroidered on a pillow. Collagen can help promote scalp health, and the good news is that the protein is trendy right now. You can find collagen in everything from bone broth, to gummies, to little individual packets that you mix with water. Bowe tells Romper, “Collagen can make hair stronger and thicker, but it works indirectly. Hair is primarily made up of the protein keratin. Keratin and collagen share a number of building blocks, called amino acids. So when you take a collagen supplement, some of [its building blocks] are utilized by your scalp to build strands of keratin that... create hair.” So keep the collagen shakes comin’ and you may start to see stronger hair.

Maybe you want fuller eyebrows, are bringing back the bush, or are embracing underarm hair. Or maybe you're trying to grow out an undercut. You may have heard that shaving will make your hair grow back coarser and thicker (and apologies here to all the well-meaning moms who have perpetuated this saying overtime), but it's just... not true. "If you shave against the grain, your hair grows back feeling coarse and thick," Bowe says. "Instead, if you first shave with the grain and then shave against the grain, this technique actually causes new hairs to grow in with a tapered end that feels thinner as it regrows."

Shaver tells Romper, "In contrast to common folklore, shaving and shampooing have absolutely no effect on hair growth. Hair that is repeatedly plucked will eventually grow back finer and at a slower rate. With continued plucking, the hair may stop growing completely."

Barring situations of extreme plucking, only electrolysis or laser hair removal, which damage the hair follicle, have the ability to change the way the hair grows permanently.

There are two FDA-approved medications for hair growth, but Shaver says, "only one, finasteride, is a prescription. Minoxidil is now over-the-counter." Finasteride (aka Propecia) hasn't yet been "approved for hair loss in women, but minoxidil can be safely used in both sexes. Minoxidil is a topical liquid or foam that can help slow hair loss... when applied diligently every day to the scalp." Heads up though, minoxidil may cause a burning sensation.

Dr. Sandy Skotnicki, dermatologist and author of Beyond Soap tells Romper that "Latisse or Bimatoprost is a topical solution that when applied to eyelashes makes the hair grow thicker and longer. It can be used on the eyebrows [but] is not to be used on the scalp."

If you're looking for something you can get quickly on Amazon, both hair stylist Marina Perkovic of Eliut Salon and celebrity makeup artist Michal Cohen tell Romper that Nutrafol, a blend of vitamins, has shown promise in helping restore thinning hair, as HuffPo reported.

I'm happy to report that this trick just requires you to pick up a new shampoo and conditioner on your next Target run and shower as normal. As if you wouldn't do that already (my shower is a graveyard of half-empty new products I had to try, so no shame.)

If you'd like some guidance, you can ask your stylist or the all-knowing internet for the best thickening products, as suggested by Dermstore. The idea is that they temporarily plump each strand for hair that appears fuller.