SUPPLEMENTS · MYTH BUSTED
MYTH BUSTED
The supplement industry depends on this belief. The science does not support it. Micronutrients operate within specific physiological ranges — below them, deficiency causes problems; above them, excess causes different problems. Toxicity from vitamin overconsumption is a documented clinical reality, not a theoretical risk.
Vitamins A, D, E and K are fat-soluble — they are stored in adipose tissue and the liver rather than excreted. A 2025 review in Pharmacy Times confirmed that excessive consumption of fat-soluble vitamins leads to hypervitaminosis, a condition with serious documented adverse effects.
Vitamin A toxicity causes liver damage, bone loss, and birth defects. Excess vitamin D raises blood calcium (hypercalcaemia) to levels that damage kidneys and the cardiovascular system. A 2025 PMC review on vitamin toxicity and the nervous system found that fat-soluble vitamins are significantly more likely than water-soluble vitamins to accumulate to harmful levels when chronically over-consumed.
While water-soluble vitamins — C and the B vitamins — are largely excreted in urine, this does not mean megadosing is harmless. High-dose vitamin C interferes with copper absorption and can cause gastrointestinal distress. Very high B6 intake is associated with peripheral neuropathy.
A 2021 computational analysis published in PMC confirmed that even hydrosoluble vitamins can exert toxicological effects at high doses or over prolonged periods — and that routine supplementation should not be assumed harmless without considering dose and duration.
“Fat-soluble vitamins A, D, E and K are stored in the body. They do not leave when you take too much. They accumulate — and at high enough levels, they cause organ damage.”
Vitamins and minerals do not operate in isolation. High-dose calcium supplementation reduces iron absorption — a significant concern for active women already at elevated risk of iron deficiency due to menstruation and training-induced losses. Excess zinc depletes copper over time. Excessive iron generates oxidative stress.
This is precisely why food — which delivers nutrients in naturally balanced ratios, alongside fibre, water and thousands of phytocompounds — consistently outperforms isolated supplementation for general health. Supplements are designed to address specific deficiencies, not to replace the complexity of a varied diet.
Vitamin D in the UK between October and March is nearly universally recommended — sunlight-derived synthesis is insufficient at northern latitudes during these months. Iron supplementation is evidence-backed when blood tests confirm deficiency, not as a precaution. Magnesium glycinate has support for improving sleep quality and reducing cramping in active individuals.
Beyond these targeted cases, a 2024 position from multiple nutrition bodies maintains that healthy adults eating a varied diet do not require broad-spectrum supplementation. The evidence-based approach: test first, identify the specific gap, supplement precisely. More is not better — targeted is better.
Taking more vitamins does not produce better health outcomes. The dose is the determining factor — and past a certain threshold, the same compounds that support health begin to impair it. Fat-soluble vitamins accumulate. Minerals compete. The physiological relationships involved are far more complex than the marketing suggests.
For active women in the UK, the evidence supports: Vitamin D supplementation through winter, iron if blood work confirms deficiency, magnesium if sleep and recovery are suffering. Everything else should come primarily from food. Before adding broad-spectrum supplementation, speak to a GP and get blood work done — guesswork is not a nutritional strategy.
SOURCES & RESEARCH
Pharmacy Times (2025). Understanding the Toxicity Profiles of Fat-Soluble Vitamins: Insights Into Vitamins A, D, E, and K.
PMC (2025). Toxic Effects of Excess Vitamins A, B6, and Folic Acid on the Nervous System. PMC12350011.
PMC (2021). Hydrosoluble and Liposoluble Vitamins: New Perspectives through ADMET Analysis. PMC8622797.
Medscape (2023). Vitamin Toxicity: Pathophysiology and Clinical Management. emedicine.medscape.com/article/819426.