You'd be surprised by how much your fingernails can reveal about your health.
Nails are part of your integumentary system, aka your body's outer layer, which also includes your skin, hair and glands, per the Cleveland Clinic. This system is a barrier between the outside environment and your internal body, says Brynna Connor, MD, a board-certified family medicine physician and ambassador for NorthWestPharmacy.com.
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"As part of our integumentary system, our fingernails are an outward manifestation of our internal health," Dr. Connor says.
All sorts of things can affect your fingernails: Certain diseases, gel manicures, dehydration — plus, simply getting older can lead to changes in your fingernails' appearance, per the National Library of Medicine (NLM). And then there's what you eat and drink.
"Vitamin and mineral deficiencies commonly affect your fingernails," Dr. Connor says.
That's why looking at fingernails is part of a nutritional evaluation, says Kristi Ruth, RD, LDN. "While several factors can cause changes in the appearance of nails, the potential for a vitamin deficiency or toxicity should be taken into consideration, especially if other causes have been ruled out."
Signs of a Vitamin or Mineral Deficiency in Your Nails
If you're falling short on certain nutrients, there may be evidence in your fingernails. The specific change depends on the vitamin or mineral you're lacking, but some nail-related symptoms include:
Nutrient Deficiencies That Can Lead to Dry, Brittle Nails
1. Vitamin B12 Deficiency
This essential vitamin helps keep the cells in your body healthy and makes DNA, per the National Institutes of Health (NIH).
"B12 is found in animal products and fortified cereals," says Amanda Lane, RD, CDCES.
Most people get enough vitamin B12 from their diet, but vegans and vegetarians can fall short as the nutrient isn't naturally found in plant-based foods (although you can get it in some fortified foods like breakfast cereals and nutritional yeast). Older adults, and people with certain conditions, might have difficulty getting enough of this vitamin, per the NIH.
"A vitamin B12 deficiency would result in vertical ridges on the nail surface," Lane says.
Not only is it important to have vitamin B12 for its own benefits, but it also helps your body absorb iron, Lane says. (Iron is also essential for nail health — more on that below.)
2. Iron Deficiency
Not getting enough iron can lead to anemia, Ruth says. "One of the most common signs of iron deficiency anemia is brittle or spoon-shaped nails," she says.
More formally, these spoon-shaped nails are known as koilonychia. They "look scooped out," Dr. Connor says. Flattened nails can also indicate the first sign of koilonychia (after a while, the indentation forms), per the Cleveland Clinic. So an iron deficiency can cause fingernails to flatten out.
As well as being a sign of anemia, spoon nails can also be due to hypothyroidism, heart disease and a certain liver condition, she says. Iron deficiency anemia can also be a reason for nails being dry or brittle, Ruth says.
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3. Biotin Deficiency
"A biotin deficiency would leave nails brittle and prone to breaking," Lane says. Biotin — a B vitamin — helps support skin and hair growth.
That's important to keep in mind — while brittle nails (along with thinning hair) are signs of a deficiency, there's not much evidence that taking biotin when you aren't experiencing a shortfall will improve your nails, per the American Academy of Dermatology Association.
That said, it's rare to fall short on biotin, per the NIH. But if you decide to supplement with biotin, know that there's no harm (aside from potentially wasting money) from doing so, per the Cleveland Clinic.
Heads up: Taking large quantities of biotin can mess with the results of certain medical tests, so do tell your doctor.
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4. Calcium Deficiency
Most likely, you're used to thinking of calcium as important for your teeth and bone health. But the mineral also plays a role in the appearance of your nails.
"Low calcium levels can cause dry, brittle nails," Dr. Connor says.
Dairy products are a great source of this nutrient, but so are sardines (with the bones), beans and seeds.
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5. Omega-3 Fatty Acid Deficiency
Omega-3 fats are essential fatty acids — that means that you can only get them through food and supplements (like fish oil), and your body does not make this fatty acid on its own.
"Low omega-3s can cause a loss of nail strength and this can result in your nails cracking," Dr. Connor says.
