Your skin can become problematic, dull, change colour. Your hair can become limp.
But your nails are one part that many of us either ignore or cover up with varnish.
From spots to breakages, we reveal what common nail issues and what they could tell you about your overall health:
1. Dry, splitting nails
It’s estimated that one in five adults suffers from weak, dry, thin and easily-breakable nails.
Why? Well, it's usually down to water intake.
Nails are made up of around 18 per cent water, and when these levels drop below 16 per cent, they can become dry and prone to breakage.
To fix the issue, try to drink two litres of water daily.
A zinc deficiency has also been found to contribute to brittle nails, so add foods such as beef, pumpkin seeds and lentils to your diet.
If these don't take your fancy, it's suggested that you take 15–30mg of zinc supplements daily for three months.
2. Dark line in nails
If you notice a new or changing dark streak appear in your nail, it's time to see your GP ASAP.
That dark streak could be melanoma - the most serious type of skin cancer.
Not every dark streak is a melanoma, but it’s always good to have a dermatologist check it out. Caught early and treated, that may be the only treatment you need.
If you let it grow, it'll only be harder to treat.
3. Soft, peeling nails
If your nails bend easily, they may be too soft - a condition known as hapalonychia.
As it's the proteins in the nail matrix that create their hardness, your best bet is upping your protein intake.
Make sure you're eating a palm-sized portion of protein with each meal.
It's also important that you're getting enough vitamin D and vitamin A.
Boost your vitamin D levels through sensible sun exposure, and eat three servings of oily fish every week.
For vitamin A, munch on plenty of green and orange vegetables, such as carrots, spinach and sweet potatoes.
4. Ridged nails
Loads of has nail ridges and that can be down to various things, from diet deficiencies to illnesses.
A common cause is a lack of sulfur in the diet - found in things like milk, nuts and raspberries.
As for illnesses, conditions like psorasis and eczema can also wreck havoc on your nail texture so chat to your GP if you're concerned.
5. White spots
Loads of us have been brought up to believe that white spots are a sign of calcium deficiency.
But according to Mavala's National Trainer, Tracey Winder, white spots are actually caused by small air bubbles getting trapped between nail cells.
"If you suffer, chances are it could be hereditary but can also be caused by other factors such as bad tissue nutrition, poor keratinization and trauma from an overzealous manicure," she told the Mail.
"These spots are also linked to menstruation."
Make sure to pack your diet out with nail-friendly foods like carrots, green veg, eggs and fish.
Try to avoid nail polish that contains parabens and nickel.
Hangnails are so tiny but can be incredibly painful.
And they tend to be caused by a lack of hydration around the cuticle.
Your best bet is to give your cuticles some TLC by using a daily cuticle oil rich in vitamins E and F.
7. Yellow nails
Stained, yellow nails tend to be caused by smoking or nail varnish that's been painted straight onto the nail plate without a protective base coat.
You can get nail whitener, like Eveline Cosmetics Nail Brightener, £4.98, from Amazon.
If your nails turn yellow, thicken, and seem to stop growing, it could also be a sign of something going on inside your body.
Lung disease and rheumatoid arthritis can cause yellow nails.
8. Grooves in nails
If you start to notice lines that run across your nail horizontally, that means that someone stopped your nails from growing for a while.
A fever, injury, chemotherapy, or major stress can cause your nails to grow slowly or stop growing.
If you can't think would could have stopped your nails from growing normally, visit your GP.
9. Spoon-shaped nails
Thin nails that dip in the middle are a sign that you're not getting enough iron.
That could be down to poor diet, a health problem with your stomach or coeliac disease.
You can easily get an iron test to see if you are lacking and once you know that, it's simple to put right.
10. Curved nails
Nails that curve downwards can be hereditary...or they could be a sign that something is wrong
As they curve, the fingertips swell and the nails start to feel spongy when pressed on.
They can be a sign of lung, heart, liver or stomach disease, so again, make sure you get to your GP as soon as you notice them.
11. Nail biting
Chronic nail biting can damage the nail bed, which, when exposed, leads to the irreversible shortening of nails.
In other words, biting far enough down the nail bed means that no nail can latch on in future
Fingertips are also hives of bacteria, fungus and yeast.
The horrible habit can even give you herpes. It's pretty rare but there have been occasions where STIs have resulted in oral lesions (lip blisters) thanks to a transference of bacteria from finger to mouth.--The Sun