For most people, whey protein supplements in recommended doses don’t pose any health threats. In fact, studies have shown that taking whey isolate may improve your blood cholesterol levels, blood sugar levels and other health factors. Like any supplement, though, whey isolate is not guaranteed to be safe for everyone, especially if you take it in large amounts.
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If you take more than the recommended serving size of whey protein isolate, you may experience an upset stomach, cramps or other digestive discomfort. Headaches, fatigue and a reduced appetite are also possible. If you are lactose-intolerant or have a milk allergy, whey protein isolate is less likely than whey protein concentrate to make you ill, but it is still a milk-derived protein and as such could still bother your stomach.
According to the results of a series of tests performed by "Consumer Reports" and published in 2010, several whey protein supplements on the market, including whey protein isolates, contain trace amounts of harmful heavy metals including lead, cadmium, arsenic or mercury. At recommended serving sizes, the metals don’t pose a threat to your health. If you’re consistently using a whey isolate that contains heavy metals on a long-term basis, however, you may be at an increased risk of chronic, low-level heavy metal poisoning, symptoms of which include muscle and joint pain, fatigue, headaches and constipation.
Whey protein isolate is usually at least 90 percent protein by weight, so a typical 30-gram scoop contains about 27 grams of protein. That’s half or more of the recommended daily allowance, which is 46 grams for women and 56 grams for men. Most Americans get more than the amount of protein they need even without using supplements, so regularly taking whey isolate could raise your risk of health problems associated with consuming too much protein, such as dehydration, kidney disease, kidney stones, osteoporosis and cancer.
If you’re using whey isolate as a substitute for other protein-rich foods, you may eventually develop nutrient deficiencies. Whey powder isn’t able to act as a stand-in for whole, natural foods, as it can’t match their nutritional quality, even if it’s fortified with vitamins and minerals. Unless instructed otherwise by your doctor, aim to get most of your daily protein from whole food sources rather than supplements.