Why two people respond differently to the same diet
The biological explanation for why personalised nutrition is not a marketingconcept. It is how the body actually works.
Most nutritional advice is built on population averages. Government guidelines, foodlabels, recommended daily intakes. All of them are designed for a hypothetical average person whose body processes nutrients in the way the studies assumed. The problem is that no one is the average person.
Two people can eat identical diets. Same foods, same portions, same timing and endup with meaningfully different nutritional outcomes. Different levels of specific vitamins and minerals in their blood. Different energy levels. Different sleep quality. Different responses to the same foods. This is not unusual or anomalous. It is the normal biological reality of how the body processes food.
Understandingwhy this happens helps explain what personalised nutrition actually means. Not as a commercial concept, but as a description of how human biochemistry works.
"Two people eating the same meal absorb different amounts of virtually every nutrient in it. The difference is not random. It is written in their biology."
The four layers that make nutritional response personal
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Layer 1
What are you actually eating?
The same food varies in nutrient content depending on how it was grown, stored, and prepared. Spinach grown in depleted soil has less iron than spinach grown in mineral-rich soil. An egg from a hen raised outdoors has more vitamin D than one from a hen kept indoors. Cooking method matters. These variations exist before individual biology even enters the picture.
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Layer 2
How efficiently does your gut absorb what you eat?
Absorption varies significantly between individuals. The health of the gut lining, the gut microbiome, stomach acid levels, and competing compounds in the same meal all affect how much of a given nutrient actually reaches the bloodstream. Non-haem iron can be absorbed at anywhere from 2 to 20 percent depending on gut conditions. That range is tenfold.
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Layer 3
What does your lifestyle add?
Stress, sleep quality, physical activity, alcohol intake, medication use, and sun exposure all influence how the body processes specific nutrients. Magnesium is depleted by stress. Vitamin D synthesis depends on sun exposure. Heavy exercise increases iron losses. Alcohol impairs B vitamin absorption. Two people eating the same diet but living differently will have different nutritional outcomes.
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Layer 4
What do your genetics say?
This is the layer most people have never had access to before. Specific variants in your DNA influence how efficiently your body converts, absorbs, and utilises particular nutrients. The same food delivers a different nutritional outcome for different people at a biological level. Not because of what they eat, but because of how their cells process what they eat.
Why this matters practically
If your body absorbs a given nutrient less efficiently than average, eating the average recommended amount leaves you short. If your body converts a nutrient less efficiently into its active form, you need more of the raw material to end up with the same usable amount. Population-level guidance cannot account for this. Which is why the same dietary advice produces different outcomes for different people.
The genetic mechanisms. How DNA shapes nutritional response
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MTHFR gene
Folate conversion
Folate from food needs to be converted into its active form before the body can use it. Common variants in the MTHFR gene reduce the efficiency of this enzyme, meaning people with these variants convert less dietary folate into its usable form. Roughly 10 to 15 percent of the UK population carries the more significant variant. For these individuals, the standard dietary folate recommendation may not be sufficient.
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VDR gene
Vitamin D receptor function
Vitamin D needs to bind to the vitamin D receptor in cells to exert its effects. Variants in the VDR gene affect how effectively this binding occurs. Two people with identical vitamin D levels in their blood can have meaningfully different outcomes at the cellular level. This helps explain why some people consistently report symptoms of insufficiency despite blood levels that appear adequate.
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TMPRSS6 and HFE genes
Iron absorption
TMPRSS6 encodes a protein that regulates hepcidin, the hormone controlling iron absorption in the gut. Variants in TMPRSS6 are associated with lower iron absorption and higher rates of iron deficiency anaemia. The HFE gene influences iron storage regulation. These variants help explain why iron deficiency is more persistent in some people than dietary changes alone would predict.
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FADS1 and FADS2 genes
Omega-3 conversion
EPA and DHA can be obtained directly from oily fish or converted by the body from the plant-based omega-3 ALA. Variants in FADS1 and FADS2 reduce this conversion efficiency further. People with these variants convert ALA particularly inefficiently, meaning plant-based omega-3 sources are even less effective for them. Direct sources of EPA and DHA become more important.
