What percentage of phytonutrients in milk does pasteurization eliminates?
Executive summary
Pasteurization reduces some heat-sensitive vitamins in milk—studies find measurable decreases in B1 (thiamine), B2 (riboflavin), vitamin C and folate, while effects on B6 are not statistically significant; authors conclude overall nutritive losses are small because many of these vitamins are present at low levels in milk to begin with [1]. Reviews of bovine and donor human milk find “minimal to no impact” on major macronutrients and many vitamins but acknowledge moderate-to-extensive loss of some heat-sensitive bioactive proteins depending on method and temperature [2] [3] [4].
1. What the systematic reviews actually measured — vitamins fall, minerals stay
Meta-analyses of pasteurization studies report statistically significant decreases in vitamin B1 (SMD –1.77), B2 (SMD –0.41), vitamin C (SMD –2.13) and folate (SMD –11.99), while vitamin B6 showed no significant change (SMD –2.66; P = 0.06) [1]. Multiple reviews emphasize that minerals such as calcium and phosphorus are largely unaffected by heat treatments used for pasteurization [5] [6].
2. “What percentage” is hard to state from available reviews
The sources provided report standardized mean differences and note statistically significant declines for several vitamins but do not supply a single, clear percentage of “phytonutrients” lost across milk [1] [7]. Available sources do not mention a consolidated percentage figure for all phytonutrients eliminated by pasteurization; individual studies report different magnitudes depending on temperature, time, and analytic method [4].
3. Phytonutrients vs. vitamins vs. bioactive factors — semantics matter
Most scientific reviews distinguish vitamins and bioactive proteins from “phytonutrients” (plant-derived compounds). Milk is an animal product and contains vitamins, minerals, enzymes, immunoglobulins and other bioactive factors rather than plant phytonutrients; the literature you provided evaluates vitamins and proteins rather than plant phytonutrients per se [1] [4]. If by “phytonutrients” you mean heat-sensitive bioactive factors (e.g., antimicrobial proteins), reviews show moderate to extensive losses for some of these after Holder pasteurization (62.5 °C for 30 min) in donor human milk [3] [4].
4. Pasteurization method and starting material change the outcome
Heat-time combinations matter: high-temperature short-time (HTST, ~72 °C for 15 s) used for commercial bovine milk differs from Holder pasteurization (62.5 °C for 30 min) used in milk banks. Modern pasteurizers and shorter exposure times tend to preserve more heat-sensitive components than older, longer treatments; reviews stress variability across methods and decades of data [2] [4].
5. Nutritional significance vs. analytical significance
Authors underscore a key point: decreases in some vitamins are measurable, but may be nutritionally small because the affected vitamins are present at low concentrations in milk and because other public-health measures (e.g., fortification of commercial milk with vitamin D) offset losses [1] [8]. Public-health authorities emphasize that pasteurization’s disease-prevention benefits greatly outweigh modest changes in certain nutrients [9] [10].
6. Competing narratives — safety and public-health versus “raw milk” advocacy
Scientific reviews explicitly counter pro‑raw‑milk claims that pasteurization “destroys important vitamins” and argue that pasteurization’s safety gains are well established [1] [9]. Advocacy sites and antigovernment or nostalgia-driven outlets claim more severe nutritional harm; those sources are present in the dataset but are not supported by the systematic reviews cited here, which report modest nutrient changes and stress methodological limits in older studies [11] [7].
7. What the evidence does not say (limitations you should note)
Current reporting in these sources does not provide a single percentage that quantifies “phytonutrients” eliminated across all forms of milk by all pasteurization methods; numerical results vary by nutrient, method, and study quality [1] [4]. Some reviews warn that older studies have methodological shortcomings and that modern equipment may yield different outcomes [7] [4].
Conclusion — how to read these findings for consumers and policy
Pasteurization measurably reduces certain heat-sensitive vitamins and some bioactive proteins, but the peer-reviewed syntheses in these sources characterize overall nutritive loss as small and highlight the dominant public-health benefit of preventing foodborne disease [1] [9]. If your priority is a single percentage figure for “phytonutrients eliminated,” available sources do not provide that consolidated number; to get one would require meta-analysis focused specifically on the compounds you mean and on the exact pasteurization method in question [1] [4].