Vitamin A (incl. Beta-carotene)Vitamin

• Night vision, where deficiency is the causeLikely helps

  Vitamin A is a structural part of rhodopsin, the retina's light-sensing pigment, and night blindness is the first clinical sign of running short [1].
  
  Correcting a real deficiency restores night vision reliably [1].
  
  NIH ODS cites no evidence that adding more on top of already-adequate status sharpens night vision in anyone else. More is not better here [1]. ^[1]

• Xerophthalmia and childhood blindnessLikely helps

  Xerophthalmia is WHO's umbrella term for what deficiency does to the eye, running from night blindness and Bitot's spots through to corneal ulceration and keratomalacia [3].
  
  NIH ODS calls it one of the leading causes of preventable blindness in children worldwide [1].
  
  A pooled analysis across 138 low- and middle-income countries found 29% of children aged 6 months to 5 years deficient in 2013 [1].
  
  Rates ran highest in sub-Saharan Africa at 48% and South Asia at 44% [1].
  
  WHO puts the global burden near 190 million preschool-age children and 9.8 million pregnant women [1].
  
  An estimated 250,000 to 500,000 deficient children go blind each year, and about half die within 12 months of losing their sight [1]. ^[1]

• Measles cases in at-risk childrenLikely helps

  A 2022 Cochrane review of 6 trials in 19,566 children aged 6 months to 5 years, in low- and middle-income countries, found supplementation cut new measles cases by 50% [1].
  
  The doses were single or repeated, at 15,000 to 60,000 mcg RAE — public-health dosing, far above any daily supplement [1]. ^[1]

• Death from measlesNot shown to help

  The same Cochrane review looked separately at mortality and found nothing [1].
  
  Across 6 trials covering 1,088,261 children, vitamin A supplementation showed no effect on death from measles [1].
  
  One review, two endpoints, opposite answers — worth holding both rather than picking the friendlier one. ^[1]

• Beta-carotene supplements in smokersNot shown to help

  This is the clearest harm signal on the page, and it points the wrong way.
  
  CARET gave 18,314 current and former smokers and asbestos-exposed workers 30 mg beta-carotene plus 7,500 mcg RAE retinyl palmitate daily [1].
  
  It was stopped early, after a mean of 4 years: lung cancer up 28%, lung cancer death up 46%, all-cause mortality up 17% [1].
  
  ATBC, in 29,133 male smokers taking 20 mg/day beta-carotene, found lung cancer risk 18% higher and overall death 8% higher [1].
  
  AREDS2 kept current smokers out of its beta-carotene arm and still counted more lung cancers there, 23 against 11, with 31 of 34 cases in former smokers [1].
  
  At 10-year follow-up an 82% higher lung cancer risk persisted among those originally assigned beta-carotene [1]. ^[1]

• Cancer risk — food and supplements disagreePossibly helps

  Observational data keeps pointing the other way from the trials, and that disagreement is not settled [1].
  
  Several systematic reviews of observational studies link higher dietary retinol and carotenoid intake to lower lung, pancreatic, and esophageal cancer risk [1].
  
  The randomized trials that found harm used high-dose supplemental beta-carotene in smokers, not food [1].
  
  Three other large trials with fewer current smokers found no excess risk at similar or higher doses [1].
  
  Those were a 12-year physicians' trial, a 9.4-year trial in women, and a China-based trial in a population with widespread micronutrient deficiency [1].
  
  The reading that fits all of it: the excess risk tracks heavy smoking and asbestos exposure rather than beta-carotene as such [1]. ^[1]

• Acne, and the isotretinoin mix-upPossibly helps

  Two different things get conflated here. Isotretinoin is a synthetic retinoid drug, not vitamin A, and a Cochrane review of 31 studies in 3,836 patients establishes it as effective for severe acne, adverse effects and all [6].
  
  Oral retinol itself was used for severe acne before isotretinoin's 1982 FDA approval [4].
  
  A 2022 literature review of 9 mostly older studies — 8 trials plus a case report — found acne improved in 8 of them [4].
  
  Doses ran from 36,000 to 500,000 IU/day, with 100,000 IU/day the most common, and improvement typically showed at 7 weeks to 4 months [4].
  
  The foundational 1981 Kligman trial found retinol did nothing at 50,000-100,000 IU/day, and worked only at 300,000-500,000 IU/day [5].
  
