Why are legumes and potatoes prominent in grain-free dog foods linked to heart issues

Grain-free dog foods linked to heart issues

Grain-free kibbles often replace rice, corn, wheat, and barley with pulses (peas, lentils, chickpeas) and sometimes potatoes or sweet potatoes as major carbohydrate and protein sources, and this shift appears in many of the diets reported to regulators and researchers in cases of diet-associated dilated cardiomyopathy (DCM) in dogs. While no single cause has been proven, several plausible mechanisms and patterns have emerged from FDA communications and peer‑reviewed studies that help explain why these ingredients, especially peas, are under scrutiny.

What the FDA and veterinary researchers have observed

• FDA case reports showed most implicated diets were labeled grain-free and contained non‑soy pulses (peas, lentils) high on the ingredient list, with potatoes or sweet potatoes also appearing in a minority of formulas, prompting a continuing investigation without a definitive causal ingredient identified.
• The FDA noted that both grain-free and grain‑inclusive diets have appeared in reports, but pulses are likely used in “grain-free” foods in higher proportions than in grain‑containing formulas, which may explain their prominence in the cases.
• Independent analyses comparing “FDA‑reported” diets to others found that peas, and to a lesser extent lentils, strongly distinguished the diets associated with DCM, with metabolomic signatures suggesting peas as a leading possible ingredient linked to the pattern, although causality was not established.

Leading hypotheses: how pulses and potatoes could contribute

1. Amino acid and taurine dynamics

• Pulses are relatively low in the sulfur amino acids methionine and cysteine that dogs use to synthesize taurine, and high dietary fiber can increase bile acid binding and fecal losses, potentially increasing taurine demand and reducing availability in some formulas and dogs.
• Historically, taurine deficiency has been linked to DCM in certain dogs; however, in many recent grain‑free cases, blood taurine has been normal, indicating that taurine deficiency is not the sole explanation and that multiple mechanisms may be involved.

2. Fiber, oligosaccharides, and digestibility

• Legumes contain fermentable fibers and oligosaccharides (e.g., raffinose family), which can alter nutrient digestibility and gut metabolism; experimental work shows that certain diets can raise NT‑proBNP (a cardiac stretch biomarker) even when taurine is unchanged, suggesting early cardiac stress that may relate to fiber profile or other dietary factors.

3. Foodomics/metabolite signatures specific to peas

• Metabolomic profiling found that diets associated with DCM (those with ≥3 pulses/potatoes/sweet potatoes high in the ingredient list) had distinctive compound patterns compared to non‑associated diets, with peas showing the strongest link to the compounds differentiating the two groups; this points to pea‑related diet chemistry as a candidate driver even if the causal pathway remains unproven.

4. Inclusion level and formulation balance

• Short controlled trials indicate that very high pea inclusion can produce subclinical, DCM‑like changes in heart function and elevate NT‑proBNP within 4–5 weeks in dogs not predisposed to DCM, whereas lower inclusion or different formulations show smaller or no echocardiographic changes, implicating both dose and overall formulation quality.

5. Potatoes versus pulses

• Potatoes and sweet potatoes appeared less frequently than peas/lentils in reported diets, and emerging commentary suggests pulses may carry higher relative concern than potatoes; nonetheless, both have appeared in cases when used prominently, so overall formulation and proportions matter more than any single label term.

Evidence from feeding trials and clinical follow‑ups

• A 28‑day Beagle trial feeding a wrinkled pea diet showed increased NT‑proBNP, increased systolic chamber size, slightly reduced ejection fraction (still >60%), and reduced cardiac output, consistent with early DCM‑like changes, whereas other test diets (including a grain‑containing control) did not produce the same magnitude of effects.
• Another controlled study comparing grain‑based, grain‑free (with peas ~30%), oligosaccharide‑supplemented, and a separate “husbandry/dental” diet found NT‑proBNP rose after the grain‑free and oligosaccharide diets versus grain‑based, with the largest rise and functional impairment occurring on the high‑insoluble‑fiber husbandry diet; taurine remained unchanged across diets, underscoring non‑taurine mechanisms and the role of fiber and formulation.
• Clinical series report that dogs with subclinical abnormalities or DCM while eating pulse‑rich grain‑free foods often show improvement in biomarkers and echocardiographic indices after switching to grain‑inclusive or pulse‑free diets (sometimes alongside taurine supplementation), supporting a nutritional component in at least some cases.

Why “grain-free” drives higher legume/potato prominence

• Removing grains from kibble demands alternative carbohydrate and plant‑protein sources for structure and macronutrient targets; peas, lentils, and potatoes efficiently replace grain starch and protein while enabling “grain‑free” marketing claims, so manufacturers often use them at higher inclusion levels than seen in grain‑inclusive recipes.
• This high inclusion increases exposure to the ingredient profiles above (fiber/oligosaccharides, lower sulfur amino acids, distinctive metabolite patterns), and in certain formulations and dogs, may contribute to cardiac stress signals and functional changes.

What’s known versus not yet proven

• Known: A disproportionate share of reported diet‑associated DCM cases involved grain‑free diets that list peas and lentils prominently, sometimes potatoes/sweet potatoes, and switching away from such diets has been associated with improvement in many dogs.
• Not proven: A single causative compound, brand, or ingredient; the FDA explicitly states the issue is multifactorial, and legumes have been used in pet foods for decades without broad harm, suggesting that inclusion levels, processing, overall formulation, and dog‑specific factors likely interact.

Practical takeaways for diet selection

• Prioritize complete‑and‑balanced diets from companies with strong nutrition expertise and quality control; avoid formulas that rely heavily on peas/lentils as top ingredients if long‑term feeding is intended, especially in dogs with cardiac risk factors.
• If feeding a grain‑free diet, consider versions with lower pulse inclusion and monitor health, including possible NT‑proBNP or echocardiographic screening in at‑risk situations, in partnership with a veterinarian.
• Remember that both grain‑inclusive and grain‑free diets can be appropriate when well formulated; the pattern of high pulse inclusion (and possibly certain potato uses) is the primary concern raised by current evidence, not the absence of grains per se.

In short, legumes—particularly peas—and, to a lesser extent, potatoes became prominent in grain‑free foods as grain replacements, and their high inclusion levels correlate with diet patterns reported in DCM cases; emerging research points to amino acid balance, fiber/oligosaccharides, and distinctive pea‑related metabolite profiles as plausible contributors to early cardiac stress and subclinical dysfunction in some dogs, although a single cause has not been proven.