Butter has butyrate. So why do oats win for your gut?

I put a block of butter on my kitchen bench, right next to my breakfast. On one side, butter. On the other, oats mixed with flax and chia, and a bowl of mixed nuts and seeds. Both of them have something to do with butyrate, a tiny molecule your gut cares about a lot. Only one of them actually gets it to where it's needed.

Before you read on: which one gets more butyrate to your colon, the butter or the bowl?

1. 01What butyrate is
2. 02The butter problem
3. 03The long way down
4. 04The colon crew
5. 05Butyrate and constipation
6. 06So who wins

01 · What butyrate is

Butyrate, or butyric acid, is a short-chain fatty acid. It's one of the main fuels for your colonocytes, the cells that line your colon. In lab studies of human colon cells, butyrate supplied up to about 70% of their energy [1, 2]. Most of it isn't made by you. It's made by the bacteria living in your large intestine, when they ferment the fibre you eat [1, 3].

Three short-chain fatty acids. Butyrate is the star.

Why care? Reviews of the research link healthy butyrate levels to a stronger gut barrier, less inflammation, and better blood sugar control and insulin sensitivity [4, 5]. Lower levels of butyrate, and of the microbes that make it, are linked with poorer health [1]. A fair bit of that evidence still comes from animal studies, and researchers are still working out what it means for people [1]. But the basic job is clear: butyrate keeps the cells of your colon fed.

Here's the twist. Butter has butyrate in it too. About 4% of the fatty acids in butter are butyric acid, roughly half a gram in a tablespoon [6, 7]. So a knob of butter on your toast should feed your colon cells, right?

Are they both the same? Not at all. The devil is in the middle.

02 · The butter problem

Follow the butter down.

It goes into your stomach, then your small intestine. The butyric acid in butter is locked inside its fat molecules, called triglycerides. Your fat-cutting enzymes, the lipases, get to work, and they tend to snip the short fatty acids like butyrate off first [6]. And then they're absorbed.

That's the catch. Reviews note that butyric acid is absorbed quickly, high up in the gut, so very little is thought to reach your colon [8, 9]. Your colon cells, the ones that actually wanted it, miss out.

Butter's butyrate is locked inside fat molecules (left), and lipases snip it free early (right).

This is also why butyrate has been tricky to use as a supplement. Plain butyric acid gets absorbed early, and it smells rancid [8]. Some supplements are coated in tiny capsules to try to carry it further down the gut, though some of it is still absorbed on the way [8, 9].

03 · The long way down

Now follow the bowl.

Oats, flax, chia, nuts and seeds. Some of their carbohydrates get broken down and absorbed on the way, like any other food. But fibre is different. We humans don't make the enzymes needed to break most fibres apart [10].

So the fibre does something butter can't. It travels the whole way down, untouched, and lands in your colon. That's exactly where the action is.

Fibre passes the stomach, and the small intestine can’t digest it.

04 · The colon crew

Waiting in your colon is a crowd of hungry gut microbes. I call them the gut kids. Tilly calls them your crew. And they've been waiting for that fibre all morning.

It works like a relay:

• The fibre-breakers go first. Microbes such as Bifidobacteria and Bacteroides carry carbohydrate-active enzymes, tiny molecular scissors our own bodies don't have [11]. Bacteroides keep the instructions for them in gene toolkits called polysaccharide utilisation loci [12]. They snip long fibres like inulin, starch and pectin into smaller pieces.
• The butyrate-makers go next. Microbes such as Faecalibacterium prausnitzii, Roseburia intestinalis and Eubacterium rectale take those pieces and leftovers and turn them into short-chain fatty acids, including butyrate [5, 3].
• The colon cells eat. The butyrate is made right next to the cells that need it, and most of it is taken up by the colon lining. Chomp, chomp, chomp [13].

The crew’s toolkits and fibre scissors (top), then butyrate made next to your colon cells and a stronger gut barrier (bottom).

