For most of my life, my understanding of food was incredibly basic.

Some foods were “healthy”.

Some foods were “unhealthy”.

That was about it.

Then, while losing weight and completely changing the way I ate, I started asking a different question:

What is this actually doing inside my body?

Why is beetroot good for me?

Why should I eat oily fish?

What does fibre actually do?

Why does everyone keep telling me to eat broccoli?

And what happens to a potato after I swallow it?

Understanding the answers changed the way I looked at food.

Instead of eating something simply because I’d been told it was healthy, I started understanding what I was actually giving my body.

So this is my attempt to put it all in one place.

Not simply what nutrients different foods contain.

But what happens when I eat them…

…and what that actually does for me.

Oily Fish and Protein

Salmon

Salmon is one of my favourite foods, and one of the main reasons is its combination of high-quality protein and long-chain omega-3 fats.

The protein is broken down during digestion into amino acids.

My body can then use those amino acids to maintain and repair tissues and to make the thousands of different proteins it needs to function.

That includes muscle, but protein isn’t just about building bigger muscles.

My skin, enzymes, immune system and many other parts of my body depend on proteins too.

Salmon also contains the omega-3 fats EPA and DHA.

These become incorporated into cell membranes and are involved in signalling throughout the body. DHA is particularly concentrated in the brain and retina, while omega-3-derived signalling molecules have roles in cardiovascular and immune processes.

What does that actually do for me?

Provides the building blocks my body needs to maintain and repair muscle and other tissues.
Supports the normal structure and function of my brain and eyes.
Supports cardiovascular health.
Provides omega-3 fats involved in regulating inflammatory and other signalling processes.

The simple version:

Salmon gives my body repair materials + important fats for my heart, brain, eyes and cells.

Mackerel

Mackerel gives me many of the same benefits as salmon.

It’s rich in protein, EPA and DHA.

That makes it particularly useful because I’m not simply getting protein from my meal.

I’m getting the amino acids my body needs for maintenance and repair alongside omega-3 fats used throughout the body.

What does that actually do for me?

Much like salmon:

Muscle and tissue maintenance + heart support + brain and eye structure + useful omega-3 fats.

Sardines

Sardines give me protein and EPA/DHA again.

But when I eat tinned sardines with their soft bones, I get something else:

Calcium.

Most of the calcium in my body is stored in my bones and teeth.

But calcium also helps my muscles contract, my nerves transmit signals and my blood vessels function normally.

What does that actually do for me?

Helps maintain strong bones and teeth.
Helps my muscles contract properly.
Helps nerves carry messages around my body.
Provides protein for tissue maintenance and repair.
Provides EPA and DHA for cardiovascular, brain and eye health.

Those tiny sardine bones are effectively contributing building material to my own skeleton.

Eggs

Eggs provide complete protein, meaning they contain all nine essential amino acids.

They also provide choline.

My body uses choline to make components of cell membranes and to produce acetylcholine, a neurotransmitter involved in muscle control, memory and other nervous-system functions.

What does that actually do for me?

Provides building blocks to maintain and repair my body.
Helps maintain the membranes surrounding my cells.
Supports communication between nerves and muscles.
Contributes to normal brain and nervous-system function.

The simple version:

Eggs provide repair materials + nutrients my cells, muscles and nervous system need.

Turkey

Turkey gives me plenty of high-quality protein without a huge amount of fat.

My digestive system breaks that protein into amino acids.

Those amino acids enter a huge pool of building materials my body can draw upon.

What does that actually do for me?

It helps my body:

Maintain muscle.
Repair tissues after physical activity.
Make enzymes and other proteins.
Recover and maintain itself.

That matters even more to me now that I want to become stronger and more physically capable.

Beans, Lentils and Pulses

Green Lentils

Lentils give me protein, carbohydrate and lots of fibre.

Some carbohydrate is digested into glucose and used for energy.

But some of the fibre travels much further through my digestive system.

When it reaches my large intestine, bacteria living there can ferment some of it and produce substances called short-chain fatty acids.

Some of these can be used as fuel by cells lining my colon and influence the environment inside my gut.

The fibre also helps add bulk to stools and contributes to feeling full after eating.

What does that actually do for me?

Provides slow, useful energy.
Helps keep me fuller for longer.
Supports normal bowel function.
Provides food for beneficial members of my gut microbiome.
Provides plant protein to contribute towards my protein intake.

