Nutrient Absorption: Are Your Supplements Working, or Just Passing Through?
By Marla Feingold MS, CNS, CKNS, LDN
- Why do I still have low vitamin levels even with supplements?
- How do I know if my body absorbs nutrients well?
- What are signs of poor nutrient absorption?
- Can your genes affect how you process vitamins?
Ever wondered whether those daily vitamins and supplements are actually doing their job or even getting into your system? Nutrient absorption varies widely between individuals. Genetics, digestive health, micronutrient metabolism, quality, and even the forms of nutrient all play a critical role in how your body processes and absorbs the supplements you consume.
Why Do Some People Have Low Vitamin Levels Despite Supplementing?
Taking supplements should theoretically boost your vitamin levels, but in reality, many people still struggle with deficiencies. This could be due to:
- Poor gut health – Conditions like celiac disease, Crohn’s, or even low stomach acid can impair nutrient absorption. A FUT2 gene variant may for example impact on how you are able to absorb vitamin B12.
- Nutrient competition – Certain vitamins and minerals can interfere with each other’s absorption. For instance, high calcium intake may inhibit magnesium absorption, while zinc competes with copper for uptake in the gut.
- Bioavailability issues – The form of the supplement matters. Some compounds are better absorbed than others methylated B vitamins vs. synthetic versions seen in Folate or B12.
- Genetic variations – different genes affecting how nutrients are metabolized, like the MTHFR gene for folate processing, and the TCN2 gene for transport of B12.
How Can You Tell If You Absorb Nutrients Well?
Understanding your body's efficiency at processing vitamins can be tricky. Here are some tell-tale signs to watch for:
- Laboratory Nutrient Testing –Blood, hair, and urine are often used to assess the absorption of vitamins.
- Energy levels and recovery – Persistent fatigue or slow healing could signal poor nutrient uptake.
- Gut health symptoms – Bloating, chronic diarrhea, or irregular digestion may indicate malabsorption. Even seeing undigested supplements in your stool.
Signs of Poor Nutrient Absorption
If your body isn’t effectively using the nutrients from food or supplements, you might notice physical or even neurological changes.
- Brittle nails or hair loss - Possible deficiencies in biotin, zinc, or iron.
- Frequent illness - Low vitamin D or vitamin C levels can weaken immunity.
- Neurological symptoms - Tingling in extremities can signal vitamin B12 deficiency.
- Persistent digestive issues - Your gut microbiome plays a huge role in nutrient absorption.
- Cognitive Changes - poor focus, anxiety, sleep disturbances, agitation or irritability, depression.
Do Genes Affect How We Process Vitamins?
Genetic variants can impact how a nutrient is metabolized, transported, and absorped. Some genes to be aware of:
- MTHFR: Impacts folate metabolism, potentially leading to deficiencies.
- FUT2: Influences gut microbiome impact on B12 absorption.
- GC: Affects vitamin D binding and transport in the bloodstream.
- TCN2: Which transports B12 into your cells and leads to deficiency even with adequate intake.
- SLC22A5: Is involved in carnitine transport for fatty acids into the mitochondria.
- HFE: Controls iron absorption; variants can lead to hereditary hemochromatosis, causing excessive iron buildup.
- CYP1A2 is responsible for metabolizing caffeine, which can impact the absorption of calcium and iron.
- HLA: human leukocyte antigens associated celiac disease from gluten can cause gut wall inflammation potentially leading poor nutrient absorption issues resulting in deficiency conditions like anemia, osteoporosis and thyroid problems.
- SLC23A1: Encodes for vitamin C transporters across epithelial layers such as gut and kidneys and can lead to reduced dietary absorption and circulating levels.
Optimising Nutrient Absorption
To ensure you’re getting the most from your supplements:
- Personalised nutrition - Genetic testing or micronutrient panels can help tailor supplements to your needs.
- Focus on gut health - Probiotic-rich foods and digestive enzymes can support absorption and consider eliminating foods that could lead to increased gut inflammation such as corn, gluten, sugar, and excessive dairy.
- Choose bioavailable forms - Look for chelated minerals and active vitamin compounds. Whole food sources of supplement may be more bioavailable. Liposomal and or micellized forms of vitamins and nutrients are tiny lipid entrapped forms of nutrients that may have greater absorption and bioavailability.
- Seek out supplements that use the following - third party testing, transparent ingredient sourcing and traceability, minimal additives, avoid synthetic additives, have positive review, do not have unrealistic label claims, and at least GMP-certified.
Conclusion:
Absorbing nutrients is just as crucial as consuming them. If your vitamin levels remain low despite supplementation, consider factors like gut health, genetic variations, nutrient interactions, and what quality and forms of nutrients you are consuming.
Optimising absorption isn't just about what you take, it's about how your body processes it. By tailoring your approach through functional testing, diet adjustments, and bioavailable nutrient forms, you can ensure your body gets the full benefit of what you consume to fuel your health.