III. Phase 2 – Engraftment and lifestyle (days 25–60)

III. 5 Protein and the gentle diet

Fibre feeds the flora, and protein feeds you: your muscles, your immune system, your healing gut wall. In the next three days you'll learn how to build enough well-tolerated protein into a gentle, recovery-supporting diet.

Summary

The past days have been about feeding your flora – now it's about you. Protein is the building material from which your body rebuilds itself: the muscles, the immune system, the healing gut wall. After a long, exhausting infection, your body has a heightened need for it. In the next three days you'll learn how to take in enough well-tolerated protein while keeping your diet gentle and easy to digest. The goal is for every main meal to have a good protein source.

Why is protein important in recovery?

Protein is the raw material of the human body: from it are built the muscles, the skin, the cells of the gut wall and the defensive molecules of the immune system. During a prolonged Clostridioides difficile^[G] infection the body loses a great deal of protein – the persistent diarrhoea, the loss of appetite and the inflammation all use up the reserves. That is why, during the recovery phase, adequate protein intake is a basic requirement: it provides the raw material for your body to rebuild itself.

Protein has a particularly important role from the gut's point of view too: it contributes to the regeneration of the gut wall. The gut lining is a very rapidly renewing tissue, and this requires a continuous supply of building material. While fibre feeds the flora, protein strengthens the "wall" itself – together they help the gut barrier to recover and resist pathogens better.

One practical trick helps a lot: spread the protein out over the course of the day, and start as early as breakfast. Many people eat hardly any protein in the morning and then a large amount all at once in the evening – yet the body makes best use of it when it comes evenly. If you pair a good protein source with every main meal, and breakfast isn't skipped either, your body gets a continuous supply for healing.

What does a gentle, protein-rich diet look like?

"Gentle" here means: easy to digest, not overburdening your healing gut, yet nourishing. Well-tolerated protein sources are generally the lean, softly prepared foods: boiled or steamed chicken and turkey, lean fish, eggs, well-cooked legumes in small portions, plain dairy if you tolerate it. The method of preparation matters here too: steaming, boiling and roasting without fat are gentler than dishes fried in plenty of oil, spicy and heavy.

For now it's worth avoiding overly fatty, heavily spiced, breaded or hard-to-digest meat dishes, as these can overburden your gut and cause bloating and discomfort. Be cautious likewise with very large, single portions: smaller, more frequent meals are better tolerated now. Legumes – although excellent protein sources, rich in fibre too – are best at first in small portions and well cooked, so they don't cause gas.

Tie together what you've learned so far. An ideal plate in these days looks like this: an easy-to-digest protein source (say, steamed chicken breast), alongside a portion of gentle fibre (steamed vegetables or a spoonful of cooked legumes), and as many kinds of plant as possible for your weekly 30 list. This way, in a single meal, you feed your flora and build your body – this is exactly the essence of the gentle, recovery-supporting diet.

The good fats: omega-3

Alongside protein, it's worth saying a word about the quality of fats too, because not all fats are alike. There is one particularly valuable group, the omega-3 fatty acids^[G], which have a marked anti-inflammatory effect – exactly what's welcome after a prolonged infection. On top of that, they also support the healing gut wall: they contribute to keeping the gut barrier intact and resilient.

The best sources of omega-3 are oily sea fish (salmon, mackerel, herring, sardine), and on the plant side flaxseed and flaxseed oil, as well as walnuts. You don't need a large amount: two or three portions of oily fish a week, or a spoonful of ground flaxseed on your oats daily, or a handful of walnuts, already makes a real difference (the serving amount comes from cardiovascular guidance: Kris-Etherton et al., 2002 [129]). Prepare the fish gently too – steamed or roasted, not fried in plenty of oil – so as not to overburden your healing gut.