The simple version:

Lentils feed me, fill me and feed my gut bacteria.

Chickpeas

Chickpeas give me a similar combination of carbohydrate, protein and fibre.

Again, not all of that fibre is digested by me.

Some becomes food for microorganisms living inside my gut.

Their combination of fibre, protein and intact carbohydrate structure also makes chickpeas much more filling than many highly processed carbohydrate foods.

What does that actually do for me?

Steady fuel + fullness + bowel health + gut-microbiome support + plant protein.

Black Beans, Kidney Beans and Borlotti Beans

These all earn their place for similar reasons.

They’re cheap, incredibly convenient and provide carbohydrate, fibre, protein, folate and minerals.

Their fibre and resistant starch mean some material makes it all the way to my large intestine.

What does that actually do for me?

They help provide:

Energy + fullness + plant protein + regular bowel movements + food for my gut microbes.

The humble tin of beans is considerably more impressive than I once realised.

Carbohydrates and Energy

Potatoes

This is an important one for me.

For years, I thought carbohydrates were something I should avoid.

Now I understand what happens when I eat them.

Much of the starch in a potato is eventually broken down into glucose.

That glucose enters my bloodstream.

Insulin helps regulate what happens next, including helping tissues take up and store glucose.

Some glucose can be used for energy immediately.

Some is stored as glycogen, particularly in my muscles and liver.

Think of glycogen as readily accessible stored fuel.

When I’m walking, working, exercising or eventually running, my body can draw on those energy stores.

Potatoes also provide potassium and vitamin C.

What does that actually do for me?

Provides fuel for my body and physical activity.
Helps replenish stored carbohydrate in my muscles and liver.
Provides potassium, which is important for nerve and muscle function.
Provides vitamin C.

The simple version:

A potato isn’t something my body needs to fear.

It’s fuel.

Sweet Potatoes

Sweet potatoes provide carbohydrate too, so again I’m getting energy.

Orange sweet potatoes also contain lots of beta-carotene.

My body can convert beta-carotene into vitamin A.

Vitamin A is required for normal vision, including the light-sensitive machinery in my retina. It also supports immune function and helps maintain tissues and organs.

What does that actually do for me?

Gives me energy.
Supports normal vision.
Supports my immune system.
Helps maintain healthy tissues throughout my body.

The simple version:

Sweet potato gives me fuel + raw material my body can turn into vitamin A for my eyes, immune system and tissues.

Brown Rice

Brown rice mainly gives me carbohydrate, along with fibre and various micronutrients.

Sometimes the benefit of a food doesn’t need to sound exotic.

What does that actually do for me?

It provides energy.

My brain, muscles and other tissues constantly require energy to function.

Food doesn’t have to be a “superfood” to be useful.

Quinoa

Quinoa gives me carbohydrate, fibre and protein.

What does that actually do for me?

Energy + some protein for my body’s building materials + fibre for my digestive system.

Again, useful doesn’t have to mean magical.

Vegetables

Beetroot

This is one of my favourite examples because I can actually follow what happens.

Beetroot contains lots of dietary nitrate.

After I eat it, some nitrate enters my saliva.

Bacteria in my mouth convert some into nitrite.

Eventually, this contributes to the production of nitric oxide.

Nitric oxide helps blood vessels relax and widen.

And now we’ve reached the important part.

What does that actually do for me?

Wider, more relaxed blood vessels can allow blood to flow more easily.

Research on nitrate-rich beetroot has found effects on blood pressure, particularly systolic blood pressure in people with hypertension, and nitrate can reduce the oxygen cost of some exercise and improve exercise tolerance or performance in some circumstances. Responses vary between people and studies.

So potentially:

Supports healthy blood-vessel function.
Can help reduce blood pressure in some populations.
May help muscles perform a given amount of work using oxygen more efficiently.
May improve exercise tolerance in some circumstances.

The simple version:

Beetroot can help my blood vessels relax and move blood more easily, and may help my muscles use oxygen more efficiently.

That’s a much better reason for me to eat it than simply:

“Beetroot is healthy.”

Broccoli

Broccoli gives me fibre, vitamin C, vitamin K, folate and a collection of plant compounds.

Vitamin C helps my body make collagen.

Collagen provides structure to things including skin, blood vessels, cartilage and connective tissues and is important in wound healing.

Vitamin K is needed to make proteins involved in normal blood clotting and bone metabolism.

