Refsum disease is one of those rare conditions where your dietitian is, quite literally, your most important medical specialist. Caused by mutations in the PHYH (formerly PAHX) gene or, less commonly, the PEX7 gene, it impairs the body's ability to break down phytanic acid — a branched-chain fatty acid found in chlorophyll-containing foods and the fat of ruminant animals. When phytanic acid accumulates, it damages peripheral nerves, the retina, cerebellum, and heart.
Here is what many South Africans with Refsum disease are not told: rapid weight loss is dangerous. Fat cells store phytanic acid, and when you lose weight too fast, stored phytanic acid floods your bloodstream, triggering acute neurological crises — retinal deterioration, loss of smell, cerebellar ataxia, and even cardiac arrhythmias. This makes weight management in Refsum disease genuinely different from ordinary dieting.
Refsum disease (hereditary motor and sensory neuropathy type IV, or HMSN IV) is classified as a peroxisomal disorder. The peroxisome is the cellular organelle responsible for alpha-oxidation of phytanic acid. When this pathway is broken, phytanic acid — which cannot be eliminated any other way — accumulates in fat, blood, and nerve myelin.
Weight gain in Refsum disease typically results from:
The cruel paradox: excess body fat = more phytanic acid stored = worse long-term prognosis. Yet losing weight too fast = acute phytanic acid release = immediate neurological crisis.
Unlike most conditions where diet is a supplement to medication, dietary phytanic acid restriction is the treatment for Refsum disease. No drug currently replaces it. The goal is to limit dietary phytanic acid to under 10 mg per day (some guidelines say <20 mg); normal Western diets deliver 50–100 mg daily.
| Food Category | High-Phytanic Sources | South African Examples |
|---|---|---|
| Dairy fat | Full-cream milk, butter, ghee, cream, hard cheese | Clover butter, Lancewood cheddar, Parmalat full-cream |
| Ruminant meat fat | Beef fat, lamb fat, mutton fat | Fatty biltong, fatty boerewors, mutton chops with fat |
| Oily fish | Tuna, herring, sardines, mackerel, salmon (skin) | Lucky Star pilchards, tinned tuna |
| Ruminant liver/organs | Beef liver, ox kidney, tripe (mogodu) | Mogodu stew, offal braai items |
| Chlorophyll (indirect) | Green plant foods contribute phytol, a phytanic acid precursor | Spinach, morogo — limit large quantities |
| Food Group | Safe Choices | Notes |
|---|---|---|
| Protein | Lean chicken breast, pork loin, eggs (whites OK, yolks moderate), legumes | Trim all visible fat from meat |
| Carbohydrates | Brown rice, mielie meal (pap), sweet potato, oats, sorghum | Low GI preferred for weight control |
| Fats | Sunflower oil, canola oil, olive oil (not butter) | Plant oils contain no phytanic acid |
| Fruits | All fruits — apples, bananas, mango, citrus, pawpaw | Free of phytanic acid |
| Vegetables | Tomatoes, carrots, butternut, onions, peppers | Cooked greens in moderation |
| Dairy | Skimmed/fat-free milk, fat-free yoghurt, fat-free cottage cheese | Fat removal eliminates most phytanic acid |
If you need to lose weight with Refsum disease, the approach must be gradual, sustained, and medically supervised. Here is a framework used by metabolic dietitians:
This is the maximum safe rate of weight loss. It equates to a calorie deficit of roughly 250–500 kcal/day — achieved mostly through dietary quality improvements and gentle activity increases, not crash dieting.
Fasting triggers fat mobilisation — exactly what you want to avoid in Refsum disease. Even intermittent fasting protocols (16:8, OMAD) are contraindicated unless your metabolic team has specifically cleared them with phytanic acid monitoring in place.
Spread calories evenly across 3–4 meals. Consistent fuelling prevents the body from dipping into fat stores rapidly. A useful South African meal template:
While losing weight, request plasma phytanic acid tests every 2–3 months. If levels rise during a weight loss phase, slow the rate of loss immediately. In South Africa, this test is available through NHLS (National Health Laboratory Service) and most private pathology labs including Ampath and Lancet.
Exercise is essential for weight management, cardiovascular health, and neurological stability in Refsum disease — but it must be adapted to your neurological status.
Some South African patients with severe Refsum disease undergo plasmapheresis (plasma exchange) to rapidly lower phytanic acid levels — particularly at diagnosis or during acute crises. After plasmapheresis, weight management becomes easier because phytanic acid levels are already reduced, and there is less risk of mobilisation-triggered crisis. This is typically done at academic hospitals (Groote Schuur, Tygerberg, Steve Biko, Chris Hani Baragwanath).
Phytanic acid restriction can occasionally limit certain nutrients. Discuss these with your dietitian:
Refsum disease is rare — most South African GPs will have never managed a case. Seek referral to:
Managing a rare metabolic condition through diet is genuinely complex work.
Bookmark this page and share it with your dietitian and metabolic team. For more condition-specific weight management guides, explore our full library at WeightLossDiets.co.za.
Disclaimer: This article is for educational purposes only and does not constitute medical advice. Refsum disease requires specialist medical management. Always consult your metabolic physician, neurologist, and registered dietitian before making any dietary changes. Sources: Komen et al. (2007) Brain; Wanders RJA (2014) Biochim Biophys Acta; OMIM #266500; NHLS test directory.