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CYP1A2 gene
Caffeine metabolism
The CYP1A2 gene encodes an enzyme responsible for metabolising caffeine in the liver. Variants produce fast metabolisers and slow metabolisers. Fast metabolisers clear caffeine quickly and can consume coffee later in the day with minimal effect on sleep. Slow metabolisers retain caffeine for longer, meaning afternoon coffee reliably disrupts sleep quality. Two people drinking the same amount of coffee at the same time can have profoundly different physiological responses.
"Genetics does not determine your nutritional fate. It describes the landscape you are working in. And understanding it changes which choices make the most difference."
What this means for dietary advice
Generic dietary advice is not wrong. It is just incomplete. Eating a varied diet richin whole foods, limiting processed foods, and meeting baseline recommended intakes are good principles for most people most of the time. The problem isthat for a meaningful proportion of people, following these principles faithfully still leaves them with specific nutritional gaps because their biology makes certain nutrients harder to absorb, convert, or utilise.
This is not about optimisation as a luxury. For people who feel consistently unwell despite eating well, who cannot explain persistent fatigue, poor sleep, or low mood through obvious causes, the genetic layer is often where the explanation sits.
The nutrients they are short of are not the ones they would expect to be short of, and dietary changes that would work for most people do not work for them in the same way.
Understanding your genetic profile does not replace the fundamentals of a good diet. It contextualises them. It tells you which parts of the standard advice matter most for you specifically, and where you might need to go further.
In the Boone app
Boone is built on this principle. It analyses the genetic variants that influence how your body processes specific vitamins and minerals, and connects those insights to the food you actually eat through the food log and scanner. The result is not a set of rules. It is a personal nutritional picture that reflects your biology, not a population average.
A practical framework for thinking about your own response
If you are eating broadly well but still experiencing persistent symptoms. Fatigue, poor sleep, low mood, frequent illness, brain fog, the question worthasking is not 'am I eating the right foods?' but 'is my body processing thesefoods the way I assume it is?'
Start with the basics: a blood test for the most commonly deficient nutrients. Iron, ferritin, vitamin D, B12, folate. These give you measured data rather than assumptions. If levels are lower than expected despite a good diet, the genetic layer is worth investigating.
Understanding which genetic variants affect your absorption of key nutrients tells you whether you need to be more deliberate than average. Higher intake, better food combinations, direct forms of nutrients rather than precursors that need conversion. It turns generic advice into personal guidance.
"Personalised nutrition is not a premium product category. It is a description of how nutrition actually works. And why the same advice does not produce the same results for everyone."
Because nutritional response is shaped by genetics, gut health, lifestyle, and individual biology, not just what you eat. Genetic variants affect how efficiently different nutrients are absorbed, converted, and used at the cellular level. What looks like the same diet produces different nutritional outcomes in different bodies.
MTHFR encodes an enzyme that converts folate from food into its biologically active form. Common variants in this gene reduce conversion efficiency. People with these variants may have lower active folate levels than their dietary intake would suggest, which has implications for energy, mood, and cellular health. Around 10 to 15 percent of the UK population carries the more significant variant.
No. Genetics describes tendencies, not fixed outcomes. Understanding your genetic profile shows you where you may need to be more deliberate: which nutrients to prioritise, which food combinations matter most for you, where supplementation might close a gap that diet alone cannot. It contextualises dietary choices rather than dictating them.
Yes, consistently and significantly. Studies comparing identical twins eating the same diet have found meaningful differences in blood nutrient levels, microbiome composition, and metabolic response. Genetic variation in absorption and conversion efficiency is a primary reason for these differences.
Boone analyses the specific genetic variants known to influence how your body absorbs and processes 14 vitamins and minerals, and connects those insights to your real diet through a food log, food scanner, and micro nutrition scores. The result is a personal nutritional picture that reflects your biology rather than a population average.
Find out what your genetics say about your nutrition.
Boone analyses the genetic variants that influence how your body processes specific vitamins and minerals, and connects those insights to the food you actually eat. Built on peer-reviewed research, developed alongside the Quadram Institute.
Download the Boone app and discover what your nutritional picture looks like.