The fibre also helps my digestive system and provides material that can be fermented by gut bacteria.

What does that actually do for me?

Helps maintain connective tissues.
Supports normal wound healing.
Supports normal blood clotting.
Contributes to maintaining bones.
Supports bowel and gut health.

The simple version:

Broccoli helps provide materials for my tissues and bones while also feeding my digestive system.

Kale

Kale gives me vitamin K, vitamin C, beta-carotene, lutein, zeaxanthin, fibre and other plant compounds.

Vitamin K supports normal blood clotting and bone metabolism.

Beta-carotene can be converted into vitamin A.

Lutein and zeaxanthin accumulate in the retina of the eye.

And the fibre contributes to digestive health.

What does that actually do for me?

Supports my eyes and normal vision.
Helps maintain my bones.
Supports normal blood clotting.
Provides vitamin C for collagen production and immune function.
Provides fibre for my gut.

The simple version:

Kale gives useful support to my eyes + bones + connective tissues + gut.

Spinach

Spinach provides folate, vitamin K, carotenoids and dietary nitrate.

That nitrate can enter the same nitrate → nitrite → nitric oxide pathway as beetroot.

What does that actually do for me?

Spinach contributes nutrients supporting:

Blood-vessel function + bones + normal blood clotting + eyes + cell growth and division.

That’s quite a lot from a handful of leaves.

Tomatoes

Tomatoes contain lycopene, the pigment responsible for much of their red colour, alongside vitamin C, potassium and other compounds.

Cooking tomatoes can make lycopene easier to absorb, and eating them with some fat can help absorption of carotenoids.

What does that actually do for me?

Lycopene and other carotenoids act within the body’s antioxidant network and are being studied for their relationship with long-term cardiovascular and other health outcomes.

But I don’t need to pretend a tomato is a medicine.

The practical benefit is simpler:

Tomatoes help increase the variety of protective plant compounds, vitamin C and potassium I’m getting as part of my overall diet.

Carrots

Carrots contain lots of beta-carotene.

My body can convert some of it into vitamin A.

Vitamin A is an essential part of rhodopsin, a light-sensitive protein in the retina.

What does that actually do for me?

It helps my eyes respond to light and maintain normal vision, particularly in low-light conditions.

Vitamin A also helps my immune system function and supports the normal maintenance of tissues.

The simple version:

Carrots help provide the raw material my body needs for vision + immune function + healthy tissues.

Peppers

Peppers — particularly red and yellow ones — can provide lots of vitamin C.

My body needs vitamin C to produce collagen.

Collagen is part of the structure of my skin, cartilage, blood vessels and other connective tissues.

Vitamin C also helps my body absorb non-haem iron, the form found in plant foods such as beans and lentils.

What does that actually do for me?

Helps maintain and repair connective tissue.
Supports wound healing.
Supports normal immune function.
Helps me absorb more iron from plant foods.

So peppers eaten alongside lentils or beans are doing more than simply adding another vegetable to the plate.

Onions

Onions provide fibre, including fermentable carbohydrates, and plant compounds such as flavonoids.

What does that actually do for me?

The clearest everyday benefit is that they add another source of fibre and diverse plant compounds to my diet.

Some of that fermentable material can be used by gut bacteria.

And there’s another benefit that shouldn’t be underestimated:

They make healthy food taste better.

If onions help turn vegetables, beans and lean protein into food I genuinely want to eat repeatedly, that’s useful too.

Garlic

When garlic is chopped or crushed, chemical reactions produce sulfur-containing compounds including allicin.

These compounds are biologically active and have been studied for possible cardiovascular and other effects.

But I don’t need to treat garlic as medicine.

What does that actually do for me?

It adds another collection of plant compounds to my diet while making nutritious meals considerably more enjoyable.

That’s enough reason for it to be there.

Fruit

Blueberries

Blueberries contain fibre, vitamin C and colourful plant compounds called anthocyanins.

These compounds and their metabolites interact with cell-signalling and antioxidant systems rather than simply acting as tiny cleaners floating around my bloodstream.

What does that actually do for me?

As part of a varied diet, blueberries give me:

Fibre for my digestive system.
Vitamin C for collagen and immune function.
A diverse collection of plant compounds associated in research with cardiovascular and metabolic health.

The simple version:

Blueberries help me add fibre + vitamin C + useful plant diversity to my diet.

Apples

Apples contain fibre, including pectin.

