FUNCTIONAL HEALTH GUIDE -- THE NUTRITIONAL DECISION TREE

Functional Health — Nutrition & Diet Selection

A Lab-Driven Nutrition Decision Tree for Dogs & Cats

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Nutrition is one of the most powerful longevity interventions available — when it is chosen based on biology, not branding.

This worksheet turns diet selection into a measured, repeatable decision process, rather than guesswork.

This is a decision-support tool, not a diagnosis.
It is organized around The 3 Core Goals.

The 3 Core Goals

This worksheet is designed to help you:

  1. Clarify what matters most right now

  2. Determine the next best test (if any)

  3. Choose the most appropriate next step

Core Goal 1: Clarify What Matters Most Right Now

The most important nutrition mistakes happen when diet is changed without understanding the biology driving the decision.

Functional Health begins with identifying which systems are under stress, because those systems dictate diet choice.

Step 1: Establish Baseline Data (Foundational)

Before changing diet, gather:

  • CBC

  • comprehensive chemistry

  • urinalysis (pH, sediment, specific gravity)

  • body condition and muscle score

  • complete diet history (protein source, format, treats, supplements)

Strongly recommended in HPLL patients:

  • SDMA

  • phosphorus

  • triglycerides & cholesterol

  • blood glucose ± fructosamine

  • taurine (cats, grain-free dogs)

  • B12 & folate

  • blood pressure

  • fecal analysis if GI signs are present

Without baseline data, nutrition decisions are assumptions, not strategy.

Core Goal 2: Determine the Next Best Test (If Any)

Not every pet needs every test — but certain red flags immediately dictate diet direction.

Functional Health prioritizes signal over volume.

Step 2: Screen for Red Flags That Dictate Diet Choice

A. Kidney Stress Present?

Indicators

  • ↑ SDMA or creatinine

  • ↑ phosphorus

  • dilute or isosthenuric urine

Nutrition direction

  • increase dietary moisture (non-negotiable)

  • moderate (not low) high-quality protein

  • reduce phosphorus burden

  • avoid ultra-processed kibble

  • favor gently cooked or balanced home-prepared diets

Avoid

  • raw diets in advanced kidney disease

  • high-phosphorus meats without binders

B. Liver Stress or Bile Abnormalities?

Indicators

  • ↑ ALT / ALP

  • low BUN

  • elevated bile acids

  • ammonium biurate crystals

Nutrition direction

  • highly digestible protein

  • moderate fat

  • avoid copper excess

  • vegetarian or mixed-protein diets (dogs only)

Cats: animal protein required; adjust digestibility and fat load.

C. Evidence of Inflammation?

Indicators

  • elevated globulins

  • chronic ear or skin disease

  • GI signs

  • orthopedic pain

  • elevated triglycerides

Nutrition direction

  • eliminate ultra-processed diets

  • reduce AGE exposure

  • simplify ingredients

  • optimize omega-3s

  • evaluate carbohydrate load

Core Goal 3: Choose the Most Appropriate Next Step

Once dominant stressors are identified, nutrition should follow a clear pathway, not trial-and-error.

Step 3: Allergy & Immune Reactivity Pathway

Signs suggestive of food sensitivity

  • chronic itching

  • recurrent otitis

  • paw licking/chewing

  • vomiting or diarrhea

  • anal gland disease

Step 3A: Elimination Trial (When Indicated)

Requirements

  • single novel protein or hydrolyzed protein

  • no treats, flavored meds, or supplements

  • duration: 8–12 weeks

If symptoms improve
→ maintain simplified diet
→ avoid unnecessary protein rotation

If symptoms persist
→ food allergy unlikely
→ proceed to environmental or GI workup

Vegetarian Diet Branch (Dogs Only)

Consider only if

  • severe protein hypersensitivity

  • multiple failed elimination trials

  • persistent GI inflammation

Requirements

  • professional formulation

  • amino acid sufficiency confirmed

  • ongoing lab monitoring

Never appropriate for cats.

Step 4: Cardiac & Taurine Safety Check

Taurine testing indicated if

  • any cat (preferred)

  • dogs on grain-free or exotic protein diets

  • murmurs or DCM present

If taurine is low or borderline

  • supplement taurine

  • reformulate diet

  • avoid poorly formulated grain-free foods

Step 5: Urinary Tract Decision Tree (Critical)

Urinalysis review

  • pH

  • crystal type

  • specific gravity

  • hematuria

Alkaline urine ± struvite

  • increase moisture

  • moderate magnesium

  • avoid excessive plant material

  • avoid vegetarian diets in cats

Acidic urine ± calcium oxalate

  • avoid over-acidification

  • ensure adequate calcium

  • avoid high-oxalate ingredients

  • moderate protein excess

Urate crystals or stones

  • reduce purines

  • moderate protein

  • increase water intake

  • evaluate liver function

Male cats — override rule
If male cat + any urinary abnormality:

  • dry food is contraindicated

  • moisture becomes the primary intervention

  • diet must actively manage pH and minerals

  • regular urine rechecks required

This is life-saving, not optional.

Step 6: Metabolic & Glycemic Assessment

Indicators

  • elevated glucose or fructosamine

  • obesity

  • elevated triglycerides

Nutrition direction

  • reduce glycemic load

  • avoid ultra-processed carbohydrates

  • increase protein quality

  • strategic fiber use (dogs)

Step 7: GI Absorption & Microbiome Pathway

Low B12 / folate or chronic GI signs

Nutrition direction

  • improve digestibility

  • reduce ingredient complexity

  • consider novel proteins

  • evaluate fat tolerance

  • supplement deficiencies

Step 8: Home-Cooked Diet Decision

If a home-cooked diet is chosen, all are mandatory:

  • professional balancing (e.g., BalanceIt)

  • regular lab monitoring

  • taurine supplementation for cats

  • verified calcium intake for dogs

Without professional balancing → not approved.

Ongoing Monitoring Loop

Nutrition is dynamic, not static.

Recheck labs:

  • every 6–12 months (healthy adults)

  • every 3–6 months (longevity patients)

  • 8–12 weeks after major diet changes

The Functional Nutrition Principle

Diet should never be chosen based on:

  • brand reputation

  • marketing claims

  • trends

  • personal ideology

Diet should be chosen based on:

  • biology

  • labs

  • response over time

When to Escalate Beyond the Worksheet

A PET LONGEVITY CONSULT  is appropriate when:

  • multiple systems influence diet choice

  • lab abnormalities conflict

  • prior diet changes have failed

  • prescription longevity medications are being considered

Expert guidance prevents missteps and unnecessary restriction.


Start a Pet Longevity Consult

Your Next Step

If diet decisions feel complex:

  • complete Functional Health — Foundations first

  • review system-specific worksheets that apply

  • escalate to expert guidance when biology overlaps

There is no single “best diet” — only the appropriate diet for your pet today.


About These Worksheets


This worksheet is part of the Functional Health system developed at PetFunctionHealth.com, designed to identify early decline and guide long-term longevity strategy.