Food basics

What do carbohydrates do for you?

Carbohydrates are your body's main source of energy: most are broken down and absorbed as glucose⁵. Starchy foods are also a main source of a range of other nutrients⁶. The NHS Eatwell Guide says they should make up just over a third of the food we eat, and suggests higher-fibre or wholegrain types, such as wholewheat pasta and brown rice, or potatoes with the skins left on⁶. Whole grains contain more fibre than refined grains, which is the main reason they are recommended⁵.

Which fats are healthy, and how much do you need?

Unsaturated fats (monounsaturated and polyunsaturated) support heart health, while saturated and trans fats can raise cholesterol and heart disease risk². The type of fat matters more than the total amount². Choose nuts, seeds, avocado, olives, olive oil or oily fish more often².

Saturated fat is found in butter, coconut oil, palm oil, fatty meat, processed meats such as bacon, cream, cheese, cakes and pastries. Trans fats are found in deep-fried foods, baked goods and products with hydrogenated oils, so check labels². Even healthy fats are high in energy, so keep oils such as olive, rapeseed or sunflower to small amounts⁶. If you cut back on saturated fat, what replaces it matters: swapping it for polyunsaturated fat looks better than swapping it for refined carbohydrates⁷.

How much protein do you need?

For healthy adults, recommended intakes are generally about 0.8–0.9 g of protein per kg of body weight a day⁸. After 65, the advice is at least 1.0 to 1.2 g per kg a day, to help maintain and regain muscle and function⁴. Older adults are also advised to spread protein across the three main meals, at about 25 g or more per meal, rather than eating most of it at one⁹. Milk, cheese and yoghurt are easy sources⁶.

How much protein above 0.8 g per kg a day protects muscle isn't settled¹⁰, so treat the higher figures as a guide rather than a target to hit exactly.

Which minerals matter most, and why?

The main minerals are calcium, phosphorus, potassium, sodium and magnesium, plus trace minerals such as iron, zinc, iodine and selenium¹¹. Calcium builds bones and supports muscle and nerve function; good sources are milk, cheese, yoghurt, green leafy vegetables, legumes and fortified breakfast cereals³. Iron supports red blood cells and helps move oxygen around the body; sources include red meat, fish, poultry, wholegrain cereals, beans and dried fruit³. Potassium (found in leafy green vegetables) and sodium help control fluid balance, and sodium also helps regulate blood pressure³.

Which vitamins matter most, and why?

Several vitamins matter, and a varied diet usually covers them³. Vitamin B12 helps make red blood cells and keeps your nervous system healthy³. If you follow a vegan diet, the only reliable sources are fortified plant milks, some fortified meat substitutes and some breakfast cereals, so ask a doctor or dietitian how to make sure you get enough³. Vitamin D is harder: diet usually provides only about 100 to 200 IU a day, so food alone often doesn't cover it¹².

Supplements can cause side effects, interact with prescribed medicines and lead to taking too much when products share an ingredient. Vitamins A and D can build up in the body, and too much vitamin D can lead to high blood calcium and kidney problems^11,12. Talk to a doctor or dietitian before taking any, and tell your doctor or pharmacist what you take³.

Why does fibre matter?

People who eat the most fibre tend to have lower risk of early death, heart disease, stroke, type 2 diabetes and bowel cancer than those who eat the least, with the biggest drop at 25–29 g a day¹. In trials, higher fibre intakes also went with lower bodyweight, blood pressure and total cholesterol¹. Fibre affects how the gut moves food along and feeds your gut bacteria⁵.

Most of this evidence shows links rather than proof, though the pattern points towards a real effect¹. Swap towards wholegrain or higher-fibre versions of foods you already eat. If you tend to be constipated, expert guidelines most often advise raising fibre gradually¹³.

What's the difference between whole and processed foods?

Whole foods are close to how they grow; ultra-processed foods are not. Whole grains keep more fibre than refined grains, which is the main reason they are recommended⁵. A European cardiology consensus statement advises choosing whole or minimally processed foods instead of ultra-processed ones, preferring high-fibre foods, and eating slowly and mindfully¹⁴.

How does sugar affect your health and energy?

How sugar affects your energy, blood sugar swings or tiredness isn't clear yet. One practical step is well supported: replace sugary drinks with water or unsweetened drinks¹⁴.

Which nutrient deficiencies are common, and how do you fix them?

Most people can get all the vitamins and minerals they need from a healthy diet. Some people may need more: those who are pregnant or breastfeeding, who smoke or drink alcohol in excess, who follow a restrictive diet, or who have conditions affecting absorption or past weight-loss surgery³.

A lack of iron, folate, vitamin B12 or vitamin A can lead to anaemia, which causes tiredness, weakness, shortness of breath and dizziness¹⁵. Intakes of magnesium, potassium and calcium can also fall short¹⁶. Unusual tiredness isn't something to push through or ease off for; get it checked by a doctor. If you think you may be low in something, ask a doctor or dietitian about testing and what to do. Start with a varied diet that includes foods from each food group.

Can what you eat affect inflammation?

Whether particular foods or diets lower inflammation isn't clear yet, so be wary of claims that a food treats or prevents it. A varied, fibre-rich, mostly whole-food way of eating is still a sound choice for the other reasons above.

What do national dietary guidelines recommend?

Look up your own country's official healthy eating guide, usually published by its health department. The NHS Eatwell Guide splits food into 5 main groups and suggests choosing a variety from each, to get the range of nutrients your body needs⁶. A sensible focus is whole foods and overall eating patterns rather than single nutrients⁷.

How do nutrition and activity work together as you age?

Protein combined with exercise is considered the best way to keep muscle working well as you get older¹⁷. Older adults who exercise and are otherwise active are advised to have at least 1.2 g of protein per kg of body weight a day⁴. Think of food and activity as working together: eating enough protein across the day supports the muscle you are trying to keep.

When to check with a health professional

If you're starting exercise after a long break, it's always a good idea to see your doctor first.

For an injury or a health condition, see a health professional, such as your doctor or a physio.

If you live with a long-term condition such as diabetes, heart or kidney disease or high cholesterol, or have special dietary needs, a registered dietitian can help adapt general food advice to you^6,18. Seeing your doctor first can help, as blood tests may make the dietitian's advice better, and a general health advice line can also answer questions. The fibre and carbohydrate advice here is for the general population, not for people who already have a condition^1,19. Higher-protein advice isn't right for everyone: older people with severe kidney disease who aren't on dialysis may need to limit protein, so check with a doctor or dietitian before raising your intake^4,17.

Call your local emergency number for chest pain or pressure (or pain spreading to the arm, neck, jaw or back, especially with sweating or feeling sick), severe breathlessness, fainting or collapse, signs of a stroke, a serious injury, or someone who isn't safe.