The “M35.4 diet” does not exist
Type “diet for eosinophilic fasciitis” into Google and you will land on dozens of pages promoting miraculous anti-autoimmune diets. Most of them rest on very weak evidence or on extrapolation from other diseases. Honestly, the state of knowledge today:
No clinical trial has shown that any diet is effective in treating M35.4. Diet does not replace pharmacotherapy. But specific dietary rules do matter — mainly because of the drugs you are taking, not the disease itself.
This distinction is crucial. Most dietary recommendations for an M35.4 patient stem from treatment side effects, not from the disease itself.
Diet during steroid therapy
Systemic steroids — primarily prednisone — have many metabolic effects, some of which diet can partly counter:
- Increased appetite — the feeling of hunger is often disproportionate to caloric need. Strategy: stick to three set meals plus one or two smaller snacks; plan them rather than grazing.
- Sodium retention — steroids hold on to sodium and water, which raises blood pressure and causes swelling. Cut salt (target: under 5 g a day). Watch for hidden salt: bread, cured meats, hard cheeses, ready meals.
- Potassium loss — steroids increase potassium excretion. Increase intake: tomatoes, jacket potatoes, bananas, dried apricots, avocados, legumes.
- Risk of steroid-induced diabetes — limit simple sugars and refined carbohydrates; choose whole grains; eat protein with every meal (stabilises blood sugar). Monitor fasting blood glucose regularly, and consider HbA1c.
- Risk of osteoporosis — increase calcium intake (target: ~1000–1200 mg/day): dairy, sardines, broccoli, tofu. Remember vitamin D (supplementation is usually advised — see below).
The scale of steroids’ effect on weight: typical weight gain in the first 3–6 months of treatment is 3–8 kg. This is not “your poor discipline”. This is biology. Most patients return to their baseline weight 6–12 months after the dose is reduced — without an aggressive diet.
An indicative curve: in the first high-dose months on prednisone, body weight rises by 3–8 kg. Once the dose is reduced, most patients return to baseline within 6–12 months.
The rise is driven by two mechanisms: prednisone increases appetite (especially for salt and carbohydrates) and shifts fluid balance, adding 1–2 kg of water on top of real fat gain. The peak almost always falls during the high-dose induction window; once the taper crosses 20 mg/day, weight starts coming back down. Patients who keep a daily food log lose the steroid weight 2–3 months faster than those who don't. Crash diets during the induction phase do not work — the body is in active fluid retention, not in caloric overshoot.
general rheumatology data · UpToDate
Methotrexate and food
If you are in second-line treatment and take methotrexate (MTX), a few things to remember:
- Folic acid is absolutely essential with MTX — most often 5 mg once a week, on a different day from the MTX dose. Without it, the risk of side effects (mucositis, hepatotoxicity) is significantly higher.
- Alcohol and MTX are a very bad combination — both stress the liver. Common advice: at most 1–2 units of alcohol per week, ideally none. Over time, in remission, milder limits can be considered with your clinician.
- Hydration — drink plenty of water on the day you take MTX and for the next 24 hours (target: ~2 litres); this helps the kidneys clear the drug.
- An abundance of folate-rich food (leafy greens, supplements) does not impair MTX’s action — that is a myth. Folic acid supplementation is in fact the standard recommendation.
- Vitamin B12 — may be indicated, especially with long-term MTX; it should be measured.
Anti-inflammatory diet — what we actually know
The idea of a diet that lowers “general” inflammation in the body is attractive. The scientific evidence is mixed — in some autoimmune diseases (e.g. rheumatoid arthritis) modest but present. In M35.4 — no dedicated studies. Nevertheless, most anti-inflammatory diet recommendations overlap with the Mediterranean diet, which has the strongest evidence in cardiology and general longevity. In short: if it is worth following anyway, the risk is minimal.
Specific rules where the greatest agreement of evidence exists:
- Fatty fish 2–3 times a week (salmon, mackerel, sardines) — omega-3 fatty acids
- Vegetables of varied colours — 5+ portions a day, including cruciferous vegetables (broccoli, cauliflower, kale)
- Fruit 2–3 portions a day, including berries (blueberries, raspberries, blackberries)
- Olive oil as the basic fat
- Whole-grain products instead of refined ones
- Nuts and seeds every day (small portion)
- Limit red and processed meat
- Limit added sugars and ultra-processed foods
- Strongly limit alcohol (especially on MTX)
What we do not recommend without consultation: elimination diets (gluten, dairy, AIP), multi-day fasting, “detoxes”, “megadose” supplements. In an autoimmune disease, aggressive dietary restrictions without a dietitian’s supervision can do more harm than good.
Supplementation — what makes sense
Supplements are overhyped as a category, but with M35.4 + steroid therapy + MTX a few of them are justified:
- Vitamin D₃ — in Poland, supplementation is widely recommended from autumn to spring (1000–2000 IU/day for adults). With long-term steroid therapy — year-round. Best to measure 25(OH)D at baseline and adjust.
- Calcium — from diet if possible; supplement (500–1000 mg/day) if diet does not cover the need (target: 1000–1200 mg/day on steroid therapy)
- Folic acid — with MTX (5 mg once a week, regimen with your clinician)
- Magnesium — for muscle cramps or sleep disturbances (200–400 mg/day citrate)
- Vitamin B12 — with long-term MTX; measure and supplement if deficient
- Omega-3 (EPA + DHA) — if you do not eat fish regularly; 1–2 g/day EPA+DHA
A priority list if you are on steroids and / or methotrexate. Every supplement should be agreed with your clinician — this is not a free-for-all from the drugstore shelf.
- Priority (1–5)
Two supplements are essentially non-negotiable: vitamin D₃ on long-term steroids, and folic acid alongside methotrexate. Skipping either is a documented mistake — vitamin D prevents the bone-density loss that begins within the first months on prednisone, and folic acid sharply reduces methotrexate's mucosal and hepatic toxicity. Calcium is the natural partner of vitamin D — ideally from food, supplemented when dietary intake falls short. Vitamin B12, magnesium and omega-3 sit lower on the priority list — useful in specific clinical contexts but not mandatory. Anything beyond this list belongs in a conversation with the treating clinician, not on a drugstore shelf.
rheumatology recommendations · ACR · MTX literature
Supplementation should be agreed with your treating clinician. Some supplements (e.g. vitamin K, St John’s wort, “immune-boosting” supplements) can interact with immunosuppressive drugs. Always tell the treating team what you are taking.
What to actually avoid
Instead of elimination diets — a short list of concrete things worth limiting during active M35.4 treatment:
- Raw / undercooked meat, seafood, raw eggs, unpasteurised dairy — infection risk for someone on immunosuppression
- Mould-ripened cheeses at high immunosuppression doses — risk of listeriosis
- Unwashed fruit and vegetables from an untrusted source
- Alcohol — especially on MTX and high steroid doses
- Salt in excess (see: steroids)
- Simple sugars and heavily processed foods (see: steroid-induced diabetes risk)
- Grapefruit juice — can interact with some immunosuppressants (check with your clinician for the specific drug)
- “Immune-boosting” supplements without consultation — some stimulate the immune system, which is undesirable in an autoimmune disease
The rest is simply sensible eating, the kind a dietitian would recommend to anyone living with a chronic illness: regular meals, plenty of vegetables, little processed food, and — in doubt — a consultation.