Marika Day: Testing old-fashioned food advice

Do carrots improve your vision? Are oysters an aphrodisiac? Does an apple a day really keep the doctor away?

When it comes to food, there is some value in folk wisdom. Many traditional cultures have passed down their own medicinal methods for generations, whether there is evidence backing them up or not. Oftentimes, there is such a strong cultural implication there that these ‘remedies’ probably do have a benefit, even if it's just though a placebo effect.

So strong beliefs can have an impact. Whether that means there is scientific truth to any of these practices, is a different thing.

Absolutely. Calcium is really important for bone strength, particularly in young people and the elderly. For the under-25s, we want to make sure they’re building enough bone, and for people over 60, we want to make sure that they're not losing bone too rapidly and they're maintaining bone strength. Milk or dairy products – like cheese and yoghurt – are a really good source of calcium, so this one does have merit to it, and is something that I would strongly recommend.

There is some theoretical basis for this: carrots are high in beta-carotene or vitamin A, and that nutrient does have a role in vision. I think the actual folk tale is that eating carrots helps you see in the dark, and I’ve heard that was spread by the British in WWII – they pretended their pilots had night vision from carrots to cover up the invention of radar. Obviously, it's not true in the sense that it would actually help your night vision. Eating carrots will not enable you to see in the dark. But there is a real mechanism behind the myth.

Oysters are high in zinc, and zinc plays a particular role in male fertility. So in that sense, there is some element of truth here – but it’s unlikely to have an immediate effect like, for instance, medication. Having adequate zinc-rich food is really important for men (and possibly also women) focusing on fertility. Meat products such as beef, lamb or turkey work well, as do non-meat-based foods like cashews, pepitas or pumpkin seeds.

I can’t say this is specific to cheese, but if you’re not digesting your food before bedtime, you may not sleep as well – which might be the basis of the nightmares. There is mixed research here. Some studies show that having carbohydrate-rich food before bed actually improves your REM sleep, because it increases tryptophan and serotonin in your brain and helps you get to sleep and stay asleep. On the other hand, having large meals and digesting when you're trying to nod off is not helpful.

It's really hard for tryptophan to cross the blood-brain barrier. When you eat a food, the nutrient goes into your blood and then, in order for it to have an effect in your brain, it's got to move through a barrier to your brain, which is really difficult to cross. Right now, it doesn't look like there's much tryptophan that gets across. We just don't know accurately at this time how much of an effect it has. I don't see any harm in having those sorts of things, and a lot of people will say if they have a banana, or a glass of milk, or turkey, they do feel better before they go to bed.

This is definitely a good one to keep! Of course I can’t guarantee you’ll never have to see a doctor again, but a daily fruit intake is a great component of a healthy lifestyle. It doesn’t have to be an apple. Fruit is beneficial in any of its forms, so this is a great recommendation. I am happy for people to keep saying, “An apple a day keeps the doctor away”.

Marika Day is a nutritionist and Accredited Practising Dietitian who knows what the body needs to function at its best. With more than five years’ experience in the health and fitness industry, Marika's holistic approach to diet and exercise is tried and true. The information in this article is general information only and is not intended as medical, health, nutritional or other advice. You should obtain professional advice from a medical or health practitioner in relation to your own personal circumstances.