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6. Zinc Deficiency
If you're deficient in zinc, a trace mineral, you may experience something known as Beau's lines in your nails, Ruth says. They are "depressions across the fingernail," she says.
Keep in mind that Beau's lines can also be the result of other things, ranging from nail injuries to other illnesses, Ruth says.
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7. Vitamin C Deficiency
Two nail-related conditions can occur with a vitamin C deficiency: koilonychia (aka spoon nails) and hapalonychia (aka eggshell nails), per a 2012 article in the Indian Journal of Dermatology, Venereology, and Leprology.
Plus, as with vitamin B12, taking vitamin C aids in iron absorption, per ConsumerLab.
8. Folic Acid Deficiency
A shortfall in another B vitamin, folic acid, can lead to central ridges in the nails, per an article in the March-April 2015 issue of Indian Dermatology Online Journal. Iron and protein deficiencies can also cause these central ridges.
"Low vitamin C and low folic acid can cause nail integrity loss resulting in an increased frequency of hangnails," Dr. Connor says.
Other Factors That Can Affect Your Nails
All sorts of everyday events and health conditions can affect the appearance of your nails — here are just a few:
- Hydration: "Brittle nails can be caused by too little or too much moisture," Ruth says.
- Manicures: The acetone used to remove manicures can lead to brittle nails, as can picking off the polish, Ruth says.
- Certain diseases: A yellow tint to your nails could indicate thyroid problems or diabetes, Lane says. "People who have advanced kidney disease can develop a white color on the upper part of their nails and a reddish-brown color below making their nails appear two-toned," Dr. Connor says. And, a condition known as Terry's nails, where most of the nail is white except for a pink band at the end, can be due to liver disease, congestive heart failure, aging or other conditions, Dr. Connor says. There are many other nail-related changes that can indicate diseases and conditions.
Tips to Care for Your Nails
Giving your nails a little TLC will help them look their best — and also ensure that you'll be familiar with their typical appearance, so you'll catch any changes early on.
Try these strategies to keep your nails healthy and well cared for:
- Clip and trim them as needed, and use sharp clippers or nail scissors, per the Mayo Clinic. Do not bite your nails or pick at hangnails.
- Keep them dry and protected. Nails become brittle and dry when they go from wet to dry several times a day, according to the American Osteopathic College of Dermatology (AOCD). Of course, that's inevitable if you wash your hands frequently. But you can limit the water by wearing gloves as you do the dishes and then applying lotions after contact with water, per the AOCD. You can also wear gloves when you're using cleaning fluids and detergents, which can also be hard on nails.
- Buff nails vertically, not horizontally. Going back and forth across your nail can lead to nail splitting, according to the AOCD.
- Opt for acetone-free nail polish remover, per the Mayo Clinic.
When to See a Doctor
Sure, we all want to avoid brittle, misshapen or discolored nails. But it's more than a matter of aesthetics: Changes in the appearance of nails can point to nutritional deficiencies or other serious health conditions.
Visit your doctor or a dermatologist as a first step, Czapek says.
"Your physician can help you figure out where the problem is so that you can correct it," Dr. Connor says, noting that it's important to address the root cause behind the aesthetic shift.
- Cleveland Clinic: "Integumentary System"
- National Library of Medicine: "Aging changes in nails"
- Office of Dietary Supplements: "Vitamin B12"
- Indian Dermatology Online Journal: "Reversible Melanonychia Revealing Nutritional Vitamin-B12 Deficiency"
- Dermatology World Insights and Inquiries: "BIOTIN SUPPLEMENTATION FOR HAIR AND NAIL HEALTH: DOES IT PASS THE TEST?"
- Cleveland Clinic: "Biotin Benefits: What the Experts Have to Say"
- Indian Dermatology Online Journal: "Nail as a window of systemic diseases"
- Indian Journal of Dermatology, Venereology, and Leprology: "Nails in nutritional deficiencies"
- ConsumerLab: "Vitamin C Supplements Review'
- Mayo Clinic: "Fingernails: Do's and don'ts for healthy nails"
- American Osteopathic College of Dermatology: "BRITTLE SPLITTING NAILS"