Are Any Foods Banned on Keto? Why the Dose Makes the Poison

2017-09-02

In this video

Eight minutes on one question: which foods are banned on keto? My answer was none. There are doses, and there are foods that tend to cause trouble.

• [0:00] In the medical sense, a ketogenic diet is judged by one thing: whether blood ketones are in the nutritional-ketosis range.
• [0:30] People get into ketosis while eating the "anti-keto" foods: sugar, soy, grain, certain oils.
• [1:00] So no food is keto or not keto. A ketogenic diet is any habitual mix of foods that keeps you in ketosis.
• [1:30] The dose makes the poison. A small amount of sugar is unlikely to push you far out, and a calorie deficit gives you more room.
• [2:00] The real problems are hidden ingredients, like maltodextrin used as a bulking agent. That's a different thing from "keto police" rules taken out of a book.
• [3:00] Omega-3s, grass-fed food and MCT oil have research behind them. None of them is required for ketosis.
• [4:00] Keto is more about what you don't eat: digestible carbs. That raises the question of net or total carbs.
• [4:30] Sugar alcohols vary, and US labels don't split soluble from insoluble fibre.
• [5:00] My example was a bar with 30 g of carbs and 20 g of fibre, which could count as anything from 10 to 30.
• [6:00] Under 50 g a day is the usual definition. Some people need under 20 g, so 20 is the number people repeat.
• [7:00] Keep three things apart: what's good for health, what's good for weight loss, and what's specific to keto.

The claim worth unpacking: what a fibre label tells you

The part of this video I'd stand behind hardest is the label problem. The bodies that write the rules back it up more than I knew in 2017.

The US label line "dietary fiber" covers intact plant fibre plus the isolated or synthetic fibres the FDA has accepted as beneficial (FDA, Questions and Answers on Dietary Fiber). That FDA page doesn't use the term "net carbs" at all. None of the six reference bodies on the fibre evidence page defines it either. "Net carbs" is a convention people made up. It isn't a labelled quantity.

Here my explanation and the definitions part ways, and both should be said plainly. In the video I said soluble fibre is digestible and insoluble fibre isn't (video ffwBPoKxlDI). The international definition calls dietary fibre carbohydrate polymers that are not hydrolysed in the human small intestine (Codex Alimentarius, CXG 2-1985). That covers both kinds. What happens to fibre further along is fermentation by gut bacteria, which produces acetate, propionate and butyrate (Koh et al., 2016).

So "soluble = digested like a carb" is too simple. The practical conclusion survives anyway. The label doesn't tell you which fibre is in the bar, so if you're stuck, counting total carbs takes the guesswork out. A month earlier I'd said I count total carbs and count avocados and green beans a little lower (video xyEZL0HuejI).

Soluble fibre isn't a villain, either. In controlled trials, more viscous fibres reduced appetite in 59% of comparisons, against 14% for less viscous ones (Wanders et al., 2011). Fibre is one more reason to keep your greens, which I'd been pushing since the fibre video (video 1vyxuWlxT5M).

Watching this in 2026

The opening is drier than it needed to be. I named lipase and three ketone bodies before saying anything a beginner could use. The answer someone actually wanted, "nothing's banned, but watch the dose and the hidden stuff," arrives about ninety seconds in.

The last minute is the best part. People do keto for epilepsy and for tumour control, not only weight loss, so "good for health," "good for weight loss" and "required for ketosis" are three separate questions (video ffwBPoKxlDI). That way of sorting things is how I'd still settle most forum fights about grass-fed butter and MCT oil. If you're thinking of keto for a medical condition like epilepsy or cancer, that's a plan to make with your specialist, not with a video. On cancer I said it bluntly in 2019: I'm not an oncologist, don't go treating your cancer with keto (video 1JbK1_ClDmY).

Then vs now: the carb number

In this video I gave 50 g as the usual definition and 20 g as the common recommendation (video ffwBPoKxlDI). That number moved around on the channel:

• July 2017, two videos uploaded the same day: work your way down to 20 (video DoSUgIr2rNo), and under 50 "and nothing else matters", ideally 20 (video xyEZL0HuejI).
• 2018: 50 as the answer, which I called unpopular (video UygKGoP_BtA).

The dose-makes-the-poison idea is what holds those together. The number is a dose, and a dose depends on who's taking it. How to pick yours is in how many carbs and why 20 grams.

Key points

• Keto has no banned foods. It's defined by ketosis, and the dose decides.
• Watch hidden, high-glycemic fillers such as maltodextrin, and read the label rather than the front of the box.
• Omega-3s, grass-fed butter and MCT oil may be good for health. None of them is required for ketosis.
• "Net carbs" isn't a defined or labelled number. US fibre labels don't split soluble from insoluble.
• By the definitions, fibre of either kind isn't digested in the small intestine. Gut bacteria ferment it.
• If you're stuck, counting total carbs removes the guesswork.

Related

• Guide: food list · net vs total carbs · fibre · sugar alcohols · hidden carbs · how many carbs
• Blog: reading nutrition labels · soluble vs insoluble fibre · is MCT oil necessary? · is grass-fed butter worth it? · dirty vs clean keto · keto-labelled products
• Videos: fibre is key · what do I need for keto? · what is keto and how does it work? · beginner questions