Some of that fibre reaches my large intestine and can be fermented by gut microbes.

The intact structure of the fruit also means I have to chew it, and digestion takes time.

What does that actually do for me?

Helps me feel full.
Supports normal bowel movements.
Provides material for my gut microbiome.
Gives me a convenient source of carbohydrate and plant compounds.

The simple version:

An apple is food for me and some of the microbes living inside me.

Bananas

Bananas give me carbohydrate, fibre, potassium and vitamin B6.

The carbohydrate provides energy.

Potassium is involved in electrical signalling, including nerve impulses and muscle contraction.

What does that actually do for me?

A banana gives me easily accessible fuel, while providing nutrients involved in normal nerve and muscle function.

That’s particularly useful around an active lifestyle.

Satsumas and Oranges

These have become a much bigger part of my diet.

They’re famous for vitamin C, and this is a good example of why I wanted to understand what vitamins actually do.

Vitamin C helps my body make collagen.

Collagen provides structure to skin, blood vessels, cartilage and connective tissues.

Vitamin C also helps my immune system function and increases absorption of iron from plant foods.

What does that actually do for me?

Helps maintain connective tissues.
Helps wounds heal normally.
Supports immune function.
Helps me absorb iron from beans, lentils and other plant foods.
Whole satsumas and oranges also give me fibre.

The simple version:

Satsumas help my body maintain and repair tissues, support immune function and get more iron from some of the other foods I eat.

That’s considerably more interesting than:

“Vitamin C stops colds.”

Nuts, Seeds and Healthy Fats

Walnuts

Walnuts provide unsaturated fats, fibre and an omega-3 fatty acid called ALA.

ALA is an essential fatty acid, meaning my body can’t make it and I need to obtain it from my diet.

My body can convert a small amount into EPA and DHA, although that conversion is limited.

That’s why walnuts and oily fish aren’t nutritionally identical.

What does that actually do for me?

Walnuts provide heart-friendly unsaturated fats, essential fatty acids, fibre and useful plant compounds.

They’re another way of replacing less useful snack foods with something that actually contributes useful raw materials.

Chia Seeds

Chia seeds contain a remarkable amount of fibre alongside ALA omega-3 and minerals.

When mixed with liquid, some of their fibre absorbs water and forms a gel.

What does that actually do for me?

Adds a lot of fibre in a small amount of food.
Helps support normal bowel function.
Provides material for gut microbes.
Can contribute to fullness.
Provides the essential omega-3 fat ALA.

The simple version:

Chia seeds are particularly useful for fibre + gut health + fullness + plant omega-3.

Pumpkin Seeds

Pumpkin seeds provide protein, unsaturated fat and minerals including magnesium.

Magnesium is involved in hundreds of enzyme systems.

But what does that actually mean?

It helps my body produce energy, supports normal nerve signalling, helps muscles contract and relax, and contributes to maintaining bone.

What does that actually do for me?

Pumpkin seeds provide nutrients supporting:

Energy production + muscles + nerves + bones.

Avocado

Avocado gives me monounsaturated fat, fibre, potassium and other nutrients.

The fat is useful in another way.

Some nutrients — including vitamins A, D, E and K and many carotenoids — are fat-soluble.

Having some fat in a meal can improve absorption of fat-soluble compounds.

What does that actually do for me?

Provides mostly unsaturated fat.
Adds fibre.
Helps make meals satisfying.
Helps my body absorb some nutrients from the vegetables eaten alongside it.

So adding avocado to vegetables isn’t “adding unhealthy fat”.

The fat is part of the nutrition.

Extra Virgin Olive Oil

Extra virgin olive oil contains mostly monounsaturated fat, particularly oleic acid, along with plant compounds including polyphenols.

Using it in place of fats richer in saturated fat can improve the overall fat profile of my diet.

And, like avocado, having some fat alongside vegetables helps my body absorb certain fat-soluble nutrients and carotenoids.

What does that actually do for me?

Supports a heart-healthy dietary pattern + helps me absorb nutrients from other foods + makes vegetables taste better.

That’s a pretty useful tablespoon of oil.

Herbs and Spices

Turmeric

Turmeric contains curcuminoids, including curcumin.

These compounds have been extensively studied.

But this is somewhere I need to be careful.

Research involving concentrated curcumin supplements doesn’t mean the teaspoon of turmeric in my dinner is treating disease.

What does that actually do for me?

