How does diet affect your health?

Is the traditional balanced diet a thing of the past? Find out what biomarkers and nutrients you need to look out for if you follow a restricted diet.

Vegan, vegetarian, flexi, paleo, gluten-free – whether through intolerance, ethical reasons, or just being more aware, there’s certainly no shortage of diet variations in today’s world. But what effect is it having on our health?

Some modern diets focus on elimination, and it is not uncommon for people to eliminate whole groups from their diets.

Examples of diets that eliminate whole food groups include:

  • Plant-based (without meat)
  • Gluten-free (avoiding anything containing gluten or wheat)
  • Carb-free (no carbohydrates, a diet often had by bodybuilders)

Other people may choose to live off vegetables and grass-fed meat, while others may live off ready meals and ultra-processed foods.

It seems the traditional “balanced” diet is a thing of the past. But are there consequences of missing out on whole food groups?

The consequences of restricted diets

Sometimes, eliminating foods from your diet, or eating a restricted diet, can have unwanted effects.

Unintended consequences from restricted diets include:

  • Reduced kidney function – Consuming too much animal protein, such as red meat, poultry, eggs, and seafood, can increase the level of uric acid and lead to kidney stones.
  • Reduced liver function – A diet high in ultra-processed food, sugar, and fat can damage the liver. Non-alcoholic fatty liver disease (NAFLD) is a build-up of fat in the liver, usually seen in people who are overweight and obese. One in three people in the UK could already have early-stage NAFLD where fat is accumulating in their liver [1]. People who carry excess weight around their middle are most at risk.
  • Decrease in calcium – Restricting or cutting out dairy can significantly reduce the amount of calcium in the diet. A long-term calcium deficiency can lead to an increased risk of osteoporosis later in life.
  • Decrease in iron – Meat is a rich source of iron, so if you cut meat out of your diet, the risk of developing iron-deficiency anaemia increases.
  • High cholesterol – Cutting back on saturated fats and increasing exercise is recommended to reduce cholesterol levels [2].
  • Vitamin and mineral deficiency – Vitamins and minerals such as vitamin B12, vitamin D, and folate help to keep the body at optimum health. A deficiency can put you at risk of developing unwanted symptoms such as fatigue and brain fog.

Whatever type of diet you choose to eat, it is possible to stay healthy – as long as you are well-informed and make sure you have a healthy balance of nutrients and minerals and are not over-eating foods high in saturated fats.

What you eat also affects other aspects of your health, such as your blood pressure, blood sugar, and digestive health.

How does diet affect your blood pressure?

Around a third of adults in the UK have high blood pressure [3].

High blood pressure (hypertension) is best managed by eating healthily, maintaining a healthy weight, regular exercise, drinking alcohol in moderation, and not smoking [4].

Eating a diet high in salt can increase your blood pressure to unhealthy levels. The NHS recommends eating less than 6g of salt a day can help reduce the risk of hypertension (and the risks associated with high blood pressure).

Ultimately, eating a healthy, balanced diet as laid out in the Eatwell guide can help to keep your blood pressure at a healthy level.

How does diet affect your blood sugar?

 Glucose (also known as blood sugar) is the body’s energy source and comes from the foods we eat [5].

When you eat, your body breaks down food and absorbs it through the digestive tract.

All foods contain nutrients that are broken down into [6]:

  • Carbohydrates
  • Proteins
  • Fats
  • Vitamins and minerals

Each of these nutrients influences blood sugar, with carbohydrates having the most influence. When you eat carbohydrates, it turns into blood sugar – the more you eat, the higher the levels of sugar you’ll have. There are two different kinds of carbohydrates – simple carbohydrates and complex carbohydrates.

Simple vs complex carbohydrates

Simple carbohydrates are broken down quickly by the body and used as energy. Because they break down so quickly, simple carbohydrates cause a sharp spike in blood sugar levels.

Simple carbohydrates can be found in:

  • Fruits
  • Milk
  • Yoghurts

Complex carbohydrates are made up of sugar molecules that aren’t as simple or easy to break down. Instead, they are strung together in long, complex chains. Because they take longer to break down, complex carbohydrates release sugars more gradually and are preferable for people with diabetes.

