Soy Versus Dairy: Which Milk Is Better For You?

There are good reasons why people may want to swap soy with dairy milk. The carbon, water and phosphate footprint of soy milk is a fraction of the latter. But the main reason for the increasing popularity of soy milk seems to be health concerns, such as inflammatory bowel disease and lactose intolerance.

Soy milk picture from Shutterstock

First, let's look at what these milks are. The milk from a cow (or goat, or sheep) is complete food for the growth and development of a young animal. It contains all the essential amino acids (the protein building blocks that your body is unable to make for itself) as well as a complex mixture of fats, carbohydrates, vitamins and minerals including calcium, phosphate and vitamin B12.

A soy bean is also complete food — for the growth and development of a soy plant seedling. The nutritional needs of plants are obviously quite different from those of animals, and accordingly, the nutritional profile of unadulterated soy milk is very different from that of animal milks.

Fresh soy milk, made from grinding and then straining soaked dried soy beans, has less fat and carbohydrate than animal milks, and only a small amount of calcium. And it's missing some of the vitamins present in animal milks as well.

The protein content of soy milk is similar to cow's milk, and all the essential amino acids are present but in smaller amounts than in cow's milk. Because it's plant food, soy milk contains small amounts of fibre, and twice as much folate as animal milks.

The contrast between the two products is significantly reduced when comparing the commonly-available commercial brands of soy and cow's milk. Both types of milk are heat-treated as part of production, to destroy bacteria and enzymes that may be harmful to health or shorten shelf life. They're also nutritionally similar.

Supermarket soy milk products are mostly made from soy protein isolate powder (rather than ground whole soy beans), reconstituted with water and adjusted with oil and often sugar, to bring the fat and carbohydrate content to levels comparable with full-cream cow's milk. A similar vitamin and mineral content is achieved by adding vitamins (including B12) and calcium.

Once this is done, the main differences between the products are in the type (rather than the amount) of carbohydrate, protein and fat.

The carbohydrate in cow's milk is lactose, the milk sugar, which is digested by the enzyme lactase. In most animals (including human ones), the amount of lactase in the intestine naturally decreases after weaning. Once this has happened, milk cannot be digested properly, causing flatulence or diarrhoea.

In humans who continue to consume lactose-rich dairy products throughout their lives, lactase enzymes are maintained in the gut. But some unlucky individuals become lactose intolerant and, for them, soy milk is a useful alternative as it contains no lactose.

For everyone else, though, lactose has some advantages over other sugars because it has a very low glycaemic index. This means that it is released slowly into the blood, avoiding abrupt spikes in blood glucose levels.

Both soy and dairy milk are good sources of protein, with different health advantages. Soy protein appears to have its own protective effect on heart health, possibly due to its content of phytochemicals (beneficial plant substances). Some of these include phytoestrogens, whose weak oestrogen-like action can help soothe hormonal swings during menopause.

Cow's milk consists of two proteins, casein and whey, both of which are popular among body-builders as effective muscle-building proteins. In controlled diets, dairy foods appear to promote fat loss, possibly due to the effect of their calcium content in conjunction with the dairy proteins and other substances in milk. This effect is not seen when the same nutrients are consumed as supplements.

The fat content is similar in both cow and soy milk, and low fat or "light" varieties are available for both. The type of fat in full-cream cow's milk is butterfat, high in saturated fat, while soybean oil is mostly polyunsaturated. The fats added to soy milk are usually canola or sunflower oil, again rich in polyunsaturated and monounsaturated fats. This means that soy milk is a source of "good" fats.

The Heart Foundation recommends we avoid saturated fats in order to control our cholesterol levels, but interestingly full-fat dairy foods don't appear to increase the risk of heart disease in the same way as other sources of saturated fat. This may be due to the protective effect of other complex elements in milk (such as the proteins or minerals) or the unsaturated fats present.

Fresh, raw soy milk and fresh, raw animal milk are very different foods. But in the form usually purchased in the supermarket, there's little difference in their nutritional profile. So rest assured that if you choose to replace some, or all, of your dairy milk intake with soy milk for environmental reasons, you will not be nutritionally disadvantaged.

