Half a Prenatal Vitamin on Keto? My 2017 Tip, Looked at Again
A three-minute clip from July 2017, about six weeks after I started keto on 2017-06-13 (video cTGYIFOTPl8) and before the YouTube channel had any uploads. I'd just done rounds of sparring, I had marks on my face, and I admitted I was hungover. The tip itself was one I hadn't seen in the keto forums: take half a dose of a prenatal vitamin while you adjust.
In this recording
- [0:00] Where the idea came from: advice I'd had before keto from a pharmacist in my family and a friend in medicine. I needed iron, but too much iron causes its own problems (live TDHN9809).
- [0:00] My complaint about ordinary multivitamins: many carry several hundred percent of the daily value for iron and other nutrients.
- [0:00] The keto-flu angle: people rush out for magnesium pills or pink Himalayan salt. If you've got cramps, poor sleep or constant thirst and suspect a food-driven shortfall, I suggested a prenatal vitamin.
- [1:24] Why prenatal: they're made for pregnant women, so I said the doses are kept close to the daily recommendation rather than huge multiples.
- [1:24] My method: pick one whose label dose is two capsules and take one. You're not trying to replace your food with a pill. You should be getting it from food.
- [2:13] The trial: a half dose once a day for six or seven days, and see if your symptoms improve. If you like it, take it now and then or daily to round out nutrients while you adjust.
Watching this in 2026
Two things hold up: "food first, pill second," and being suspicious of mega-doses. I said outright that I didn't want anyone relying on a vitamin for their nutrition.
What I'd change is the framing. A vitamin isn't really a keto-flu fix. The cramps and thirst I listed are mostly about sodium, potassium and magnesium. A month later I said the multivitamin I'd moved to covered two of the four electrolytes, magnesium and calcium, and I pointed people to salt and light salt for the rest (video lbRPlGZ3Rvw). So even by my own account, a pill only does part of that job.
I'd also add the doctor step I left out. Prenatal formulas are designed for pregnancy, and I picked one for its iron levels without saying who should and shouldn't take extra iron. If you're pregnant or trying to be, your prenatal is your doctor's or midwife's call, not a keto hack. If you take prescription medication, or you already take other supplements, check with a pharmacist or doctor before adding one. Stacking products is how intakes creep past upper limits.
Then vs now: from prenatal to a plain multivitamin
The prenatal idea didn't last. A month later, in my electrolytes video, I was recommending a common one-a-day multivitamin because it has two of the four electrolytes, magnesium and calcium (video lbRPlGZ3Rvw). In the 2018 basics video I called a multivitamin a kind of silver bullet for the micronutrient gaps people get when they're not careful about their keto diet (video UygKGoP_BtA). By 2019, my fastest weight-loss menu had a common adult multivitamin and a calcium-plus-minerals supplement built in (Stall Breaker live; live SMGI5574). In 2020 I said I already tell everybody to take a multivitamin (live SPWR4007).
So the constant is the reason: a restricted diet can leave gaps. The product changed.
What the research says about the gap and the pill
The gap is real on paper. In the A TO Z trial, women on Atkins had shifted toward inadequate intakes of thiamine, folate, vitamin C, iron and magnesium by eight weeks, and the other diets had other shortfalls (Gardner 2010). Menu modelling of four diet plans, including Atkins for Life, found none met the RDI for all 27 micronutrients from food alone (Calton 2010).
Whether a pill improves health outcomes is a separate question, and the answer is weaker. The US Preventive Services Task Force calls the evidence insufficient to weigh the benefits and harms of multivitamins for preventing heart disease and cancer (USPSTF 2022). An umbrella review of 277 trials found most supplements, multivitamins included, had no significant effect on mortality or cardiovascular outcomes (Khan 2019).
Put together: a multivitamin may cover a shortfall while your food is still narrow. It isn't a health booster on top of a good diet. That's close to what I said in 2017, minus the prenatal part.
Key points
- My 2017 tip: half a dose of a prenatal vitamin for a week while adjusting, food first (live TDHN9809).
- Within a month I'd moved to a regular one-a-day multivitamin, and I kept recommending one through 2020.
- Restricted diets can fall short on micronutrients from food alone (Gardner 2010; Calton 2010).
- For preventing disease, multivitamin evidence is rated insufficient (USPSTF 2022).
- Pregnant, on medication, or already taking supplements: ask your doctor or pharmacist first.
- Cramps and thirst are mostly an electrolyte question. See the related pages.