Anchor claims its “light-proof” bottles protect the nutrients in milk from the ravages of daylight. Is there really a difference in nutrient content between milk in light-proof bottles and other containers? We tested 5 brands – Anchor, Home Brand, Meadow Fresh, Pams and Signature Range – to find out.

Launched in 2013, “light-proof” bottles were marketed as being able to prevent the vitamin A and B2 in milk from breaking down. Fonterra’s Anchor-brand website stated, “light damages milk. We couldn’t let that happen, as we know how important it is to lock in those vital nutrients and minerals your body needs”.

But our test of the levels of vitamin A, vitamin B2 and calcium found the light-proof bottle didn’t make a discernible difference to vitamin content.

Vitamin results

Fonterra’s Anchor-brand website promotes its light-proof bottles stating, “Light can cause damage to vitamin B2 and A. This isn’t good. Why? Well, because vitamin A is important in aiding healthy eyesight and [the] immune system, whereas vitamin B2 helps your body turn food into fuel, helping you feel less tired and run down.”

It also refers to a lab experiment where vitamin A started breaking down after milk was continuously exposed to light for 16 hours.

Trim milk was the most susceptible to this degradation, which is why we chose it for our tests. The company says it’s done other experiments on the degradation of vitamin B2 in light-exposed milk.

But the differences in vitamin A and B2 content between the 5 brands we tested – Anchor, Home Brand, Meadow Fresh, Pams and Signature Range – were miniscule. For a person eating a balanced diet, these tiny differences would have no significant impact on their overall vitamin intake.

Product[sort;desc] Price/100ml Bottle type Calcium on label (mg)[sort;asc] Calcium tested (mg)[sort;asc] Vitamin B2 on label (mg)[sort;asc] Vitamin B2 tested (mg)[sort;asc] Vitamin A tested (μg)[sort;asc]
Anchor 22¢ Opaque 133 116 0.2 0.27 4.78
Home Brand 17¢ Transparent 130 125 n/a 0.26 3.72
Meadow Fresh 22¢ Semi-opaque 140 151 n/a 0.32 4.25
Pams 19¢ Transparent 130 129 n/a 0.27 3.62
Signature Range 19¢ Transparent 130 124 n/a 0.27 3.45

GUIDE TO THE TABLE PRODUCT listed alphabetically. Pams trim milk is only available in the South Island. PRICE is based on 2L bottles, priced in May and June 2017. CALCIUM, VITAMIN B2, VITAMIN A is per 100ml of trim milk, independently tested by the Institute of Environmental Science and Research and an affiliate lab. No milk brand listed Vitamin A content in its nutrition information panel.

When we asked Fonterra for evidence of the nutritional superiority of milk stored in a light-proof bottle, it agreed there wasn’t any. Despite the statements on its website, it said it had never claimed a health benefit from milk in its special bottle and any benefit was solely taste-related.

The company says when vitamin A and B2 degrade, this impacts the fats and proteins in the milk, and ultimately its taste. It says it’s run 2 blind taste tests, 1 with about 100 consumers tasting samples of light-protected and light-exposed blue-top milk, and a similar-sized experiment on the different types of milk in coffee. Seven out of 10 preferred light-protected, it says.

The company has now changed its website to refer to the taste difference of milk in its light-proof bottles instead of the nutritional benefits.

Health impacts

Milk is an important dietary source of some vitamins, but not others. Though referenced in light-proof bottle claims, vitamin A is an example of the latter.

Fish oil, green vegetables and yellow- and orange-coloured produce are far better sources of Vitamin A than trim milk. A cup of raw carrot sticks has about 100 times the vitamin A as a glass of trim milk – no matter which brand you buy.

Alongside red meat, dairy products are important sources of vitamin B2. A 250ml glass of any of the 5 trim milks we tested would provide a woman with about two-thirds of her vitamin B2 recommended daily intake and a man just over half.

Nutrients in milk can vary seasonally, but if you have a balanced diet, your overall vitamin A and B2 intake won’t be significantly impacted by the brand of milk you buy.

Vitamin enhanced

The vitamin most commonly added to milk in New Zealand is vitamin D, typically in yellow-top milks. This vitamin helps the body to absorb more calcium from food. However, as the body can make its own vitamin D from sunshine, most people can easily get their daily intake without supplements. Added vitamins must be included on the list of ingredients.

Calcium results

Calcium isn’t mentioned in claims about light-proof bottles. But like vitamins in milk, levels of this mineral can vary with the seasons.

Apart from Meadow Fresh, all milk brands recorded calcium levels slightly lower than what was listed in their nutrition information panels. Our sample of Meadow Fresh milk had 8% more calcium than stated.

Our tests were done in winter and these levels could slightly change for milk you drink in summer. However, University of Auckland associate medical professor Dr Mark Bolland says fluctuating calcium levels in the diet aren’t anything to worry about.

“There is strong evidence that most New Zealanders have enough calcium in their diet, and that getting a little less calcium at certain times of the year shouldn’t affect their health, even for older adults at higher risk of osteoporosis or broken bones.”