Bioavailability – what is most bio-efficacious?
We might assume when we feed our dogs that every ingredient on the label has a role to play. But we’d be wrong: not all of those ingredients are absorbed or utilised (bio-efficacious).
Everything depends on bioavailability: the all-important difference between intake and effect. Nutrients need to complete a complex journey before their benefits can be felt. So many factors influence whether they make it across the line – which is why form, processing methods, gut health and nutrient combinations matter. What, when and how we feed can make a real difference.
The Three Pillars
Bioavailability is the first, quantitative test: what proportion of a nutrient is absorbed into the bloodstream after digestion. Nutrients may fail this early stage by being trapped within the food matrix, prematurely destroyed or blocked by competing compounds. If they don’t make it into circulation, they’re lost.
Bio-delivery is the intermediate stage. Once in circulation, nutrients must be transported to the sites where they will perform their respective functions. The nutrients undergo a filtering process; some are stored, some cleared; those that remain compete for transport carriers and may, even then, degrade before arrival.
Bio-efficacy is the functional outcome: can and will the nutrient carry out its intended function when it reaches its destination? Some compounds, such as vitamin D or riboflavin, still need to be activated after arrival if they are to become biologically active. Without this activation, bio-efficacy declines.
The digestive hurdle
This initial phase, where nutrients are broken down and passed into the bloodstream, takes place in the gut. And it’s where the processing method will make a difference.
High heat from extrusion or baking is intended to improve shelf life – but at the same time it can reduce protein digestibility and damage sensitive vitamins, resulting in the loss of certain amino acids.[1] Conversely, less intensive preparation methods, such as mild cooking or soaking, result in superior nutrient utilisation and beneficial shifts to the gut microbiome[2].
It shouldn’t be forgotten that this first hurdle is reliant on the physical environment: good hydration and healthy gut motility are essential to thoroughly mix food with digestive enzymes and ensure that it moves at the right speed for nutrient liberation and absorption.
The nutrient’s own structure is just as critical. Minerals illustrate this perfectly: taken from natural sources like meat or bone, minerals are typically presented in an organic complex, already bound to amino acids. This binding acts like an escort, protecting the mineral from competitive compounds and ushering it efficiently across the gut wall. Inorganic forms dissolve immediately in the gut and are highly vulnerable to blocking by fibre components like phytates or blocked by calcium.
Transport and delivery
Once absorbed, nutrients undergo first-pass metabolism in the liver. This filtering process, although it is essential for detoxification and storage, further reduces the effective dose that continues into general circulation.
Those that continue beyond the liver enter a crowded field, many of them relying on the same transport systems and competing for transport pathways that are already prone to saturation. Unfortunately, without the right carrier, a nutrient may never reach its destination – and the bar is raised even higher for compounds that need to cross the selective blood-brain barrier.
Efficacy within the cell
The last part of the journey is where the nutrient is ultimately available to perform its intended function.
Some nutrients like glucose are delivered in their final, usable form; their efficacy depends solely on whether cellular conditions are right for their utilization. Others, like Vitamin D, require yet another conversion before they are considered fully bio-efficacious.
Plant compounds like flavonoids and polyphenols are too bulky or polar for direct absorption. The microbiome is integral to efficacy: gut bacteria will break these compounds down into smaller metabolites that can then be absorbed and, in some cases, cross into the brain.
Like everything else, bio-efficacy declines with age: reduced enzyme production and decreased microbial diversity in older dogs can slow digestion and reduce the overall efficiency of nutrient utilisation. Supporting gut health through varied, fibre-rich foods and probiotic sources can help maintain microbial balance and keep the system running more efficiently.
Closing the gap: being practical
If losses occur at every stage – digestion, absorption, transport and activation – how can they be mitigated? Bioavailability is about coordination and impact, not increased intake: how we feed, not how much. Absorption depends on the company nutrients keep; nutrient losses can occur simply through interactions on the plate.
Fat-soluble vitamins A, D, E and K need dietary fat for proper uptake; vitamin E and selenium help protect delicate omega-3 fatty acids from oxidation. Understanding this can be of practical use in everyday cooking and make a measurable difference to nutrient uptake.
Soak or sprout to soften the first hurdle
Soaking dried beans, legumes and certain seeds like lentils, chickpeas or broccoli seeds helps reduce phytates and oxalates that bind minerals and hinder digestion. Sprouting takes this a step further, increasing enzyme activity and improving mineral availability at the very start of the course. (This doesn’t apply to mucilaginous or oil-rich seeds such as chia or flax, which behave differently when soaked.)