Complex carbohydrates can be found in:

  • Peas
  • Beans
  • Whole grains
  • Vegetables

If you have diabetes, your doctor may recommend an allowance of carbohydrates to make sure your blood sugar remains steady.

A diet high in fat, calories, and cholesterol can increase your risk of developing diabetes. Therefore, it is best to keep to a healthy, balanced diet to keep your blood sugar in check.

You can check if you are at risk of diabetes and see how well your body is controlling glucose with a simple finger-prick test Diabetes (HBA1c) Blood Test.

How does diet affect your digestive health?

Did you know that your gut is overflowing with trillions of bacteria (an estimated 30-50 trillion of them)?

Some of these bacteria break down nutrients and release substances that are beneficial to the body.

Good bacteria can benefit the body by regulating:

  • Blood glucose and fat levels
  • Appetite
  • The body’s immune system and inflammatory processes

Some bacteria even have anti-cancer properties [7].

Foods to help bacteria fuel your body

For bacteria to work well in the body, it needs to be fuelled by the right foods.

  1. Foods high in fibre

Food high in fibre helps keep the gut cells healthy, support the immune system, and clear out waste. Certain fibre types can also act as prebiotics to help support a healthy gut [8].

These fibres can be found in:

  • Onions
  • Garlic
  • Bananas
  1. Fermented foods

Fermented foods are made using a process that involves the breakdown of sugars by bacteria and yeast. They are rich in probiotics that help restore a healthy gut.

Fermented foods include:

  • Natural yoghurt
  • Sauerkraut
  • Kimchi
  • Kefir
  • Tempeh
  • Kombucha

These fermented foods promote a variety of healthy gut bacteria [9] and reduce the family of bacteria linked to several chronic diseases.

An increasing amount of evidence points towards the use of probiotics to treat certain gut conditions such as irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD).

  1. Foods low in sugar

Excess sugar is generally known for being something we should avoid when eating a healthy, balanced diet. Increasingly, more research suggests that this may also be true for the healthy balance of our gut.

Bacteria that live in the gut need to eat, and if we eat too much sugar, the excess can feed bad bacteria and yeasts, and ultimately cause inflammation in the body [9].

Getting tested

Do you wonder whether your diet could be healthier or think that you could be missing out on certain nutrients because of a special diet you follow? Our Nutrition Blood Test can help you get the answers.

Our comprehensive health MOTs for men and women can give you the answers to help you take steps to improve your health and identify health risks like diabetes or heart disease.

If you are struggling to find the right test for you then try our test finder or look at our health and wellness buying guide.


  1. N., 2021. Introduction. [online] Available at: <> [Accessed 21 December 2021].
  2. Imbard, A., Benoist, J. and Blom, H., 2013. Neural Tube Defects, Folic Acid and Methylation. International Journal of Environmental Research and Public Health, 10(9), pp.4352-4389.
  3. NHS. 2021. High blood pressure (hypertension). [online] Available at: <> [Accessed 21 December 2021].
  4. NHS. 2021. High blood pressure (hypertension) - Prevention. [online] Available at: <> [Accessed 21 December 2021].
  5. Live Science. 2021. What Is Blood Sugar?. [online] Available at: <> [Accessed 21 December 2021].
  6. Healthline. 2021. Blood Sugar After Eating: What Happens, Levels, and More. [online] Available at: <> [Accessed 21 December 2021].
  7. Gut Microbiome and dysbiosis testing. Personalised diet based on an individuals microbiome profile from a gut microbiome test.
  8. Baindara, P. and Mandal, S., 2020. Bacteria and bacterial anticancer agents as a promising alternative for cancer therapeutics. Biochimie, 177, pp.164-189.
  9. Zou, J., Chassaing, B., Singh, V., Pellizzon, M., Ricci, M., Fythe, M., Kumar, M. and Gewirtz, A. (2019). Fiber-Mediated Nourishment of Gut Microbiota Protects against Diet-Induced Obesity by Restoring IL-22-Mediated Colonic Health.
  10. BDA. 2021. Probiotics. [online] Available at: <> [Accessed 29 December 2021].

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