While millets are extraordinarily nutritious, excessive consumption without dietary balance can lead to some adverse effects. Nutritional research and clinical guidance universally recommend moderate, well-varied millet consumption rather than over-reliance on a single grain. A 2023 review on millet health benefits (Sabuz et al., Separations, MDPI) also addressed the anti-nutritional compounds that can become problematic in large quantities.

Potential side effects of excessive millet consumption:

Thyroid interference: Very high intake of goitrogenic millets (particularly pearl millet and foxtail millet) without adequate iodine may reduce thyroid hormone production.

Anti-nutrient effects: Phytates, tannins, and oxalates in unprocessed millets can bind to calcium, iron, and zinc, reducing their absorption — problematic if millets constitute the sole dietary staple.

Slow digestion: High insoluble fiber content can cause delayed gastric emptying, bloating, and flatulence in individuals with sensitive digestive systems or intestinal disorders.

Reduced protein digestibility: Tannins in finger millet form complexes with proteins and inhibit digestive enzymes, potentially reducing protein availability if consumed in excess.

Celiac-safe but not protein-complete: Millets are gluten-free but low in lysine — exclusive millet diets without complementary protein sources may lead to amino acid imbalances.

Water intake: Increased fiber demands increased hydration; insufficient water with high millet intake may worsen constipation.

Mitigation: Soaking, fermenting, sprouting, and cooking millets significantly reduces anti-nutrient loads and improves overall nutritional bioavailability.