🩺 Clinical block

Adequate protein intake is a key factor in post-infectious convalescence: in multimorbid medical inpatients a deteriorating nutritional state is an independent risk factor, so meeting energy and protein targets is a priority (Gomes et al., 2018 [133], ESPEN); the geriatric sarcopenia literature shows that sufficient protein intake attenuates muscle loss (Deutz et al., 2014 [099]) – extending this to rCDI with persistent diarrhoea and a catabolic state is an analogy. Butyrate^[G] is the primary energy substrate of the colonocytes and, together with the other SCFA products^[G] of the fibre-degrading flora, modulates the integrity of the mucosal barrier (Hamer et al., 2008 [062]); sufficient enteral protein intake is in turn a general precondition of tissue regeneration (Wu, 2013 [091]). No human data directly examining the combined, post-FMT synergy of the two pathways are available.

Even daily distribution of protein (particularly morning protein intake) is more favourable for synthesis than a single large evening portion: at identical total daily intake, even distribution produced higher 24-hour muscle protein synthesis in healthy adults (Mamerow et al., 2014 [128]) – this has not been studied in convalescing gastrointestinal patients. The gentle, low-fat and low-spice preparation aims, in the healing gut, to reduce discomfort and motility disturbance – the link between high fat intake and symptom burden is described by a systematic review in functional dyspepsia (Duncanson et al., 2018 [131]), though that is a different patient group, so this is a guiding analogy rather than direct evidence; the gradual, well-cooked introduction of legumes balances high protein and fermentable fibre content against tolerability (FODMAP^[G] consideration): the link between fermentable carbohydrates and gut symptoms was demonstrated by a randomised dietary trial in IBS (Halmos et al., 2014 [070]), while the recommendation on the portion size and preparation of legumes is a practical analogy derived from it. In immunosuppressed patients, raw-material hygiene (thoroughly cooked meat, pasteurised products, avoidance of raw or insufficiently heat-treated foods) is especially important: in vulnerable groups the risk and severity of foodborne infection is substantially greater (Lund 2015 [130]).

Fatty-acid quality is an independent modulating factor: omega-3 polyunsaturated fatty acids (EPA, DHA in sea fish; ALA in flaxseed, walnuts) act through anti-inflammatory eicosanoid and resolvin mechanisms, and they also modify microbiota composition – though in a mixed direction: in human supplementation studies the proportion of Faecalibacterium falls, while Bacteroidetes and the butyrate-producing Lachnospiraceae increase (Costantini et al., 2017 [066]). A balanced omega-6/omega-3 ratio favours SCFA-producing genera over pro-inflammatory, LPS-producing bacteria (Zou et al., 2025 [093]), and EPA/DHA dampens the inflammatory cascade (Calder, 2017 [065]); this has not been examined directly in post-FMT convalescence – the relevance is a mechanistic extrapolation.

The choice of protein source is also worth weighing from a food-safety perspective. Poultry meat is an excellent biological raw material; the effect on the human gut flora of any residues of the antibiotics and coccidiostats used in husbandry has, however, not been studied. As a precaution – not because of a demonstrated risk – we prefer meat from pastured animals during convalescence. This is our practical consideration, not a recommendation from the literature.

Day 37 – Protein at breakfast

Today we start with the most frequently skipped meal: breakfast. A good protein source in the morning kicks off the day's healing supply.

Add a protein source to breakfast: egg, plain yoghurt, or a small portion of lean cheese;
Keep the morning fibre too (oats, fruit) – protein and fibre together;
Prepare it gently: boiled or steamed, not fried in plenty of oil;
Diary: stool count, Bristol, bloating, fluids; the breakfast protein source.

Day 38 – Protein at every main meal

Today we extend it: let every main meal have a well-tolerated protein source, in gentle form.

Pair a protein source with lunch and dinner too (steamed chicken, lean fish, egg);
Avoid fatty, breaded, heavily spiced meat dishes today;
Rather smaller, more frequent portions than one large, heavy dish;
Bring in an excellent fat and omega-3 source: a portion of oily sea fish, or a spoonful of ground flaxseed on your oats, or a handful of walnuts;
Diary: stool count, Bristol, bloating, fluids; the day's protein sources.