Suzie Ferrie is a Clinical Affiliate at University of Sydney. She does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations. The ConversationThis article was originally published at The Conversation. Read the original article.


Comments

    This is old thinking. New research shows firstly the increasing lack of nutrients in milk, and secondly some concerns with non-organic genetically modified and processed soy on thyroid function.

    You forgot to mention that we now have lactose free milk available as an alternative to soy if you are lactose intolerant. Soy tastes like foot. :p

    It's a really bad idea for men to consume a lot of soy. Unless you like the oestrogen-like action that it has.

    I still eat tofu and drink soy milk sometimes. But I woudn't be doing it all the time.

      Pure misinformation. Soy products contain phyto-oestrogen which doesn't affect a males hormone levels. Soy products are infact beneficial for males as they reduce the chance of developing prostate cancer

      http://www.flickr.com/photos/vegetarian-vegan-bodybuilding-info/6691266425/

      Last edited 07/03/13 8:38 am

        Don't confuse the fact that drinking whole-milk may increase chances of prostate cancer with misinformation that drinking something else would be more beneficial and REDUCE chance of prostate cancer. You see, your statement suggests and can be taken that if I drink Soy and not water, that I would reduce chance of prostate cancer, which I am sure is not what you want to say, but this is the way FUD gets produced.

          http://www.ncbi.nlm.nih.gov/pubmed/10189040

          Although results aren't definitive, I'm not confusing any facts here buddy, there have been studies to suggest what I am saying.

        +1 for misinformation

        http://zenhabits.net/soy/

    Here's another option. Skip milk all together. Why are you really worried about milk when what you mix it with is nearly just solid sugar and corn anyway. I'd say nearly 90% of breaky cereals aren't as healthy as you think. You'd be better off with some berries and a bit of yoghurt if you really want some dairy.

    The headline is "Soy Versus Dairy: Which Milk Is Better For You?", not "Soy and dairy - where they come from!" There is nothing in this article. I'm quite surprised, the Conversation is usually better than this.

      "Fresh, raw soy milk and fresh, raw animal milk are very different foods. But in the form usually purchased in the supermarket, there’s little difference in their nutritional profile. So rest assured that if you choose to replace some, or all, of your dairy milk intake with soy milk for environmental reasons, you will not be nutritionally disadvantaged."

      So you didn't read the final paragraph that wrapped up the article and answered the question posed in the title? That is, neither. They have equal benefits according to the author.

      I'd like to think you were just to busy to read the entire article which is an entirely reasonable thing.

      But funnily enough you did have time to post...

        "Which is better for you: NEITHER!" certainly suckers in less readers than merely "Which is better?" Article = uninformative.

          Comment = uninformed. As the article points out, the answer varies depending on your circumstances. If you were already completely across the composition of soy versus dairy, more power to you, but I suspect most people aren't aware of the distinctions.

          Now had the title not included that pesky "you" at the end you may have had a case...

    It's all about moderation. If you moderate the amount of milk you drink, either cow or soy, you will reduce any negative affects. I rarely drink any milk these days, when i do it tends to be homemade almond milk (almonds, water and a pinch of cinnamon in a blender).

    So if you're a baby cow drink cow milk, if you're a soy plant use soy milk, unless you're a human buying it from the supermarket in which case it doesn't make much difference unless your lactose intolerant?

    If you're a man, enjoy the manboobs you'll grow from soy milk
    http://www.menshealth.com/nutrition/soys-negative-effects

    Women and soy can be classed as a risk in terms of breast cancer. It is well established that estrogen is linked to hormonally-sensitive cancers in women, such as breast and endometrial cancer. Breast cells contain estrogen receptors, and when the "key" (estrogen) joins with the "lock" (the estrogen receptor), a series of signals are sent which can spur on estrogen-receptor (ER) positive breast tumor growth. Common risk factors for breast cancer include conditions that involve longer exposure of breast tissue to estrogen:

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