Pair iron with vitamin C
Iron is notoriously resistant to absorption. Serving iron-rich foods, such as meat or liver, alongside small amounts of vitamin-C-rich ingredients – parsley, bell pepper or even a touch of fruit – converts ferric iron (Fe³⁺) into the more readily absorbed ferrous form (Fe²⁺).
Support fat-soluble vitamins
Vitamins A, D, E and K rely on dietary fat for absorption. Combine vegetables like carrots or pumpkin with a small amount of healthy fat – egg yolk, kefir or oily fish – to help these vitamins clear the intestinal barrier efficiently.
Keep mineral balance in check
Too much of one mineral can hold others back. Calcium and zinc, for example, compete for the same transport systems. Balancing phosphorus-rich foods such as meat or seeds with a safe calcium source, like ground eggshell or plain yoghurt, keeps the course fair and prevents nutritional bottlenecks.
Feed the microbiome
A balanced microbiome is essential. Pairing berries or leafy greens with probiotic foods such as kefir or fermented vegetables provides fibre, antioxidants and beneficial bacteria that support digestion, absorption and activation.
Avoid unintentional nutrient loss
We can sometimes reduce nutrient intake without realising it. Water-soluble vitamins, especially the B-group and vitamin C, are easily lost through leaching or prolonged heat. Vegetables cooked by steaming or sous vide are better preserved than boiled vegetables. If you do boil, use those ‘lost’ nutrients by incorporating the cooking water into the meal as a broth or stock.
Bioavailability isn’t an academic nicety. It is the practical essence of whether a diet is truly working. Learning to use this three-pillar journey as a guide, strategic preparation and pairing helps us to move beyond surface-level nutritional claims. Aiming to unlock the full potential of every ingredient is often more impactful than simply feeding more.
References:
[1] Oba PM, Hwisa N, Huang X, Cadwallader KR, Swanson KS. Nutrient and Maillard reaction product concentrations of commercially available pet foods and treats. J Anim Sci. 2022 Nov 1;100(11):skac305. doi: 10.1093/jas/skac305. PMID: 36082767; PMCID: PMC9667973.
[2] Geary, E. L., Oba, P. M., Applegate, C. C., Clark, L. V., Fields, C. J., & Swanson, K. S. (2022). Effects of a mildly cooked human-grade dog diet on gene expression, skin and coat health measures, and fecal microbiota of healthy adult dogs. Journal of Animal Science, 100(10), skac265. https://doi.org/10.1093/jas/skac265
Want to know more? These studies might be useful:
Renzone G, Arena S, Scaloni A. Cross-linking reactions in food proteins and proteomic approaches for their detection. Mass Spectrom Rev. 2022 Sep;41(5):861-898. doi: 10.1002/mas.21717. Epub 2021 Jul 12. PMID: 34250627.
[Tanprasertsuk J, Perry LM, Tate DE, Honaker RW, Shmalberg J. Apparent total tract nutrient digestibility and metabolizable energy estimation in commercial fresh and extruded dry kibble dog foods. Transl Anim Sci. 2021 May 27;5(3):txab071. doi: 10.1093/tas/txab071. PMID: 34278234; PMCID: PMC8279163.
Oba PM, Utterback PL, Parsons CM, Swanson KS. True nutrient and amino acid digestibility of dog foods made with human-grade ingredients using the precision-fed cecectomized rooster assay. Transl Anim Sci. 2019 Dec 6;4(1):442-451. doi: 10.1093/tas/txz175. PMID: 32705002; PMCID: PMC6994059.
Important Considerations:
- Always consult your veterinarian before making any significant dietary changes, particularly where there are pre-existing health conditions or dietary restrictions.
- If you are feeding commercial food, check the label for ingredients before giving more. Excessive intake of any foods can have adverse effects.
- Ensure (where possible) that you use high-quality, organic products specifically formulated for pets (or better still, human grade ingredients) to avoid any potential adverse effects.
- Introduce new foods gradually to avoid adverse effects such as gastrointestinal upset or diarrhoea.
- I provide nutritional information purely as a helpful guide. Nutritional information on ingredients is obtained from the US Department of Agriculture’s FoodData Central site (https://fdc.nal.usda.gov/index.html) and any nutritional information provided in recipes is based on an online calculator: calories and other information will vary based on brands, ingredients and other factors.
- Check nutrient levels and recommendations for your dog’s weight, age and activity. For example this nutritional guideline produced by FEDIAF.
- I am not a professional canine nutritionist but supporting research is cited.
- The recipes shared were created by me and tested in my kitchen – and tasted and approved by our doggy friends!