Understanding the Coronary Artery Calcium Score
A coronary artery calcium (CAC) score is a measure used to assess your risk of cardiovascular disease (CVD). A CAC scan, performed using a computed tomography (CT) scan, measures the amount of calcified plaque in the walls of the coronary arteries. A positive score (any value greater than zero) indicates the presence of atherosclerosis, or plaque buildup, which can increase the risk of heart attack. The Agatston scoring method is most commonly used to quantify the extent of this calcification.
The presence of calcium in the arteries is an active, highly regulated biological process that involves a transformation of cells and the expression of proteins similar to those in bone formation. It is not merely the passive accumulation of excess calcium from the diet. While calcium is a component of the plaque, its presence is a marker of underlying disease rather than a direct result of dietary intake.
Dietary Calcium vs. Vascular Calcification
One of the most persistent health myths is that consuming calcium-rich foods like milk directly leads to calcified arteries. However, the available scientific evidence overwhelmingly suggests this is not the case for calcium obtained from food.
Several large, population-based studies have investigated the link between dietary calcium intake and coronary artery calcification, with consistent results:
- The Framingham Offspring Study: An analysis found that over a four-year period, baseline calcium intake from both diet and supplements showed no association with an increase or decrease in vascular calcification. The study concluded that high calcium intake does not increase CAC.
- The ARIC Study: This longitudinal study found an inverse association between dietary calcium intake during middle age and coronary artery calcification at an older age. Participants with the highest calcium consumption had significantly lower calcification levels.
- The Multi-Ethnic Study of Atherosclerosis (MESA): In a sub-study of MESA, researchers found that higher total calcium intake was associated with a lower incidence of CAC over a 10-year follow-up period.
These findings suggest that fears about dietary calcium from sources like milk contributing to arterial plaque are unfounded. The body's intricate calcium regulatory system, which is optimized for managing the steady intake of calcium from food, prevents such a straightforward deposition.
The Calcium Paradox: Dietary Calcium vs. Supplementation
While dietary calcium has a neutral or even beneficial association with heart health, some past research raised concerns about calcium supplements. The so-called "calcium paradox" highlighted the observation that high calcium intake in some populations, particularly from supplements, coincided with higher rates of heart disease. Concerns focused on large, bolus doses of calcium supplements potentially causing transient spikes in blood calcium levels, which could theoretically promote vascular calcification.
However, this theory is heavily debated and lacks consensus. Many studies questioning the link have found no association or only a weak one, and methodological issues in the studies showing harm have been raised. Furthermore, a large study in the journal Circulation showed that higher total calcium intake (from both food and supplements) was actually associated with a decreased risk of incident CAC. The key takeaway remains that dietary calcium is generally safe, and the focus on supplements is less certain and potentially flawed.
The Role of Vitamin K2 in Preventing Calcification
Instead of blaming milk for calcification, a better understanding of the process involves other key nutrients, particularly Vitamin K2. While Vitamin D helps the body absorb calcium from the gut, Vitamin K2 is responsible for activating proteins that direct calcium to the right places, like bones, and keep it out of soft tissues like arteries.
One of these crucial proteins is Matrix Gla Protein (MGP). When activated by Vitamin K2, MGP inhibits vascular calcification. When Vitamin K2 levels are insufficient, MGP remains inactive, allowing for increased calcium deposition in the arteries. Dairy products, especially fermented ones like cheese, can be a source of Vitamin K2.
Whole Milk vs. Low-Fat Milk and Your Heart
Recommendations regarding dairy often focus on fat content. Here is a comparison based on heart health and calcium content:
| Feature | Whole Milk | Low-Fat (1%) Milk |
|---|---|---|
| Fat Content | High in saturated fat | Low in saturated fat |
| Calcium Content | Approximately 304 mg per 250ml cup | Approximately 367 mg per 250ml cup |
| Heart Association Recommendations | Not explicitly recommended; choose reduced-fat for existing heart conditions | Better option for those with heart disease or high cholesterol |
| Saturated Fat Concerns | Can raise LDL ('bad') cholesterol, but impact is complex | Less impact on LDL cholesterol due to lower fat content |
| Other Studies | Some observational studies suggest whole-fat dairy has neutral or beneficial effects on heart health. Some showed inverse CAC risk | Often viewed as a heart-healthy choice due to lower saturated fat. Some studies link low-fat dairy with reduced CVD risk |
| The Verdict | Evidence is mixed and depends on individual risk factors and overall diet | Often the recommended choice for those managing cholesterol or heart disease |
The overall effect of milk on heart health is debated, and the fat content appears to be a major factor in these discussions. The Heart Foundation suggests that unflavored milk, yogurt, and cheese have a 'neutral' effect on heart health overall, with reduced-fat options being preferable for those with existing heart conditions. Some studies have also found beneficial associations, particularly with fermented dairy products like cheese and yogurt.
Factors That Actually Drive Calcium Score
Instead of dietary calcium, the progression of coronary artery calcification is influenced by well-established risk factors for atherosclerosis. These include:
- Aging: Older individuals are naturally at a higher risk for vascular calcification.
- Hypertension: High blood pressure is a significant risk factor for both CVD and CAC.
- High Cholesterol: Elevated cholesterol levels contribute to the formation of arterial plaque.
- Smoking: Smoking is a major, modifiable risk factor for heart disease.
- Diabetes: Chronic hyperglycemia and related metabolic issues accelerate vascular damage.
- Inflammation: Chronic, low-grade inflammation is a shared mechanism linking osteoporosis and atherosclerosis.
- Sedentary Lifestyle: A lack of physical activity increases the risk of both heart disease and poor bone health.
These factors are far more influential in determining your calcium score than the calcium content of your milk.
Conclusion: The Bottom Line on Milk and Your Calcium Score
In summary, the notion that drinking milk increases your calcium score by directly depositing calcium into your arteries is a myth not supported by robust scientific evidence. The process of vascular calcification is complex and regulated by various factors, with dietary calcium playing a minimal or even protective role. The true drivers of a high calcium score are traditional cardiovascular risk factors such as smoking, high cholesterol, and hypertension. Including milk and other dairy products as part of a balanced, healthy diet is generally considered safe for cardiovascular health, especially when fortified with Vitamin D and consumed alongside sufficient Vitamin K2 to ensure proper calcium utilization.
The Verdict: Drinking Milk and Your Calcium Score
For most people, drinking milk is an effective way to obtain calcium for bone health and does not pose a risk for increasing their coronary artery calcium score. However, individuals should consider their overall dietary patterns and risk factors in consultation with a healthcare provider. The focus should be on managing established risks like smoking, inactivity, and blood pressure, rather than demonizing a dietary staple based on a misunderstanding of cardiovascular biology.
Radiologyinfo.org offers extensive information about the Cardiac CT for Calcium Scoring procedure.