Day 39 – The complete plate

Today we put together what you've learned: protein, gentle fibre and plant diversity^[G] on a single plate.

Assemble a "complete plate": a protein source + a gentle fibre + as many kinds of plant as possible;
If you use a legume as protein, eat it in a small portion and well cooked;
Notice whether there's less bloating with the gentle preparation;
Diary: stool count, Bristol, bloating, fluids; the plate's composition and tolerability.

🍽️ Eating during these days

The theme of these three days is protein and the gentle diet, and the three days' concrete eating task builds on this: put a well-tolerated protein source (egg, plain yoghurt, lean cheese) into breakfast already, alongside the morning fibre (day 37); then pair a gentle protein source (steamed chicken, lean fish, egg) and a good omega-3 source with every main meal (day 38); and finally put together the "complete plate": a protein source + a gentle fibre + as many kinds of plant as possible (day 39). The preparation throughout is gentle: boiled, steamed, not in plenty of oil.

The Plant Calendar (Appendix F) recommends gentle, pectin-rich fruit for these days: kiwi (day 37), pear (day 38) and strawberry (day 39). These days fall into the calendar's "gradual expansion" (days 31–50) phase, where the goal is to gradually increase plant diversity and fermentable fibre intake. The soluble fibre (pectin) of kiwi and pear gently supports regularity, and strawberry is a polyphenol source; fermentable fibre is substrate for fibre-degrading bacteria, from which short-chain fatty acids, including butyrate, are formed – this nourishes and regenerates the healing gut wall, exactly the surface that protein also builds. So the diversity of fruit and protein act complementarily in mucosal healing.

📊 Data

During these days, record daily:

DiffBiome dose (capsules/day) and LOT number, if the course is still ongoing;
daily stool count;
stool Bristol scale (1–7), with 3–4 as the target;
bloating (0–5);
bloody stool (yes/no);
fluid intake (litres);
the day's protein sources, with particular attention to the morning protein;
wellbeing (1–5);
Movement: type + minutes, step count (target/actual);
Stress level (1–5) and mood (1–5);
Sleep (hours + quality 1–5).

Why does this matter?

Recovery needs building material, and that building material is protein: from it your muscles, your immune system and your healing gut wall renew themselves. In these days you learned how to take in enough well-tolerated protein in a gentle diet – spread over the day, starting at breakfast already. And the best part: on a single smart plate you can simultaneously feed your flora (fibre, plant diversity) and build your body (protein). In the next three days we'll talk about meal timing.

References

[062] Hamer HM, Jonkers D, Venema K, Vanhoutvin S, Troost FJ, Brummer RJ. The role of butyrate on colonic function. Aliment Pharmacol Ther. 2008. Link

Narrative review summarizing the bioactivity of butyrate — a SCFA produced by colonic microbial fermentation of dietary fibre — and its mechanisms in human colonic function. Butyrate is the primary energy source for colonocytes and modulates inflammation, carcinogenesis, mucosal barrier integrity, oxidative stress, permeability, and satiety. The review consolidates evidence on butyrate as a central effector of colonic homeostasis and a target for dietary interventions in colonic disease.

[065] Calder, P. C. Omega-3 fatty acids and inflammatory processes: from molecules to man. Biochem Soc Trans. 2017. Link

Review of omega-6 and omega-3 fatty acid roles in inflammation. EPA and DHA from oily fish or fish-oil supplements partly inhibit leucocyte chemotaxis, adhesion molecule expression, leucocyte-endothelial interactions, and the production of arachidonic-acid-derived eicosanoids and pro-inflammatory cytokines. EPA-derived eicosanoids are typically less potent than those from arachidonic acid, and EPA/DHA give rise to anti-inflammatory and inflammation-resolving mediators (resolvins, protectins, maresins), supporting their use in inflammatory conditions.

