“Too much vitamin D as bad as too little”: ANSES warns of overdose dangers as winter demand picks up

30 Sep 2021 --- As the days draw shorter across the Northern Hemisphere and flu season beckons, attention is turning toward vitamin D, with supplement retailer Holland & Barrett recently celebrating the first day of fall as “Vit D Day.”

However, the French Agency for Food, Environmental and Occupational Health & Safety (ANSES) is warning of the dangers of vitamin D overdose, especially for infants. As a result, it is urging the French public to opt for vitamin D medication rather than food supplementation.

“Although food supplements are regulated to ensure their safe use, the package leaflets for medicines containing vitamin D provide clear information on doses, precautions for use, risk of adverse effects and overdose,” Gwenn Vo Van Regnault, nutrivigilance project officer at ANSES, tells NutritionInsight. 

Isabel Tarrant, nutritionist at Holland & Barrett, adds that it is important that consumers stick to the daily recommended dose unless advised otherwise by a doctor, as high levels of vitamin D can be harmful to the body.One in five UK adults has low vitamin D levels. 

Dangers of too much vitamin D
Vitamin D is essential for bone growth in children. To ensure this growth, vitamin D is prescribed in France from the first few days of a baby’s life to prevent rickets, which is a disease of growth and ossification.

However, ANSES stresses that giving your child too much vitamin D can be just as harmful as not giving enough. 

Vitamin D plays a vital role in aiding the absorption of calcium from food. However, excessive intake of vitamin D can lead to elevated blood calcium levels, known as hypercalcemia.

Tarrant explains that prolonged high levels of calcium in the blood can result in calcification of the arteries, in which calcium combines with cholesterol and forms plaques that are deposited on the artery wall. 

This can also increase the risk of atherosclerosis and coronary heart disease, as well as kidney injury and digestive issues. 

Medicines versus supplements 
Medicines have a higher level of requirement in terms of the quality of raw materials, manufacture and control of dosage in each batch, compared to food supplements, Van Regnault explains. 

“Medicines are products subject to a marketing authorization whereas food supplements are only subject to a declaration. Moreover, the control of food supplements is made difficult by the increase in the offer on the internet in particular.” 

Notably, ANSES has received three reports of cases of hypercalcemia in infants over the last year – all of which were traced to products designed for adults purchased online. 

“The increase in internet purchases and supply is likely to increase the risk of overdose,” says Van Regnault. 

ANSES has also had a case of hypercalcemia in an 81 year old person following an overdose of a food supplement bought on the internet, which contained 40,000 IU per day. The upper safe limit for adults is 4,000 IU per day, with 400-800 IU per day being sufficient to support the immunity of the average healthy adult. 

Last year, a UK study argued that health professionals perceiving vitamin D as a medicine, rather than as a key nutrient, are constraining practice and jeopardizing elderly care home residents’ health. Hypercalcemia is only a risk when vitamin D is taken in excessive amounts. 

A solution in vitamin K2?
Tarrant notes that people who are required to take a high dose of vitamin D daily should also take a vitamin K2 supplement to avoid the build-up of calcium in the arteries. Vitamin K2 transports calcium from the arteries to the bones, supporting healthy bone function and preventing calcification of the arteries.

Kappa Bioscience goes as far as to call this combination the “perfect pair,” noting that vitamins D3 and K2 each function more effectively in the presence of the other. 

ANSES has not investigated whether consuming vitamin K2 would help prevent overdoses, but Van Regnault notes that two reported cases of hypercalcemia involved a food supplement containing both vitamin D and vitamin K2.

A new immunity star
Tarrant emphasizes that the consequences of vitamin D toxicity should not scare consumers off from taking vitamin D supplements, as it is an essential nutrient for immune and bone health.

“Pre-pandemic, vitamin D was most commonly recognized for supporting bone health and vitamin C was known as the ‘star’ for immune support. During the pandemic, public health knowledge on the importance of vitamin D for the immune system significantly increased as the UK became aware of the scientific literature, and public health messaging surrounding vitamin D was introduced.” 

According to Holland & Barrett, despite the government guidelines on vitamin D, almost half (48%) of UK consumers still do not take a vitamin D supplement at all. Additionally, only 12% say they now take one much more regularly than they did prior to the start of the pandemic in March 2020.

Therefore, it is urging consumers to supplement through the fall and winter months as part of a holistic approach to immunity, which includes good sleep, exercise and stress relief. 

In February, German scientists flagged that vitamin D supplementation could be a simple and inexpensive way to reduce cancer mortality. 

By Katherine Durrell