If you’ve been feeling like your overall health hasn’t been great lately, then take heed: this could be a sign that your body is in desperate need of protein. Your body needs protein to function. That’s why it’s called the building block of life.

And when this building block is lacking, your body gives you plenty of signals to tell you that it needs this nutrient, because the amount you’re consuming isn’t enough. Here are 7 signs that suggest you’re lacking protein:

1. Increased hunger

Increased food cravings and the need to snack frequently between meals could be a sign that you’re lacking protein. Protein is the most satiating nutrient, which means it helps keep you full for longer.

2. Muscle weakness or joint pain

A lack of protein can lead to muscle loss. In one study, it was found that older men and women who consumed a low amount of protein had a higher rate of muscle loss.

Animal protein, in particular, is good for your joints, as the collagen in these protein sources has been shown to ease joint pain. One study found that daily protein intake can ease pain in patients with osteoarthritis.

3. Slower recovery from injuries

Research has shown that we need enough protein to heal and rebuild new cells, tissues, and skin.

One study also found that eating protein can speed up recovery from hip fractures in older adults. In other words, a protein deficiency can significantly slow your recovery time if you ever get injured.

4. Hair, skin, and nail problems

Thin hair, hair loss, peeling skin, and nail problems are some of the first signs that your body may be lacking protein. Biotin, a water-soluble B vitamin, helps keep our skin, hair, and nails healthy and looking good.

Protein loss and biotin loss often go hand in hand, which is why many people experience hair loss when they don’t consume enough protein.

5. Fluid retention

Edema, or fluid build-up: Protein plays an internal role in preventing fluid build-up in the tissues, especially in the feet and ankles.

Edema can also cause swelling in the abdomen, with a swollen belly as the hallmark symptom. However, this condition reflects a fairly severe protein deficiency (and is unlikely in developed countries).

6. Getting sick regularly

Frequent illness means you have a weak immune system, and immune cells are made of protein. One study in particular found that elderly women who consumed a low amount of protein for nine weeks had a significantly lower immune response.

7. Brain fog

Brain fog, fatigue, and poor concentration can all be linked to protein deficiency. Protein deficiency can also impact mood, anxiety, and sleep.