[066] Costantini L, Molinari R, Farinon B, Merendino N. Impact of Omega-3 Fatty Acids on the Gut Microbiota. Int J Mol Sci. 2017. Link

Long-term dietary habits shape host-specific gut microbiota, but dietary fat effects are less well characterised than those of carbohydrates. The few adult human omega-3 PUFA supplementation studies show consistent changes: decreased Faecalibacterium, increased Bacteroidetes and butyrate-producing Lachnospiraceae. Because dysbiosis of these taxa occurs in inflammatory bowel disease, omega-3 PUFAs may exert a beneficial effect by restoring microbial composition and increasing anti-inflammatory short-chain fatty acid production.

[070] Halmos EP, Power VA, Shepherd SJ, Gibson PR, Muir JG. A diet low in FODMAPs reduces symptoms of irritable bowel syndrome. Gastroenterology. 2014. Link

Randomised single-blind cross-over trial in 30 IBS patients and 8 controls compared a low-FODMAP diet (<0.5 g/meal) with a typical Australian diet for 21 days each (>=21-day washout). Almost all food was provided. The low-FODMAP arm produced significantly greater reduction in IBS symptoms measured on 0-100 mm visual analogue scales, supporting the low-FODMAP diet as an effective intervention for symptom control in IBS compared with a standard Western diet.

[091] Wu, G. Functional amino acids in nutrition and health. . 2013. Link

The recent years have witnessed growing interest in biochemistry, physiology and nutrition of amino acids (AA) in growth, health and disease of humans and other animals. This results from the discoveries of AA in cell signaling involving protein kinases, G protein-coupled receptors, and gaseous molecules (i.e., NO, CO and H2S). In addition, nutritional studies have shown that dietary supplementation with several AA (e.g., arginine, glutamine, glutamate, leucine, and proline) modulates gene expression, enhances growth of the small intestine and skeletal muscle, or reduces excessive body fat. These seminal findings led to the new concept of functional AA, which are defined as those AA that participate in and regulate key metabolic pathways to improve health, survival, growth, development, lactation, and reproduction of the organisms. Functional AA hold great promise in prevention and treatment of metabolic diseases (e.g., obesity, diabetes, and cardiovascular disorders), intrauterine growth restriction, infertility, intestinal and neurological dysfunction, and infectious disease (including viral infections).

[093] Zou T, Zhao Y, Zhou X, Kang Y, Wang X. Insight into the effects of Omega-3 fatty acids on gut microbiota: impact of a balanced tissue Omega-6/Omega-3 ratio. Front Nutr. 2025. Link

Review of how omega-3 fatty acids and a balanced tissue omega-6:omega-3 ratio shape gut microbiota composition and function: a high ratio favours pro-inflammatory/LPS-producing bacteria, a balanced ratio favours SCFA-producers (Bifidobacterium, Roseburia, Lactobacillus); supports a personalized dietary approach based on fatty-acid ratios.

[099] Deutz NE, Bauer JM, Barazzoni R, Biolo G, Boirie Y, Bosy-Westphal A, Cederholm T, Cruz-Jentoft A, Krznaric Z, Nair KS, Singer P, Teta D, Tipton K, Calder PC. **. Clinical Nutrition. 2014. Link

Ageing brings a gradual, progressive loss of muscle mass, strength and physical endurance (sarcopenia), most marked in sedentary older adults. This ESPEN Expert Group review concludes that regular aerobic and resistance exercise counteracts most aspects of sarcopenia, and that adequate protein and energy intake helps limit and treat age-related declines in muscle mass, strength and function. The group recommends a higher dietary protein intake than the traditional 0.8 g/kg/day — about 1.0–1.2 g/kg body weight per day for healthy older adults and 1.2–1.5 g/kg/day for those with acute or chronic illness — combined with physical activity. The aim is to preserve muscle function, mobility and independence in later life.

