You’ve probably grown up hearing the same advice: eat a balanced diet, and your body will get everything it needs. It sounds simple and logical, and for a long time, it was generally true.
But today, this mindset is not quite as clear-cut.
Even people who make an effort to eat well often feel low on energy or notice small but persistent health concerns. And it raises an important question. If the diet looks good on paper, why does it still lack in practice?
What You Eat Is Not Always What You Absorb
The amount of a nutrient on a food label is not the amount your body actually takes in. The share you absorb is called bioavailability, and it can be smaller than you would guess. And these three things are what usually get in the way:
Antinutrients
These are natural compounds in plants that bind to minerals and stop them from being absorbed. Phytates in grains and beans, oxalates in spinach and beetroot, and tannins in tea and coffee all slow down the uptake of calcium, iron, and zinc. Calcium from spinach is only around 5% absorbed, while calcium from dairy sits closer to 30%. Iron in red meat is much easier for the body to use than iron in lentils or kale.
Lifestyle and Age Factors
The way you live also shapes how much you actually pull from each meal. Stomach acid drops with age, which lowers the uptake of B12, magnesium, and iron. Common medications like antacids, the contraceptive pill, and metformin can cut absorption further. Smoking, heavy drinking, and chronic stress all add to the load. Needs also change across life stages, which is why dedicated supplements for women and supplements for men can be a good fit when generic stacks are inadequate.
The Need for Fat
Vitamins A, D, E, and K are fat-soluble, which means they need dietary fat to be absorbed properly. Strict low-fat eating, often picked up for weight loss, can quietly drain these four. So, adding a little olive oil, avocado, or oily fish to a meal helps the body lock in the vitamins that come with it.
The Nutritional Decline of Modern Food
Even the foods you trust are not what they used to be. The carrots, the broccoli, and the apples you ate before looked the same as the ones on shelves today, but the vitamin and mineral content has shifted, all due to:
Soil Depletion
Decades of intensive farming and heavy fertiliser use have pulled essential minerals out of the ground faster than they can be put back. A 2024 review of farming data found a steep drop in nutritional quality, with fruit and vegetables now showing far less calcium, iron, and phosphorus than they did 50 to 70 years ago.
The Dilution Effect
Most modern produce is grown for high yield, fast growth, and a long shelf life. When a plant grows bigger and quicker, it does not pull more minerals from the soil to match. So you get a larger tomato that contains less per bite. Scientists call this the dilution effect, and it shows up across nearly every staple crop.
Nutrient Loss in Transport
Lots of fresh produce is picked before it ripens, packed into a lorry, and stored for days or weeks before it lands on your plate. Light, heat, and air all chip away at vitamin levels along the way. Broccoli alone can lose up to 70% of its vitamin C between farm and table. As a matter of fact, frozen veg often holds more nutrients than the “fresh” tray that has travelled across Europe.
What RDAs Are Measuring (And What They’re Not)
The RDA, or Recommended Dietary Allowance, is one of the most misunderstood numbers in nutrition. Most people read it as a target for great health; it is not.
The RDA was set as the minimum needed to avoid deficiency diseases like scurvy and rickets in 97 to 98 per cent of the population. In the UK, the equivalent figure is the Reference Nutrient Intake (RNI), and food labels often show the Nutrient Reference Value (NRV) instead. All three were built around the same idea, keeping people from getting sick instead of helping them feel their best.
Here are five blind spots that keep the RDA from showing what your body really needs:
Insufficient for Optimal Health
The RDA is a floor, not a ceiling. It tells you the minimum needed to dodge a serious deficiency, but says nothing about the level that supports steady energy, sharp focus, strong immunity, or long-term well-being. Most adults need more than the RDA to actually feel their best.
Individual Variability
The RDA is a single number aimed at almost everyone, but no two bodies handle nutrients the same way. Genetics, gut health, age, sex, and life stage all change how much a person needs. Two people eating identical meals can absorb and use very different amounts of the same vitamin or mineral.
Modern Stress Loads
The original RDAs were set in a different timeline, before chronic stress, screen time, broken sleep, and high caffeine intake became the norm. All of these raise the body’s demand for magnesium, vitamin C, and B vitamins. The number on the label has not moved, but the load on your body has.
Incomplete Data
For many useful compounds, no RDA exists at all. Antioxidants, polyphenols, probiotics, and most plant-based bioactives sit outside the system, even though research keeps pointing to their role in everyday health. You can technically meet every official guideline and still miss out.
Subclinical Deficiency
The biggest blind spot is the in-between. You might not have full-blown scurvy, but a low-grade vitamin C deficiency can still leave you tired and prone to colds. This grey zone is called subclinical deficiency, and it is far more common than most people think. The UK RNIs were last formally published in 1991, a long time to leave a guideline standing while everything around it changes.
How Modern Lifestyles Raise the Bar Further
If the food and the guidelines are working against you, the way you live tips the balance even further. The body needs more nutrients under pressure, while modern routines pile on the pressure and serve up fewer of the foods that replace what you lose.
Chronic Stress as a Nutrient Drain
When cortisol stays high for weeks at a time, the body burns through magnesium, vitamin C, and B vitamins faster than food can put them back. Add caffeine, alcohol, and broken sleep, and the nutrient imbalance widens. Stress is not just a mood thing; it is a steady tax on your nutrient reserves, and most people are paying it without noticing.
Ultra-processed Food Volume
Ultra-processed foods now make up a big portion of the average UK plate. They are built for taste, texture, and shelf life rather than nutrition. They fill you up with calories but leave little behind in vitamins or minerals, and when they take up space on the plate, real food gets pushed off it.
Picking Up Where Your Diet Might Miss
You cannot fix the soil your food was grown in, nor rewrite the RDA. What you can change is what lands on your plate, what your body absorbs from it, and how you cover the rest. And below are three ways to do that:
Go Organic Where You Can
Organic and regenerative growing systems produce food with richer mineral content. The soil is rotated, fed, and rested, which lets crops draw more out of the ground as they grow. The same carrot, raised in healthier soil, reaches the plate with more behind it.
Prioritise Whole Food
Fresh, minimally processed, varied plates carry the broadest range of nutrients. The more colours and textures on the plate, the wider the spread of vitamins, minerals, fibre, and plant compounds you take in.
Smart Supplementation
For the gaps food cannot reach, the right supplements act as a top-up. A test through your GP, paired with an honest look at how you eat and live, gives you a real starting point.
Eat Well, Top Up
For most people, ‘enough nutrients’ means scraping past the line where the body avoids serious illness. But that’s the old definition, and it is the one RDAs were drawn around. The new one is bigger: ‘enough nutrients’ means having the nourishment your body wants for sustained energy, and the kind that puts you back together for every stage in life.
By that measure, food alone rarely gets you there. And by that measure, supplements are not only a backup plan, but a part of how the modern body reaches ‘enough’.