  That upper figure is roughly 30 to 50 times the adult upper limit for preformed vitamin A, with genuine teratogenic risk attached [5].
  
  The evidence base is decades old, small, and lightly controlled by current standards [4].
  
  Modern dermatology guidance does not recommend high-dose oral vitamin A for acne; the 2022 review frames it only as a fallback where isotretinoin access is restricted [4]. ^[4]

• Night blindness — difficulty seeing in low light — which NIH ODS identifies as the first clinical sign, from too little rhodopsin in the retina
• Bitot's spots, the foamy white patches that form on the conjunctiva
• Corneal xerosis, ulceration, and necrosis (keratomalacia) — the potentially blinding end of the xerophthalmia spectrum
• Abnormal lung development and higher risk of respiratory disease such as pneumonia
• More severe infections and a higher risk of dying from them, measles and infectious diarrhea in particular
• Anemia
• On bloodwork: WHO sets subclinical deficiency at serum retinol below 0.70 micromol/L and severe deficiency below 0.35 micromol/L, matching ODS's 20 and 10 mcg/dL
• WHO cautions that serum retinol reads a population well but an individual poorly, since the body buffers it except at the extremes^[1]

• Preformed vitamin A — retinyl acetate or retinyl palmitateCorrecting a diagnosed deficiency .

  Elemental content

  Retinol esters. 1 mcg retinol equals 1 mcg RAE, the reference point the whole scale is built on [1]

  Absorption

  70-90% absorbed from supplements [1].
  
  Dietary retinol from food runs higher still, at 75-100% [1].

  Best for

  Correcting a diagnosed deficiency [1].
  
  This is also the only form the upper limit applies to, and the only one linked to birth defects [1].

• Provitamin A — beta-caroteneA vitamin A source with no teratogenic signal and no upper limit set .

  Elemental content

  Converted in the body. 2 mcg of supplemental beta-carotene yields 1 mcg RAE, but 12 mcg is needed from food [1]

  Absorption

  Wide and unpredictable: 8.7% to 65% from supplements [1].
  
  From food it is lower again, roughly 10-30% [1].

  Best for

  A vitamin A source with no teratogenic signal and no upper limit set [1].
  
  Not for current or former smokers — the CARET and ATBC findings above apply [1].

• Oil-filled softgels versus water-miscible, emulsified, or solid formsOil-filled softgels, on safety margin alone .

  Elemental content

  Same labeled retinol, different physical carrier — an oil fill against an emulsified, water-dispersible, or dry preparation [11]

  Absorption

  This is a safety difference, not an efficacy one.
  
  Water-miscible, emulsified, and solid retinol preparations were roughly 10 times as toxic as oil-based ones at equal doses [11].
  
  Chronic hypervitaminosis A followed a few weeks at 0.2 mg retinol/kg body weight per day in those forms [11].
  
  Oil-based retinol needed about 2 mg/kg/day, sustained for months to years, to do the same [11].

  Best for

  Oil-filled softgels, on safety margin alone [11].
  
  The comparison was published in the American Journal of Clinical Nutrition, so physical form is not just a manufacturing detail [11].

• Acute hypervitaminosis A

  One or a few very large doses — typically more than 100 times the RDA — bring severe headache, blurred vision, nausea, dizziness, aching muscles, and coordination problems [1].
  
  In severe cases cerebrospinal fluid pressure rises, which can progress to drowsiness, coma, and death [1]. ^[1]

• Chronic hypervitaminosis A

  Regular high intake over time produces dry cracked skin, coarse hair, partial hair loss including the eyebrows, brittle nails, and painful joints, muscles, and bones [1].
  
  StatPearls adds fatigue, loss of appetite, abnormal liver tests, and hepatomegaly, meaning an enlarged liver [7].
  
  It can progress to liver damage [7]. ^[7]

• Birth defects from preformed vitamin A

  Preformed vitamin A above the upper limit can cause birth defects — malformations of the eye, skull, lungs, and heart [1].
  
  NIH ODS advises anyone pregnant, possibly pregnant, or breastfeeding not to exceed 3,000 mcg RAE (10,000 IU) per day of preformed vitamin A [1].
  
  Retinoid medicines such as isotretinoin and etretinate carry the same hazard [1].
  
