Low vitamin D before breast cancer surgery, more pain and more opioids after

Pain control after surgery is normally framed around anesthesia technique, the drugs used, and the patient's own pain tolerance. A study published this year adds a variable that rarely comes up in that conversation: how much vitamin D was in the patient's blood before anyone made an incision.

The study

Researchers led by Mahdy Ahmed Abdelhady at Fayoum University in Egypt followed 184 women, ASA physical status II to III, scheduled for elective unilateral modified radical mastectomy at Fayoum University Hospital between September 2024 and April 2025. This is a prospective observational study, published in the journal Regional Anesthesia & Pain Medicine: preoperative blood was drawn to measure 25-hydroxyvitamin D, patients were split into a deficient group (below 30 nmol/L) and a sufficient group (above 30 nmol/L), and pain, opioid use and nausea were tracked afterward without the researchers intervening in anyone's vitamin D status.

The finding

The gap was large. 17% of the vitamin D-deficient group reported moderate to severe pain in the first 24 hours after surgery, versus 2% of the sufficient group, commonly described as roughly a three-fold difference in the odds of that outcome. The deficient group also used substantially more analgesia after surgery: about 112 mg more tramadol through patient-controlled analgesia. Differences during the operation itself were smaller, roughly 8 micrograms more intraoperative fentanyl in the deficient group, and postoperative nausea was also more common in that group.

What this design can and cannot tell you

This is an observational comparison between two groups defined by a blood test result, not a trial where some patients were given vitamin D and others were not. That means it can show an association between low vitamin D and a rougher recovery, but it cannot show that raising vitamin D beforehand would have prevented it. Women who are vitamin D deficient may differ from women who are not in other ways that also affect pain and recovery, chronic illness, body composition, time spent outdoors, diet quality, and a single-hospital study of 184 women cannot rule that out.

It is also worth being precise about the cutoff used. The study's deficient group was defined as below 30 nmol/L (about 12 ng/mL), which is stricter than the commonly used clinical threshold of 20 ng/mL (50 nmol/L) for deficiency and 20 to 30 ng/mL for insufficiency. So this comparison is closer to severely deficient versus everyone else, rather than deficient versus clearly sufficient. That does not make the finding less real, but it does mean the size of the effect should not be assumed to hold at milder, more common degrees of low vitamin D.

The authors' own conclusion stays inside what the data supports: they suggest preoperative vitamin D supplementation in deficient patients "may have a role in modulating postoperative pain," framed as something worth testing, not something already shown to work.

Getting enough vitamin D from food

Vitamin D is one of the few nutrients where diet alone is a poor plan for most people, since the biggest source for most of the population is sunlight on skin. Amounts below are per realistic serving, ordered by density:

• Cod liver oil, 1 tablespoon: about 1,360 IU
• Maitake mushrooms, UV-exposed, cooked, 3.5 oz: up to about 780 IU (mushrooms grown without UV exposure carry very little)
• Swordfish, cooked, 3.5 oz (100 g): about 666 IU
• Rainbow trout, farmed, cooked, 3 oz: about 645 IU
• Sockeye salmon, cooked, 3 oz: about 570 IU
• Salmon, farmed, cooked, 3 oz: roughly 100 to 250 IU, well below wild-caught
• Oat milk, fortified, 1 cup: about 200 IU
• Halibut, cooked, 3.5 oz: about 190 IU
• Sardines, canned, 3 oz: about 175 IU
• Herring, Atlantic, 3.5 oz: about 167 IU
• Tuna, canned in water, drained, 3 oz: 154 IU
• Shrimp, cooked, 3.5 oz: about 150 IU
• Cow's milk, fortified, 1 cup: roughly 110 to 120 IU
• Yogurt, plain, 8 oz: about 116 IU
• Almond milk, fortified, 1 cup: about 107 IU
• Orange juice, fortified, 8 oz: about 100 IU
• American cheese, fortified, 1.5 oz: about 85 IU
• Breakfast cereal, fortified, 1 serving: about 80 IU
• Soy milk, fortified, 1 cup: about 68 IU
• Egg yolk, one large: about 44 IU
• Beef liver, cooked, 3 oz: about 42 IU

Fortification amounts vary a great deal by brand, sometimes by 50% or more for the same category of product, so the label is the only reliable number for a fortified food in your own kitchen.

How much you need

The US RDA for vitamin D, from the National Academies:

• Infants 0–12 months (AI): 400 IU
• Children and adults 1–70 years, both sexes: 600 IU
• Adults 71 and older: 800 IU
• Pregnancy and breastfeeding: 600 IU

The tolerable upper intake level for most adults and children over 8 is 4,000 IU a day from food and supplements combined. Clinicians routinely prescribe short courses above that limit to correct a confirmed deficiency, which is a supervised medical decision rather than a reason to self-dose.

A blood test for 25-hydroxyvitamin D is the only way to know where you stand. Under 20 ng/mL (50 nmol/L) is generally considered deficient, 20 to 30 ng/mL insufficient, and 30 ng/mL and above sufficient.

Too little, and too much

Too little is common, especially with darker skin, limited sun exposure, northern latitudes, older age and higher body weight, all of which reduce how much vitamin D the skin makes or how efficiently the body uses it. Deficiency shows up as bone pain, muscle weakness and fatigue, and in children as rickets, with bowed legs and impaired growth; in adults, the equivalent bone-softening condition is osteomalacia.

Too much is a real risk only at sustained, high intakes, almost always from supplements rather than food or sun, since the skin regulates its own production. Vitamin D toxicity causes hypercalcemia: nausea, vomiting, weakness, frequent urination and confusion, and in severe cases kidney problems and abnormal heart rhythm. The clinical hallmark is a blood level above roughly 150 ng/mL, far beyond what food or moderate supplementation reaches.

Tracking it in AIM

AIM does not track vitamin D as standard, so add it as a custom metric: give it a name, a unit (IU) and a daily target of 600 IU (800 IU past age 70), and it is estimated on every meal from then on, pinned to your cards or left behind "more".

Estimates from a photograph carry real uncertainty for micronutrients, because content varies with soil, cultivar, storage and cooking in ways no image contains. Vitamin D is a particularly poor fit for photo estimation specifically, since the biggest source for most people is sunlight rather than food, and a log will always undercount it for that reason. Treat the week as meaningful and any single day as approximate, and treat a real deficiency question as a job for a blood test, not an app.