Protein Powder

Lactose
Take it from me first hand if you are lactose intolerant, you will want to get the whey protein isolate. Isolate will contain less than 1% lactose, which is the sugar in milk that causes lactose intolerant individuals to get sick. Digesting a small 1% concentration of lactose is usually tolerated pretty well by lactose intolerant people.
Standard whey protein powder has about 5-6% lactose. I have heard of several lactose intolerant individuals, including myself, who have a hard time with the lactose concentration of regular whey protein powder.
Excess Protein
Your kidneys will have a very hard digesting too much of any protein. Excess protein is responsible for two reactions in the body:
Your blood will turn acidic.
Your blood pH should be in the 7.0 range. When blood becomes very acidic, the body must correct itself by making your blood more basic. The most basic available element in your body is calcium (showing off my college degree here). Your bones will release calcium into your blood, which will then bond to the acidic byproducts of the protein, turning your blood back to a neutral level. Goodbye healthy bones, hello osteoporosis.
You could develop kidney stones.
That doesn’t sound too bad, until you realize that your body is going to need to remove those little calcium deposits that are floating around in your blood. These calcium deposits end up in your kidneys to await your next trip to the restroom. I’m sure you have heard of kidney stones and now you know one of their causes. Ouch! Be sure to limit your initial intake of protein in order to ensure your body responds to well to it.
Ketosis
Another thing excess protein can do, is to put your body into a state known as ketosis. It doesn’t matter what you have heard in the past, prolonged ketosis is bad on your kidneys. Your body will begin to burn fat for energy, which is good; but this is the result of a complete lack of carbohydrates, which is bad.
Most medical resources regard ketosis as a physiological state associated with chronic starvation. Glucose is regarded as the preferred energy source for all cells in the body with ketosis being regarded as a crisis reaction of the body to a lack of carbohydrates in the diet. Ketosis would thus be a dangerous state which unnecessarily stresses the liver and causes destruction of muscle tissues.
This is still the view of the majority in the medical and nutritional science communities, although in recent years it has been challenged by a number of doctors and adherents of low-carbohydrate diets, who dispute both the body’s preference for glucose and the dangers associated with ketosis.
The Protein Shake Diet
Some people also drink straight protein shakes all day long. This wrecks havoc on your body because it loses it’s ability to properly digest fats and carbs. A good principal for protein supplementation, is that that your diet should be consistent by consuming protein, fats, and carbs in moderation.
A 40/30/30 (p/f/c) diet is much better than a protein shake diet, at least over the long term. Moderation is key for healthy eating.
In general there are no side effects related to supplementing with whey protein. Follow some of the tips above to make protein supplementation an important and useful aspect of your diet.