  Beta-carotene is not known to be teratogenic — one of the sharpest places the two forms part ways [1]. ^[1]

• Hair loss is one symptom, not an early warning light

  Consumer-facing sources often present hair loss as the near-defining sign of vitamin A toxicity [8].
  
  The clinical sources are more measured. StatPearls and MSD Manuals place it inside a broader chronic picture — dry skin, brittle nails, joint pain, liver changes — rather than as an isolated or early signal [7].
  
  MSD Manuals also notes most people recover completely once they stop the supplement responsible [8]. ^[7]

• Large beta-carotene doses if you smoke, or used to

  Beta-carotene's ordinary excess effect is carotenodermia — harmless, reversible yellow-orange skin discoloration [1].
  
  The exception is large supplemental doses in current or former smokers, where the lung cancer findings above apply [1]. ^[1]

• Orlistat (Alli, Xenical)

  This weight-loss medication reduces absorption of vitamin A, beta-carotene, and the other fat-soluble vitamins [1].
  
  Its manufacturers recommend taking a multivitamin containing vitamin A and beta-carotene alongside it [1]. ^[1]

• Acitretin (Soriatane) and bexarotene (Targretin)

  Both are synthetic retinoids derived from vitamin A, used for psoriasis and cutaneous T-cell lymphoma respectively [1].
  
  The body does not distinguish their retinoid activity from supplemental vitamin A, so combining them raises hypervitaminosis A risk [1]. ^[1]

• Cholestyramine, mineral oil, and beta-carotene supplements

  Cleveland Clinic's drug-interaction reference for vitamin A capsules and tablets flags all three [15].
  
  It gives no mechanism, so read this as a flag worth raising with a pharmacist rather than a quantified interaction [15]. ^[15]

Preformed vitamin A concentrates in liver, fish, eggs, and dairy. Provitamin A comes from leafy greens, orange and yellow vegetables, tomato products, fruit, and some vegetable oils [1].

In the US and other high-income countries 65-80% of intake is preformed; in low-income countries plant carotenoids dominate [1].

By RAE per serving, from NIH ODS's compilation of USDA FoodData Central figures [1]:

Beef liver, pan fried, 3 oz — 6,582 mcg RAE (731% DV), far ahead of everything else [1].

Sweet potato baked in its skin, 1 whole — 1,403 mcg RAE (156% DV) [1].

Frozen boiled spinach, half a cup — 573 mcg RAE (64% DV) [1].

Commercially prepared pumpkin pie, 1 piece — 488 mcg RAE (54% DV) [1].

Raw carrots, half a cup — 459 mcg RAE (51% DV) [1].

Pickled Atlantic herring, 3 oz — 219 mcg RAE (24% DV) [1].

Skim milk fortified with vitamins A and D, 1 cup — 149 mcg RAE (17% DV) [1].

Cantaloupe, half a cup — 135 mcg RAE (15% DV); part-skim ricotta, half a cup — 133 mcg RAE (15% DV) [1].

One large hard-boiled egg gives 75 mcg RAE (8% DV), with smaller contributions from red bell peppers, mangoes, fortified cereal, and broccoli [1].

Cooking is not a uniform rule.

Heat softens cell walls and frees carotene in broccoli, chard, mallow, and spinach — but retention fell specifically in carrots, blamed on their crystalline chromoplast structure [9].

Measured beta-carotene retention across vegetables and methods ranged from about 40% to over 125% of the raw value [9].

For carrots, a separate study found that cooking with added oil improved how much carotene the body could actually take up [10].

No government or clinical guideline sets a time of day for vitamin A, and NIH ODS's fact sheets do not address timing at all [1].

What is left is general pharmacology from a medically reviewed consumer source, not a vitamin A trial [13].

Per Cleveland Clinic, fat-soluble vitamins need dietary fat: fat triggers the bile-acid release that forms the micelles carrying them across the intestinal wall [14].

So take it with a meal or snack containing some fat, rather than on an empty stomach [13].

Even a small amount does the job — low-fat milk, yogurt, or food cooked in oil [13].

That is the opposite of the advice for B vitamins and vitamin C, which Cleveland Clinic says go down better on an empty stomach with water [13].

Morning versus evening has no clinical evidence behind it either way [13].