Soy milk is milk that comes from soy beans as opposed to coming from a mammal. This is the milk-drink of choice for the lactose intolerant and for vegan vegetarians, and some other people also choose it over cow's milk for reasons of personal preference.
The question is though, which is the healthier source of milk, and is it possible to get all of the same health benefits by drinking soy milk as you would do from drinking cow's milk? Here we will have an objective look at the differences and whether one is decisively superior. Let's get ready to rumble!
One of the important aspects of milk is that it's a great source of protein and one of the few ways in which we can actually drink protein. In fact the protein shakes that bodybuilders drink are generally made from 'whey' which itself comes from milk and is a by-product of the cheese making process.
The good news for the lactose intolerant is that soy milk has roughly the same amount of protein in it (around 3.5%) and that soy can also be made into protein shakes called 'soy protein' unsurprisingly. And this is what the vegan bodybuilders' protein shake of choice is of course.
However note that this is the 'vegan bodybuilders' protein of choice' and not all bodybuilders' protein shake of choice. The question is then – why do most athletes prefer to get their protein from milk? And the answer is that although both have roughly the same amount of protein they vary in terms of their 'protein profile'. Essentially protein is made up of 'amino acids' which are themselves carbon compounds. In other words they are made up of carbon molecules combined in a specific way and this structure varies depending on the source of the protein. Likewise there are multiple amino acids (around 21) and these all perform different roles and very few protein sources contain all of the amino acids.
When we use protein we use it for specific processes around the body such as building muscle and maintaining healthy brain function. If the amino acids are already in the correct 'format' with more BCAAs (Branch Chained Amino Acids) and a greater number of the amino acids, then it will be easier for our body to use that protein to perform the important tasks it has to around the body. Unfortunately for soy-lovers, soy milk is less 'bioavailable' for this reason meaning that it doesn't contain as many of the essential amino acids and that they are in a less 'useable' form. Thus the protein can be used for fewer jobs around the body, and it requires more energy for the protein to be converted into a useable structure. Thus, in terms of protein content, cow's milk does win out over soybean. For bodybuilders, and when choosing a protein shake, good old fashioned cow's milk is the drink of choice.
Cow's Milk: 1
Soy Milk: 0
On the other hand though, soy milk is the better choice when it comes to fat content. It has little saturated fat (2.5% roughly; which is nevertheless more than most people think) and it has no LDL cholesterol. LDL cholesterol is 'bad' cholesterol (LDL stands for Low Density Lipoprotein) and this can cause fatty deposits to build up in our arteries and veins which increase blood pressure and which make it more difficult for our heart to circulate blood and oxygen around our bodies. In serious cases LDL cholesterol can make you more likely to suffer a heart attack or stroke. That said, some cholesterol is actually good for you and for the majority of us the fat content in milk won't be a huge concern (and you can always opt for skimmed milk).
Another benefit of soy is that the soy bean has one of the lowest glycemic index of any food meaning they trigger less of an insulin response – better for diabetics and better for dieting. If you have high cholesterol or if you are trying to diet, then it is a very good idea to reduce your fat intake by switching to soy milk.
Cow's Milk: 1
Soy Milk: 1
Vitamins and Minerals
When it comes to vitamins and minerals, cow's milk once again slightly wins out. The first and most documented way in which cow's milk is superior for its content of minerals is that it contains high quantities of calcium – which is something that does not occur naturally in soy milk. The high calcium content of cow's milk is one of the reasons that many people go out of their way to make sure they drink enough and this can help to strengthen bones and muscle contractions. At the same time cow's milk is higher in riboflavin, vitamin A and phosphorous all of which serve important roles around the body. Another problem with soy milk is that it contains oxolates, which may actually reduce the body's ability to absorb calcium meaning you get less calcium as a result of drinking soy (oxolates may also be damaging for those with existing liver and kidney issues).
This of course gives cow's milk the edge in that respect, but it's also important to remember that too much calcium can be bad too and can cause kidney stones. Likewise soy milk does contain B vitamins, potassium, and iron which are also very good for you. It is possible to buy both cow's milk and soy milk that comes fortified with more minerals and vitamins. However cow's milk just about edges it on this one.
Cow's Milk: 2
Soy Milk: 1
Soy milk has one very big thing going for it – it is an antioxidant meaning that it can help you to fight cancer and the visible signs of aging by reducing the free radicals in your body. Free radicals are substances in the body that 'float around' and then bombard the walls of cells. When the free radicals do this they alter their physical appearance causing aging, and in some cases they make it all the way through the cell walls and into the nuclei of the cells where they can damage the DNA and cause mutations that spread – AKA cancer. By consuming soy milk you can 'sweep up' those free radicals and prevent this from happening.
Do take this with a pinch of salt though – antioxidants are very powerful and useful substances, but they are also highly abundant and are found in about half the things you eat.
Cow's Milk: 2
Soy Milk: 2
Soy milk is higher in fiber than regular milk and this means that when we eat it we are able to further reduce our cholesterol as well as improving our digestive tracts. This is because fiber remains undigested as it passes through our system and this allows it to 'sweep through' and clear our various passageways as it does. Fiber is highly important for good digestion and helps to 'detox' the body. In soy milk the remaining fiber is called 'okara'.
Cow's Milk: 2
Soy Milk: 3
Another way though in which soy milk is believed to help fight cancer is through the inclusion of isoflavones which are believed to prevent breast cancer and to help ease the menopause. This is because isoflavones are essentially very similar to the hormone estrogen which is the female hormone and by drinking soy milk it is believed that you can help to reduce the effects of the menopause much like using hormone replacement medications – though no studies have supported this belief.
At the same time it's unsure as to whether men would want to be inducing extra estrogen – especially as this already happens when we drink water from the tap. Meanwhile the calcium in regular milk helps the body to produce tryptophan which in turn is used to manufacture melatonin – the sleep hormone. This is why warm cow's milk is often used as a sleeping aid, and by lulling us into a deeper sleep it can result in the better repair of wounds, building of muscle and forming of neural pathways in the brain.
Cow's Milk: 3
Soy Milk: 3
Of course it's not all about health and there are other considerations to bear in mind when you drink a glass of milk. For instance is it good value? Do you like it? Is it versatile?
Well unfortunately for soy-lovers most of us would admit that cow's milk does taste slightly nicer, is better for when you have guests, is more versatile in cooking and is certainly cheaper. While taste is a subjective matter, and while the taste of milk varies depending on brand, even most vegans if they're completely honest with themselves would admit that cow's milk is nicer tasting – and you can't argue that it's not more versatile or cheaper.
Cow's Milk: 4
Soy Milk: 3
So it would appear that cow's milk just about wins as they both have many health benefits, but cow's milk is more versatile, cheaper and tastier. However it's hard to say whether one is better than the other as it really depends on how much weight you give to each factor and what it is you're looking for. If you're a bodybuilder after protein then you should stick to cow's milk, but if you're diabetic or have high cholesterol then making a change to soy might be a smart move.
Of course this debate will rage for a long time and a lot of vegan vegetarians would disagree with this verdict. It comes down ultimately to personal preference, but the important take home message is that both are very good for you, and that any difference between the two is really marginal.