Anyone that caught my grocery cost-saving column on Monday may have done a double-take when it comes to my not-so-hot mathematical skills.

I'm unsure how, but I essentially told you all that 2 + 2 = 5 when it comes to comparing the cost of single and bagged apples. My over-riding message was that pre-packed bags of fruit are cheaper, but the maths I used to illustrate the point was completely wrong. When I went back to the store today on a sanity check, I did find that bags of apples were cheaper but bizarrely, pre-packed trays are not.

It seems that grocery stores can be just as bad as me when it comes to maths and actually charge you more for buying something in bulk.

I found out the same applied when I made a special trip to buy epic quantities of paper towel and toilet rolls. When I got home I discovered I'd saved approximately 14 cents – not worth the time or the effort – and then I had to find room for 80 loo rolls. So unfortunately, rather than using buying in bulk as a rule of thumb, you'll have to do a cost comparison each time – just don't ask me to do it for you!

What I can do is pass on one more cost-saving tip this Halloween – and that is, if you're carving out pumpkins for the kids, don't throw away the insides (aside from the seeds). Pumpkin makes brilliant soup and is great for warming everyone up as the weather gets colder. So cosy up with your little goblins and enjoy a hot mug of nutritious soup after the not-so-nutritious trick or treating!

Pumpkin Soup:

As pumpkin is currently in season, it's particularly good to cook with at this time of year – maximising both the flavour and nutrient content. Pumpkin is naturally rich in beta-carotene, folic acid, vitamin E and calcium. It is also lower in carbs than potato, yet provides you with enough energy to keep you going through the day.

One quick tip: it's generally best to eat meals and snacks that combine carbohydrates and protein together, as the protein helps to slow the release of the glucose from the carbohydrate. A slow release of glucose is ideal as it results in a steady, gentle energy supply, rather than a quick burst that's followed by a big dip (snooze time.) Therefore, you may like to add some protein to your soup – diced chicken, tofu or even a tablespoon of hummus all work really well in this recipe.

Ingredients:

2 ½ cups of skinned and chopped pumpkin

3 large tomatoes, skinned and chopped

4 sticks celery, chopped

1 large red onion, chopped

1 vegetable stock cube

¼ tsp ground coriander seed

1 tsp chili powder (mild or hot)

1 tsp cinnamon

black pepper

1 tbsp olive oil

4 8oz cups boiling water

Method:

1. Skin the tomatoes – it's very easy to do! Etch a shallow X in the top and bottom of each tomato, place in a heat-proof bowl and cover with boiling water for two minutes. You will see the skin split and begin to peel off. Drain, cover with cold water and peel/chop when cool enough.

2. Gently heat the olive oil in a large saucepan with one tsp water.

3. Add the chopped onion and celery, turn up the heat and stir for a few minutes. Then reduce the heat to 'simmer', cover the pan and let the vegetables sweat for a few minutes.

4. Uncover the pan and add four cups of boiling water.

5. Then add the pumpkin, chopped tomatoes, stock cube, coriander, chili powder and cinnamon.

6. Bring to the boil and then simmer for approx 25 minutes until the pumpkin is well cooked. Blend (you may have to do this in batches) until smooth.

This keeps in the fridge for three days and freezes well. Enjoy!

The advice given in this article is not intended to replace medical advice, but to complement it. Always consult your GP if you have any health concerns. Catherine Burns is a fully qualified Nutritional Therapist. She can be contacted at clinicalnutrition@gmail.com.