If you are older than 5 years old, chances are you can't digest lactose. Lactose, a type of sugar found in dairy products, it's generally not digestible by adults, causing belly discomfort, gas, bloating, etc.
See, our bodies need an enzyme called "Lactase" in order to be able to digest and break down lactose. This enzyme is naturally produced by our bodies between the ages of 1 and 5 but after that, our bodies stop the production of this enzyme so when we eat any type of dairy, undigested sugars end up in our colon, start fermenting and cause the intolerance.
The majority of people don't realize this but, being able to digest lactose as an adult is actually a weird generic adaptation, in fact, less than 40% of people on the planet maintain the ability to digest lactose after childhood.
Lactose and our ability to digest it (or lack thereof) is not the only issue with milk or dairy products in general. Bet most of you have heard at some point or another that milk will make your bones stronger due to its high content of calcium. While this statement is true, it only applies to children in the midst of their development.
Milk contains about 300 mg of calcium per cup so it is a wonderful source of it for children who are growing every day but when that progress stops, calcium actually becomes counterproductive. Hundreds of scientific studies show that not only do we barely absorb the calcium from a glass of milk but consuming it actually increases the loss of calcium on our bones leading us to a series of detrimental health conditions.
This is what happens when we consume milk: Any animal protein, including milk, acidifies the pH in our bodies so, in turn, our body's response is to try to autocorrect by pulling out calcium from our bones to neutralize the acidity caused by the milk. Calcium is an excellent acid neutralizer and our biggest calcium storage is our bones so naturally, this calcium is used to balance our PH and every time we consume milk, our bones get a bit more decalcified as it all gets disposed of through urine.
The milk industry has spent millions and millions of dollars trying to cover all of these studies and facts and trying to promote the consumption of milk and all dairy products but your body will not lie to you so listen to it.
Fortunately, nowadays we enjoy a wide verity of lactose-free products and non-dairy products that really make our lives easier. Personally, my transition from cow's milk to almond milk was a hard and bumpy one but I now enjoy my morning cup of coffee on almond milk and a yummy almond milk-based creme cheese alternative, having ran a full marathon my bones are strong and I am healthier than ever.