Missing Your Period on a Plant-Based Diet? What You Need to Know About Functional Hypothalamic Amenorrhea

When your period disappears, it can feel confusing, worrying, and even a little isolating. The medical name for this is Functional Hypothalamic Amenorrhea (FHA), which happens when the brain switches off reproduction because it senses the body doesn’t have enough energy or safety to sustain it.

The effects are far from invisible. Women with FHA often notice fatigue, mood changes, hair thinning, and an increased risk of bone loss. For many, fertility concerns arise too.

As a naturopath and nutritionist, I’ve seen FHA in women following what looks like on a paper, really healthy plant-based diets. That’s not because vegan or vegetarian diets are inherently problematic—they can be wonderfully supportive for hormone health and disease prevention when done right. The issue arises when energy intake is too low, sometimes without the woman realising it.

The Case of the “Perfect” Vegan Diet

One of the most common things I’ve seen in clinic is women presenting with what looks like a flawless diet. Every food group is represented, colourful vegetables, legumes, nuts, and seeds. But when I dig into the quantities, the reality is different.

I remember one young woman who hadn’t had her period in over two years. Blood testing showed her hormone levels were virtually non-existent. It didn’t surprise me—she was eating tiny amounts despite her diet looking impeccable on paper.  Her portion of oats was a couple of tablespoons; I can assure you that this is not meeting anybody’s needs!

Together we increased her intake to a truly nourishing level and I prescribed a personalised herbal formula to support her endocrine system. Within a few weeks, she had her first period in years. It was extraordinary how quickly her body responded once it felt safe and replenished.  The most joyous part of this story is that she recently gave birth to a beautiful girl; something that would never have been possible without a drastic change to her diet.

Why Plant-Based Women Can Be Vulnerable

Plant-based diets can absolutely sustain menstrual health, but they do have some qualities that can make women more vulnerable to FHA:

• Low calorie density: Vegetables and legumes can be filling but not always energy-rich. Unless portions are large and more calorie-dense foods (certain fruits, seeds, nuts, avocado, grains) are included, it’s easy to slip into an energy deficit.
• High fibre satiety: Fibre is fantastic for health, but it can blunt appetite, leading women to unintentionally under-eat.
• Lifestyle overlap: Many plant-based women are also highly active (yoga, running, fitness). Combined with lower calorie intake, this can tip the balance further.

Clinical research confirms this. A large study of amenorrheic women found that reduced energy availability—even without weight loss—was enough to disrupt cycles (Loucks & Thuma, 2003). More recent evidence highlights that stress, exercise, and under-eating together amplify the risk (Misra & Klibanski, 2014; De Souza & Williams, 2004).

Restoring Menstrual Health Naturally

The foundation of FHA recovery is always adequate nutrition. That means:

• Eating enough calories to reassure the body that it’s safe.
• Including energy-dense plant foods such as tahini, nuts, seeds, avocado, and Ahiflower oil.
• Ensuring plant-based protein sources like lentils, tofu, and quinoa are part of daily meals.
• Supporting with key nutrients: iron, zinc, B12, iodine, and omega-3 fats (from flax, chia, walnuts, or Ahiflower oil).

Alongside this, herbal medicine can provide support:

• Vitex agnus-castus (Chaste
  Your period has been absent for three months or more.
• You feel constantly fatigued despite rest.
• Recovery from exercise is slow.
• Libido has declined.
• You’ve experienced stress fractures or unexplained bone pain.Tree Berry): Used for regulating progesterone.
• Withania somnifera (Ashwagandha): Calms the stress response and supports resilience.
• Rehmannia glutinosa: A traditional Chinese medicine herb for restoring cycles.

In my clinical experience, the combination of nutritional adequacy and herbal support creates the conditions for the body to trust it can safely restart ovulation and menstruation.

Signs You Might Have FHA

• Your period has been absent for three months or more.
• You feel constantly fatigued despite rest.
• Recovery from exercise is slow.
• Libido has declined.
• You’ve experienced stress fractures or unexplained bone pain.

Listening to the Body’s Wisdom

Philosopher Lao Tzu wrote: “Nature does not hurry, yet everything is accomplished.” FHA is the body’s way of whispering: I need more nourishment, more rest, and more safety.

The good news? With the right nutrition and support, periods can—and typically do—return readily, sometimes surprisingly quickly. Your cycle is not just about fertility—it’s a reflection of your overall vitality. If it’s missing, it’s worth listening closely.

References

• Loucks, A. B., & Thuma, J. R. (2003). Luteinizing hormone pulsatility is disrupted at a threshold of energy availability in regularly menstruating women. Journal of Clinical Endocrinology & Metabolism, 88(1), 297–311.
• Misra, M., & Klibanski, A. (2014). Endocrine consequences of anorexia nervosa. Lancet Diabetes & Endocrinology, 2(7), 581–592.
• De Souza, M. J., & Williams, N. I. (2004). Physiological aspects and clinical sequelae of energy deficiency and hypoestrogenism in exercising women. Human Reproduction Update, 10(5), 433–448.

Photo by cottonbro studio