It contributes another source of plant compounds and, perhaps more importantly, helps me create flavourful healthy meals I actually want to eat.

That’s a perfectly good reason to use it.

Black Pepper

Black pepper contains piperine, which creates much of its characteristic pungency and can influence the absorption and metabolism of certain substances.

But again, I don’t need to turn my spice rack into a pharmacy.

Its biggest everyday benefit might be incredibly simple:

Healthy food tastes better, so I’m more likely to keep eating it.

Paprika

Paprika contains plant pigments including carotenoids, although amounts vary considerably depending on the type.

Again, it adds another small source of plant compounds.

But its biggest contribution to my actual life?

It makes turkey, potatoes, vegetables and other healthy foods taste good.

Cayenne Pepper

Cayenne contains capsaicin.

Capsaicin activates receptors involved in sensing heat and pain.

That’s why my mouth feels hot even though the chilli hasn’t actually raised its temperature enough to burn me.

There are interesting areas of research around capsaicin and metabolism, but I don’t need those to justify using it.

It gives flavour without needing huge amounts of sugar, salt or heavy sauces.

What Happens When I Eat an Entire Meal?

This is where it all comes together.

Imagine one of my meals contains:

Salmon + green lentils + broccoli + beetroot + extra virgin olive oil.

My body doesn’t see a “healthy meal”.

It sees raw materials.

The salmon protein is broken down into amino acids my body can use to maintain and repair itself.

The EPA and DHA become available for cell membranes and signalling, supporting systems including my heart, brain and eyes.

The lentil carbohydrate helps provide energy.

Their fibre helps fill me up, supports bowel function and provides material for my gut bacteria.

The broccoli provides vitamin C that helps make collagen, vitamin K used in normal blood clotting and bone metabolism, and more fibre.

The beetroot nitrate enters a pathway that can increase nitric oxide availability, helping my blood vessels relax and potentially improving the efficiency of some exercise.

The olive oil provides unsaturated fat and helps me absorb some of the fat-soluble compounds from the vegetables.

All from one ordinary plate of food.

What Is My Body Actually Getting?

Put even more simply:

Protein → maintain and repair me.

Carbohydrates → fuel me.

Healthy fats → help build cells, provide essential fats and absorb nutrients.

Fibre → fill me, keep my digestive system working and feed my gut microbes.

Vitamin C → help maintain connective tissues, heal wounds, support immunity and absorb plant iron.

Vitamin A / beta-carotene → support my eyes, immune system and tissues.

Vitamin K → support normal clotting and bone metabolism.

Calcium → build and maintain bones while helping nerves and muscles work.

Magnesium → help produce energy and keep muscles and nerves functioning.

Omega-3 EPA/DHA → contribute to my cells, brain, eyes and cardiovascular system.

Dietary nitrate → help produce nitric oxide, supporting blood-vessel function and potentially exercise efficiency.

Suddenly the food on my plate looks rather different.

My Biggest Takeaway

Understanding what food actually does inside me has completely changed the way I eat.

I’m no longer eating beetroot simply because somebody told me it’s healthy.

I’m eating something that can help my blood vessels relax and may help my muscles use oxygen more efficiently.

I’m not eating salmon simply because fish is supposed to be good for me.

I’m giving my body protein to maintain and repair itself and omega-3 fats used by my cells, brain, eyes and cardiovascular system.

I’m not eating satsumas simply to tick off another piece of fruit.

I’m providing vitamin C that my body needs to maintain connective tissue, heal wounds, support my immune system and absorb plant iron.

And I’m not eating lentils because they’re boring “health food”.

I’m getting energy and protein while providing fibre that fills me up and reaches the ecosystem living inside my gut.

Takeaway

Salmon, mackerel and sardines → repair + heart + brain + eyes.
Eggs and turkey → repair + maintain muscle and tissues.
Beans and lentils → energy + fullness + gut health + plant protein.
Potatoes, rice and quinoa → fuel and stored energy.
Beetroot → blood flow + blood pressure support + potential exercise efficiency.
Broccoli and kale → bones + tissues + gut + protective nutrients.
Carrots and sweet potatoes → eyes + immune system + tissues.
Peppers and satsumas → collagen + healing + immunity + iron absorption.
Fruit generally → fibre + micronutrients + plant compounds.
Nuts, seeds, avocado and olive oil → healthy fats + fibre + nutrient absorption.
Variety matters because different foods help my body in different ways.