What vitamin is milk fortified with in the US to combat rickets?

November 14, 2025 •

2 min read

In the 1930s, the US began fortifying milk with vitamin D in a public health initiative to eradicate rickets, a debilitating bone disease that was once rampant, especially among poor children. This successful program directly answers what vitamin is milk fortified with in the US to combat rickets.

Quick Summary

This article explores the fortification of milk with vitamin D in the United States. It details the history of this public health strategy, the vital role of vitamin D in bone health, and its significant impact on preventing rickets.

Key Points

The Fortification Vitamin: Milk in the US is fortified with Vitamin D to prevent rickets.
Why Vitamin D is Critical: This vitamin is essential for the body's absorption of calcium and phosphorus, the key minerals for strong bones.
A Historic Public Health Triumph: Milk fortification was a highly successful public health initiative started in the 1930s that dramatically reduced the incidence of rickets.
Voluntary, but Widespread: In the US, milk fortification is voluntary for manufacturers, but it is a nearly universal practice for processed dairy milk.
Fortification Isn't the Only Source: While milk is a primary source, vitamin D also comes from sunlight, fatty fish, supplements, and other fortified foods like cereal and plant-based milks.
Modern Risks for Deficiency: Despite fortification, risk factors for deficiency include limited sun exposure, darker skin, and exclusive breastfeeding without supplementation.

The Historical Fight Against Rickets

Rickets was a serious health issue in the US during the late 19th and early 20th centuries, causing weak bones and skeletal deformities in children, particularly in areas with limited sun exposure. The discovery of vitamin D's importance for bone health in the 1920s led public health officials to fortify milk, a common food for children, with this vitamin starting in the 1930s. This initiative significantly reduced rickets cases, making it rare in the US today.

The Importance of Calcium and Vitamin D

Vitamin D is crucial because it helps the body absorb calcium and phosphorus, minerals necessary for strong bones. Without enough vitamin D, calcium absorption is poor, leading the body to take calcium from bones, thus weakening them. Fortified milk provides both calcium and the vitamin D needed for its effective use.

Milk Fortification in the US Today

While voluntary for most manufacturers, vitamin D fortification of milk is standard in the US. Most processed dairy milk contains around 100-120 IU of vitamin D per 8-ounce serving. This widespread practice helps maintain a baseline vitamin D level for many Americans.

Key points about modern fortification:

Fortification is not universal: Cheese and ice cream are typically not fortified.
Other foods are also fortified: Many cereals, infant formulas, and some juices contain added vitamin D.
Milk alternatives: Plant-based milks are also often fortified.

Comparison of Vitamin D Sources

Here is a comparison of various vitamin D sources:


Source	Natural Vitamin D Content	Fortification Status	Average Vitamin D (per serving)
Fortified Cow's Milk	Low	Routinely fortified in the US	~100 IU per 1 cup (8 oz)
Unfortified Cow's Milk	Very low trace amounts	No fortification added	Minimal or none
Fatty Fish (e.g., Salmon)	High	Not fortified	570 IU per 3 oz (sockeye)
Cod Liver Oil	Very high	N/A (supplement)	1,360 IU per 1 tbsp
Sunlight	Your skin naturally produces Vitamin D	N/A (not a food source)	Variable
Fortified Cereal	None naturally	Often fortified	~40-140 IU per serving
Fortified Plant Milk	None naturally	Often fortified	~100-144 IU per 1 cup

The Resurgence and Modern Relevance of Vitamin D

Despite past success, rickets cases have slightly increased, partly due to reduced sun exposure and feeding practices like exclusive breastfeeding without supplementation, as breast milk has low vitamin D. Individuals with darker skin also produce less vitamin D from sun.

Modern strategies for adequate vitamin D include sensible sun exposure, fortified foods, and supplements for those at risk, like breastfed infants. Monitoring vitamin D levels may also be advised. For more information, consult the National Institutes of Health Office of Dietary Supplements.

Conclusion

Milk in the US is fortified with vitamin D to combat rickets. This historic and ongoing public health measure has been highly effective in preventing this bone disease. Understanding its history and importance highlights the significant positive impact of nutritional improvements on public health.

Frequently Asked Questions

Vitamin D is added to milk to help the body absorb calcium, which is vital for building and maintaining strong bones. This fortification was introduced to combat rickets, a bone-softening disease caused by a vitamin D deficiency.

Almost all processed cow's milk sold in the US is fortified with vitamin D. However, it's not federally mandated, and products like cheese and ice cream are not always fortified. Plant-based milks and cereals are also commonly fortified voluntarily.

While fortified milk is a good source of vitamin D, relying on a single source may not be enough. Adequate vitamin D intake depends on diet, sun exposure, and individual needs. A balanced approach with other fortified foods, natural sources, and sometimes supplements is recommended.

Rickets is a disease that causes the bones to soften and weaken in children. It is primarily caused by a severe deficiency of vitamin D. Vitamin D is necessary for the body to absorb the calcium and phosphorus needed for proper bone mineralization.

Yes, exclusively or partially breastfed infants should receive a vitamin D supplement, as human milk contains very little vitamin D. The American Academy of Pediatrics recommends a daily 400 IU supplement for breastfed infants until they are weaned onto formula or milk fortified with vitamin D.

Yes, both vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol) can be used. Vitamin D3 is commonly used in milk and is thought to be slightly more effective at raising blood levels, but both are effective at preventing rickets.

Milk was chosen in the 1930s because it is a nutrient-rich staple consumed widely, especially by children. Its consistent consumption made it an effective way to deliver vitamin D to a broad population and address the rickets epidemic.