1. Low Vitamin D Level
Although it may not seem important, a low level of vitamin D that lasts for a longer period (even just a few weeks) can cause severe damage to the heart and blood vessels, can lead to diabetes, multiple sclerosis, and even some types of cancer can develop from this. Vitamin D helps with calcium absorption, which otherwise negatively affects the bones. The good thing about this is that the deficiency can be easily treated. Half an hour of walking per day is enough for your body to get the energy it needs to produce sufficient amounts of vitamin D on its own, and in winter, you can also use nutritional supplements.

2. Thyroid Problems
The thyroid gland regulates metabolism and a bunch of other key processes in the body. An underactive thyroid does not produce enough hormones, so the body cannot function properly. This is called hypothyroidism, and symptoms include fatigue, feeling cold all the time, frequent drowsiness, and lack of motivation. The problem with these symptoms is that you don’t associate them with any disease—you just assume it's normal due to tiring work. Insufficient thyroid function can also cause heart disease, high cholesterol, infertility, depression, nerve damage... If you suspect your thyroid isn’t functioning well, consult your doctor. After age 35, it is recommended to have your thyroid function checked by a doctor every 5 years.

3. Type 2 Diabetes
If your body does not produce enough insulin to break down glucose, your health is seriously at risk. The pancreas, which is heavily burdened in this process, gradually slows down, and it’s worst when it stops functioning. The lack of insulin in the blood can damage the eyes, heart, kidneys, nervous system... If you are overweight and have a family history of diabetes, you must be very careful with your diet after the age of 45.

4. High Blood Pressure
High blood pressure, or hypertension, does not hurt. Many people live with it and don’t even know they have pressure problems. Possible complications are heart attack, stroke, kidney disease... You can influence your blood pressure by eating 60 grams of dark chocolate every evening. High blood pressure is, after all, the result of several different factors—including stress.

5. Anemia
With age, the number of red blood cells in the blood gradually decreases, but the symptoms are very subtle (occasional fatigue), which is why most people don’t even notice. Red blood cells carry oxygen, and their shortage can cause permanent organ damage and increase the risk of heart attack. If you are often tired and also have digestive issues, and occasionally experience sensitivity to gluten (celiac disease), check your blood count.