Soy Milk

Soy Milk

Soy milk (in Hebrew, “חלב סויה”) is made by soaking soybeans, grinding them with water and straining out the solids. Of all the plant-based milk alternatives it is the only one that comes close to cow’s milk in the quantity and quality of its protein — a fact that makes it especially relevant in vegan diets and in children’s menus.

100 ml of unsweetened soy milk provides about 33-45 calories, 3.3 grams of protein, 1.8 grams of fat and about 1 gram of carbohydrates. For comparison, almond milk provides only about 0.5-1 gram of protein — a gap of three to seven times.

Protein — the distinguishing advantage

Protein quality is measured not only by quantity but also by amino acid composition and digestibility. Soy protein is one of the few plant proteins considered complete — it provides all nine essential amino acids in sufficient amounts.

On the PDCAAS score (the accepted measure of protein quality), isolated soy protein scores close to 1.0 — the same as milk protein and egg, and significantly higher than most plant protein sources. Its limiting amino acid is methionine, but not in amounts that create a deficiency in a varied diet.

The practical meaning: of the milk alternatives, fortified soy milk is the only one that can reasonably replace cow’s milk nutritionally — which is why many health bodies explicitly name it as the acceptable substitute for children over the age of two (unlike almond or rice milk).

Isoflavones — what the evidence really says

This is the topic around which most of the anxiety about soy is concentrated, so it is worth being precise.

Soy contains isoflavones (genistein, daidzein) — phytoestrogens that bind to estrogen receptors. It is important to understand the structure: they bind mainly to the beta receptor rather than the alpha receptor, and with a strength thousands of times lower than human estrogen. The receptors serve different functions, so the effect is not “weak estrogen” but an entirely different activity profile.

In men: a meta-analysis that reviewed dozens of controlled trials found no effect on testosterone levels, estrogen or sperm quality from soy consumption in dietary amounts. The isolated cases reported in the literature involved extremely high consumption — on the order of 12-20 servings a day — and are not relevant to normal consumption. The claim that soy “feminizes” men is not supported by the evidence.

Breast cancer: cohort studies, mainly in Asian populations with high soy consumption from childhood, link soy consumption to a reduced risk. In women with an existing diagnosis, follow-up studies showed better survival or a neutral effect. The leading organizations — the American Cancer Society and the World Cancer Research Fund — do not recommend avoiding soy, including for breast cancer survivors.

The thyroid: in people with normal function and adequate iodine intake, soy has no effect. In people with hypothyroidism, soy may interfere with the absorption of the drug thyroxine — so the recommendation is to separate taking the medication and consuming soy by at least 4 hours.

Health benefits

• Complete protein in a meaningful amount: as detailed above — the main advantage.

• Fat profile: soy milk contains mostly unsaturated fat, and no cholesterol. The FDA approved a health claim that 25 grams of soy protein a day, as part of a diet low in saturated fat, may reduce the risk of heart disease. The claim is somewhat disputed but still in effect.

• Fortification: fortified products provide calcium (usually 120 mg per 100 ml, equivalent to cow’s milk), vitamin B12 and vitamin D — the three most critical nutrients in a vegan diet. This is the most important practical consideration when choosing: unfortified soy milk misses most of the benefit.

• Lactose-free: completely suitable for lactose intolerance, which is the most common condition in the world’s population.

• Environmental impact: the carbon footprint and water use of soy milk are significantly lower than those of cow’s milk. A distinction should be made between soy for human food, usually grown on a small scale, and soy for the animal-feed industry — which is responsible for the vast majority of deforestation attributed to soy.

Downsides and health considerations

• Soy allergy: one of the leading allergens, especially in children. It is more common than allergy to most nuts and requires complete avoidance.

• Added sugar: versions marketed as “regular” or “vanilla flavored” usually contain 3-6 grams of sugar per 100 ml. Look explicitly for “no sugar” or “unsweetened”.

• Dependence on fortification: unlike cow’s milk, where the calcium is natural, in soy milk it is added — and tends to settle at the bottom of the carton. Shake well before every pour, otherwise you get considerably less of the calcium on the label.

• Phytate: somewhat reduces the absorption of iron and zinc.

• Culinary behavior: soy protein tends to curdle in hot, acidic drinks — a familiar phenomenon in coffee. “Barista” versions contain stabilizers that prevent this.

• A processed product: commercial soy milk sometimes contains stabilizers, acidity regulators and additives. These are not worrying in themselves, but a short ingredient list is preferable.

• Infants: regular soy milk is not infant formula and is not suitable as a main food under the age of one. Dedicated soy formula is an entirely different product and requires medical guidance.

Comparison of milk alternatives (per 100 ml, unsweetened)

Practical use

What to look for on the label: “no sugar” or “unsweetened”; fortification with calcium, vitamin B12 and vitamin D; and a high soy percentage (a short ingredient list).

Shake well: the added calcium settles. This is the simplest action that changes how much calcium you actually get.

In coffee: add the milk to the coffee (not the other way around), and wait for the coffee to cool slightly — this reduces curdling. Barista versions solve the problem.

In cooking and baking: substitutes almost 1:1 for cow’s milk. The beany taste is more noticeable in delicate dishes.

Summary

Soy milk is the only milk alternative that comes within a small gap of cow’s milk in protein quantity and quality, and therefore the only one considered a genuinely reasonable nutritional substitute. The fear of isoflavones is not supported by the evidence — meta-analyses find no effect on hormones in men, and the evidence on breast cancer leans toward protective or neutral. The two choices that matter in practice: pick a product that is fortified and sugar-free, and shake the carton before pouring.