Most people who workout or lift weights know the importance of protein. But with all of the different protein supplements, there’s a lot of confusion and many people don’t know which claims are grounded by scientific evidence.
Good sources of protein tend to be meat, fish, dairy, and eggs, and can be divided into whether they are lean protein sources (not too much fat or carbohydrates) or whether they are not lean (usually half or more of the calories come from dietary fats). The lean protein sources tend to be select cuts of red meat, chicken, egg whites and warm water fish such as tilapia or tuna.
Lean protein sources aside from tuna and egg whites tend to be more expensive than their non-lean counterparts such as ground beef or whole eggs. This can make it tough to get enough protein without increasing your fat intake. The good news is protein supplements are a simple and tasty way to fulfill protein requirements. They are also pretty cheap on a cost-per-serving basis.
Whey protein is a component of dairy protein, and is specifically the 20% of the protein fragment that is water soluble. The USDA definition is “the group of milk proteins that remain soluble in milk serum or whey after precipitation of CN at pH 4.6 and 20°C”. Whey protein can come in a ‘concentrate form’ (35-80% protein by weight) and an isolate form (more than 90% protein by weight).
Soy protein is derived from the soybean, and also comes in two forms as soy concentrate and soy isolate. The big misconception about soy protein has to do with Isolflavones - the plant based estrogen imitators genistein and daidzein.
Soy isoflavones are selective estrogen modulators (SERMs). They are ONLY pro-estrogenic in states of estrogen deficiency, such as menopause. Men taking soy are not in a state of estrogen deficiency. Therefore there is no reason the SERMs will have a negative effect on testosterone levels. As matter of fact, the isoflavone genistein is also a weak selective androgen receptor modulators (SARM) and may actually increase the signalling of testosterone in states of testosterone deficiency.
Bottom line: soy protein is a viable form of protein that will not send testosterone levels plummeting nor estrogen skyrocketing.