[128] Mamerow MM, Mettler JA, English KL, Casperson SL, Arentson-Lantz E, Sheffield-Moore M, Layman DK, Paddon-Jones D. Dietary protein distribution positively influences 24-h muscle protein synthesis in healthy adults. J Nutr. 2014. Link

Randomised crossover study in **healthy adults**: at identical total daily protein intake, an **evenly distributed** pattern (about 30 g protein at breakfast, lunch and dinner) was compared with the usual **evening-skewed** pattern (little in the morning, much at night). 24-hour muscle protein synthesis was **significantly higher** with even distribution. This entry is the source for the III.5 claim that distributing protein across the day — particularly protein at breakfast — is preferable to a single large evening portion. **IMPORTANT LIMITATION:** healthy adults, with muscle protein synthesis as the endpoint; the study was **not** conducted in convalescing gastrointestinal patients and did **not** measure intestinal mucosal regeneration.

[129] Kris-Etherton PM, Harris WS, Appel LJ. Fish consumption, fish oil, omega-3 fatty acids, and cardiovascular disease. Circulation. 2002. Link

American Heart Association scientific statement on fish consumption, fish oil and omega-3 fatty acids. It is the origin of the familiar practical recommendation: **at least two servings of (preferably oily) fish per week**, plus plant-source ALA (flaxseed, walnuts). **IMPORTANT LIMITATION — decisive for the handbook:** this statement concerns **cardiovascular prevention**. It addresses neither intestinal mucosal healing, nor post-FMT convalescence, nor microbiota composition. In III.5 it is therefore used **solely as the source for the practical serving amount**; the mucosal and microbiota effects are sourced to ref-066, ref-093 and ref-065.

[130] Lund, B. M. Microbiological Food Safety for Vulnerable People. Int J Environ Res Public Health. 2015. Link

Review of microbiological food safety for **vulnerable groups** — the immunosuppressed, transplant recipients, cancer patients, pregnant women, older people and young children. The author summarises that in these groups the risk and severity of foodborne infection (Listeria, Salmonella, Campylobacter, E. coli) is **substantially greater**, and that this can be reduced in part through **food choice and handling**: thoroughly cooked meat, pasteurised dairy, avoidance of raw or insufficiently heat-treated foods, and adherence to the cold chain and cross-contamination prevention. This entry is the source for the III.5 claim that raw-material hygiene is especially important in immunosuppressed patients. **LIMITATION:** a review, not an interventional study; not conducted in an FMT or CDI population.

[131] Duncanson KR, Talley NJ, Walker MM, Burrows TL. Food and functional dyspepsia: a systematic review. J Hum Nutr Diet. 2018. Link

Systematic review of which foods and nutrients trigger or worsen the symptoms of functional dyspepsia (FD) — early satiety, post-prandial fullness and epigastric pain. Sixteen of 6451 screened publications met the inclusion criteria. The authors report that a **high-fat diet** is associated with FD symptoms; wheat-containing foods appeared as symptom triggers in six studies. This entry is the source for the III.5 claim that **low-fat, gentle preparation** reduces symptom burden. **IMPORTANT LIMITATION:** the studies were conducted in **adults with functional dyspepsia** — not in patients convalescing after CDI — and did not separately measure the effect of spicing, breading or cooking method. In III.5 it therefore serves as a **guiding analogy, not direct evidence**.

[133] Gomes F, Schuetz P, Bounoure L, Austin P, Ballesteros-Pomar M, Cederholm T, Fletcher J, Laviano A, Norman K, Poulia KA, Ravasco P, Schneider SM, Stanga Z, Weekes CE, Bischoff SC. **. Clin Nutr. 2018. Link

ESPEN guideline on nutritional support for **polymorbid internal medicine patients** — the population closest to someone convalescing from a protracted infection. The guideline records that in this group **deterioration of nutritional status is common and an independent risk factor**, so intake must be screened and monitored, and **energy and protein targets must be met** rather than intake being restricted. Sustained energy and protein deficit worsens the catabolic state and muscle loss, can impair recovery and may increase complications. This entry is the source for the III.6 claim that **fasting-type protocols are not advisable during convalescence**. Important: the guideline is not about time-restricted eating; it states that in the convalescing polymorbid patient the goal is to SECURE intake.