That's the whole trick. Butter brings butyrate to the wrong place. Fibre brings the butyrate-makers their food, and they make it in the right place.

Well-fed colon cells help keep your gut barrier strong [5]. Reviews also link butyrate to lower inflammation and better insulin sensitivity [4, 5], and researchers are studying its protective role in conditions such as inflammatory bowel disease and bowel cancer [1]. Most of that work is still in cells and animals.

Butter brings butyrate to the wrong place. Fibre feeds the crew that makes it in the right place.

05 · Butyrate and constipation

You might have read that butyrate helps with constipation. One of the reviews I used is even called Butyric acid in functional constipation [8]. Here's what it actually shows.

The idea makes sense. In lab studies, butyrate calms inflammation in the gut lining [8]. In rats, a diet that raised butyrate moved things along faster, and butyrate made colon muscle contract more strongly [14]. In one small trial of 66 people with irritable bowel syndrome, a coated butyrate supplement eased pain when passing a stool. But it didn't make a clear difference to their overall symptoms [15].

But butyrate itself hasn't been properly tested for constipation yet. The review says so too: it still needs to be confirmed in well-run studies [8].

The good news is that the strongest evidence points back to fibre. Across 16 trials, fibre supplements helped about two in three people with constipation, compared with about two in five in the control groups. Psyllium, at more than 10 g a day for at least four weeks, did best [16]. And fibre is exactly what feeds the microbes that make butyrate. If constipation is new for you, lasts more than a few weeks, or comes with blood, weight loss or a lot of pain, see your GP.

06 · So who wins

The bowl wins. Easily.

Butter does have butyrate on paper, but it never makes the trip. And butter is still butter. It's about 82% fat, and more than half of its weight is saturated fat: about 8 g and 430 kJ in every tablespoon [7].

That last line comes from the World Health Organization's advice to keep saturated fat under 10% of your energy [17]. On the 8,700 kJ average adult day that Australian food labels use, that's about 23 g, so three tablespoons of butter uses up the lot.

Why it matters: eating less saturated fat lowers your cholesterol, and in trials it cut heart attacks, strokes and other heart problems by about 17%. It made little or no difference to deaths over the length of those trials, but fewer heart problems is reason enough [18]. The WHO suggests swapping saturated fat for unsaturated fats, like olive oil, nuts and seeds, or for foods with natural fibre [17]. Too much energy and too little movement add to the risk. Excess body fat and long hours of sitting are both linked with heart disease [19, 20].

From the video: three tablespoons of butter, and none of its butyrate reaches your colon.

It also depends on you: how much you eat, how active you are, and your heart health. But the science points the same way for most of us. Keep saturated fat low. So my advice is to keep butter to a minimum.

One more thing. If you want to make your gut kids happy, it's not about one magic food or one supplement. Different fibres feed different microbes [21]. In one large study, people who ate more than 30 kinds of plants a week had more diverse gut microbes than people who ate 10 or fewer [22].

Variety beats any one supplement.

Whole foods first. Fibre supplements, and even butyrate supplements, have their place. Psyllium helps many people with constipation [16]. But a supplement is usually one isolated compound. Whole plant foods bring many kinds of fibre at once, plus polyphenols and other plant compounds that your gut microbes interact with [23]. That mix is what feeds a varied crew and helps keep the whole ecosystem in balance. And efforts to raise butyrate in people with supplements have had mixed results so far [1]. So reach for food first.

My breakfast porridge alone has 10 to 15 different types of fibre in it: oats, flax, chia, and a mix of nuts and seeds. That's a lot of different meals for a lot of different microbes.

And it doesn't matter what time you eat it. I often have my first meal at noon. Front-loading your first meal with fibre and variety can help you stay full for longer. In one trial, people ate less at lunch after oat porridge than after an oat cereal from a box [24]. Not every fibre works that way [25], but over time, eating more fibre is linked with a lower body weight [26]. Staying full makes it easier to keep your energy in check for the rest of the day.

A few questions people asked about the video.