When preparing for weight-loss surgery or making lifestyle changes, such as using GLP 1 medications for weight management, good nutrition is essential.
Supplements can play a role in filling gaps or supporting specific health goals, but they should never replace a healthy, balanced diet.
Your foundation should always be:
- Adequate protein from foods such as fish, lean meat, dairy, soya, lentils and beans to preserve muscle mass.
- Plenty of fibre from wholegrains, legumes and pulses to support gut health and keep blood sugar steady.
- A wide range of vitamins and minerals from whole foods such as fruits and vegetables.
- Some healthy fats from oily fish, nuts, seeds, avocados and olive oil.
When considering taking new supplements, it’s always best to do so in discussion with your surgeon, GP, dietitian, nurse or healthcare team, especially before surgery or if you are taking prescription medication.Below we explore some of the most common supplements, the evidence for and against them, and the practical take home message for each.
Protein Powder
Why people take it: Protein is crucial for muscle repair and maintenance, wound healing, and immune function - all vital before and after bariatric surgery. If you’re on a GLP 1 medication, your appetite may be reduced, so hitting your protein targets can be harder.Evidence for and against:
- For: Protein powders (whey, casein, soya, or pea) can help people meet their daily needs if they struggle to get enough from food. Whey protein is well studied and effective for supporting muscle protein synthesis.
- Against: Whole food sources like fish, poultry, eggs, beans, and dairy also rovide additional nutrients such as iron, zinc, and B vitamins. Over reliance on protein powders can mean missing out on these.
- Take home message: Aim for 1.2 to 1.6g of protein per kg of ideal body weight per day (at least 60-80g of protein a day), if you’re preparing for surgery or on GLP 1s, and use protein powder as a convenient top up rather than your main source.
Collagen
Why people take it: Collagen is a structural protein in skin, joints, and connective tissue. Interest in supplementation has grown for skin health, joint support, and wound healing.
Evidence for and against:
- For: Some studies, many funded by supplement companies, show collagen peptides can improve skin elasticity and hydration and may support joint comfort.
- Against: Collagen is broken down into amino acids in digestion, so your body can’t direct it specifically to the skin or joints. A balanced diet with enough protein and vitamin C will also provide the raw materials for collagen production.
- Take home message: If you enjoy taking collagen and can afford it, choose hydrolysed collagen peptides and combine them with vitamin C rich foods. But remember, adequate overall protein is just as important.
Creatine
Why people take it: Creatine supports short bursts of high intensity exercise and may help maintain muscle strength during periods of reduced activity, such as post surgery recovery.
Evidence for and against:
- For: Well researched for improving strength and lean mass when combined with resistance exercise. Some evidence also suggests benefits for brain health and recovery in older adults.
- Against: Benefits are most pronounced in people doing regular strength training. For sedentary individuals, the impact is smaller.
- Take home message: If you are resistance training pre or post surgery, 3-5g/day of creatine monohydrate is safe for most healthy adults. Stay well hydrated and check with your healthcare provider if you have kidney issues before starting.
Adaptogenic Mushrooms
Why people take it: Varieties such as reishi, lion’s mane, and cordyceps are promoted for immune support, energy, stress resilience, and cognitive health.
Evidence for and against:
- For: Some promising preliminary studies on certain mushroom extracts suggest potential immune modulating and anti inflammatory effects.
- Against: Most research is early stage, small scale, or in animals. Quality and potency vary hugely between brands.
- Take home message: They may be worth exploring as part of a healthy diet rich in mushrooms generally, but don’t expect dramatic results. Choose reputable brands and use them in addition to, not instead of, proven strategies like good sleep and nutrition.
Multivitamins
Why people take it: To cover general nutrient needs, particularly if diet quality is inconsistent.
Evidence for and against:
- For: Can be a useful “safety net” for people with restricted diets or reduced appetite (common on GLP 1s).
- Against: They are not a substitute for a balanced diet and often provide nutrients in amounts you already get from food.
- Take home message: A basic once a day multivitamin can be helpful if your food intake is reduced, but prioritise whole foods for the wider range of beneficial plant compounds they provide. Following bariatric surgery, you may be advised to take a multivitamin such as Forceval, a calcium and vitamin D supplement such as Calci D, an iron tablet such as ferrous fumarate (taken 2 hours away from the calcium supplement), and vitamin B12 injection every 3 months to prevent deficiencies.
Greens Powders
Why people take it: Marketed as a way to get concentrated fruit, vegetable, and herbal extracts.
Evidence for and against:
- For: May offer an easy source of certain vitamins and phytonutrients.
- Against: They don’t contain the same levels of fibre and diverse plant compounds as whole fruit and veg. Evidence for specific health benefits is limited.
- Take home message: Greens powders shouldn’t replace your 5 a day. They may be a useful travel back up, but whole fruit, vegetables, pulses, nuts, and seeds remain the gold standard.
Magnesium
Why people take it: Magnesium plays a role in muscle function, bone health, energy production, and sleep quality.
Evidence for and against:
- For: Helpful for those with low dietary magnesium (often due to low intake of nuts, seeds, leafy greens, and wholegrains). May help with mild sleep issues and muscle cramps.
- Against: If your diet is already rich in magnesium containing foods, supplements are unlikely to provide extra benefit.
- Take home message: Food sources should come first, but supplements (200-400mg/day) can be useful for people with low intakes or certain health conditions. Magnesium citrate or glycinate forms tend to be better absorbed.
Biotin
Why people take it: Biotin (vitamin B7) is marketed for healthy hair, skin, and nails.
Evidence for and against:
- For: True biotin deficiency is rare, but supplementation can improve symptoms in those with deficiency.
- Against: In healthy individuals, extra biotin has limited proven benefit. High doses can interfere with certain blood tests, including thyroid function and cardiac markers.
- Take home message: If you take biotin, stop at least 3 days before any blood test. For most people, biotin from a balanced diet (eggs, nuts, seeds, wholegrains) is sufficient.
Final Thoughts
For patients preparing for weight-loss surgery or using GLP 1 medications, supplements can support nutrition, but only when used on top of a diet rich in protein, fibre, vitamins, and minerals.
The best approach is to:
- Optimise your diet first with nutrient dense whole foods.
- Identify genuine gaps with the help of your healthcare team.
- Choose reputable brands with clear labelling and third party testing where possible.
- Avoid unnecessary mega dosing and remember that more isn’t always better.
Your health, recovery, and long term wellbeing depend more on daily habits than on any single supplement - but the right one, at the right time, can give your nutrition a helpful boost.