After undergoing gastric sleeve surgery, it’s absolutely vital to stay on top of your nutrition. The surgery doesn’t just reduce your stomach size – it also changes how your body absorbs nutrients.
This issue tends to be more pronounced after a gastric bypass, but even with a sleeve, deficiencies can develop quickly if you’re not proactive. We’ve both learned that first-hand – James developed iron deficiency anaemia within the first year, and managing that has become part of our long-term health routine.
Here’s what we’ve learned about staying nourished and balanced post-surgery, and what your body really needs to function at its best.
Understanding Nutrient Absorption After Surgery
Before surgery, your stomach played a key role in breaking down food and releasing digestive enzymes that helped you absorb vitamins and minerals effectively. After the sleeve, your smaller stomach produces fewer of those enzymes and less acid, meaning some nutrients – particularly iron, calcium, and vitamin B12 – are harder to absorb.
This doesn’t mean you’re doing something wrong – it’s simply how the body adapts. But it does mean you’ll need to be more intentional about what you eat and how you supplement.
Iron
Iron is one of the most common deficiencies after gastric sleeve surgery. It’s essential for making haemoglobin – the protein in red blood cells that carries oxygen around your body.
When iron is low, you might notice symptoms like:
- Constant fatigue or weakness
- Dizziness or light-headedness
- Pale skin or cold hands and feet
- Shortness of breath, even with light activity
James experienced this about 11 months post-op. Despite eating well, his blood tests showed iron deficiency anaemia. His GP explained that his smaller stomach wasn’t releasing enough acid to absorb the iron properly from food.
How to Increase Your Iron Intake
Iron-rich foods:
- Lean red meat (especially beef)
- Chicken and Turkey
- Pork
- Beans, lentils, and chickpeas
- Leafy greens like spinach and kale
If you’re not a fan of greens, try blending spinach or kale into smoothies or soups – you’ll barely taste it but still get the benefit.
Supplements:
If diet alone isn’t enough (and it often isn’t), your GP may recommend iron tablets or liquid iron supplements. Always take these separately from calcium, as the two compete for absorption.
Keeping your iron levels balanced helps prevent fatigue and supports long-term recovery and energy.
Calcium
Calcium is essential for bone health – and after surgery, your ability to absorb it can drop significantly.
Over time, low calcium can lead to bone thinning (osteopenia or osteoporosis). It’s especially important for anyone who isn’t getting enough dairy or fortified alternatives in their diet.
How to Increase Your Calcium Intake
Food sources:
- Milk, yoghurt, cheese
- Leafy greens like kale and broccoli
- Fortified plant milks such as almond, oat, or soy
If your blood tests show low calcium, your GP will likely recommend calcium citrate (not carbonate, as it absorbs better post-surgery) alongside vitamin D3, which helps your body use the calcium effectively.
We both take calcium and vitamin D3 daily – one of the simplest but most important habits to maintain strong bones and teeth long-term.
Vitamin B12
Vitamin B12 supports your nervous system, helps form red blood cells, and aids DNA production. After gastric sleeve surgery, your stomach produces less intrinsic factor – a protein that helps absorb B12 – making it common for patients to become deficient.
Symptoms of Low B12 Include:
- Memory issues or brain fog
- Tingling or numbness in fingers and toes
- Fatigue or mood changes
Because absorption is tricky, many patients need injections or sublingual (under-the-tongue) tablets rather than standard oral supplements.
We both receive regular B12 monitoring through our GP. James’s multivitamin now includes the full B12 dose, while Kirsten continues to take additional B12 tablets daily as part of her supplement plan.
Regular Follow-Up Appointments
Your nutritional needs won’t stay static – they’ll evolve over time. That’s why regular blood tests are essential, especially during the first 18 months post-surgery.
Your GP or bariatric team will typically check:
- Iron and ferritin
- Vitamin B12
- Folate
- Vitamin D and calcium
- Liver function
- Electrolyte balance
Early detection means deficiencies can be corrected before they cause long-term issues.
How We Track Our Nutrition
Tracking isn’t about perfection – it’s about awareness. Here’s what we do to stay on top of things:
- Log food intake: We use a simple tracker to ensure our meals include enough protein, iron, and calcium.
- Meal prep: Prepping a few nutrient-rich meals each week stops us reaching for quick fixes.
- Fluid intake: We aim for at least 2 litres of water or non-protein liquids daily (excluding shakes).
- Supplement schedule: Sticking to a set supplement routine prevents gaps – we take ours at specific times across the day.
Even now, over a year later, this structure helps us stay consistent without overthinking it.
Good nutrition isn’t just about weight loss – it’s about protecting your long-term health. After gastric sleeve surgery, deficiencies can creep up slowly and silently, but they’re easy to prevent with the right habits.
We’ve learned that eating well and supplementing properly make all the difference. When your nutrition is balanced, your energy returns, your healing speeds up, and your overall quality of life improves.
Disclaimer: This post is based on our personal experience. It is not medical advice. Always consult your GP or bariatric dietitian before making any changes to your supplement or nutrition plan.