Soy Milk: Nutrients, What Research Shows and Safety

Soy milk is a drink made from soybeans, the seeds of Glycine max, a legume (see our soy foods page). The National Center for Complementary and Integrative Health (NCCIH) lists soy milk with tofu, miso, tempeh and edamame as common soy foods. [1] People drink it as a dairy-free milk, for its protein, or because they have lactose intolerance or follow a plant-based diet. This page covers soy milk as a drink. It keeps soy protein or isoflavone supplements apart, because most research used those.

Read this first

• Allergy: soybeans are one of the nine major food allergens named by the U.S. FDA, and the NHS lists soy among common food allergens. [2] [3] For trouble breathing or swelling of the face or throat, call 911 (or your local emergency number).
• If it replaces milk, check the label. USDA lists about 301 mg calcium in a cup of unsweetened, calcium-fortified soy milk but about 61 mg in an unfortified original and vanilla one. [4] [5] CDC says fortified dairy alternatives are the only milk alternatives that help meet a child's dairy needs, and not before 12 months. [6]
• Thyroid medicine: MedlinePlus says foods with soybeans, walnuts and fiber may affect how levothyroxine works, so talk with your doctor. [7] A review found the evidence mostly case reports and said the effect of soy milk is unresolved. [8]
• Evidence in one line: pooled trials of soy protein show a small drop in LDL cholesterol; the abstract does not say how many used soy milk. [9] Evidence for hot flashes, cancer and other claims is mixed or limited.

What is in it (USDA values)

The main table is for unsweetened soy milk with added calcium and vitamins A and D (USDA FoodData Central item 175215, SR Legacy). [4] The serving column is the USDA household portion of 1 cup, 243 g. USDA lists no values for vitamin D, vitamin A or zinc in this record in the data we used, even though the record name says vitamins A and D were added, so we show no figures for them.

% Daily Value uses the FDA 2016 Daily Values; values vary by brand and recipe. The serving figures are the 100 g values multiplied by 2.43. Products differ a lot, as this second USDA record shows (original and vanilla soy milk with no added nutrients, FDC 172446). [5]

USDA does not say how much of the 9.7 g of sugars in the original and vanilla record is added sugar. [5]

Plant compounds: soy contains isoflavones, which bind to estrogen receptors, mostly the beta type, in laboratory work. [10] USDA lists no isoflavone values for these soy milk records, and we did not find isoflavone amounts for soy milk in the sources we read.

What research says

NCCIH also says isoflavones probably help bone density after menopause and may modestly lower blood pressure, and that it is uncertain whether soy improves blood sugar control in people who already have diabetes; those findings concern isoflavones, and the summary we read does not separate out soy milk. [1] The FDA proposed in October 2017 to revoke the soy protein heart claim, saying the evidence was inconsistent; comments were due in January 2018. [16] We did not find the final outcome. The eCFR text we read (version dated 2025-01-01) still contains the claim. [11]

Eaten as food vs taken as supplement. The trials above tested soy protein, soy foods, extracts or isoflavone supplements, and the abstracts we read do not break out soy milk. A cup of soy milk has about 7 g protein, from USDA values. [4] Do not assume a soy milk trial result exists because a soy protein result does.

How much is a normal serving

Safety, allergy and medicines

• Soy allergy: soy is a major U.S. allergen and NCCIH notes that U.S. labels must indicate its presence. [2] [1] Soy is not automatically a safe swap for milk allergy: the milk allergy guideline lists soy formula as one option and does not assess how well soy is tolerated. Ask an allergist. [18]
• Thyroid medicine: see the bullet near the top of this page. MedlinePlus says levothyroxine is usually taken on an empty stomach 30 minutes to 1 hour before breakfast. [7] Do not change a medicine on your own; ask your prescriber or pharmacist.
• Hormone-sensitive conditions: soy foods are often asked about after breast cancer. The sources we read show mixed observational findings and no clear advice. Ask your cancer care team. [10] [1]
• Pregnancy and breastfeeding: NCCIH says soy during pregnancy may be unsafe in amounts greater than those usually found in foods, and little is known about larger amounts while breastfeeding. [1]
• Babies: CDC says not to give soy or other fortified dairy alternatives as a milk before 12 months. [6] This is about soy milk as a drink, not infant formula.
• Digestion: NCCIH lists bloating, constipation, diarrhea and nausea as possible side effects of soy. [1]
• Antidepressants called MAOIs: NCCIH names tofu and soy sauce, which are high in tyramine, as risky with MAOIs. It does not name soy milk, and we did not find tyramine values for soy milk. Ask your pharmacist. [1]
• Kidney disease: NIDDK suggests asking a dietitian about plant or soy milk. [19] USDA lists 120 mg potassium per 100 g, about 292 mg a cup. [4]
• Sweetened and flavored soy milk: the 2025-2030 Dietary Guidelines say no amount of added sugars is recommended. [20] CDC says to choose unsweetened versions for children. [6]

Choosing, storing and food safety

• Look for "unsweetened" and for added calcium and vitamin D on the label. [6]
• Shake the carton. In a laboratory analysis, protein and calcium in some plant drinks differed between shaken and unshaken samples. [15]
• Salt was the most common added ingredient in a review of plant drinks, so check sodium. [21] USDA lists 37 mg sodium per 100 g in the unsweetened fortified record. [4]
• We did not read storage or shelf-life rules; follow the package.

Related pages

• Soy foods
• Plant milks: oat, almond, soy and others
• Fortified plant milks and cereals
• Tofu
• Food allergy basics and emergency signs
• Foods and medicine interactions