Table 2.

The role of diet in early life and during childhood on timing of puberty.

Period	Dietary Source	Mechanism of Action	BMI Dependent and/or Independent Action	Effect on Puberty	References
Early-life nutrition	Breastfeeding	Overweight prevention through normal hormonal and microbiome balance and positive psychosocial influence	Both	Precocious puberty prevention	[102,107,120,130,131,132,133,140,141,142,143,162]
	Formula feeding	Overweight development and predisposition to childhood obesity through increased IGF-1 and consequent enhanced sex steroid production	BMI dependent	Increased risk for precocius puberty	[136,153,154,158,159]
	Soy-based formulas	Weak estrogenic effects of soy isoflavones	BMI independent	Uncertain increased risk for precocius puberty	[166,167,171,172,173]
	Complementary feeding	Overweight development in case of age-inappropriate feeding and high protein consumption	BMI dependent	Increased risk for precocius puberty	[174,175,176,178,179]
	Soy-based foods	Weak estrogenic effects of soy isoflavones	BMI independent	Uncertain increased risk for precocius puberty	[166,172,180,181,186,187]
Childhood nutrition	High-energy diet	Higher levels of leptin, IGF-1 activation, adrenal androgen overproduction, and increased conversion of androgens to estrogens	BMI dependent	Increased risk for precocius puberty	[192,199,204,205,206]
	Macronutrients
	Protein intake	Adiposity rebound before pubertal onset, IGF-1 secretion	Both	Increased risk for precocius puberty	[2,192,209,210]
	Fat intake	Direct effect on steroidogenesis and mammary gland development, indirect effect through induction of low-grade hypothalamic inflammation	BMI independent	Increased risk for precocius puberty (PUFAs). Uncertain increased risk for precocius puberty (MUFAs)	[2,192,217,221]
	Carbohydrate intake	Rapid increase in insulin concentration in high-glycemic-index diets resulting in increased availability of sex hormones and IGF-1	BMI independent	Uncertain increased risk for precocius puberty	[221,224]
	Micronutrients
		Further studies are needed to identify the possible mechanisms	BMI independent	Uncertain increased risk for precocius puberty	[2,192,217,226]
	Dietary Pattern
	Mediterranean diet	Reduction in circulating levels of estrogen, follicle-stimulating hormone, and luteinizing hormone. Increased excretion of estrogen. Stimulation of hepatic synthesis of SHBG, which reduces the biological availability of sex hormones	BMI independent	Precocious puberty prevention	[236]
	Vegetarian diet	Lower leptin levels	BMI dependent	Uncertain increased risk for later puberty	[238,239,240,242]
	New dietary patterns	A combination of the above mechanisms of high energy, fat, glycemic, and protein intake associated with unbalanced micronutrient supplies	Both	Increased risk for precocius puberty	[191,244,245]